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AbstractPlatelets are terminally differentiated anucleated cells, but they still have cell-like functions and can even produce progeny platelets. However, the mechanism of platelet sprouting has not been elucidated so far. Here, we show that when platelet-rich plasma(PRP) was cultured at 37°C, platelets showed a spore phenomenon. The number of platelets increased when given a specific shear force. It is found that AMP-related signaling pathways, such as PKA and AMPK are activated in platelets in the spore state. Meanwhile, the mRNA expression levels of genes, such as CNN3, CAPZB, DBNL, KRT19, and ESPN related to PLS1 skeleton proteins also changed. Moreover, when we use the AMPK activator AICAR(AI) to treat washed platelets, cultured platelets can still appear spore phenomenon. We further demonstrate that washed platelets treated with Forskolin, an activator of PKA, not only platelet sprouting after culture but also the AMPK is activated. Taken together, these data demonstrate that AMPK plays a key role in the process of platelet budding and proliferation, suggesting a novel strategy to solve the problem of clinical platelet shortage.

Background: Platelet-rich plasma (PRP) is a therapeutic approach that is gaining attention for its potential in the treatment of poor ovarian response. This meta-analysis aimed to systematically review and analyze clinical studies to evaluate the impact of PRP on poor responders undergoing ovarian stimulation for IVF. Methods: A comprehensive search was conducted in electronic databases, including PubMed, Embase, Scopus, Web of Science, and the Cochrane Library to identify relevant studies published in English. The pooled data, such as pregnancy outcome, number of MII oocytes, number of transferable embryos, and ovarian reserve markers were analyzed using R version 4.2.3. Results: A total of 10 trials were enrolled in the present meta-analysis. Following PRP treatment, live birth rate was found to be 16.6% (95% CI 8.8%-26.1%), while clinical pregnancy rate was observed to be 25.4% (95% CI 13.1%-39.9%). PRP pretreatment resulted in a higher number of MII oocytes (MD 1.073, 95% CI 0.720 to 1.427), a higher number of embryos (MD 0.946, 95% CI 0.569 to 1.323), a higher antral follicle count (MD 1.117; 95% CI 0.689 to 1.544), and the change of hormone levels. Conclusions: Among the studies evaluated in this review, PRP showed promising results in poor responder. Further research is required to clarify the potential role of PRP in female reproductive health. [ABSTRACT FROM AUTHOR]

Platelet-rich plasma (PRP) holds promise as a therapeutic modality for wound healing; however, immediate utilization encounters challenges related to volume, concentration, and consistency. Cryopreservation emerges as a viable solution, preserving PRP's bioactive components and extending its shelf life. This study explores the practicality and efficacy of cryopreserved platelet-rich plasma (cPRP) in wound healing, scrutinizing both cellular mechanisms and clinical implications. Fresh PRP and cPRP post freeze-thaw underwent assessment in macrophage, fibroblast, and endothelial cell cultures. The impact of cPRP on active component release and cell behavior pertinent to wound healing was evaluated. Varied concentrations of cPRP (1%, 5%, 10%) were examined for their influence on cell polarization, migration, and proliferation. The results showed minimal changes in cPRP's IL-1β levels, a slight decrease in PDGF-BB, and superior effects on macrophage M2 polarization and fibroblast migration, while no statistical significance was observed in endothelial cell angiogenesis and proliferation. Remarkably, 5% PRP exhibited the most significant stimulation among all cPRP concentrations, notably impacting cell proliferation, angiogenesis, and migration. The discussion underscores that cPRP maintains platelet phenotype and function over extended periods, with 5% cPRP offering the most favorable outcomes, providing a pragmatic approach for cold storage to extend post-thaw viability and amplify therapeutic effects. [ABSTRACT FROM AUTHOR]

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) restricts platelet activation via platelet collagen receptor GPVI/FcRγ-chain. In this study, screening against collageninduced platelet aggregation was performed to identify functional CEACAM1 extracellular domain fragments. CEACAM1 fragments, including Ala-substituted peptides, were synthesized. Platelet assays were conducted on healthy donor samples for aggregation, cytotoxicity, adhesion, spreading, and secretion. Mice were used for tail bleeding and FeCl3-induced thrombosis experiments. Clot retraction was assessed using platelet-rich plasma. Extracellular segments of CEACAM1 and A1 domain-derived peptide QDTT were identified, while N, A2, and B domains showed no involvement. QDTT inhibited platelet aggregation. Ala substitution for essential amino acids (Asp139, Thr141, Tyr142, Trp144, and Trp145) in the QDTT sequence abrogated collagen-induced aggregation inhibition. QDTT also suppressed platelet secretion and "insideout" GP IIb/IIIa activation by convulxin, along with inhibiting PI3K/Akt pathways. QDTT curtailed FeCl3-induced mesenteric thrombosis without significantly prolonging bleeding time, implying the potential of CEACAM1 A1 domain against platelet activation without raising bleeding risk, thus paving the way for novel antiplatelet drugs. [ABSTRACT FROM AUTHOR]

Platelet Rich Plasma (PRP) is a biological treatment which, thanks to its enhanced growth factors content, is widely used in the field of regenerative medicine for its reparative effects. Although it is usually used fresh immediately after preparation, its freezing for preservation for future usage could be key in increasing its versatility and new applications. To assess the suitability of freezing, after collecting PRP and platelet lysates (PL) from 6 patients, they were preserved for 1 or 3 months at temperatures of -20°C and -80°C. Measurements were then made on platelet number and integrity, growth factor levels, biomechanical properties of the clot and its bioactivity on cultured cells. Fresh PRP and PL were used as controls. The results showed an increase in platelet size (p < .01) and clot elasticity (p < .01), as well as decrease in levels of PDGF (P < .05) and VEGF (p < .05), though the overall bioactivity was not affected as culture cells showed the same responsiveness to both frozen and fresh PRP and PL in terms of cell viability. Based on these results, it could be assumed that preservation of PRP by freezing is a feasible and suitable option for its further use. [ABSTRACT FROM AUTHOR]

Statins inhibit the mevalonate pathway by impairing protein prenylation via depletion of lipid geranylgeranyl diphosphate (GGPP). Rab27b and Rap1a are small GTPase proteins involved in dense granule secretion, platelet activation, and regulation. We analyzed the impact of statins on prenylation of Rab27b and Rap1a in platelets and the downstream effects on fibrin clot properties. Whole blood thromboelastography revealed that atorvastatin (ATV) delayed clot formation time (P < .005) and attenuated clot firmness (P < .005). ATV pre-treatment inhibited platelet aggregation and clot retraction. Binding of fibrinogen and P-selectin exposure on stimulated platelets was significantly lower following pre-treatment with ATV (P < .05). Confocal microscopy revealed that ATV significantly altered the structure of platelet-rich plasma clots, consistent with the reduced fibrinogen binding. ATV enhanced lysis of Chandler model thrombi 1.4-fold versus control (P < .05). Western blotting revealed that ATV induced a dose-dependent accumulation of unprenylated Rab27b and Rap1a in the platelet membrane. ATV dose-dependently inhibited ADP release from activated platelets. Exogenous GGPP rescued the prenylation of Rab27b and Rap1a, and partially restored the ADP release defect, suggesting these changes arise from reduced prenylation of Rab27b. These data demonstrate that statins attenuate platelet aggregation, degranulation, and binding of fibrinogen thereby having a significant impact on clot contraction and structure. [ABSTRACT FROM AUTHOR]

Blood platelets are crucial to prevent excessive bleeding following injury to blood vessels. Platelets are crucial for the formation of clots and for clot strength. Platelet activation involves aggregation, attachment to fibrin and clot retraction. Most assays that address platelet function measure platelet aggregation, not clot retraction. Here, we describe a 96-well-based clot retraction assay that requires a relatively short runtime and small sample volume. The assay involves continuous optical density monitoring of platelet-rich plasma that is activated with thrombin. The data can be analyzed using time-series analytical tools to generate quantitative information about different phases of clot formation and clot retraction. The assay demonstrated good repeatability and reproducibility and was robust to different calcium concentrations. Impairment of platelet bioenergetics, actin polymerization, fibrin interaction, and signaling significantly affected clot retraction and was detected and showed good agreement with light transmission aggregometry, suggesting that clot retraction is predictive of platelet function. Using this microplate clot retraction assay, we showed a significant difference in platelets stored in autologous plasma compared with platelet additive solution after 7 days of room temperature storage. [ABSTRACT FROM AUTHOR]

