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Hypertrophic burn scars (HTBSs) remain a significant source of morbidity. Contemporary treatment has evolved to use CO2 lasers and/or pulse-dye lasers (PDLs) to reduce scar thickness (ST) and erythema. This study seeks to compare treatment efficacy with CO2 or PDL individually and in combination.Patients undergoing laser treatments for HTBSs were enrolled. Three 3 × 3 cm squares of HTBSs were randomized to receive treatment with CO2 laser, PDL or CO2 + PDL. Patients underwent 3 treatments, 4 to 6 weeks apart and were followed up over 3 to 6 months. Scar assessments occurred at each visit before treatment and consisted of photographs, ultrasound, colorimetry, and the Patient and Observer Scar Assessment Score.Twenty-five patients were enrolled. Twenty completed 2 treatments (80%) and 11 completed all 3 treatments (44%). Median initial ST was 0.3 cm. Median time since injury was 8 months. Hypertrophic burn scars treated with CO2 or PDL showed a significant decrease in Patient and Observer Scar Assessment Scale score from visit 1 to 3 (P = 0.01 and 0.01, respectively). When separated by ST, thick scars (≥0.3 cm) showed a significant decrease in thickness between visit 1 and 2 using all laser modalities (CO2 + PDL, P = 0.01; CO2, P = 0.02; PDL, P = 0.03). Thin scars (0.3 cm) showed a reduction in thickness by visit 3 after CO2 + PDL or PDL alone (P = 0.01 and 0.04, respectively). Separating scars by age, younger scars (9 months) showed a significant reduction in thickness between visit 1 and 2 for CO2 treatment (P = 0.04), and between visit 2 and 3 for CO2 + PDL treatment (P = 0.04). Hypertrophic burn scars treated with PDL did not demonstrate a significant reduction in thickness until visit 3 (P = 0.002). Older scars (≥9 months) showed a significant reduction in thickness between visit 1 and 2 only after CO2 + PDL (P = 0.01).Hypertrophic burn scars of varying ages, etiologies, and thicknesses were examined in this study with greater degree of early reduction seen in thicker scars using all laser modalities of CO2, PDL or in combination. However, there was no clinically meaningful benefit found with combination as compared with individual treatment. These data support the use of laser to improve HTBS but does not support one modality or combination of modalities over another.

The platform wound device (PWD) is a wound coverage system that is designed to decrease wound infection rates by allowing for direct delivery of topical antibiotics and antimicrobials while creating a sealed, protective barrier around the area of injury. This study evaluated the safety and efficacy of the PWD as a protective dressing and a delivery system for topical antibiotics compared to the current standard of care (SoC). This was a multi-center, prospective, randomised, controlled clinical trial. The wounds were treated with the PWD with gentamicin cream or SoC dressings. The wounds were evaluated before the start of treatment and after 48-96 hours via clinical assessment, photographs, and qualitative bacterial swabs for bacterial analysis. The delivery of gentamicin via the PWD was safe and did not cause any adverse effects. The treatment decreased both inflammation and bacterial growth during the study period. No significant differences in the SoC were observed. The PWD is a transparent and impermeable polyurethane chamber that encloses and protects the injured area. The delivery of topical gentamicin via the PWD was safe and effective. Clinical assessment for infection found the PWD to be non-inferior to the current SoC treatment options.

The ability of skeletal muscle to regenerate declines significantly with aging. The expression of aryl hydrocarbon receptor nuclear translocator (ARNT), a critical component of the hypoxia signaling pathway, was less abundant in skeletal muscle of old (23‐25 months old) mice. This loss of ARNT was associated with decreased levels of Notch1 intracellular domain (N1ICD) and impaired regenerative response to injury in comparison to young (2‐3 months old) mice. Knockdown of ARNT in a primary muscle cell line impaired differentiation in vitro. Skeletal muscle‐specific ARNT deletion in young mice resulted in decreased levels of whole muscle N1ICD and limited muscle regeneration. Administration of a systemic hypoxia pathway activator (ML228), which simulates the actions of ARNT, rescued skeletal muscle regeneration in both old and ARNT‐deleted mice. These results suggest that the loss of ARNT in skeletal muscle is partially responsible for diminished myogenic potential in aging and activation of hypoxia signaling holds promise for rescuing regenerative activity in old muscle.

Autologous split-thickness skin grafts (STSGs) are the standard of care for closure of deep and large burns. However, perforation and extensive fishnet-like expansion of the grafts to achieve greater area wound coverage can lead to treatment failures or esthetically poor healing outcomes and scarring. The purpose of this study was to validate an autologous advanced therapy medicinal product (ATMP)-compliant skin cell suspension and evaluate its efficacy to promote epithelialization.Cells isolated from a piece of STSG according to ATMP classification requirements were sprayed onto 20 patients during a single operation in a validation study. Comparative evaluation of treatment efficacy was carried out using side-by-side skin graft donor site wounds that were standardized in depth. Firstly, we characterized wound healing transcriptomes at 14 and 21 days from serial wound biopsies in seven patients. Then, side-by-side wounds in four patients were treated with or without the skin cells. The wounds were photographed, clinical outcomes assessed, and the treatment and control wound transcriptomes at 14 days were compared to the untreated wounds' healing transcriptomes.The average cell yield after isolation from the STSG was 2.4 × 10We showed that rapid and scalable ATMP-classified processing of skin cells is feasible, and application of the skin cells effectively promotes healing and epithelization of donor site wounds.

Introduction Burns are common injuries in the battlefield. Given austere environments, prolonged field care (PFC) is often necessary. Delays in surgical debridement create a risk of infection and deranged healing for burn patients. As such, this study attempts to identify the best commercially available off-the-shelf (OTS) dressings with field-deployable potential. Methods Deep-partial thickness burns (1" diameter) were created on the dorsum of 3 anesthetized pigs utilizing a thermocoupled burn device at 100°C for 15s. Non-surgical debridement was done 1-h post-burn creation and either an OTS dressing or standard-of-care (SOC) treatment (Silver Sulfadiazine) was applied to the wound in order to simulate a PFC environment. OTS dressings were randomized and included irradiated sterile human skin allograft (ISHSA), alloplastic absorbable skin substitute (AASS), and synthetic polyurethane dermal matrix (SPDM). Wounds were serially assessed on post-burn days 3, 7, 14, 21, and 28. Assessments were conducted using a combination of photographs, histology, and quantitative bacteriology. Endpoints included burn wound progression, re-epithelialization, wound contraction, scar elevation index (SEI), and colony forming units (CFU). Results No statistically significant differences in burn wound progression were seen on days 3 and 7 for the ISHSA or SPDM and the SOC. The differences between the AASS and the SOC were statistically significant on both days (p≤0.05). Day 21 re-epithelialization results for the ISHSA, AASS, SPDM and SOC treated wounds were 30%, 85%, 95%, and 78% re-epithelialized, respectively. The difference between the AASS and the SOC was statistically significant (p≤0.05). Results showed that by day 28, wound contraction for the ISHSA, AASS, SPDM and SOC treated wounds were 65%, 80%, 82%, and 78%, respectively. No statistically significant differences in wound contraction were seen for any of the OTS dressings and the SOC. SEI showed no statistically significant difference in scar hypertrophy between the OTS dressings and the SOC on day 28. CFU results showed no statistically significant differences between the OTS dressings and the SOC on days 3 and 7. Conclusions Three OTS dressings were compared to the SOC for use in the PFC setting. Generally, all the dressings performed well when compared to the SOC in terms of burn wound progression, re-epithelialization, wound contraction, SEI, and CFU. Although significant differences in burn progression and re-epithelialization for burns treated with AASS were seen. In the future, we hope to continue to discover and test various OTS dressings to determine their appropriateness for use in the PFC setting.

