Search

Gordon M Riha,1 Alyssa Johnson,2 Sadie Arnold,3 Michael S Englehart,1 Simon J Thompson4 1Trauma & General Surgery, Billings Clinic, Billings, MT, USA; 2EMS & Trauma Systems Montana, Chronic Disease Prevention and Health Promotion Bureau, Montana Department of Public Health and Human Services, Helena, MT, USA; 3Laboratory Services, Billings Clinic, Billings, MT, USA; 4Collaborative Science & Innovation, Billings Clinic, Billings, MT, USACorrespondence: Simon J Thompson, Collaborative Science & Innovation, Billings Clinic, Billings, MT, USA, Tel +1 503 267 7314, Fax +1 406 435-1586, Email sthompson11@billingsclinic.orgPurpose: The state of Montana encompasses and defines rural health care as it is known in the United States (US) today. This vast area is punctuated by pockets of health care availability with varying access to blood products for transfusion. Furthermore, timely transport is frequently challenged by weather that may limit air transportation options, resulting in multiple hours in ground transport to definitive care.Patients and Methods: The Montana State Trauma Care Committee (MT-STCC) developed the Montana Interfacility Blood Network (MT-IBN) to ensure blood availability in geographically distanced cases where patients may otherwise not survive. The index case that led to the formal development of the MT-IBN is described, followed by a second case illustrating the IBN process.Results: This process and development manuscript details the innovative efforts of MT-STCC to develop this fledgling idea unique to rural US health care. We review guidelines that have been developed to define broad aspects of the MT-IBN including the reason to share resources, proper packaging, paperwork necessary for transfer, and how to provide resources directly to the patient. Finally, we describe implementation within the state.Conclusion: The MT-IBN was developed by MT-STCC to facilitate the hand-off of lifesaving blood to patients being transported by ground to definitive care in Montana without having to stop at an intermediary facility. This has already led to lives saved in areas that are limited in blood availability due to rurality.Keywords: rural health care, blood transfusion, health services accessibility, trauma

Background: The balanced transfusion of blood components plays a leading role in traumatic hemostatic resuscitation. Yet, previous whole blood studies have only focused on urban trauma center settings., Objective: To compare component vs whole blood therapy on wastage rates and mortality in the rural setting., Methods: This study was a nonrandomized, retrospective, observational, single-center study on a cold-stored whole blood program implementation for adult massive transfusions from 2020 to 2022 at a Level II trauma center. Trauma registry data determined the facility's whole blood needs and facilitated sustainable blood supplies. Whole blood use protocols were established, and utilization and laboratory compliance for incompatible ABO antibody hemolysis was monitored and reviewed monthly at stakeholder and trauma services meetings., Results: From 2018 to 2019, the facility initiated component therapy massive transfusions every 9 days (n = 41). Therefore, four units of low-titer, O-positive whole blood delivered fortnightly was determined to provide patient coverage and minimize wastage. Across the study time frame (2020-2022), there were n = 68 hemodynamically unstable patients, consisting of those receiving whole blood, n = 37, and patients receiving component therapy, n = 31. Mortality rates were significantly lower (p = .030) in the whole blood population (n = 3, 8%) compared to those solely receiving component therapy (n = 9, 29%). Wastage rates were constantly evaluated; in 2021, 43.4% was not utilized, and in 2022, this was reduced to 38.7%. Anecdotally, nurses appreciated the ease of administration and documentation of transfusing whole blood, as it negated ratio compliance., Conclusion: This evidence-based whole blood program provides vital care to severely injured trauma patients in a vast, rural region., (Copyright © 2024 Society of Trauma Nurses.)