Platelet Rich Plasma (PRP) is a biological treatment which, thanks to its enhanced growth factors content, is widely used in the field of regenerative medicine for its reparative effects. Although it is usually used fresh immediately after preparation, its freezing for preservation for future usage could be key in increasing its versatility and new applications. To assess the suitability of freezing, after collecting PRP and platelet lysates (PL) from 6 patients, they were preserved for 1 or 3 months at temperatures of −20ºC and −80°C. Measurements were then made on platelet number and integrity, growth factor levels, biomechanical properties of the clot and its bioactivity on cultured cells. Fresh PRP and PL were used as controls. The results showed an increase in platelet size (p

Several clinical trials exploring the effect of platelet-rich plasma (PRP) on Achilles tendon rupture (ATR) or Achilles tendinopathy (AT) have been published. However, current evidence is limited to small-sized trials. This study aims to evaluate whether PRP improves the outcomes of ATR or AT. PubMed, Web of Science, EMBASE, and Cochrane Library databases were searched to identify randomized controlled trials comparing PRP injection versus placebo for ATR or AT. Eleven studies with 574 patients were included. Quantitative synthesis suggested that compared with placebo, AT patients in PRP group had higher VISA-A score improvement at six-week follow-up (mean difference (MD) = 2.64; 95% CI) = 1.12 to 4.15). However, there was no significant difference between two groups for VISA-A score improvement at three-month follow-up (MD = 0.93; 95% CI = −2.75 to 4.62), or 6-month follow-up (MD = 5.46; 95% CI = −1.19 to 12.11). In ATR patients, quantitative synthesis suggested that no significant difference was seen between PRP and control group at 3-month, 6-month, and 1-year follow-up. In addition, no significant difference was detected between the two groups in improving tendon thickness and pain for AT patients, and no significant difference was seen in improving heel-rise work, maximum heel-rise height, dorsal and plantar flexion, rate of returning to sports activities, and complication for ATR patients. To conclude, no evidence indicates that PRP injection can improve the patient-reported/clinical/functional outcomes of AT or ATR. The increasing times of PRP injection could improve the outcomes, and further clinical randomized controlled trials are expected to be conducted to verify this hypothesis.

Anterior cruciate ligament (ACL) rupture is a common musculoskeletal injury, most frequently affecting young and physically active patients. Platelet-rich plasma (PRP) has been widely used in ACL reconstruction to augment the graft healing. However, high-level studies addressing its clinical efficacy could not reach a consensus. In this study, we assess the efficacy of PRP on pain relief, functional improvement along with radiological changes in patients who underwent ACL reconstruction. We performed comprehensive literature search and included 17 RCTs containing 970 participants who underwent ACL reconstruction. The combined data showed significant difference between PRP and control with regard to VAS score (MD: −1.12, 95% CI −1.92, −0.31; P = .007), subjective IKDC score (MD: 6.08, 95% CI 4.39, 7.77; P

Aspirin's clinical efficacy may be influenced by body weight and mass. Although inadequate platelet inhibition by aspirin is suggested as responsible, evidence for this in non-diabetic patients is sparse. We investigated the influence of body weight and mass on aspirin's inhibition of platelet aggregation in healthy adults without diabetes. Cohort one (NYU, n = 84) had light transmission aggregometry (LTA) of platelet-rich plasma to submaximal adenosine diphosphate (ADP) and arachidonic acid (AA) before and following 1 week of daily 81 mg non-enteric coated aspirin. Subjects in the validation cohort (Duke, n = 66) were randomized to 81 mg or 325 mg non-enteric coated aspirin for 4 weeks, immediately followed by 4 weeks of the other dose, with LTA to submaximal collagen, ADP, and AA before and after each dosage period. Body mass index (BMI) range was 18.0–57.5 kg/m2 and 25% were obese. Inhibition of platelet aggregation was similar irrespective of BMI, body weight and aspirin dose. There was no correlation between platelet aggregation before or after aspirin with BMI or body weight. Our data demonstrate that aspirin produces potent inhibition of direct and indirect COX1-mediated platelet aggregation in healthy adults without diabetes regardless of body weight or mass – suggesting that other mechanisms explain lower preventive efficacy of low-dose aspirin with increasing body weight/mass. [ABSTRACT FROM AUTHOR]

Platelet-rich plasma (PRP) is widely used clinically to treat tendon injuries, and often contains leukocytes. However, the debate regarding the concentration of leukocytes in PRP is still ongoing. This study aimed to evaluate the therapeutic effects of leukocyte-rich platelet-rich plasma (LR-PRP) and leukocyte-poor platelet-rich plasma (LP-PRP) on the healing of the bone-tendon interface (BTI) of the rotator cuff. A total of 102 C57BL/6 mice were used. Thirty mice were used to prepare the PRP, while 72 underwent acute supraspinatus tendon injury repair. The animals were then randomly assigned to three groups: LR-PRP, LP-PRP and control groups. The mice were euthanized at 4 and 8 weeks postoperatively, and histological, immunological and biomechanical analyses were performed. The histological results showed that the fusion effect at the bone-tendon interface at 4 and 8 weeks after surgery was greater in the PRP groups and significantly increased at 4 weeks; however, at 8 weeks, the area of the fibrocartilage layer in the LP-PRP group increased significantly. M2 macrophages were observed at the repaired insertion for all the groups at 4 weeks. At 8 weeks, M2 macrophages withdrew back to the tendon in the control group, but some M2 macrophages were retained at the repaired site in the LR-PRP and LP-PRP groups. Enzyme-linked immunoassay results showed that the concentrations of IL-1β and TNF-α in the LR-PRP group were significantly higher than those in the other groups at 4 and 8 weeks, while the concentrations of IL-1β and TNF-α in the LP-PRP group were significantly lower than those in the control group. The biomechanical properties of the BTI were significantly improved in the PRP group. Significantly higher failure load and ultimate strength were seen in the LR-PRP and LP-PRP groups than in the control group at 4 and 8 weeks postoperatively. Thus, LR-RPR can effectively enhance the early stage of bone-tendon interface healing after rotator cuff repair, and LP-PRP could enhance the later stages of healing after rotator cuff injury. [ABSTRACT FROM AUTHOR]

Mass cytometry (CyTOF) is a new technology that allows the investigation of protein expression at single cell level with high resolution. While several protocols are available to investigate leukocyte expression, platelet staining and analysis with CyTOF have been described only from whole blood. Moreover, available protocols do not allow sample storage but require fresh samples to be obtained, processed, and measured immediately. We provide a structured and reproducible method to stain platelets from platelet-rich plasma to study thrombocyte protein expression and reactivity using mass cytometry. With our method, it is possible to acquire a large number of events allowing deep bioinformatic investigation of platelet expression heterogeneity. Integrated in our protocol is also a previously established freezing protocol that allows the storage of stained samples and to delay their measurement. Finally, we provide a structured workflow using different platelet stimulators and a freely available bioinformatic pipeline to analyze platelet expression. Our protocol unlocks the potential of CyTOF analysis for studying platelet biology in health and disease. [ABSTRACT FROM AUTHOR]

Steroid-associated necrosis of the femoral head (SANFH) is one of the most common and refractory chronic diseases with increasing incidence. The typical pathological changes of SANFH include decreased osteogenic differentiation, enhanced intramedullary adipocytes deposition and impaired osseous circulation. In this study, we investigated the effects and potential mechanisms of Platelet-rich plasma (PRP) on SANFH. Sixty Sprague-Dawley rats were randomly divided into the control, PRP donor, model, and PRP groups. Compared to the model group, PRP treatment significantly increased the hemorheological indexes and serum levels of bone gla-protein (BGP) and vascular endothelial growth factor (VEGF), while decreased the levels of triglyceride (TG) and total cholesterol (TC). Meanwhile, Micro-CT and histopathological stain (Hematoxylin-eosin and Alcian blue-hematoxylin/orange G staining) were performed on the femoral head for morphological and histopathological evaluation, indicating that bone trabecular microstructure and bone mineral density (BMD) were significantly improved after PRP treatment. Immunohistochemical analysis revealed that PRP remarkably up-regulated the expression of osteogenic markers including β-catenin and alkaline phosphatase (ALP), angiogenic markers containing VEGF and platelet endothelial cell adhesion molecule-1 (CD31), while down-regulated adipogenic markers involving fatty acid-binding protein (FABP-4), and peroxisome proliferator-activated receptor gamma (PPAR-γ) in SANFH rat models. In summary, for the first time, PRP was demonstrated to prevent the development of SANFH through stimulating bone formation and vascularization as well as retarding adipogenesis.