Introduction Infection and prolonged inflammation in deep partial-thickness burns can lead to inadequate healing. In addition to their role in hemostasis, activated platelets also contain granules with anti-inflammatory properties which may impact wound healing. However, portability and storage of platelets remain a challenge. Synthetic platelet-mimetics (SPM) avoid these difficulties, but like natural platelets, SPM have vesicles that can transport bioactive agents, such as antibiotics. We sought to evaluate wound healing outcomes in deep partial-thickness burns treated topically with SPM. Methods A total of 30 circular, deep partial-thickness burns were created on the dorsum of 2 porcine models. Each wound measured 5cm in diameter and was standardized using a thermocoupled burn device. Sets of six wounds were randomized into five groups: SPM, gentamicin alone, SPM with gentamicin, a vehicle control (saline), or dry gauze (the standard of care, SOC). Additionally, two separate 5cm diameter circular areas were demarcated to serve as normal skin controls. Wounds were assessed at post-burn days 3, 7, 14, 21, 28, 60 and 90 with a variety of non-invasive imaging and punch biopsies. Treatments were re-applied at each assessment. The primary outcome was the amount of wound re-epithelialization, measured histologically, at post-burn day 28. Secondary outcomes consisted of the percentage of wound contraction, amount of superficial blood flow, and mean bacterial load. Results The amount of wound re-epithelialization in wounds treated with SPM was 96% whereas those treated with the SOC measured only slightly less at 92% (p = 0.56). The percentage of wound contraction was 39% in the SPM with gentamicin group, while in the SOC group contraction was higher at 45% (p = 0.20). Moreover, superficial blood flow in the SPM group was measured to be 168% of normal skin controls, while wounds in the SPM with gentamicin group were slightly lower at 160%, and in wounds treated with the SOC blood flow was 110% of normal skin controls (p = 0.27). The mean bacterial load in each group was measured at post-burn day 3 and notably consisted of bacterial load being the lowest in wounds treated with gentamicin alone at 17/100, meanwhile in wounds treated with the SOC or those in the SPM with gentamicin group, mean bacterial loads were significantly higher at 43/100 and 47/100, respectively (p = 0.02). Conclusions SPM applied to deep partial-thickness burns did not significantly improve measured outcomes over the SOC. Although numerical improvements were shown in all measured outcomes, no significant differences were noted. The theoretical and observed potential for SPM to improve wound healing deserves additional evaluation in larger preclinical studies.

Introduction Combat-related burn wounds can be caused by exposure to a wide variety of agents including heat, electricity, radiation, chemicals, and friction. Early intervention can decrease injury severity by preventing excess inflammation and improve long term healing outcomes. In recent years, numerous studies have demonstrated that cannabinoids can trigger anti-inflammatory responses and promote wound closure. This study investigates whether a proprietary, non-euphoric, topical cannabinoid formulation (NEPE-14) facilitates burn wound healing when compared with Silverlon®, the military standard of care for burns incurred while in the field. Methods Forty-eight deep-partial thickness burns were created on the dorsum of four anesthetized swine (Sus scrofa domestica) using a thermocoupled burn device at 100°C. One hour following burn, biopsies from each site were collected and either NEPE-14, NEPE-14 Vehicle Control, Silverlon®, or dry gauze was placed on the wound. Wounds were assessed on post-burn days (PBD) 3, 7 and 14. Assessments consisted of digital photographs, Laser-Speckle imagery (blood perfusion), FLIR imagery, MolecuLight® imagery and biopsies for histology and immunohistochemistry. Results By PBD 14, no significant differences in re-epithelialization or contraction were observed between any of the tested treatment groups. Silverlon® had the highest percent re-epithelialization with 42%, and the Vehicle control has the lowest percent re-epithelialization with 28 %. Both NEPE-14 and dry gauze performed intermediately with 29% and 34% re-epithelialization, respectively. On PBD 14, the wounds of the NEPE-14 treated wounds contracted 8%, the vehicle control 7%, Silverlon® treated wounds 10%, and gauze treated wounds showed 9% contraction compared with the original wound area. Blood perfusion at PBD 14 indicated that NEPE-14 treated wounds had the lowest amount of observed blood flow and the gauze treated wounds contained the highest amount of observed blood flow. However, no statistically significant differences were observed. Conclusions No statistically significant results were seen between treatment groups for contraction, re-epithelialization, or blood perfusion. Although not significant, blood perfusion results indicate that NEPE-14 treatment had the lowest amount of blood flow, which can be seen as an indicator of healthy underlying tissue and a wound re-epithelializing. At PBD 14, all treatment groups had slightly contracted after increasing in wound area on PBD 3 and 7, which is a pattern seen in similar burn injury studies. We are currently awaiting histological analysis to strengthen our re-epithelialization results and evaluate burn wound progression.

Volumetric muscle loss (VML) is a segmental loss of skeletal muscle which commonly heals with fibrosis, minimal muscle regeneration, and loss of muscle strength. Treatment options for these wounds which promote functional recovery are currently lacking. This study was designed to investigate whether the collagen-GAG scaffold (CGS) promotes functional muscle recovery following VML. A total of 66 C57/Bl6 mice were used in a three-stage experiment. First, 24 animals were split into three groups which underwent sham injury or unilateral quadriceps VML injury with or without CGS implantation. Two weeks post-surgery, muscle was harvested for histological and gene expression analysis. In the second stage, 18 mice underwent bilateral quadriceps VML injury, followed by weekly functional testing using a treadmill. In the third stage, 24 mice underwent sham or bilateral quadriceps VML injury with or without CGS implantation, with tissue harvested six weeks post-surgery for histological and gene expression analysis. VML mice treated with CGS demonstrated increased remnant fiber hypertrophy versus both the VML with no CGS and uninjured groups. Both VML groups showed greater muscle fiber hypertrophy than non-injured muscle. This phenomenon was still evident in the longer-term experiment. The gene array indicated that the CGS promoted upregulation of factors involved in promoting wound healing and regeneration. In terms of functional improvement, the VML mice treated with CGS ran at higher maximum speeds than VML without CGS. A CGS was shown to enhance muscle hypertrophy in response to VML injury with a resultant improvement in functional performance. A gene array highlighted increased gene expression of multiple growth factors following CGS implantation. This suggests that implantation of a CGS could be a promising treatment for VML wounds.