Time to definitive surgical debridement has been recognized as a predictor for morbidity and mortality in necrotizing soft-tissue infections (NSTI). Rural patients are at particular risk due to limited local resources, decreased access to care, and prolonged transport times. The aim of the current study was to examine the outcomes of NSTI requiring surgical treatment in a previously non-described setting. This retrospective study (2010-2020) from a single tertiary care center in Montana reviewed patients ≥18 years old with a NSTI via ICD9/10 codes. Rural-Urban Continuum Codes (RUCC; characterizing counties by population size) were used to distinguish urban versus rural counties. Race (White and American Indian/Alaskan Native (AI/AN)) was self-described. Qualitative and quantitative comparisons between groups were determined using the appropriate two-tailed statistical tests. An aggregate of 177 patients was identified. Mean age in AI/AN was significantly lower ( P <0.0001) compared to White patients with no preexisting condition delineation. NSTI demonstrated an elevated incidence in both rural areas and AI/AN patients. Diabetes was also significantly higher ( P =0.0073) in rural versus urban patients. Both rural and AI/AN patients faced extended travel distance for treatment. AI/AN patients had a significantly different infection location than White. Furthermore, polymicrobial species were significantly more prevalent in AI/AN patients. Morbidities (defined as septic shock and/or amputation) were significantly higher in AI/AN patients and rural environments ( P <0.01). There was no significant difference in all-cause mortality between respective groups. The state of Montana presents unique challenges to optimizing NSTI treatment due to excessive distances to regional tertiary care facilities. This delay in treatment can lead to increased morbidity., Competing Interests: None., (IJBT Copyright © 2023.)

Objectives: The goal of this study was to evaluate a low fixed-dose versus weight-based dosing strategy for four-factor prothrombin complex (4F-PCC) time to administration in intracranial hemorrhage (ICH) patients., Methods: A retrospective analysis was conducted at a single rural Tertiary referral center in patients ≥18 years old on warfarin with ICH who received 4F-PCC. Continuous variables were summarized using mean (±95% CI) and compared using two-tailed tests; p values ≤0.05 were considered statistically significant., Results: A total of 46 ICH patients were reversed using 4F-PCC (Fixed, n = 27 and Weight, n = 19). Baseline characteristics were equivalent. Total units of 4F-PCC (mean dose units 2525.1 versus 1623.3) and dose per kg were significantly reduced in the fixed-dose group. Total time from order to delivery was significantly reduced with the fixed-dose strategy (mean time 43.0 versus 29.0 minutes). Hospital length of stay (LOS), intensive care unit LOS, and mortality were equivalent with a similar mechanism. International Normalized Ratio (INR) reversal success (≤1.5) and total INR change was comparable with no difference in adverse thromboses between groups., Conclusions: A fixed-dosed strategy reduced time to 4F-PCC administration for warfarin reversal in ICH, as compared to a weight-based strategy; with no increase in LOS, mortality, or need for additional dosing. This also resulted in significant cost savings., Competing Interests: None., (IJPPP Copyright © 2023.)