In order to prepare optimal platelet and extracellular vesicle (EV)-rich plasma for the treatment of chronic temporal bone inflammation, we studied effects of centrifugation parameters on redistribution of blood constituents in blood samples of 23 patients and 20 volunteers with no record of disease. Concentrations of blood cells and EVs were measured by flow cytometry. Sample content was inspected by scanning electron microscopy. A mathematical model was constructed to interpret the experimental results. The observed enrichment of plasma in platelets and EVs after a single spin of blood depended on the erythrocyte sedimentation rate, thereby indicating the presence of a flow of plasma that carried platelets and EVs in the direction opposite to settling of erythrocytes. Prolonged handling time correlated with the decrease of concentration of platelets and larger EVs in platelet and EV-rich plasma (PVRP), R = −0.538, p = 0.003, indicating cell fragmentation during the processing of samples. In further centrifugation of the obtained plasma, platelet and EV enrichment depended on the average distance of the sample from the centrifuge rotor axis. Based on the agreement of the model predictions with observations, we propose the centrifugation protocol optimal for platelet and EV enrichment and recovery in an individual sample, adjusted to the dimensions of the centrifuge rotor, volume of blood and erythrocyte sedimentation rate. [ABSTRACT FROM AUTHOR]

To be faced with an infected bone defect and the need to accelerate bone union while controlling infection is a welcome challenge for orthopedists. Platelet-rich plasma (PRP) has been applied in tissue defects given their composition of growth factors however the weak antibacterial effects have limited the use of PRP in the clinical setting. Therefore, the aim of this study was to explore the feasibility of using PRP in a local antibiotic delivery system (PADS) with the characteristics of promoting wound healing of bone infection. PADS was prepared with the addition of antibiotics or no antibiotics as control after PRP was prepared by a two-step centrifugation procedure. Antibacterial tests showed zones of inhibition produced by antibiotics were not significantly different with antibiotics combined with PRP. HPLC analysis demonstrated that about 60% of the total vancomycin (VAN) and ceftazidime (CAZ) dose were released within 10 min, then the release rate gradually decreased. However, 90% clindamycin was released within 10 min. Interestingly, above 10 times the minimum inhibitory concentration was presented after 72 h. Additionally, ELISA and morphology studies of PADS indicated that loaded antibiotics could reduce the PRP-released growth factor concentration and disturb the structure of platelet-fibrin beams and fibrin network in a dose-dependent manner. Fortunately, the lower dose of antibiotics maintained their anti-microbial effect, meanwhile growth factors released from PADS, the structure of platelet-fibrin beams, fibrin network remained unaffected. In addition, a patient experiencing infected bone defect receiving this PADS treatment achieved union within the 15-month follow-up. Therefore, this novel PADS approach might represent a potential therapy for patients who have sustained infected bone defects.

Several clinical trials exploring the effect of platelet-rich plasma (PRP) on Achilles tendon rupture (ATR) or Achilles tendinopathy (AT) have been published. However, current evidence is limited to small-sized trials. This study aims to evaluate whether PRP improves the outcomes of ATR or AT. PubMed, Web of Science, EMBASE, and Cochrane Library databases were searched to identify randomized controlled trials comparing PRP injection versus placebo for ATR or AT. Eleven studies with 574 patients were included. Quantitative synthesis suggested that compared with placebo, AT patients in PRP group had higher VISA-A score improvement at six-week follow-up (mean difference (MD) = 2.64; 95% CI) = 1.12 to 4.15). However, there was no significant difference between two groups for VISA-A score improvement at three-month follow-up (MD = 0.93; 95% CI = −2.75 to 4.62), or 6-month follow-up (MD = 5.46; 95% CI = −1.19 to 12.11). In ATR patients, quantitative synthesis suggested that no significant difference was seen between PRP and control group at 3-month, 6-month, and 1-year follow-up. In addition, no significant difference was detected between the two groups in improving tendon thickness and pain for AT patients, and no significant difference was seen in improving heel-rise work, maximum heel-rise height, dorsal and plantar flexion, rate of returning to sports activities, and complication for ATR patients. To conclude, no evidence indicates that PRP injection can improve the patient-reported/clinical/functional outcomes of AT or ATR. The increasing times of PRP injection could improve the outcomes, and further clinical randomized controlled trials are expected to be conducted to verify this hypothesis. [ABSTRACT FROM AUTHOR]

Platelet-rich plasma (PRP) is an autologous preparation that has been claimed to improve healing and mechanobiological properties of tendons both in vitro and in vivo. In this sub-study from the PATH-2 (PRP in Achilles Tendon Healing-2) trial, we report the cellular and growth factor content and quality of the Leukocyte-rich PRP (L-PRP) (N = 103) prepared using a standardized commercial preparation method across 19 different UK centers. Baseline whole blood cell counts (red cells, leukocyte and platelets) demonstrated that the two groups were well-matched. L-PRP analysis gave a mean platelet count of 852.6 x 109/L (SD 438.96), a mean leukocyte cell count of 15.13 x 109/L (SD 10.28) and a mean red blood cell count of 0.91 x 1012/L (SD 1.49). The activation status of the L-PRP gave either low or high expression levels of the degranulation marker CD62p before and after ex-vivo platelet activation respectively. TGF-β, VEGF, PDGF, IGF and FGFb mean concentrations were 131.92 ng/ml, 0.98 ng/ml, 55.34 ng/ml, 78.2 ng/ml and 111.0 pg/ml respectively with expected correlations with both platelet and leukocyte counts. While PATH-2 results demonstrated that there was no evidence L-PRP is effective for improving clinical outcomes at 24 weeks after Achilles tendon rupture, our findings support that the majority of L-PRP properties were within the method specification and performance.

There is a global interest in optimizing post-surgical tissue repair strategies, leading to better patient outcomes and fewer complications, most ideally with reduced overall cost. In this regard, in recent years, the interest in autologous biological treatments in orthopedic surgery and sports medicine has increased greatly, and the addition of platelet-rich plasma (PRP) to the surgical armamentarium is of particular note. Unfortunately, the number of PRP preparation devices has also grown immensely over the recent decades, raising meaningful concern for the considerable variation in the qualities of currently available PRP preparations. The lack of consensus on the standardization of PRP preparation and of agreement on condition specific PRP formulations is largely responsible for the sometimes contradictory outcomes in the literature. Furthermore, the full potential of PRP technology, the concept of individualized treatment protocols based on bioformulation options, and platelet dosing, angiogenesis, and antimicrobial and painkilling effects of PRP relevant to orthopedic surgery have rarely been addressed. In this review, we will discuss recent developments regarding PRP preparations and potential therapeutic effects. Additionally, we present a synopsis of several published data regarding PRP applications in orthopedic surgery for treating tendon injuries, inducing bone repair, strengthening spinal fusion outcomes, and supporting major joint replacements.

The application of platelet-rich plasma (PRP) in oral and maxillofacial surgery has been thoroughly studied in the last two decades. Currently, different types of PRP are applied in the clinical practice, being the presence or absence of leukocytes one of the classification criteria. However, there is poor evidence assessing the influence of the PRP composition in their efficacy. In this context, the aim of this narrative review is to compile the existing evidence covering the efficacy of PRP in oral and maxillofacial surgery, starting from a systematic literature search and to qualitatively describe the efficacy outcomes from the composition perspective. According to the results of this review, the application of PRP in oral and maxillofacial surgery is a potential strategy to improve soft- and hard-tissue regeneration, observing differences in the efficacy of PRP depending on its composition and the studied application. P-PRP (the absence of leukocytes) has been more consistent in achieving beneficial effects in alveolar ridge preservation, management of post-extraction complications, bone augmentation and temporomandibular joint disorders. For that, the composition and methodology used to prepare the PRP should be a critical point when evaluating the efficacy of PRP.