A major impediment preventing normal wound healing is insufficient vascularization, which causes hypoxia, poor metabolic support, and dysregulated physiological responses to injury. To combat this, the delivery of angiogenic factors, such as vascular endothelial growth factor (VEGF), has been shown to provide modest improvement in wound healing. Here, the importance of specialty delivery systems is explored in controlling wound bed drug distribution and consequently improving healing rate and quality. Two intradermal drug delivery systems, miniaturized needle arrays (MNAs) and liquid jet injectors (LJIs), are evaluated to compare effective VEGF delivery into the wound bed. The administered drug's penetration depth and distribution in tissue are significantly different between the two technologies. These systems' capability for efficient drug delivery is first confirmed in vitro and then assessed in vivo. While topical administration of VEGF shows limited effectiveness, intradermal delivery of VEGF in a diabetic murine model accelerates wound healing. To evaluate the translational feasibility of the strategy, the benefits of VEGF delivery using MNAs are assessed in a porcine model. The results demonstrate enhanced angiogenesis, reduced wound contraction, and increased regeneration. These findings show the importance of both therapeutics and delivery strategy in wound healing.

Background All common negative-pressure wound therapy systems include a material, usually foam or gauze, at the wound/device interface. In this preclinical study, the authors have compared the effects on different wound healing parameters in the three most common negative-pressure wound therapy systems (i.e., V.A.C.VIA, PREVENA, and PICO) with a new device without foam or gauze (i.e., Platform Wound Dressing). A strong effort was made to avoid bias. The study was conducted under good laboratory practice conditions, with the presence of an independent observer. Methods In pigs, three types of wounds were studied: full-thickness excisions, open incisions, and sutured closed incisions. Several macroscopic and microscopic parameters were studied. The pigs were euthanized on day 9 and all wounds were processed for histology and excisions for immunohistochemistry. Results In general, the devices produced similar results, with only a few significant differences. In the excisions, the Platform Wound Dressing reduced wound area more than the V.A.C.VIA and the PICO. In the excisional wounds, reepithelialization was the same. In open incisions, PREVENA was better than the Platform Wound Dressing. Histologic examination showed that, in open incisions, there was less inflammation in the PREVENA-treated in comparison with the Platform Wound Dressing- and the PICO-treated wounds. Immunohistochemical analyses showed that the Platform Wound Dressing-treated excisions had significantly more blood vessels (von Willebrand factor) than the V.A.C.VIA-treated ones and that the PICO caused less T-cell activation (CD3) than the other two. Conclusion The devices-with foam, with gauze, or without either and just an embossed membrane-performed equally in general.

Significance: A moist wound environment has several benefits that result in faster and better quality of healing. It facilitates autolytic debridement, reduces pain, reduces scarring, activates collagen synthesis, facilitates and promotes keratinocyte migration over the wound surface, and supports the presence and function of nutrients, growth factors, and other soluble mediators in the wound microenvironment. Recent Advances: Wound dressings can be utilized to create, maintain, and control a moist environment for healing. Moist wound dressings can be divided into films, foams, hydrocolloids, hydrogels, and alginates. We are also including negative pressure wound therapy systems in the moist dressings. Critical Issues: An optimal wound dressing should provide a moist environment and have an optimal water vapor transmission rate (WVTR) and absorptive capacity. It should also protect the wound against trauma and contamination and be easy to apply, painless to remove, and esthetically acceptable or even pleasing. Future Directions: Interventions, particularly dressing changes, by medical caregivers are labor intensive and expensive and there should be a continuous effort to reduce their number per week. Smart dressings with integrated microsensors and delivery capabilities that would allow wireless real-time monitoring and treatment of the wound would be very advantageous. This way the state of the wound as well as the wear time of the dressing could be assessed without dressing removal or visit to the wound care center. In addition, an ability to adjust the WVTRs to the exudate level of the wound (or having a large absorptive capacity without changing the WVTR) would be useful. This feature would guarantee an optimal level of hydration of the wound surface throughout the treatment.

Significance: Hair follicles are complex miniorgans that reside in the dermal layer of the skin. When the skin is wounded, epidermal stem cells in the hair follicle activate and start migrating into the wound site, differentiating into epidermal cells. and contributing to the reepithelialization of the wound. The hair follicles represent the deepest epidermal elements in the skin, which are extremely beneficial in partial-thickness burns and abrasions where the skin can regenerate from the hair follicles. Recent Advances: Advanced animal models have demonstrated that the contribution of epidermal stem cells in the hair follicle bulge and isthmus regions is important for wound healing. In addition, several clinical studies have shown successful harvesting and transplantation of hair follicles as a treatment modality to accelerate wound healing. Critical Issues: Deep and large wounds require hospitalization and, without exception, surgical treatment. Harvesting and direct transplantation of hair follicles could provide a great source of autologous epidermal stem cells for wound healing. The procedure can be done in an outpatient setting, quickly and without creating a large donor site wound. Future Directions: Transplantation of hair follicles in a combination with novel biomaterials could provide advantageous treatment possibilities for both chronic wounds and burns. There is a substantial amount of molecular signaling data available on the role of hair follicles during wound repair, but almost all the data are derived from rodent models, and thus, more information from large animals and most importantly from humans would be beneficial and help to advance this promising treatment further.

Introduction Deep and large burns require hospitalization and, without exception, surgical treatment. Skin graft expansion in major burns currently is restricted to a 1:6 expansion ratio (possibly 1:9) by current methods. For this reason, skin transplants are limited by donor site availability for patients with extensive burns, who may have only small areas of healthy skin for use as donor sites. The objective of this project is to demonstrate the efficacy of pixel grafting, to produce split-thickness skin grafts (STSG) and dermal grafts which can be expanded at least 100 times (1 cm2 donor skin will cover 100 cm2). Pixel grafts are skin grafts that are prepared from split-thickness donor skin that is 0.3 mm (12/1000 of an inch) thick and minced into pieces that are 0.3 x 0.3 mm. The methodology relies on mincing a small area of donor skin using a hand-held mincer to create uniform skin pieces, each of which will serve as a small center of skin regeneration. Methods Deep partial-thickness burns were created on the dorsum of Yorkshire pigs. Three days post injury the burns were debrided and grafted with epidermal/dermal and dermal pixel grafts using expansion ratios from 1:2 to 1:500. The pixel grafts were prepared by harvesting 0.3 mm thick skin grafts from the same donor site going down in depth (Layer 1: STSG; Layer 2: dermal graft). Subsequently, the grafts were minced to 0.3 x 0.3 x 0.3 mm pixel grafts, suspended in a small volume of hydrogel and transplanted onto debrided porcine burn wounds. Healing was monitored up to 28 days and biopsies were collected on days 6, 10 and 14. The wounds were excised and fixed in formalin for histologic analysis. In addition, to measure wound area reduction and wound depth, wound images were taken. Multiple wound healing parameters were used to assess the quality of healing and the results were compared to STSG (standard of care treatment). Results Histology demonstrated that when both STSG pixel grafts and dermal grafts were transplanted onto porcine full-thickness wounds in a 1:2 ratio they were able to fully re-epithelialize the wounds in 14 days. At day 14, re-epithelialization-% using other expansion ratios varied from 46 % (1:500) to 64 % (1:10) and by day 28 all the wounds were fully re-epithelialized. Wound images obtained at different time points showed that by day 28 all the pixel graft grafted wounds had reduced in area efficiently, from 70 % (dermal pixel grafts 1:50) to 81% (STSG 1:100). No statistically significant differences were observed between the pixel graft study groups and STSG (standard of care). Conclusions This study concluded that both epidermal/dermal and dermal pixel grafts can be suspended in a hydrogel and transplanted onto wounds regardless of orientation (dermal side up or down), making the transplantation greatly simplified.