Background: The International Normalized Ratio (INR) is commonly used to guide therapy after hepatectomy. We hypothesized that the use of thrombelastography (TEG) would demonstrate a decreased incidence of hypocoagulability in this patient population., Methods: Seventy-eight patients were prospectively enrolled before undergoing hepatectomy. INR, TEG, and coagulation factors were drawn before incision, postoperatively, and on postoperative days 1, 3, and 5., Results: Patients demonstrated an elevated INR at all postoperative time points. However, TEG demonstrated a decreased R value postoperatively, with subsequent normalization. Other TEG measurements were equivalent to preoperative values. All procoagulant factors save factor VIII decreased postoperatively, with a simultaneous decrease in protein C., Conclusions: TEG demonstrated a brief hypercoagulable state after major hepatectomy, with coagulation subsequently normalizing. The INR significantly overestimates hypocoagulability after hepatectomy and these data call into question current practices using the INR to guide therapy in this patient population., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: The incidence of deep venous thrombosis (DVT) remains high in general surgery and trauma patients despite widespread prophylaxis with enoxaparin. A recent study demonstrated decreased incidence of DVT if patients on enoxaparin had a change in R time (ΔR) of greater than 1 minute when heparinase-activated thromboelastography (TEG) was compared with normal TEG. We hypothesized that using ΔR-guided dosing would result in decreased DVT rates., Methods: A prospective, randomized controlled trial was performed at a Level 1 trauma center. Both trauma and general surgery patients were included. Upon enrollment, demographic data including age, sex, body mass index, and Acute Physiology and Chronic Health Evaluation II score were obtained. Enrolled patients were randomized to standard (30 mg twice a day) or TEG-guided dosing. Dose-adjusted patients underwent daily enoxaparin titration to achieve an ΔR of 1 minute to 2 minutes. Venous thromboembolism screening was performed per institutional protocol. Antithrombin III (AT-III) and anti-Xa levels were drawn at peak enoxaparin concentrations., Results: A total of 87 patients were enrolled. There was no difference in demographic data between the groups. No pulmonary emboli were identified. The control group had a DVT rate of 16%, while the experimental group had a rate of 14% (p = nonsignificant). The experimental group's median enoxaparin dosage, 50 mg twice a day, was significantly higher than that of the control (p < 0.01). TEG ΔR was not different between the control and experimental groups. Beginning at Day 3, anti-Xa levels were higher in the experimental group (p < 0.05). There was no difference in AT-III activity between the two groups; 67% of the patients demonstrated AT-III deficiency., Conclusion: TEG adjusted enoxaparin dosing led to significant increases in anti-Xa activity, which did not correlate with a decreased DVT rate. Failure to reduce the DVT rate and increase ΔR despite increased dosing and increased anti-Xa activity is consistent with the high rate of AT-III deficiency detected in this study cohort. These data suggest that the future of DVT prevention may not lie in the optimization of low molecular weight heparin therapy but rather in compounds that increase antithrombin directly or operate independently of the AT-III pathway., Level of Evidence: Therapeutic study, level III.

Importance: Enoxaparin sodium is widely used for deep vein thrombosis (DVT) prophylaxis, yet DVT rates remain high in the trauma and general surgery populations. Missed doses during hospitalization are common., Objective: To determine if missed doses of enoxaparin correlate with DVT formation., Design, Setting, and Participants: Data were prospectively collected among 202 trauma and general surgery patients admitted to a level I trauma center., Main Outcomes and Measures: Deep vein thrombosis screening was performed using a rigorous standardized protocol., Results: The overall incidence of DVT was 15.8%. In total, 58.9% of patients missed at least 1 dose of enoxaparin. The DVTs occurred in 23.5% of patients who missed at least 1 dose and in 4.8% of patients who did not (P < .01). On univariate analysis, the need for mechanical ventilation (71.8% vs 44.1%), the performance of more than 1 operation (59.3% vs 40.0%), and male sex (75% vs 56%) were associated with DVT formation (P < .05 for all). A bivariate logistic regression was then performed, which revealed age 50 years or older and interrupted enoxaparin therapy as the only independent risk factors for DVT formation. The DVT rate did not differ between trauma and general surgery populations or in patients receiving once-daily vs twice-daily dosing regimens., Conclusions and Relevance: Interrupted enoxaparin therapy and age 50 years or older are associated with DVT formation among trauma and general surgery patients. Missed doses occur commonly and are the only identified risk factor for DVT that can be ameliorated by physicians. Efforts to minimize interrupted enoxaparin prophylaxis in patients at risk for DVT should be optimized.

Background: Prothrombin time-international normalized ratio (PT-INR) is widely utilized to guide plasma therapy and initiation of thromboprophylaxis after a hepatectomy. Thrombelastography (TEG) monitors shear elasticity, which is sensitive to cellular and plasma components in blood, allowing for functional assessment of the life of the clot. The objective of this study was to prospectively compare PT-INR and TEG in liver resection patients., Methods: Forty patients were enrolled before undergoing an elective hepatectomy. Patients underwent a liver resection utilizing a low central venous pressure (CVP) anaesthetic technique and intermittent Pringle manoeuver. PT-INR and TEG were drawn prior to incision, post-operatively, and post-operative days 1, 3 and 5., Results: All post-operative PT-INR values increased significantly when compared with pre-operative PT-INR (P < 0.01). The time of onset to clot (R-value) decreased significantly at the post-operative time point (P = 0.04), consistent with a relative hypercoagulability. Subsequent R-values were not different compared with the pre-operative R-value. The strength of the clot (maximum amplitude, MA) was unchanged when comparing pre- and post-operative time points., Discussion: In spite of an elevation in PT-INR, patients undergoing a liver resection demonstrated a brief hypercoagulable state, followed by normal coagulation function based on TEG. These data call into question the practice of utilizing PT-INR to guide plasma transfusion and timing of prophylactic anticoagulation after a liver resection., (© 2013 International Hepato-Pancreato-Biliary Association.)