Platelets play a crucial role in hemostasis, tissue regeneration and host defense. Based on these settings, platelet-rich plasma (PRP) and its derivatives are therapeutically used to promote wound healing in several scenarios. This review summarizes the biological mechanisms underlying the most traditional as well as innovative applications of PRP in wound healing. These mechanisms involve the combined action of platelet-derived growth factors and cytokines, together with the role of plasma-derived fibrillar, antioxidant and homeostatic factors. In addition, regenerative treatments with PRP consist of personalized and non-standardized methods. Thus, the quality of PRP varies depending on endogenous factors (e.g., age; gender; concomitant medication; disease-associated systemic factors; nutrition) and exogenous factors (anticoagulants and cellular composition). This review also analyses whether these factors affect the biological mechanisms of PRP in wound healing applications.

Background: Platelet-rich plasma (PRP) is a therapeutic approach that is gaining attention for its potential in the treatment of poor ovarian response. This meta-analysis aimed to systematically review and analyze clinical studies to evaluate the impact of PRP on poor responders undergoing ovarian stimulation for IVF., Methods: A comprehensive search was conducted in electronic databases, including PubMed, Embase, Scopus, Web of Science, and the Cochrane Library to identify relevant studies published in English. The pooled data, such as pregnancy outcome, number of MII oocytes, number of transferable embryos, and ovarian reserve markers were analyzed using R version 4.2.3., Results: A total of 10 trials were enrolled in the present meta-analysis. Following PRP treatment, live birth rate was found to be 16.6% (95% CI 8.8%-26.1%), while clinical pregnancy rate was observed to be 25.4% (95% CI 13.1%-39.9%). PRP pretreatment resulted in a higher number of MII oocytes (MD 1.073, 95% CI 0.720 to 1.427), a higher number of embryos (MD 0.946, 95% CI 0.569 to 1.323), a higher antral follicle count (MD 1.117; 95% CI 0.689 to 1.544), and the change of hormone levels., Conclusions: Among the studies evaluated in this review, PRP showed promising results in poor responder. Further research is required to clarify the potential role of PRP in female reproductive health.

Platelets are terminally differentiated anucleated cells, but they still have cell-like functions and can even produce progeny platelets. However, the mechanism of platelet sprouting has not been elucidated so far. Here, we show that when platelet-rich plasma(PRP) was cultured at 37°C, platelets showed a spore phenomenon. The number of platelets increased when given a specific shear force. It is found that AMP-related signaling pathways, such as PKA and AMPK are activated in platelets in the spore state. Meanwhile, the mRNA expression levels of genes, such as CNN3 , CAPZB , DBNL , KRT19 , and ESPN related to PLS1 skeleton proteins also changed. Moreover, when we use the AMPK activator AICAR(AI) to treat washed platelets, cultured platelets can still appear spore phenomenon. We further demonstrate that washed platelets treated with Forskolin, an activator of PKA, not only platelet sprouting after culture but also the AMPK is activated. Taken together, these data demonstrate that AMPK plays a key role in the process of platelet budding and proliferation, suggesting a novel strategy to solve the problem of clinical platelet shortage.

Anterior cruciate ligament (ACL) rupture is a common musculoskeletal injury, most frequently affecting young and physically active patients. Platelet-rich plasma (PRP) has been widely used in ACL reconstruction to augment the graft healing. However, high-level studies addressing its clinical efficacy could not reach a consensus. In this study, we assess the efficacy of PRP on pain relief, functional improvement along with radiological changes in patients who underwent ACL reconstruction. We performed comprehensive literature search and included 17 RCTs containing 970 participants who underwent ACL reconstruction. The combined data showed significant difference between PRP and control with regard to VAS score (MD: −1.12, 95% CI −1.92, −0.31; P =.007), subjective IKDC score (MD: 6.08, 95% CI 4.39, 7.77; P <.00001) and Lysholm score (MD: 8.49, 95% CI 1.63, 15.36; P =.02) by postoperative 6 months, but only pain reduction was deemed clinically important. At the end of one year's follow-up, no clinically meaningful improvement in VAS (MD: −0.47, P =.04), subjective IKDC score (MD: 3.99, P =.03), Lysholm score (MD: 2.30, P =.32), objective IKDC score (RR: 1.03, P =.09) and knee joint laxity (MD: 0.17, P =.28) was seen. In terms of radiological findings, about one-third of the studies favored PRP to facilitate the graft healing, improve the harvest site morbidity and prevent tunnel widening. In summary, moderate quality of evidence suggested that PRP could provide short-term but not long-term clinically important pain reduction. [ABSTRACT FROM AUTHOR]

Here, we report the in vitro characterization of the P2Y12 receptor antagonist selatogrel (ACT-246475). Binding studies with radiolabeled selatogrel demonstrated that selatogrel is a competitive antagonist of ADP binding to the P2Y12 receptor with a fast onset of action. Consequently, selatogrel was confirmed to be a potent inhibitor of P2Y12-mediated intra-platelet signaling and ADP-induced platelet activation. Characterization of selatogrel in platelet-rich plasma in vitro demonstrated that the mode of anti-coagulation affected the anti-platelet potency. Specifically, in platelet-rich plasma containing physiological calcium concentration (anticoagulated with a direct thrombin inhibitor), selatogrel achieved half-maximal inhibition of ADP-induced platelet aggregation at a 3-fold lower concentration than in conditions with low calcium concentration (anticoagulated with citrate). Furthermore, calcium-dependent reduction in selatogrel potency was observed in whole blood platelet aggregation using the VerifyNow™ system with a 3.7-fold potency loss in low calcium conditions. A comparable potency loss was also observed with the reversible P2Y12 receptor antagonists ticagrelor, cangrelor and elinogrel. Furthermore, receptor-binding experiments using radiolabeled selatogrel confirmed a 3-fold lowering of selatogrel binding affinity to the P2Y12 receptor in low calcium conditions. In conclusion, our data suggest that in low calcium conditions (i.e., citrate-anticoagulated blood), there is a risk of underestimating the potency of reversible P2Y12 receptor antagonists. To avoid overdosing, and a potential increase in bleeding risk, we propose that the ex vivo evaluation of reversible P2Y12 receptor antagonists should be performed with platelet assay systems containing physiological calcium concentration. [ABSTRACT FROM AUTHOR]

Previous in vitro studies suggest a direct relevance for the peptide–free lipid fraction (LF) of platelet-rich plasma (PRP) in biological mechanisms related to wound healing. However, there are no scientific reports to date on the wound healing activities of this lipid component in vivo. Thus, the present study provides a scientific evaluation for the wound healing potential of the lipid portion of the activated PRP. For the wound healing activity assessment, in vivo full‐thickness excisional wounds were created on the dorsal skin of Sprague-Dawley rats. Lipid extract from pooled PRP was applied topically to the wounds on 0, 3, and 7 days after injury. Histological assessment of epidermal and dermal regeneration, granulation tissue thickness and angiogenesis by Sirius red and Masson’s trichrome staining, in addition to immunohistochemical staining for transforming growth factor beta-1 (TGF-β1), collagen type I (COL I), and collagen type III (COL III) were performed on skin biopsies at 3, 7 and 14 days. The total histological scores of the LF group were significantly higher than the 25% dimethylsulfoxide-control group. According to the immunohistochemical staining, the observed expression changes for TGF-β1, COL I and III at 3, 7, and 14 days after wounding were significantly better in the study group than the control group. Furthermore, COL I/III ratio in the lipid extract-treated group at day 14 was much higher than that of the control group. Meanwhile, analysis of the data also indicated that the LF has less positive effects on all evaluated parameters than PRP. From the present data, it could be concluded that the peptide–free LF of PRP has potent wound healing capacity in vivo for cutaneous wounds, although not as much as that of PRP. Strengthening our understanding of the wound healing potential of lipid components of PRP and platelet-derived lipid factors may provide new avenues for improving the healing process of a wound with elevated protease activity.