Introduction Burn injuries are common to all military conflicts. In combat, eradication and prevention of burn wound infection is complicated by high rates of soft tissue contamination and prolonged delays to definitive stateside care. Furthermore, in the battlefield setting the salvage rate for infected burned extremities is low. Therefore, a simple, easy, non-invasive and rapid method to protect the wound, while also inhibiting infection, would represent a significant advance in the treatment of combat burn wounds. The purpose of this clinical trial was to investigate the efficacy of an FDA approved disposable and easily portable, wireless electroceutical dressing (WED) in the treatment of burn wounds. The hypothesis was that a low electric field generated by the moisture-activated WED will reduce infection load, improve graft survival and take, enhance wound healing and restore skin barrier function of biofilm infected wounds. Methods A phase I, prospective, randomized, controlled clinical trial was performed to evaluate the efficacy of the WED dressing as compared to the standard of care (SoC) dressing to prevent and disrupt biofilms. Subjects were screened from inpatient admissions for traumatic burns >300cm2 in size. In total 38 subjects were enrolled to the study. Subject burn wounds were divided into two parts and randomized to receive either the SoC dressing or the WED dressing. Dressings were changed on day 4, removed on day 7 and the burns were followed for 30 days. Small biopsies were collected on days 4 and 7 for histology, SEM examination of biofilm and for quantitative bacteriological analysis. In addition, non-invasive wound imaging techniques were utilized to study wound healing. Furthermore, Vancouver scar scale and patient observer scar assessment were used to evaluate quality of healing. Results The results showed that at the time of dressing removal, non-grafted burns that were treated with the WED dressing presented statistically significantly less biofilm in comparison to the SoC treated burns (p < 0.05). The results also demonstrated that the WED dressing was more efficient at eradicating biofilm than the SoC dressing. At the time of the dressing removal, biofilm score [0-3] had decreased in 48% of the WED dressing treated burns in comparison to 28% in the SoC treated burns. In terms of wound healing and quality of healing no significant differences were observed between the WED and the SoC dressings. Conclusions This trial demonstrated that the WED dressing was more efficient against biofilm infection than the SoC dressing. In addition, the study concluded that the WED dressing performed equally well as the SoC in terms of burn wound healing.

Negative pressure wound therapy (NPWT) promotes healing in acute or chronic wounds. Conventional NPWT devices consist of a filler (such as foam or gauze) that covers the wound and of a permeable membrane and tubing that connects the space under the membrane to a suction pump. The permeable membrane increases airflow and thus increases the required pump capacity that can cause patient discomfort or even ischemia in wounds with compromised vascularity. In addition, foam or gauze may fragment and become colonized with bacteria over time. To mitigate these, negative aspects, we have developed a new impermeable single layer component membrane dressing to deliver NPWT that does not need a foam or gauze to function. Therefore, the purpose of this study was to introduce this novel NPWT system (platform wound device, PWD) and evaluate its usability and effectiveness in the treatment of porcine full-thickness burns. A total of 48 burn wounds were created across four Yorkshire pigs on the dorsum. Wounds were created on day 0 and continuous NPWT with -50 mmHg and - 80 mmHg was initiated immediately. Subsequently, the burns were debrided on day 3 and animals were euthanized on day 7. The efficacy of the PWD on wound healing and reduction of bacterial burden was measured and compared to wounds that did not receive NPWT. The results showed that PWD promoted wound healing by outperforming the wounds that did not receive NPWT and that PWD was efficient at reducing bacteria from the burn eschar and from the wound bed. In conclusion, this study demonstrated that PWD promoted wound healing with a negative pressure as low as -50 mmHg, which likely benefits healing and avoids potential safety issues.

Cutaneous injury causes underlying tissue damage that must be quickly repaired to minimize exposure to pathogens and to restore barrier function. While the role of growth factors in tissue repair is established, the role of lipid mediators in skin repair has not been investigated extensively. Using a mass spectrometry-based lipid mediator metabolomics approach, we identified D-series resolvins and related pro-resolving lipid mediators during skin injury in mice and pigs. Differentiation of human epidermal keratinocytes increased expression of 15-lipoxygenase and stereospecific production of 17S-hydroxydocosahexaenoic acid, the common upstream biosynthetic marker and precursor of D-series resolvins. In human and pig skin, specific receptors for D-series resolvins were expressed in the epidermal layer and mice deficient in RvD1 receptor Alx/Fpr2 showed an endogenous defect in re-epithelialization. Topical application of D-series resolvins expedited re-epithelialization during skin injury and they enhanced migration of human epidermal keratinocytes in a receptor-dependent manner. The enhancement of re-epithelialization by RvD2 was lost in mice genetically deficient in its receptor and migration of keratinocytes stimulated with RvD2 was associated with activation of the PI3K-AKT-mTOR-S6 pathway, blockade of which prevented its pro-migratory actions. Collectively, these results demonstrate that resolvins have direct roles in the tissue repair program.

Objective: Split-thickness skin graft (STSG) donor site dressings can play an integral role in reducing donor site morbidity. This study tested a novel, chitosan-based wound dressing, Opticell Ag, as an STSG donor site dressing for wounds Method: Between January and December 2016, the chitosan-based dressing was placed on participating patients' donor sites immediately following graft harvest and covered with a transparent occlusive dressing. Pain was evaluated on postoperative day one, before dressing change between days 5–7, and before and after dressing removal between days 10–14 using the Visual Analog Scale (VAS). The extent of re-epithelialisation was determined between day 10–14 and at one month, and healing quality was also evaluated at one month post-operatively using the Vancouver Scar Scale (VSS). Results: A total of 19 patients were recruited, of which 16 completed the study. Patients experienced mild-to-moderate pain in their donor sites when the chitosan-based dressing was used. Pain decreased significantly between postoperative day one and days 10–14, as well as between days 5–7 and 10–14. The mean percentage of re-epithelialisation on days 10–14 was 92% and by one month was 99%. The mean VSS at one month was 3.2±1.4. There were no statistically significant differences between patients' re-epithelialisation rates or VSS scores. There were unplanned dressing changes in four patients. No donor site infections or other adverse events were identified. Conclusion: The chitosan-based dressing tested in this study is safe, effective, and associated with reasonable pain control and acceptable healing quality. The results suggest that it is a promising STSG donor site dressing.