Background: Previous studies have shown large-volume resuscitation modulates coagulopathy and inflammation. Our objective was to analyze the effects of initial bolus fluids used in military and civilian settings on coagulation and inflammation in a prospective, randomized, blinded trial of resuscitation of uncontrolled hemorrhage., Methods: Fifty swine were anesthetized, intubated, and ventilated and had monitoring lines placed. A Grade V liver injury was performed followed by 30 minutes of hemorrhage. After 30 minutes, the liver was packed, and randomized fluid resuscitation was initiated during a 12-minute period with 2 L of normal saline, 2 L of lactated Ringer's solution, 250 mL of 7.5% saline with 3% Dextran, 500 mL of Hextend, or no fluid (NF). Animals were monitored for 2 hours after injury. Thrombelastograms (TEGs), prothrombin time (PT), partial thromboplastin time, fibrinogen as well as serum interleukin 6, interleukin 8, and tumor necrosis factor α levels were drawn at baseline and after 1 hour and 2 hours., Results: The NF group had less posttreatment blood loss compared with other groups (p < 0.01). Blood loss was similar in the other groups. TEG R values in each group decreased from baseline at 1 and 2 hours (p < 0.02). The groups receiving 2 L of normal saline, 250 mL of 7.5% saline with 3% Dextran, or 500 mL of Hextend had lower TEG maximum amplitude values compared with NF group (p < 0.02). All fluids except lactated Ringer's solution resulted in significant increases in PT compared with NF, whereas all fluids resulted in significant decreases in fibrinogen compared with NF (p < 0.02). Fluid resuscitation groups as well as NF group demonstrated significant increases in inflammatory cytokines from baseline to 1 hour and baseline to 2 hours. There were no significant differences in inflammatory cytokines between groups at 2 hours., Conclusion: Withholding fluid resulted in the least significant change in PT, fibrinogen, and maximum amplitude and in the lowest posttreatment blood loss. Resuscitation with different initial fluid resuscitation strategies did not result in increased proinflammatory mediators compared with animals that did not receive fluid.

Background: The purpose of this study was to compare standard gauze (SG) and advanced hemostatic dressings in use by military personnel in a no-hold model., Methods: A randomized, controlled trial was conducted using 36 swine. Animals underwent femoral arteriotomy, followed by 60 seconds of uncontrolled hemorrhage. After hemorrhage, packing with 1 of 3 dressings-SG, Combat Gauze (CG), or Celox Rapid gauze (XG)-and a 500-mL bolus of Hextend were initiated. Pressure was not held after packing, and animals were followed for 120 minutes. Physiologic parameters were monitored continuously, and electrolyte and hematologic laboratory assessments were performed before injury and 30 and 120 minutes after injury. Dressing failure was determined if bleeding occurred outside the wound., Results: All animals survived to study end. Baseline characteristics were similar between groups. No statistical difference was seen in initial blood loss or dressing success rate (SG, 10 of 12; CG, 10 of 12; and XG, 12 of 12). Secondary blood loss was significantly less with XG (median, 12.8 mL; interquartile range, 8.8 to 39.7 mL) compared with SG (median, 44.7 mL; interquartile range, 17.8 to 85.3 mL; P = .02) and CG (median, 31.9 mL; interquartile range, 18.6 to 69.1 mL; P = .05). Packing time was significantly shorter with XG (mean, 37.1 ± 6.2 seconds) compared with SG (mean, 45.2 ± 6.0 seconds; P < .01) and CG (mean, 43.5 ± 5.6 seconds; P = .01)., Conclusions: XG demonstrated shorter application time and decreased secondary blood loss in comparison with both SG and CG. These differences may be of potential benefit in a care-under-fire scenario., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Definitive management of the exsanguinating patient continues to challenge providers in multiple specialties. Significant hemorrhage may be encountered in a variety of patient care circumstances. Over the past two decades, the vast majority of data and evidence regarding transfusion in the exsanguinating patient has been based upon the trauma literature, and a large amount of recent research has investigated this subject area. In addition to the care of trauma patients, the data which have emerged can also be extrapolated to the treatment of nontrauma patients undergoing transfusion for major hemorrhage. The concept of massive transfusion is an evolving paradigm, and numerous investigations have challenged old principles while creating new controversies. The current review will examine the latest developments in the management of patients with profound hemorrhage. The challenges of dealing with the "lethal triad" will be discussed, as will the various aspects of damage control and hemostatic resuscitation. The latest literature and controversy regarding massive transfusions and massive transfusion protocols will be elucidated with inclusion of data from recent military experiences. Finally, adjuncts including the most recent advances in hemorrhage control, identification of early predictors for massive transfusion, and utilization of pharmacologic and complementary factor agent therapy will be discussed.