Platelet-rich plasma (PRP) is increasingly used in the treatment of musculoskeletal diseases. Its preservation by freezing it for the realization of multiple injections in clinical use has never been discussed. Calcaneal tendons of rats were surgically sectioned. Platelet concentration of the PRP was 2.5 x 106/µl with autologous plasma of rats. Frozen-thawed PRP was prepared by performing two cycles of freezing and thawing on PRP aliquots. Both platelet preparations were injected in the lesion. Biomechanical and histological evaluations were carried out after 7, 20 or 40 days post surgery. After 7 and 40 days, no significant difference was observed between the PRP and the frozen-thawed PRP group. There is however a difference 20 days after surgery: the ultimate tensile strength (UTS) was greater in the fresh PRP group. No obvious difference with histological aspect was observed between the two groups. In conclusion, fresh PRP and frozen-thawed PRP injections can lead to similar results in the healing process of section calcaneal tendons of rats. Improvements with fresh PRP are slight. PRP could thus be frozen to be preserved if multiple injections are needed (e.g. osteoarthritis).

In this work, we present a new method—Thrombodynamics-4D—for the assessment of both plasma and platelet contributions to clotting. Thrombodynamics-4D potentially allows for the determination of plasma or platelet disorders and the effects of various drugs on plasma clotting or on platelet procoagulant function. In this assay, clot formation in platelet-rich plasma or platelet-free plasma supplemented with phospholipids is activated with tissue factor immobilized on a surface. Spatial fibrin clot growth and thrombin concentration dynamics are registered by measuring light scattering of the fibrin clot and fluorescence of the product formed by cleavage of the synthetic fluorogenic substrate by thrombin, respectively. Here, we describe the preanalytical requirements, measurement methodology and calculation principles of assay parameters. Preanalytical and analytical variability and reference ranges of the assay are given. Additionally, we show some clinical examples, which determine the effect of anticoagulants, measure clotting dysfunction in patients with platelet or coagulation disorders and evaluate the effect of surgery. [ABSTRACT FROM AUTHOR]

Steroid-associated necrosis of the femoral head (SANFH) is one of the most common and refractory chronic diseases with increasing incidence. The typical pathological changes of SANFH include decreased osteogenic differentiation, enhanced intramedullary adipocytes deposition and impaired osseous circulation. In this study, we investigated the effects and potential mechanisms of Platelet-rich plasma (PRP) on SANFH. Sixty Sprague-Dawley rats were randomly divided into the control, PRP donor, model, and PRP groups. Compared to the model group, PRP treatment significantly increased the hemorheological indexes and serum levels of bone gla-protein (BGP) and vascular endothelial growth factor (VEGF), while decreased the levels of triglyceride (TG) and total cholesterol (TC). Meanwhile, Micro-CT and histopathological stain (Hematoxylin-eosin and Alcian blue-hematoxylin/orange G staining) were performed on the femoral head for morphological and histopathological evaluation, indicating that bone trabecular microstructure and bone mineral density (BMD) were significantly improved after PRP treatment. Immunohistochemical analysis revealed that PRP remarkably up-regulated the expression of osteogenic markers including β-catenin and alkaline phosphatase (ALP), angiogenic markers containing VEGF and platelet endothelial cell adhesion molecule-1 (CD31), while down-regulated adipogenic markers involving fatty acid-binding protein (FABP-4), and peroxisome proliferator-activated receptor gamma (PPAR-γ) in SANFH rat models. In summary, for the first time, PRP was demonstrated to prevent the development of SANFH through stimulating bone formation and vascularization as well as retarding adipogenesis. [ABSTRACT FROM AUTHOR]

To be faced with an infected bone defect and the need to accelerate bone union while controlling infection is a welcome challenge for orthopedists. Platelet-rich plasma (PRP) has been applied in tissue defects given their composition of growth factors however the weak antibacterial effects have limited the use of PRP in the clinical setting. Therefore, the aim of this study was to explore the feasibility of using PRP in a local antibiotic delivery system (PADS) with the characteristics of promoting wound healing of bone infection. PADS was prepared with the addition of antibiotics or no antibiotics as control after PRP was prepared by a two-step centrifugation procedure. Antibacterial tests showed zones of inhibition produced by antibiotics were not significantly different with antibiotics combined with PRP. HPLC analysis demonstrated that about 60% of the total vancomycin (VAN) and ceftazidime (CAZ) dose were released within 10 min, then the release rate gradually decreased. However, 90% clindamycin was released within 10 min. Interestingly, above 10 times the minimum inhibitory concentration was presented after 72 h. Additionally, ELISA and morphology studies of PADS indicated that loaded antibiotics could reduce the PRP-released growth factor concentration and disturb the structure of platelet-fibrin beams and fibrin network in a dose-dependent manner. Fortunately, the lower dose of antibiotics maintained their anti-microbial effect, meanwhile growth factors released from PADS, the structure of platelet-fibrin beams, fibrin network remained unaffected. In addition, a patient experiencing infected bone defect receiving this PADS treatment achieved union within the 15-month follow-up. Therefore, this novel PADS approach might represent a potential therapy for patients who have sustained infected bone defects. [ABSTRACT FROM AUTHOR]

Platelet-rich plasma (PRP) has a potential effect on tissue repair through proliferation and differentiation of tissue progenitor cells. The aim of this study was to evaluate the effect of PRP on the testis structure and function in infertile rat model by stereological method. Thirty-two male rats were divided into four groups. Infertility was induced by the administration of busulfan (BUS) (10mg/kg, I.P., single dose). PRP (80μl, testis local injected, single dose) was administered for the subjects. After 48 days, semen analysis was performed and blood samples were taken from the heart to measure the testosterone. Then, the left testis was removed, fixed, embedded, sectioned, and stained by H&E; after that the testes were analyzed. The results showed that BUS can decrease the sperm count, motility, normal morphology, length of the spermatozoon tail, volume of the testis, seminiferous tubules, germinal epithelium height, and the number of spermatogenesis lineage cells in comparison with the control group (p

The aim of the present study was to evaluate the effect of injectable platelet-rich fibrin (i-PRF) on cultivated chondrocytes and osteochondral regeneration in critical-sized osteochondral defect of the rabbit’s knee in comparison to autologous platelet-rich plasma (PRP). Chondrocytes were first investigated for their ability to proliferate and differentiate in response to PRP and i-PRF. Thereafter, full-thickness critical-sized osteochondral defects 5 mm in diameter and 5 mm in depth were created in the knee joint of 12 adult female New Zealand White rabbits. Defects were regenerated with either PRP or i-PRF and compared to control. Animals were sacrificed at 4 and 12 weeks postoperatively and evaluated histologically by macroscopic and microscopic examination for cartilage regeneration. i-PRF significantly promoted chondrocyte proliferation and mRNA levels of Sox9, collagen type II, and aggrecan when compared to PRP and control. Histological analysis revealed that at 4 weeks, macroscopic ICRS scores from the i-PRF group were significantly enhanced when compared to the PRP and control groups. At 12 weeks post surgery, the microscopic ICRS scores demonstrated that the i-PRF group significantly improved cartilage regeneration when compared to PRP. In conclusion, the use of i-PRF using the low speed centrifugation concept significantly promoted chondrocyte activity and further improved cartilage regeneration when compared to PRP. The histological results revealed early and better cartilage regeneration within 4 weeks postoperatively when i-PRF was utilized and the results were maintained at 12 weeks. Future clinical studies are now needed investigating the regenerative potential of i-PRF in comparison to PRP for knee regeneration.