Background Skin grafting is the current standard of care in the treatment of full-thickness burns and other wounds. It is sometimes associated with substantial problems, such as poor quality of the healed skin, scarring, and lack of donor-site skin in large burns. To overcome these problems, alternative techniques that could provide larger expansion of a skin graft have been introduced over the years. Particularly, different cell therapies and methods to further expand skin grafts to minimize the need for donor skin have been attempted. The purpose of this study was to objectively evaluate the efficacy of cell and micrograft transplantation in the healing of full-thickness wounds. Materials and methods Allogeneic cultured keratinocytes and fibroblasts, separately and together, as well as autologous and allogeneic skin micrografts were transplanted to full-thickness rat wounds, and healing was studied over time. In addition, wound fluid was collected, and the level of various cytokines and growth factors in the wound after transplantation was measured. Results Our results showed that both autologous and allogeneic micrografts were efficient treatment modalities for full-thickness wound healing. Allogeneic skin cell transplantation did not result in wound closure, and no viable cells were found in the wound 10 d after transplantation. Conclusions Our study demonstrated that allogeneic micrografting is a possible treatment modality for full-thickness wound healing. The allografts stayed viable in the wound and contributed to both re-epithelialization and formation of dermis, whereas allogeneic skin cell transplantation did not result in wound closure.

Chronic, non-healing wounds place a significant burden on patients and healthcare systems, resulting in impaired mobility, limb amputation, or even death. Chronic wounds result from a disruption in the highly orchestrated cascade of events involved in wound closure. Significant advances in our understanding of the pathophysiology of chronic wounds have resulted in the development of drugs designed to target different aspects of the impaired processes. However, the hostility of the wound environment rich in degradative enzymes and its elevated pH, combined with differences in the time scales of different physiological processes involved in tissue regeneration require the use of effective drug delivery systems. In this review, we will first discuss the pathophysiology of chronic wounds and then the materials used for engineering drug delivery systems. Different passive and active drug delivery systems used in wound care will be reviewed. In addition, the architecture of the delivery platform and its ability to modulate drug delivery are discussed. Emerging technologies and the opportunities for engineering more effective wound care devices are also highlighted.

Injuries to the skin are often complicated by invasive infections. Standard treatment with intravenous antibiotics has limited tissue penetration and sometimes, major systemic toxicity. Traditional topical delivery of antimicrobials also has limited effectiveness and duration of action. We demonstrate the use of a new Platform Wound Device (PWD) for delivery of topical, ultrahigh concentrations of minocycline as well as lidocaine onto the burn eschar and on the surface of excisional wounds in a total of 56 burn wounds and 24 excisional wounds in a porcine model. Wounds were created on day 0, debrided on day 3, and pigs were killed on day 7. After 3 days of PWD with minocycline treatment, bacterial count was 5.44 log CFU/g in dorsal wound tissue inoculated with methicillin-resistant Staphylococcus aureus, less than that after treatment with silver sulfadiazine cream (7.64 log CFU/g). Pain was also relieved or eliminated in burn wounds and full-thickness excisional wounds when lidocaine was delivered by the PWD. The results demonstrate that ultrahigh concentrations of antibiotics can be delivered effectively by the PWD, and will accelerate wound bed preparation.

Cellular grafts used for skin repair require rapid integration with the host tissue to remain viable and especially to nourish the epidermal cells. Here, we evaluated the responses in the split-thickness skin grafts (STSGs) grafted on three differently treated wound beds: directly on excised wound bed (EX), on an artificial dermal template (DT) and on granulation tissue (GT) induced by cellulose sponge. In ten burn patients, after excision, a test area was divided into three sections: One transplanted with STSG instantaneously and two sections had a pre-treatment for 2 weeks with either DT or a cellulose sponge inducing granulation tissue formation and thereafter grafted with STSGs. One week after grafting, the STSGs on GT demonstrated most endothelial CD31(+) staining, largest average vessel diameters as well as most CD163(+) staining of M2-like macrophages and most MIB1(+) proliferating epidermal cells, suggesting an active regenerative environment. STSGs on DT had smallest vessel diameters and the least CD163(+) macrophages. STSGs on EX had the least CD31(+) cells and the least MIB1(+) proliferating cells. After 3 months, this reactivity in STSGs had subsided, except increased dermal cell proliferation was observed in STSGs on EX. Results show that pre-treatment of wound bed and induction of granulation tissue formation can accelerate host-graft interaction by stimulating graft vasculature and inducing cell proliferation.

Background Skin grafting is the current standard care in the treatment of full thickness burns. It was first described around 1500 BC but the vast majority of advancements have been achieved over the past 200 years. Methods An extensive literature review was conducted on Pubmed, Medline and Google Scholar researching the evolution of skin grafting techniques. The authors concentrated on the major landmarks of skin grafting and also provide an overview of ongoing research efforts in this field. Results The major innovations of skin grafting include Reverdin pinch grafting, Ollier grafting, Thiersch grafting, Wolfe grafting, Padgett dermatome and modifications, Meek-wall microdermatome and Tanner mesh grafting. A brief description of the usage, advantages and limitations of each technique is included in the manuscript. Conclusions Skin grafting technique have evolved significantly over past 200 years from Reverdin pinch grafting to modern day meshed skin grafts using powered dermatome. Increasing the expansion ratio and improving the cosmetic and functional outcome are the main focus of ongoing skin grafting research and emerging techniques (such as Integra®, Recell®, Xpansion®) are showing promise.

Volumetric muscle loss (VML), usually occurring following traumatic injury, results in a composite loss of muscle mass. These injuries manifest as decreased strength and functional impairments. Clinically, these injuries often heal with fibrosis, as opposed to skeletal muscle regeneration. This study examines the healing patterns of a skeletal muscle following VML in a murine model. Eight-week old male C57BL/6J mice used in the study underwent either bilateral VML injury or cryoinjury, a widely used model known to induce skeletal muscle regeneration. Skeletal muscle was harvested at 2 and 4 weeks following injury and subjected to histological analysis. H&E staining demonstrated skeletal muscle regeneration following cryoinjury, but not VML, at either timepoint post-injury. Additionally, samples were analyzed using a wound-healing PCR array to identify differentially regulated genes of interest in VML and cryoinjury, as compared to noninjured controls. The gene array data further demonstrated prolonged inflammation and increased pro-fibrotic activity in the VML injured muscles, as compared to cryoinjury. In addition, IGF1, a known myogenic factor, was significantly decreased following VML, as compared to cryoinjury, in both ELISA and PCR. This study offers an insight into the pathophysiology of VML injury and reveals a gene profile of a nonregenerating skeletal muscle.