Objective: To evaluate factors that are predictive of delayed abdominal closure in patients injured during military conflict., Design, Setting, and Patients: Seventy-one patients managed with an open abdomen were identified from records at Landstuhl Regional Medical Center from 2005 and 2006. Follow-up data were available from Walter Reed Army Medical Center. Records were reviewed through all echelons of care. Ordinal logistic regression was used to predict delayed abdominal closure., Results: Patients sustained injury from blunt (n = 2), penetrating (n = 30), and blast (n = 39) mechanisms. The median Injury Severity Score was 25 (interquartile range, 17-34). Abdominal injury was observed in 85% of patients, and 48% underwent a massive transfusion. The median time to transfer to the United States was 5.3 days (interquartile range, 4.3-6.8 days). Abdomens were definitively closed downrange (11%), at Landstuhl Regional Medical Center (33%), or at Walter Reed Army Medical Center (56%). The median time until abdominal closure was 13 days (interquartile range, 4-40 days) in 2005 compared with 4 days (interquartile range, 1-14.5 days) in 2006 (P = .02). The multivariate model identified massive transfusion (odds ratio, 3.9), presence of complications (odds ratio, 5.1), and an injury date in 2005 (odds ratio, 3.4) as independently predictive variables for later abdominal closure., Conclusions: Massive transfusion, occurrence of complications, and earlier injury date were predictive of delayed abdominal closure in casualties managed with an open abdomen. These data suggest an evolving approach to the management of severely injured combat casualties that involves earlier abdominal closure.