The application of platelet-rich plasma (PRP) in oral and maxillofacial surgery has been thoroughly studied in the last two decades. Currently, different types of PRP are applied in the clinical practice, being the presence or absence of leukocytes one of the classification criteria. However, there is poor evidence assessing the influence of the PRP composition in their efficacy. In this context, the aim of this narrative review is to compile the existing evidence covering the efficacy of PRP in oral and maxillofacial surgery, starting from a systematic literature search and to qualitatively describe the efficacy outcomes from the composition perspective. According to the results of this review, the application of PRP in oral and maxillofacial surgery is a potential strategy to improve soft- and hard-tissue regeneration, observing differences in the efficacy of PRP depending on its composition and the studied application. P-PRP (the absence of leukocytes) has been more consistent in achieving beneficial effects in alveolar ridge preservation, management of post-extraction complications, bone augmentation and temporomandibular joint disorders. For that, the composition and methodology used to prepare the PRP should be a critical point when evaluating the efficacy of PRP. [ABSTRACT FROM AUTHOR]

Platelets play a crucial role in hemostasis, tissue regeneration and host defense. Based on these settings, platelet-rich plasma (PRP) and its derivatives are therapeutically used to promote wound healing in several scenarios. This review summarizes the biological mechanisms underlying the most traditional as well as innovative applications of PRP in wound healing. These mechanisms involve the combined action of platelet-derived growth factors and cytokines, together with the role of plasma-derived fibrillar, antioxidant and homeostatic factors. In addition, regenerative treatments with PRP consist of personalized and non-standardized methods. Thus, the quality of PRP varies depending on endogenous factors (e.g., age; gender; concomitant medication; disease-associated systemic factors; nutrition) and exogenous factors (anticoagulants and cellular composition). This review also analyses whether these factors affect the biological mechanisms of PRP in wound healing applications. [ABSTRACT FROM AUTHOR]

Platelet-rich plasma (PRP) is an autologous preparation that has been claimed to improve healing and mechanobiological properties of tendons both in vitro and in vivo. In this sub-study from the PATH-2 (PRP in Achilles Tendon Healing-2) trial, we report the cellular and growth factor content and quality of the Leukocyte-rich PRP (L-PRP) (N = 103) prepared using a standardized commercial preparation method across 19 different UK centers. Baseline whole blood cell counts (red cells, leukocyte and platelets) demonstrated that the two groups were well-matched. L-PRP analysis gave a mean platelet count of 852.6 x 109/L (SD 438.96), a mean leukocyte cell count of 15.13 x 109/L (SD 10.28) and a mean red blood cell count of 0.91 x 1012/L (SD 1.49). The activation status of the L-PRP gave either low or high expression levels of the degranulation marker CD62p before and after ex-vivo platelet activation respectively. TGF-β, VEGF, PDGF, IGF and FGFb mean concentrations were 131.92 ng/ml, 0.98 ng/ml, 55.34 ng/ml, 78.2 ng/ml and 111.0 pg/ml respectively with expected correlations with both platelet and leukocyte counts. While PATH-2 results demonstrated that there was no evidence L-PRP is effective for improving clinical outcomes at 24 weeks after Achilles tendon rupture, our findings support that the majority of L-PRP properties were within the method specification and performance. [ABSTRACT FROM AUTHOR]

There is a global interest in optimizing post-surgical tissue repair strategies, leading to better patient outcomes and fewer complications, most ideally with reduced overall cost. In this regard, in recent years, the interest in autologous biological treatments in orthopedic surgery and sports medicine has increased greatly, and the addition of platelet-rich plasma (PRP) to the surgical armamentarium is of particular note. Unfortunately, the number of PRP preparation devices has also grown immensely over the recent decades, raising meaningful concern for the considerable variation in the qualities of currently available PRP preparations. The lack of consensus on the standardization of PRP preparation and of agreement on condition specific PRP formulations is largely responsible for the sometimes contradictory outcomes in the literature. Furthermore, the full potential of PRP technology, the concept of individualized treatment protocols based on bioformulation options, and platelet dosing, angiogenesis, and antimicrobial and painkilling effects of PRP relevant to orthopedic surgery have rarely been addressed. In this review, we will discuss recent developments regarding PRP preparations and potential therapeutic effects. Additionally, we present a synopsis of several published data regarding PRP applications in orthopedic surgery for treating tendon injuries, inducing bone repair, strengthening spinal fusion outcomes, and supporting major joint replacements. [ABSTRACT FROM AUTHOR]

Bone tissue engineering (BTE) is a strategy for reconstructing bone lesions, which is rapidly developing in response to higher demands for bone repairing. Recently, this method, along with the emergence of functionally graded, biocompatible and biodegradable materials, has been expanded. Moreover, scaffolds with chemical, physical and external patterns have induced bone regeneration. However, the maintenance of healthy bone and its regeneration in the human body needs a series of complex and accurate processes. Hence, many studies have been accompanied for reconstructing bone by using blood-derived biomaterials, especially platelet-rich fabricates. The most important reason for using platelet-rich formulations in bone regeneration is based on releasing growth factors from alpha granules in platelets, which can induce osteogenesis. Moreover, the presence of fibrin nano-fiber structures as a constituent can provide a good substrate for cell attachments. This study attempts to review the history, structure, and biology of platelet-rich fibrin (PRF) as well as in vitro, pre-clinical, and clinical studies on the use of PRF for bone regeneration. [ABSTRACT FROM AUTHOR]

Platelet-rich plasma (PRP) has seen increased interest and utilization over the past decade, particularly in the field of musculoskeletal disease. This growth has been accompanied by the development of medical devices to realize PRP preparation which includes blood collection, centrifugation, and PRP isolation. The final PRP composition is directly influenced by this preparation step and absence of biological quality control led to a lack of comparability between PRP products that could explain the large variability in the clinical benefit of PRP reported in literature. To circumvent this issue, the scientific community developed different PRP classifications but none of them have been adopted. The goal of this review is to furnish both technical and biological characteristics from PRP commercial systems. On review of 1379 studies, 105 studies were selected according to inclusion criteria for technical analysis and led to the identification of 50 commercial systems that have been classified in three technical categories based on the blood harvesting technique (tubes, syringes or bags). Twelve studies were selected and sufficiently describe biological characteristics from only 14 commercial systems from the 50 identified in the technical analysis. Inclusion of duplicates characterization from a same PRP system lead to the final analysis of 36 PRP preparations that met the inclusion criteria of the biological analysis. All these PRP preparations have been classified among the seven existing classifications. Comparison from all biological parameters and classifications revealed a large heterogeneity among the available current PRP commercial systems. Index of biological sensitivity of classifications to distinguish PRP preparations were also variable. Although these findings should help clinicians in selecting a system that meets their specific needs, this also raises the question to standardize the parameters to biologically define PRP preparation among users and to systematically performed PRP qualification when used. [ABSTRACT FROM AUTHOR]

The skeletal muscle stretch injuries are commonly observed in sports. In order to stimulate tissue healing, the platelet-rich plasma (PRP) and cold water immersion (CWI) are widely used in clinical practice. This study investigated the effects of isolated or combined PRP and/or CWI on the oxidative damage determined by a stretch injury induced in gastrocnemius muscle of rats. PRP and CWI are applied immediately after the injury, and the biochemical analysis was performed after 1, 3, 5, or 7 days. The levels of o thiobarbituric acid reactive substances and oxidized dichlorofluorescein were significantly increased, both in skeletal muscle tissue and erythrocytes preparations, and the combined PRP and CWI minimized these parameters. Moreover, combined PRP and CWI were more effective than the isolated treatments to increase catalase activity, also the ratio of reduced/oxidized glutathione, and the non-protein thiols (-SH) group levels. In conclusion, we could infer that the combination of these regular treatments used in an isolated form shows a great potential for treatments of muscular injuries. [ABSTRACT FROM AUTHOR]

The aim of the present retrospective observational study was to evaluate the time of functional recovery following a specific combined therapeutic approach characterized by an active exercise therapy carried out immediately after Platelet-rich plasma (PRP) injections for the treatment of the muscular lesion of the distal musculotendinous junction of the gastrocnemius medial head.Medical records of 31 subjects treated with three PRP intra-lesional ultrasound guided injections and 30 patients treated with the standard therapeutic approach (control group) were analyzed. Both groups followed the same rehabilitation therapy. Patients in the control group were able to start active exercise with a significant delay when compared to the PRP treated subjects: 17 ± 7.2 days and 9 ± 3.8 days (p = 0.0001), respectively. This delay was mainly due to the persistence of pain in the subjects in the control group. The time necessary to return to walk without pain was significantly shorter in the PRP treated group: 24.27 ± 12.36 days versus 52.4 ± 20.03 days in the control group (p