Wound microenvironment plays a major role in the process of wound healing. It contains various external and internal factors that participate in wound pathophysiology. The pH is an important factor that influences wound healing by changing throughout the healing process. Several previous studies have investigated the role of pH in relation to pathogens but studies concentrating on the effects of pH on wound healing itself are inconclusive. The purpose of this study was to comprehensively and in a controlled fashion investigate the effect of pH on wound healing by studying its effect on human primary keratinocyte and fibroblast function in vitro and on wound healing in vivo. In vitro, primary human keratinocytes and fibroblasts were cultured in different levels of pH (5.5-12.5) and the effect on cell viability, proliferation, and migration was studied. A rat full-thickness wound model was used to investigate the effect of pH (5.5-9.5) on wound healing in vivo. The effect of pH on inflammation was monitored by measuring IL-1 α concentrations from wounds and cell cultures exposed to different pH environments. Our results showed that both skin cell types tolerated wide range of pH very well. They further demonstrated that both acidic and alkaline environments decelerated cell migration in comparison to neutral environments and interestingly alkaline conditions significantly enhanced cell proliferation. Results from the in vivo experiments indicated that a prolonged, strongly acidic wound environment prevents both wound closure and reepithelialization while a prolonged alkaline environment did not have any negative impact on wound closure or reepithelialization. Separately, both in vitro and in vivo studies showed that prolonged acidic conditions significantly increased the expression of IL-1 α in fibroblast cultures and in wound fluid, whereas prolonged alkaline conditions did not result in elevated amounts of IL-1 α.

Wound infections cause inflammation, tissue damage, and delayed healing that can lead to invasive infection and even death. The efficacy of systemic antibiotics is limited due to poor tissue penetration that is especially a problem in burn and blast wounds where the microcirculation is disrupted. Topical administration of antimicrobials is an attractive approach because it prevents infection and avoids systemic toxicity, while hydrogels are an appealing vehicle for topical drug delivery. They are easy to apply to the wound site by being injectable, the drug release properties can be controlled, and their many characteristics, such as biodegradation, mechanical strength, and chemical and biological response to stimuli can be tailored. Hydrogels also create a moist wound environment that is beneficial for healing. The purpose of this study was to formulate an agarose hydrogel that contains high concentrations of minocycline or gentamicin and study its characteristics. Subsequently, the minocycline agarose hydrogel was tested in a porcine burn model and its effect as a prophylactic treatment was studied. The results demonstrated that 0.5% agarose in water was the optimal concentration in terms of viscosity and pH. Bench testing at room temperature demonstrated that both antibiotics remained stable in the hydrogel for at least 7 days and both antibiotics demonstrated sustained release over the time of the experiment. The porcine burn experiment showed that prophylactic treatment with the agarose minocycline hydrogel decreased the burn depth and reduced the number of bacteria as efficiently as the commonly used silver sulfadiazine cream.

Objective: There is an unmet need to improve immediate burn care, particularly when definitive treatment is delayed. Therefore, the purpose of this project was to formulate a hydrogel that contains very high concentrations of antibiotics and validate its use together with a platform wound device (PWD) for the immediate care of burns. Approach: The hydrogel properties were optimized by using a rheometer, differential scanning calorimetry, and liquid chromatography–mass spectrometry and were tested in an infected porcine burn model. Immediately, after burn creation, the burns were infected with different bacteria. Subsequently, the burns infected with Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii were covered with the PWD and treated with a single dose of hydrogel containing 1000 × minimum inhibitory concentration of vancomycin, gentamicin, and minocycline, respectively. On day 7 or 45, the animals were euthanized, and the burns were harvested for histology and quantitative bacteriology. Results: 0.625% was the best alginate concentration for the hydrogel in terms of viscosity, stability, and drug release. The porcine studies demonstrated that vancomycin-, gentamicin-, and minocycline-treated tissues contained significantly less bacteria and reduced depth of tissue necrosis in comparison to controls. Innovation: The PWD represents a platform technology that begins at the point of the first treatment by protecting the wound and allowing administration of topical therapeutics. The device can be adapted to enclose any size burn over any contour of the body. Conclusion: Antibiotics can be delivered safely in very high concentrations in a hydrogel using the PWD, and burn infections can be treated successfully with this method.

BACKGROUND Wound infection can impair postoperative healing. Topical antibiotics have potential to treat wound infection and inflammation and minimize the adverse effects associated with systemic antibiotics. METHODS Full-thickness porcine wounds were infected with Staphylococcus aureus. Using polyurethane wound enclosure devices, wounds were treated with topical 100 μg/ml minocycline, topical 1000 μg/ml minocycline, topical saline control, or 4 mg/kg intravenous minocycline. Bacteria were quantified in wound tissue and fluid obtained over 9 hours. Immunosorbent assays were used to analyze inflammatory marker concentrations. Minocycline's effect on in vitro migration and proliferation of human keratinocytes and fibroblasts was tested using scratch assays and metabolic assays, respectively. RESULTS After 6 hours, 100 and 1000 μg/ml topical minocycline decreased bacteria in wound tissue to 3.5 ± 0.87 and 2.9 ± 2.3 log colony-forming units/g respectively, compared to 8.3 ± 0.9 log colony-forming units/g in control wounds (p < 0.001) and 6.9 ± 0.2 log colony-forming units/g in wounds treated with 4 mg/kg intravenous minocycline (p < 0.01). After 2 hours, topical minocycline reduced concentrations of the inflammatory cytokines interleukin-1β, interleukin-6, and tumor necrosis factor-α (p < 0.01), and inflammatory cell counts in wound tissue (p < 0.05). In noninfected wounds, topical minocycline significantly reduced interleukin-1β, interleukin-6, and inflammatory cell counts after 4 hours (p < 0.01). Matrix metalloproteinase-9 concentrations decreased after 1-hour treatment (p < 0.05). Keratinocyte and fibroblast in vitro functions were not adversely affected by 10 μg/ml minocycline or less. CONCLUSIONS Topical minocycline significantly reduces bacterial burden and inflammation in infected wounds compared with wounds treated with intravenous minocycline or control wounds. Minocycline also decreases local inflammation independently of its antimicrobial effect.

Standardized and reproducible animal models are crucial in medical research. Rodents are commonly used in wound healing studies since, they are easily available, affordable and simple to handle and house. However, the most significant limitation of rodent models is that the wounds heal by contraction while in humans the primary mechanisms of healing are reepithelialization and granulation tissue formation. The robust contraction results in faster wound closure that complicates the reproducibility of rodent studies in clinical trials. We have developed a titanium wound chamber for rodent wound healing research. The chamber is engineered from two pieces of titanium and is placed transcutaneously on the dorsum of a rodent. The chamber inhibits wound contraction and provides a means for controlled monitoring and sampling of the wound environment in vivo with minimal foreign body reaction. This technical report introduces two modalities utilizing the titanium chambers in rats: (1) Wound in a skin island model and, (2) Wound without skin model. Here, we demonstrate in rats how the "wound in a skin island model" slows down wound contraction and how the "wound without skin" model completely prevents the closure. The titanium wound chamber provides a reproducible standardized models for wound healing research in rodents.