Background: The purpose of this study was to analyze whether 2 standard dosing regimens of enoxaparin (30 mg twice daily vs 40 mg once daily) would result in different deep vein thrombosis (DVT) rates and anti-factor Xa activity (anti-Xa) in surgical patients., Methods: Patients who required enoxaparin for prophylaxis were followed prospectively. Demographics were recorded. Patients underwent standardized duplex screening. Peak anti-Xa levels were drawn on 4 consecutive days., Results: Sixty-three patients were followed up (28 patients on 30 mg twice daily, 35 patients on 40 mg once daily). There was no significant difference in demographics between groups. Twenty-five percent of patients on 30 mg twice daily developed a DVT, whereas 2.9% of patients on 40 mg once daily developed a DVT. Patients on 30 mg twice daily had significantly lower anti-Xa levels., Conclusions: The incidence of DVT is increased in surgical patients who receive 30 mg twice daily dosing of enoxaparin compared with 40 mg daily. Dosing of 40 mg once daily results in significantly higher peak anti-Xa levels compared with 30 mg twice daily., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: The optimal fluid strategy for the early treatment of trauma patients remains highly debated. Our objective was to determine the efficacy of an initial bolus of resuscitative fluids used in military and civilian settings on the physiologic response to uncontrolled hemorrhagic shock in a prospective, randomized, blinded animal study., Methods: Fifty anesthetized swine underwent central venous and arterial catheterization followed by celiotomy. Grade V liver injury was performed, followed by 30 minutes of uncontrolled hemorrhage. Then, liver packing was completed, and fluid resuscitation was initiated over 12 minutes with 2 L normal saline (NS), 2 L Lactated Ringer's (LR), 250 mL 7.5% hypertonic saline with 3% Dextran (HTS), 500 mL Hextend (HEX), or no fluid (NF). Animals were monitored for 2 hours postinjury. Blood loss after initial hemorrhage, mean arterial pressure (MAP), tissue oxygen saturation (StO2), hematocrit, pH, base excess, and lactate were measured at baseline, 1 hour, and 2 hours., Results: NF group had less post-treatment blood loss compared with other groups. MAP and StO2 for HEX, HTS, and LR at 1 hour and 2 hours were similar and higher than NF. MAP and StO2 did not differ between NS and NF, but NS resulted in decreased pH and base excess., Conclusions: Withholding resuscitative fluid results in the least amount of posttreatment blood loss. In clinically used volumes, HEX and HTS are equivalent to LR with regard to physiologic outcomes and superior to NF. NS did not provide a measurable improvement in outcome compared with NF and resulted in increased acidosis.

Background: Mesenteric vein thrombosis (MVT) can result in intestinal ischemia and is associated with high morbidity and mortality due in part to its frequent delay in diagnosis. The purpose of this study was to evaluate clinical presentation, diagnostic evaluation, and treatment outcome of MVT., Methods: Hospital records and clinical data of all patients treated for MVT were reviewed during a recent 14-year period. Clinical outcome and factors affecting survival were analyzed., Results: A total of 68 patients were included in the study. Abdominal exploration was performed in 23 patients (34%), and second-look operation was necessary in 18 patients (26%). Three patients (4%) underwent unsuccessful operative mesenteric vein thrombectomy, whereas percutaneous transhepatic mesenteric thrombectomy was performed successfully in 3 patients (4%). The 30-day mortality rate was 20%. Forty-six of the 54 survivors were treated with long-term oral anticoagulation therapy. Actuarial survival at 2, 4, 6, and 10 years was 68%, 57%, 43%, and 22%, respectively. Risk factor analysis showed malignancy (P < .002), age >60 years (P < .005), cirrhosis (P < .02), symptom duration (P < .005), and bowel resection (P < .03) were associated with mortality. Logistic regression analysis showed age >60 years (odds ratio [OR], 3.64; P = .03), malignancy (OR, 3.88; P = .02), and prolonged symptom duration (OR, 5.62; P = .01) were independent predictors of mortality., Conclusions: MVT is associated with significant mortality. Prompt diagnostic evaluation with computed tomography may reduce potential treatment delay. Underlying malignancy, advanced age, and prolonged symptom duration are predictive of poor outcome.

Background: Hemodynamic forces play a crucial role in regulating vascular cell phenotype. However, the underlying molecular mechanisms are largely unknown. The objective of this study was to test our hypothesis that cyclic strain could affect smooth muscle cell (SMC) differentiation., Methods: A murine embryonic mesenchymal progenitor cell line (C3H/10T1/2) was cultured with or without cyclic strain for 6 days. Changes in cell morphology were studied with fluorescence dye Calcein-AM staining. Expression of specific SMC markers, smooth muscle specific alpha-actin (alpha-SMA), and smooth muscle myosin heavy chain (SMMHC), was determined by real-time polymerase chain reaction (PCR) and Western blot. Transforming growth factor- beta (TGF-beta) was used as a positive control., Results: With cyclic strain, CH3/10T1/2 cells demonstrated spindle-shaped morphology and parallel alignment. Cells exposed to cyclic strain illustrated significantly increased mRNA levels of alpha-SMA and SMMHC by 3- and 2-fold, respectively, compared with static cells (P<.05). In addition, cells cultured under cyclic strain with TGF-beta (2 ng/ml) supplementation demonstrated increased mRNA levels of alpha-SMA and SMMHC by 10- and 2-fold, respectively, compared with static cells (P<.05). Furthermore, protein levels of alpha-SMA and SMMHC were also significantly increased by more than 3-fold in cyclic strain-treated cells compared with static cultures (P<.05). TGF-beta synergistically enhanced the effect of cyclic strain on alpha-SMA mRNA expression in CH3/10T1/2 cells., Conclusions: This is the first study to demonstrate that cyclic strain significantly induces expression of two of the most important SMC markers in a murine embryonic mesenchymal progenitor cell line. Cyclic strain and TGF-beta have a synergistic effect on alpha-SMA mRNA expression.