Although platelets are widely recognized as having a critical role in primary hemostasis and thrombosis, increasing experimental and clinical evidence identifies these enucleated cells as relevant modulators of other physiopathological processes including inflammation and tissue regeneration. These phenomena are mediated through the release of growth factors, cytokines, and extracellular matrix modulators that sequentially promote (i) revascularization of damaged tissue through the induction of migration, proliferation, differentiation, and stabilization of endothelial cells in new blood vessels; (ii) restoration of damaged connective tissue through migration, proliferation, and activation of fibroblasts; and (iii) proliferation and differentiation of mesenchymal stem cells into tissue-specific cell types. For these reasons, platelet-rich plasma (PRP) derivatives are used in regenerative medicine for the treatment of several clinical conditions including ulcers, burns, muscle repair, bone diseases, and tissue recovery following surgery. The benefits of PRP administration are associated with an economical advantage, taking into consideration that PRP administration does not require complex equipment or training for its execution. Moreover, due to their primary autologous origin, concerns of disease transmission or immunogenic reactions can be disregarded. Thus, platelet-enriched materials have become highly relevant in the last decade and constitute a growing focus of experimental and clinical study in the context of wound healing and tissue regeneration. However, despite the diverse applications, the efficacy of regenerative treatments using PRP is being called into question due to the lack of large controlled clinical trials and the lack of consensus regarding the PRP preparation techniques. This review describes the biological mechanisms underlying PRP’s regenerative effects, the different methods of preparation and application of these biomaterials, and the controversies and future prospects related to the use of PRP in regenerative medicine.

Platelet-Rich Plasma (PRP) is an autologous biological therapy obtained by centrifuging the patient’s own blood to concentrate platelets. The addition of autologous thrombin and calcium chloride to PRP allows the production of a semi-solid form called PRP gel. PRP gel is increasingly used in a variety of tissue defects and predominantly in the management of non-healing chronic wounds. The topical application of PRP gel seems promising due to the capability of platelets to store and secrete growth factors (GF), fibrin and cytokines, which are essentials for wound healing. Most patients who suffered from chronic wounds are elderly patients with co-morbidities and polypharmacy including antithrombotic drugs such as antiplatelet agents (AP) or anticoagulants (AC), which could hamper the feasibility of this autologous platelet-derived therapy. To date, no study has investigated PRP gel formation in patients with AP or AC. The aim of this study was to evaluate the influence of AP or AC drugs on the production of PRP gel formation from elderly patients. Different biological characteristics were determined to qualify the production of PRP gel from such patients (Interquartile range (IQR) = 75–92 years) compared to healthy volunteers (IQR = 23–37 years). No significant difference was observed in the volume, composition (quantity of platelets, leukocytes and red blood cells) and functionality of platelets from PRP except a higher ADP-induced P-selectin expression in healthy donors compared with elderly patients. Autologous thrombin characteristics were similar in the two groups. Gel time formation (IQR: 120–195 seconds for controls and 135–210 seconds for elderly patients) and final composition of PRP gel were not significantly modified. Concentrations of theoretical thrombin generated in the serum and in the gel were inversely correlated with the time of formation of PRP gel (r2 = 0.57, p = 0.012). Altogether these data indicate that PRP gel preparation is not impacted by the use of antithrombotic drugs. Such results support the feasibility of using this innovative autologous biotherapy in the management of elderly patients with non-healing chronic wounds.

In the presence of large bone defects, delayed bone union, or nonunion and fractures, bone reconstruction may be necessary. Different strategies have been employed to enhance bone healing among which the use of autologous platelet concentrates (APCs). Due to the high content of platelets and platelet-derived bioactive molecules (e.g., growth factors, antimicrobial peptides), they are promising candidates to enhance bone healing. However, both preclinical and clinical studies produced contrasting results, mainly due to a high heterogeneity in study design, objectives, techniques adopted, and outcomes assessed. The aim of the present systematic review was to evaluate the efficacy of APCs in animal models of bone regeneration, considering the possible factors that might affect the outcome. An electronic search was performed on MEDLINE and Scopus databases. Comparative animal studies with a minimum follow up of 2 weeks, at least five subjects per group and using APCs for regeneration of bone defects were included. Articles underwent risk of bias assessment and quality evaluation. Fifty studies performed on six animal species (rat, rabbit, dog, sheep, goat, mini-pig) were included. The present part of the review considers studies performed on small ruminants, dogs, and mini-pigs (14 articles). The majority of the studies were considered at low risk of bias. In general, APCs’ adjunct positively affected bone regeneration. Animal species, platelet and growth factors concentration, type of bone defect and of platelet concentrate used seemed to influence their efficacy in bone healing. However, sound conclusions were not drawn since too few studies for each large-size animal model were included. In addition, characterization of APCs’ content was performed only in a few studies. Further studies with a standardized protocol including characterization of the final products will provide useful information for translating the results to clinical application of APCs in bone surgery.

Platelet-rich plasma (PRP) is blood plasma with a high concentration of autologous platelets which constitute an immense reservoir of growth factors. The clinical use of PRP is widespread in various medical applications. Although highly popular with athletes, the use of PRP for the treatment of tendinopathies remains scientifically controversial, particularly due to the diversity of products that go by the name of “PRP.” To optimize its use, it is important to look at the various stages of obtaining PRP. In this literature review, we take a closer look at eight parameters which may influence the quality of PRP: 1) anticoagulants used to preserve the best platelet function, 2) the speed of centrifugation used to extract the platelets, 3) the platelet concentrations obtained, 4) the impact of the concentration of red and while blood cells on PRP actions, 5) platelet activators encouraging platelet degranulation and, hence, the release of growth factors, and 6) the use or nonuse of local anesthetics when carrying out infiltration. In addition to these parameters, it may be interesting to analyze other variables such as 7) the use of ultrasound guidance during the injection with a view to determining the influence they have on potential recovery.

L-PRF (leukocyte- and platelet-rich fibrin) is one of the four families of platelet concentrates for surgical use and is widely used in oral and maxillofacial regenerative therapies. The first objective of this article was to evaluate the mechanical vibrations appearing during centrifugation in four models of commercially available table-top centrifuges used to produce L-PRF and the impact of the centrifuge characteristics on the cell and fibrin architecture of a L-PRF clot and membrane. The second objective of this article was to evaluate how changing some parameters of the L-PRF protocol may influence its biological signature, independently from the characteristics of the centrifuge. In the first part, four different commercially available centrifuges were used to produce L-PRF, following the original L-PRF production method (glass-coated plastic tubes, 400 g force, 12 minutes). The tested systems were the original L-PRF centrifuge (Intra-Spin, Intra-Lock, the only CE and FDA cleared system for the preparation of L-PRF) and three other laboratory centrifuges (not CE/FDA cleared for L-PRF): A-PRF 12 (Advanced PRF, Process), LW-UPD8 (LW Scientific) and Salvin 1310 (Salvin Dental). Each centrifuge was opened for inspection, two accelerometers were installed (one radial, one vertical), and data were collected with a spectrum analyzer in two configurations (full-load or half load). All clots and membranes were collected into a sterile surgical box (Xpression kit, Intra-Lock). The exact macroscopic (weights, sizes) and microscopic (photonic and scanning electron microscopy SEM) characteristics of the L-PRF produced with these four different machines were evaluated. In the second part, venous blood was taken in two groups, respectively, Intra-Spin 9 ml glass-coated plastic tubes (Intra-Lock) and A-PRF 10 ml glass tubes (Process). Tubes were immediately centrifuged at 2700 rpm (around 400 g) during 12 minutes to produce L-PRF or at 1500 rpm during 14 minutes to produce A-PRF. All centrifugations were done using the original L-PRF centrifuge (Intra-Spin), as recommended by the two manufacturers. Half of the membranes were placed individually in culture media and transferred in a new tube at seven experimental times (up to 7 days). The releases of transforming growth factor β-1 (TGFβ-1), platelet derived growth factor AB (PDGF-AB), vascular endothelial growth factor (VEGF) and bone morphogenetic protein 2 (BMP-2) were quantified using ELISA kits at these seven experimental times. The remaining membranes were used to evaluate the initial quantity of growth factors of the L-PRF and A-PRF membranes, through forcible extraction. Very significant differences in the level of vibrations at each rotational speed were observed between the four tested centrifuges. The original L-PRF centrifuge (Intra-Spin) was by far the most stable machine in all configurations and always remained under the threshold of resonance, unlike the three other tested machines. At the classical speed of production of L-PRF, the level of undesirable vibrations on the original centrifuge was between 4.5 and 6 times lower than with other centrifuges. Intra-Spin showed the lowest temperature of the tubes. A-PRF and Salvin were both associated with a significant increase in temperature in the tube. Intra-Spin produced the heaviest clot and quantity of exudate among the four techniques. A-PRF and LW produced much lighter, shorter and narrower clots and membranes than the two other centrifuges. Light microscopy analysis showed relatively similar features for all L-PRF types (concentration of cell bodies in the first half). However, SEM illustrated considerable differences between samples. The original Intra-Spin L-PRF showed a strongly polymerized thick fibrin matrix and all cells appeared alive with a normal shape, including the textured surface aspect of activated lymphocytes. The A-PRF, Salvin and LW PRF-like membranes presented a lightly polymerized slim fibrin gel and most of the visible cell bodies appeared destroyed (squashed or shrunk). In the second part of this study, the slow release of the three tested growth factors from original L-PRF membranes was significantly stronger (more than twice stronger, p