Wound healing is traditionally divided into inflammation, proliferation, and remodeling phases. Several inflammatory mediators and cells regulate the inflammation phase. The specific roles for different mediators have not been clearly defined. The effects of inflammation phase modulation on wound healing were evaluated in this study. Rat full-thickness wounds were divided into different experimental groups: (1) sterile hyper-inflammatory wounds/endotoxin (topical endotoxin), (2) sterile hypo-inflammatory/inhibitor group (cocktail of topical COX-1 plus COX-2 plus lipoxygenase inhibitors), and (3) control groups: topical saline or DMSO. After full-thickness wound creation, custom-made titanium chambers enclosed the wound, creating an isolated well-controlled environment. Wound healing was followed over time; tissue biopsies and wound fluid samples were collected on days 1, 4, and 8 postoperatively. The validity of the inflammation model was confirmed by increased IL-1a expression, increased CD45+ leukocytes recruitment in the hyper-inflamed group as compared to the inhibitor and control groups. The reepithelialization percentage was significantly increased in the endotoxin group as compared to the inhibitor group on day 4 (60.75 vs. 22.05, p-value

Extremity skeletal muscle injuries result in substantial disability. Current treatments fail to recoup muscle function, and properly designed and implemented tissue engineering and regenerative medicine techniques can overcome this challenge. In this study, we present a nanoengineered, growth factor eluting bioink that utilizes Laponite® nanoclay for the controlled release of vascular endothelial growth factor (VEGF) and a GelMA hydrogel for a supportive and adhesive scaffold that can be crosslinked in vivo. The bioink is delivered with a partially-automated handheld printer for the in vivo formation of an adhesive and three dimensional (3D) scaffold. The effect of the controlled delivery of VEGF alone or paired with adhesive, supportive, and fibrilar architecture has not been studied in volumetric muscle loss (VML) injuries. Upon direct in vivo printing, our constructs were adherent to skeletal muscle and sustained release of VEGF. The in vivo printing of Muscle Ink in a murine model of volumetric muscle loss (VML) injury promotes functional muscle recovery, reduced fibrosis, and increased anabolic response compared to untreated mice. The in vivo construction of a therapeutic eluting 3D scaffold paves the way for the immediate treatment of a variety of soft tissue traumas.

Background CCHCR1 (Coiled-Coil α-Helical Rod protein 1) is a putative psoriasis candidate gene with the risk alleles CCHCR1*WWCC and *Iso3, the latter inhibiting the translation of isoform 1. CCHCR1 was recently shown to be a centrosomal protein, as well as a component of cytoplasmic processing bodies (P-bodies) that regulate mRNA turnover. The function of CCHCR1 has remained unsettled, partly because of the inconsistent findings; it has been shown to play a wide variety of roles in divergent processes, e.g., cell proliferation and steroidogenesis. Here we utilized RNA sequencing (RNAseq) using HEK293 cells overexpressing isoforms 1 or 3 (Iso1, Iso3 cells), in combination with the coding non-risk or risk (*WWCC) haplotype of CCHCR1. Our aim was to study the overall role of CCHCR1 and the effects of its variants. Results The overexpression of CCHCR1 variants in HEK293 cells resulted in cell line-specific expression profiles though several similarities were observable. Overall the Iso1 and Iso3 cells showed a clear isoform-specific clustering as two separate groups, and the Non-risk and Risk cells often exhibited opposite effects. The RNAseq supported a role for CCHCR1 in the centrosomes and P-bodies; the most highlighted pathways included regulation of cytoskeleton, adherens and tight junctions, mRNA surveillance and RNA transport. Interestingly, both the RNAseq and immunofluorescent localization revealed variant-specific differences for CCHCR1 within the P-bodies. Conclusions CCHCR1 influenced a wide variety of signaling pathways, which could reflect its active role in the P-bodies and centrosomes that both are linked to the cytoskeleton; as a centrosomal P-body protein CCHCR1 may regulate diverse cytoskeleton-mediated functions, such as cell adhesion and -division. The present findings may explain the previous inconsistent observations about the functions of CCHCR1. Electronic supplementary material The online version of this article (10.1186/s12864-018-4810-y) contains supplementary material, which is available to authorized users.

Introduction Burns are a very frequent injury type in the battlefield, comprising 5-20% of combat casualties in the recent conflicts. Almost 80% of the burns occur to the face, in part because the face is often not protected. Immediate treatment is critical in the first hours after severe burn injury in order to prevent infection and wound progression. Immediate treatment in the battlefield can be a serious challenge especially if the injury occurs in a remote area with limited transport options. Therefore, novel treatment modalities for prolonged field care when transport to the definitive care is delayed are needed. The purpose of this study was to utilize the platform wound device (PWD) with negative pressure capabilities for the immediate and definitive treatment of porcine full-thickness head burns. Materials and methods Full-thickness burn wounds were created on foreheads of seven Yorkshire pigs. Burns were created on day 0, immediately enclosed with the PWD and treated topically with minocycline and lidocaine. On day 3, the burns were surgically debrided. Subsequently, new PWDs were placed on the wounds and continuous negative pressure wound therapy was initiated with either -50 mmHg or -80 mmHg. On day 7, the animals were euthanized and wounds were harvested for analyses. Control wounds were treated with silver sulfadiazine cream. Results The PWD treatment with negative pressure significantly reduced erythema and edema in the injured tissue and promoted granulation tissue and neocollagen formation by day 7 in comparison to control wounds. In addition, the PWD with both topical minocycline and negative pressure (-80 mmHg or -50 mmHg) reduced bacterial counts in the wounds similar to the current standard of care. Conclusion This study demonstrates that the PWD is an effective platform for delivery of antibiotics and negative pressure wound therapy for the treatment of full-thickness burns. Therefore, the PWD may be utilized for both prolonged field care and definitive treatment of burn- and blast-injured warfighters.

Background Split-thickness skin grafting is the gold standard for treatment of major skin loss. This technique is limited by donor-site availability in large burn injuries. With micrografting, a technique where split-thickness skin graft is minced into 0.8 × 0.8-mm pieces, the authors have demonstrated an expansion ratio of 1:100 and healing comparable to that achieved with split-thickness skin grafting. Methods In this study, the authors explore the regenerative potential of a skin graft by cutting split-thickness skin grafts to pixel size (0.3 × 0.3 mm) grafts. Wound healing was studied in full-thickness wounds in a porcine model by creating an incubator-like microenvironment using polyurethane wound chambers. Multiple wound healing parameters were used to study the outcome of pixel grafting and compare it to micrografting and nontransplanted wounds. Results The authors' results show that 0.3 × 0.3-mm pixel grafts remain viable and contribute to skin regeneration. The pixel graft-transplanted wounds demonstrated a faster reepithelialization rate, decreased wound contraction, and increased mechanical stability compared with nontransplanted wounds. The reepithelialization rates of the wounds were significantly increased with pixel grafting at day 6 after wounding compared with micrografting. Among the other wound healing parameters, there were no significant differences between wounds transplanted with pixel grafts and micrografts. Conclusions Pixel grafting technique would address the most commonly encountered limitations of the split-thickness skin graft with the possibility of an even larger expansion ratio than micrografting. This technique is simple and fast and can be conducted in the operating room or in the clinic.