The objective of this study was to determine whether cyclic strain could promote human umbilical vein endothelial cells (HUVECs) to express markers in common with the mature smooth muscle cell (SMC) phenotype, suggesting endothelial cell to SMC transdifferentiation. HUVECs were cultured on stretched membranes at 10% stretch and 60 cycles/min for 24-96 hr, and demonstrated elongation with enhanced and organized F-actin distribution. By using real-time polymerase chain reaction analysis, the mRNA levels of five specific SMC markers, SM22-alpha, alpha-smooth muscle actin (alpha-SMA), caldesmon-1, smooth muscle myosin heavy chain (SMMHC), and calponin-1 were significantly increased in cyclic strain-treated HUVECs as compared with those in static control cells. Protein levels of SM22-alpha and alpha-SMA were also substantially increased by Western blot and immunofluorescence staining. In addition, two specific endothelial markers, von Willebrand factor (vWF) and vascular endothelial growth factor receptor-2 (VEGFR-2), showed a reduction in mRNA expression. In addition, cyclic strain-induced increase of SM22-alpha and alpha-SMA expression were reversible when cells were cultured back to the static condition. These results demonstrate a possible endothelial cell to SMC transdifferentiation in response to cyclic strain. Hemodynamic forces in modulating endothelial phenotype may play an important role in the vascular system.

Smooth muscle cells (SMCs) under shear stress may alter their gene expression patterns to adapt to a new hemodynamic environment. Their plasticity may play an important role in vascular development, healing, and remodeling as well as vascular lesion formation under abnormal environmental conditions. A mouse vascular SMC line (P53LMACO1) cultured under shear stress significantly increased the mRNA levels of endothelial cell markers including Platelet-endothelial cell adhesion molecule-1 (PECAM-1), von Willebrand factor (vWF), and VE-cadherin, while significantly decreasing the mRNA levels of SMC markers including alpha-smooth muscle actin (alpha-SMA), calponin-1, smooth muscle myosin heavy chain (SMMHC), and transgelin as compared to static control cells. Protein levels of PECAM-1 and vWF were significantly increased, while protein levels of alpha-SMA were substantially decreased in the shear stress-cultured cells. In addition, shear stress-cultured cells showed an enhanced capability to form capillary-like structures on Matrigel. Thus, shear stress may promote endothelial cell transdifferentiation from SMCs.

As the prevalence of vascular disease has continued to expand, the need for a suitable arterial replacement has prompted researchers to look beyond synthetic and autologous grafts toward the field of tissue engineering. Advances in vascular tissue engineering have utilized both mesenchymal and hematopoietic stem cells as a cell source in an attempt to create a fully engineered small-diameter graft. Stem cells offer enormous potential as a cell source because of their proliferative and growth potential, and the application of stem cell technology has far-reaching implications for future applications. The innovative use of stem cells for vascular tissue engineering has opened new possibilities for a fully engineered blood vessel. The purpose of this review is to summarize the current perspective on the use of stem cells for vascular tissue engineering. It focuses principally on the classes of stem cells used, techniques for differentiation scaffolding technology, and the successes and failures of models.