Activated platelet concentrates are autologous blood preparations containing supraphysiological concentration of platelets. Platelet concentrates are commonly used for bone regeneration purposes based on the fact that growth factors released from activated platelets alpha granules have osteoinductive effects on bone cells. Although most preclinical and clinical studies show that platelet concentrates improve the outcomes of bone regeneration procedures, some studies reported conflicting results and even negative effects on bone healing. Several confounding parameters have been suggested as possible reasons for such inconsistencies (i.e. preparation and activation methods). However, heterogeneity in clinical studies makes drawing evidence-based conclusions difficult. On the other hand, recent findings show that the constituents of platelets dense granules (i.e. serotonin, ATP, Ca2+) have potential inhibitory effects on bone metabolism. Accordingly, we suggest that a partial explanation for the conflicting results could be the potential negative effects that dense granules may have on bone healing.

Mitochondria regulate intracellular metabolism and are also involved in intercellular transfer in vitro and in vivo, thereby affecting the function of adjacent cells. Mitochondria can also be transferred to various differentiated cells to improve their respiratory function, ATP production, as well as protect damaged cells from apoptosis. Both in vivo and in vitro, mitochondria can be transferred from one cell to another to regulate cellular metabolism under physiological or pathophysiological conditions, referred to as "mitochondrial translocation". Mitochondrial translocation is associated in various situations such as repairing damaged cells, promoting cancer progression and enhancing chemoresistance. Platelets contain mitochondria that promote energy metabolism and various growth factors, thus playing an important role in pathophysiological processes such as thrombosis, hemostasis, inflammation and wound healing. Current studies suggest that mesenchymal stem cells (MSCs) can communicate with their microenvironment through bidirectional alternation of mitochondria to improve their wound healing capacity. Platelets or platelet-containing preparations such as platelet-rich plasma (PRP) can stimulate the proliferation and pro-angiogenic properties of MSCs under oxidative stress to enhance their survival. Recent studies by Levoux et al. have shown that activated platelet-derived mitochondria have the respiratory capacity to translocate to MSCs and stimulate the pro-angiogenic properties of MSCs through metabolic reprogramming, thereby promoting angiogenesis and wound healing. The mechanism of mitochondrial internalization of cells and energy metabolism is a new example of mitochondrial translocation altering somatic cell behavior and viability. Therefore, we aim to comment the mechanisms of platelet mitochondrial translocation and metabolic reprogramming of MSCs, suggesting that platelets or platelet-containing preparations such as platelet-rich plasma (PRP) may provide a practical guide for tissue injury treatment. [ABSTRACT FROM AUTHOR]

Previous in vitro studies suggest a direct relevance for the peptide–free lipid fraction (LF) of platelet-rich plasma (PRP) in biological mechanisms related to wound healing. However, there are no scientific reports to date on the wound healing activities of this lipid component in vivo. Thus, the present study provides a scientific evaluation for the wound healing potential of the lipid portion of the activated PRP. For the wound healing activity assessment, in vivo full‐thickness excisional wounds were created on the dorsal skin of Sprague-Dawley rats. Lipid extract from pooled PRP was applied topically to the wounds on 0, 3, and 7 days after injury. Histological assessment of epidermal and dermal regeneration, granulation tissue thickness and angiogenesis by Sirius red and Masson's trichrome staining, in addition to immunohistochemical staining for transforming growth factor beta-1 (TGF-β1), collagen type I (COL I), and collagen type III (COL III) were performed on skin biopsies at 3, 7 and 14 days. The total histological scores of the LF group were significantly higher than the 25% dimethylsulfoxide-control group. According to the immunohistochemical staining, the observed expression changes for TGF-β1, COL I and III at 3, 7, and 14 days after wounding were significantly better in the study group than the control group. Furthermore, COL I/III ratio in the lipid extract-treated group at day 14 was much higher than that of the control group. Meanwhile, analysis of the data also indicated that the LF has less positive effects on all evaluated parameters than PRP. From the present data, it could be concluded that the peptide–free LF of PRP has potent wound healing capacity in vivo for cutaneous wounds, although not as much as that of PRP. Strengthening our understanding of the wound healing potential of lipid components of PRP and platelet-derived lipid factors may provide new avenues for improving the healing process of a wound with elevated protease activity. [ABSTRACT FROM AUTHOR]

Dabigatran, a direct oral thrombin inhibitor, has two therapeutic effects: anticoagulation; and antiplatelet activity. In the clinical field, evaluation of the effect of dabigatran on thrombin-induced platelet aggregation is difficult because of fibrin clot formation and platelet aggregation. The aim of this study was to establish a new platelet aggregation method and to investigate the effects of dabigatran on thrombin-induced platelet aggregation. Platelet aggregation with thrombin was performed with automated light transmission aggregometry (CS2400; Sysmex, Kobe, Japan) in 40 healthy subjects. Thrombin-induced platelet aggregation was performed using thrombin and platelet-rich plasma (PRP), and thrombin-induced fibrin polymerization was inhibited by adding the peptide Gly-Pro-Arg-Pro (GPRP). The effect of dabigatran was then evaluated using the above method. Thrombin at < 0.2 U/mL did not induce platelet aggregation in most normal subjects. Median maximum aggregation percent (MA%) (25th–75th percentile) with 0.5 and 1.0 U/mL of thrombin was 87.0% (79.3–90.8%), and 90.2% (86.5–92.2%), respectively. The anti-platelet effects of dabigatran were then evaluated with these concentrations of thrombin. Dabigatran (final concentration, 2.5–1000 nM) inhibited platelet aggregation by 0.2–1.0 U/mL of thrombin in a concentration-dependent manner in vitro. Dabigatran showed potent inhibitory effects against platelet aggregation induced by 0.5 and 1.0 U/mL thrombin with half maximal inhibitory concentrations of 10.5 and 40.4 nM, respectively. A standard for thrombin-induced platelet aggregation was developed using the CS2400 in healthy subjects, and dabigatran was confirmed to inhibit thrombin-induced platelet aggregation in vitro with PRP. [ABSTRACT FROM AUTHOR]

Platelet-rich plasma (PRP) is increasingly used in the treatment of musculoskeletal diseases. Its preservation by freezing it for the realization of multiple injections in clinical use has never been discussed. Calcaneal tendons of rats were surgically sectioned. Platelet concentration of the PRP was 2.5 x 106/µl with autologous plasma of rats. Frozen-thawed PRP was prepared by performing two cycles of freezing and thawing on PRP aliquots. Both platelet preparations were injected in the lesion. Biomechanical and histological evaluations were carried out after 7, 20 or 40 days post surgery. After 7 and 40 days, no significant difference was observed between the PRP and the frozen-thawed PRP group. There is however a difference 20 days after surgery: the ultimate tensile strength (UTS) was greater in the fresh PRP group. No obvious difference with histological aspect was observed between the two groups. In conclusion, fresh PRP and frozen-thawed PRP injections can lead to similar results in the healing process of section calcaneal tendons of rats. Improvements with fresh PRP are slight. PRP could thus be frozen to be preserved if multiple injections are needed (e.g. osteoarthritis). [ABSTRACT FROM AUTHOR]