Background Although wound contraction is an essential part of healing, excessive contraction can compromise healing through induction of scarring and fibrosis. This in turn leads to development of wound contractures that limit elasticity and function. Major research efforts have focused on development of novel therapeutic approaches to gain inhibitory control over wound contraction. Despite these efforts, the need for cost-effective, clinically feasible, and effective agents to inhibit wound contraction remains. Methods In this study, the authors investigated the effect of nanofibrillar cellulose hydrogel on wound contraction both in vitro and in vivo. Two different porcine full-thickness wounds (8-mm punch-biopsy wounds and 4 × 4-cm wounds covered with a 1:3-meshed split-thickness skin graft) were treated with or without nanofibrillar cellulose or carboxymethylcellulose (Purilon hydrogel), which was used as a reference treatment. Wound contraction was observed macroscopically, and histologic sections were taken at 14-day follow-up. Results Nanofibrillar cellulose hydrogel inhibited 70 percent of punch-biopsy wound contraction, whereas the carboxymethylcellulose hydrogel was ineffective. Importantly, application of nanofibrillar cellulose on split-thickness skin grafts did not inhibit epithelialization of the interstices or cell migration from the graft. Conclusion The authors' results, although preliminary, indicate a potential for nanofibrillar cellulose hydrogel as a novel material for controlling excessive wound contraction.

Background: Epidermal stem cells present in the skin appendages of the dermis might be crucial in wound healing. In this study, the authors located these cells in the dermis and evaluated their contribution to full-thickness wound healing in a porcine model. Methods: Four sequentially deeper 0.35-mm-thick skin grafts were harvested from the same donor site going down to 1.4 mm in depth (layers 1 through 4). The layers were minced to 0.8 × 0.8 × 0.35-mm micrografts and transplanted (1:2) onto full-thickness porcine wounds. Healing was monitored up to 28 days and biopsy specimens were collected on days 6 and 10. Multiple wound healing parameters were used to assess the quality of healing. Results: The authors' results showed that wounds transplanted with layer 2 (0.35 to 0.7 mm) and layer 3 (0.7 to 1.05 mm) micrografts demonstrated reepithelialization rates comparable to that of split-thickness skin graft (layer 1, 0.00 to 0.35 mm; split-thickness skin graft) at day 10. At day 28, dermal micrografts (layers 2 and 3) showed quality of healing comparable to that of split-thickness skin grafts (layer 1) in terms of wound contraction and scar elevation index. The amounts of epidermal stem cells [cluster of differentiation (CD) 34 +] and basal keratinocytes (KRT14) at each layer were quantified by immunohistochemistry. Conclusions: The analysis showed that layers 2 and 3 contained the most CD34 + cells and layer 1 was the richest in KRT14 + cells. The immunohistochemistry also indicated that, by day 6, CD34 + cells had differentiated into KRT14 cells, which migrated from the grafts and contributed to the reepithelialization of the wound.

Negative-pressure wound therapy (NPWT) is widely used to improve skin wound healing. Although NPWT has been studied as a treatment for wound closure and healing, the molecular mechanisms explaining its therapeutic effects remain unclear. To investigate the effect of NPWT on gene expression, and to discover the genes most dominantly responding to this treatment during skin wound healing, we applied negative pressure on split-thickness skin graft donor sites from the first postoperative day (POD) to the seventh POD. Biopsies were collected from 4 NPWT-treated and 2 control patients. Two biopsy samples were taken from each patient: one from intact skin before graft harvesting, and one on the seventh POD from the donor site wound. Genome-wide microarrays were performed on all samples. Gene expression changes on the seventh POD were compared between NPWT and control patients, and were analyzed for statistical significance. In addition, we analyzed wound exudates for volume, and for concentrations of leukocytes, erythrocytes, and haemoglobin. NPWT induced major changes in gene expression during healing. These changes ranged from 10-fold induction to 27-fold suppression. The genes most induced were associated with cell proliferation and inflammation, and the most down-regulated genes were linked to epidermal differentiation. Our results provide the first insight into the molecular mechanisms behind NPWT, and suggest that NPWT enhances specific inflammatory gene expression at the acute phase associated with epithelial migration and wound healing. However, its continued use may inhibit epithelial differentiation.

Complex skin wounds, such as chronic ulcers and deep burns, require lengthy treatments and cause extensive burdens on healthcare and the economy. Use of biomaterials and cell transplantation may improve traditional treatments and promote the healing of difficult-to-treat wounds. In this study, we investigated the use of recombinant human collagen III (rhCol-III) gel as a delivery vehicle for cultured autologous skin cells (keratinocytes only or keratinocyte–fibroblast mixtures). We examined its effect on the healing of full-thickness wounds in a porcine wound-healing model. Two Landrace pigs were used for the study. Fourteen deep dermal wounds were created on the back of each pig with an 8 mm biopsy punch. Syringes containing acellular rhCol-III gel (n = 8) or rhCol-III gel with autologous keratinocytes (n = 8) or rhCol-III gel with autologous keratinocytes and fibroblasts (n = 8) were applied into wounds. Untreated wounds were used as controls for the treatment groups (n = 4). We used rhCol-III gel to manufacture a cell-delivery syringe containing autologous skin cells. In a full-thickness wound-healing model, we observed that rhCol-III gel enhances early granulation tissue formation. Interestingly, we found cell type-dependent differences in the stability of rhCol-III in vivo. Fibroblast-containing gel was effectively removed from the wound, whereas gels without cells or with keratinocytes only remained intact. Our results demonstrate that the properties of rhCol-III gel for skin cell transplantation can be significantly altered in a cell type-dependent manner. Copyright © 2013 John Wiley & Sons, Ltd.

Wound microenvironment plays a major role in the process of wound healing. It contains various external and internal factors that participate in wound pathophysiology. The pH is an important factor that influences wound healing by changing throughout the healing process. Several previous studies have investigated the role of pH in relation to pathogens but studies concentrating on the effects of pH on wound healing itself are inconclusive. The purpose of this study was to comprehensively and in a controlled fashion investigate the effect of pH on wound healing by studying its effect on human primary keratinocyte and fibroblast function in vitro and on wound healing in vivo. In vitro, primary human keratinocytes and fibroblasts were cultured in different levels of pH (5.5-12.5) and the effect on cell viability, proliferation, and migration was studied. A rat full-thickness wound model was used to investigate the effect of pH (5.5-9.5) on wound healing in vivo. The effect of pH on inflammation was monitored by measuring IL-1 α concentrations from wounds and cell cultures exposed to different pH environments. Our results showed that both skin cell types tolerated wide range of pH very well. They further demonstrated that both acidic and alkaline environments decelerated cell migration in comparison to neutral environments and interestingly alkaline conditions significantly enhanced cell proliferation. Results from the in vivo experiments indicated that a prolonged, strongly acidic wound environment prevents both wound closure and reepithelialization while a prolonged alkaline environment did not have any negative impact on wound closure or reepithelialization. Separately, both in vitro and in vivo studies showed that prolonged acidic conditions significantly increased the expression of IL-1 α in fibroblast cultures and in wound fluid, whereas prolonged alkaline conditions did not result in elevated amounts of IL-1 α.