Objective: Recent studies have illustrated that mesenchymal stem cells possess the potential to differentiate along an endothelial lineage, but the effect of shear on mesenchymal differentiation is unknown. Thus, we developed an in vitro shear stress system to examine the relationship between shear stress and the endothelial differentiation of a murine embryonic mesenchymal progenitor cell line, C3H/10T1/2., Methods and Results: The parallel plate system of fluid shear stress was used. Shear stress significantly induced expression of mature endothelial cell-specific markers in CH3H/10T1/2 cells such as CD31, von Willebrand factor, and vascular endothelial-cadherin at both the mRNA and protein levels with real-time polymerase chain reaction and immunofluorescence analyses, respectively. In addition, shear-induced augmentation of functional markers of the mature endothelial phenotype such as uptake of acetylated low-density lipoproteins and formation of capillary-like structures on Matrigel. Furthermore, shear stress significantly upregulated angiogenic growth factors while downregulating growth factors associated with smooth muscle cell differentiation., Conclusions: This study demonstrates, for the fist time, endothelial differentiation in a mesenchymal progenitor CH3H/10T1/2 cell line resulting from shear exposure. Thus, this analysis may serve as a basis for further understanding the effect of shear on mesenchymal and vascular cell differentiation.

Background: The isolation, differentiation, and expansion of endothelial progenitor cells (EPCs) from peripheral blood have potential applicability in areas of therapeutic neovascularization, vascular repair, and tissue engineering. The purpose of the current study was to elucidate a simple method of isolation and differentiation of EPCs by defining the endothelial morphology, surface marker expression, and proliferative capacity of EPC outgrowth from canine peripheral blood mononuclear cells (PBMCs)., Materials and Methods: PBMCs were isolated from fresh canine blood and cultured in fibronectin-coated plates in which EPCs were identified from cell morphology and outgrowth characteristics. Cell surface markers were determined with flow cytometry analysis to identify differentiation of cultured and subcultured colonies. A hematologic counter with phase contrast microscopy was used to study cell growth curves of EPCs as compared with mature human coronary artery endothelial cells., Results: During the first week of canine PBMC culture, cells were morphologically round and varied in size, but in the course of the second and third week of culture, the cells, respectively, became spindle-shaped and displayed an endothelium-like cobblestone morphology with outgrowth. CD34 was significantly decreased at 21 days as compared with 7 days culture (36.04% to 21.37%), whereas vWF (from 77.26% to 96.37%) and eNOS (from 0% to 14.97%) were significantly increased. VEGFR-2 was slightly increased, and P1H12 (CD146) was unchanged. Subcultured canine EPCs displayed a higher proliferation rate as compared to mature human coronary artery endothelial cells in the same culture conditions., Conclusions: These data demonstrate that canine EPCs can be isolated and cultured from the canine PBMC fraction. These outgrowth cells displayed characteristics of endothelial morphology with endothelial cell-specific surface markers. Furthermore, it was revealed that canine EPCs have a greater growth potential as compared to mature endothelial cells. This study suggests that PBMCs could be used as a source of EPCs for potential applications in tissue engineering and vascular therapy.

The pulsatile nature of blood flow is a key stimulus for the modulation of vascular cell differentiation. Within the vascular media, physiologic stress is manifested as cyclic strain, while in the lumen, cells are subjected to shear stress. These two respective biomechanical forces influence the phenotype and degree of differentiation or proliferation of smooth muscle cells and endothelial cells within the human vasculature. Elucidation of the effect of these mechanical forces on cellular differentiation has led to a surge of research into this area because of the implications for both the treatment of atherosclerotic disease and the future of vascular tissue engineering. The use of mechanical force to directly control vascular cell differentiation may be utilized as an invaluable engineering tool in the future. However, an understanding of the role of hemodynamics in vascular cell differentiation and proliferation is critical before application can be realized. Thus, this review will provide a current perspective on the latest research and controversy behind the role of hemodynamic forces for vascular cell differentiation and phenotype modulation. Furthermore, this review will illustrate the application of hemodynamic force for vascular tissue engineering and explicate future directions for research.