Cellular Therapies in Trauma and Critical Care Medicine: Forging New Frontiers

Regulation of vascular endothelial integrity by mesenchymal stem cell extracellular vesicles after hemorrhagic shock and trauma

BACKGROUND

Patients with hemorrhagic shock and trauma (HS/T) are vulnerable to the endotheliopathy of trauma (EOT), characterized by vascular barrier dysfunction, inflammation, and coagulopathy. Cellular therapies such as mesenchymal stem cells (MSCs) and MSC extracellular vesicles (EVs) have been proposed as potential therapies targeting the EOT. In this study we investigated the effects of MSCs and MSC EVs on endothelial and epithelial barrier integrity in vitro and in vivo in a mouse model of HS/T. This study addresses the systemic effects of HS/T on multiorgan EOT.

METHODS

In vitro, pulmonary endothelial cell (PEC) and Caco-2 intestinal epithelial cell monolayers were treated with control media, MSC conditioned media (CM), or MSC EVs in varying doses and subjected to a thrombin or hydrogen peroxide (H2O2) challenge, respectively. Monolayer permeability was evaluated with a cell impedance assay, and intercellular junction integrity was evaluated with immunofluorescent staining. In vivo, a mouse model of HS/T was used to evaluate the effects of lactated Ringer's (LR), MSCs, and MSC EVs on endothelial and epithelial intercellular junctions in the lung and small intestine as well as on plasma inflammatory biomarkers.

RESULTS

MSC EVs and MSC CM attenuated permeability and preserved intercellular junctions of the PEC monolayer in vitro, whereas only MSC CM was protective of the Caco-2 epithelial monolayer. In vivo, both MSC EVs and MSCs mitigated the loss of endothelial adherens junctions in the lung and small intestine, though only MSCs had a protective effect on epithelial tight junctions in the lung. Several plasma biomarkers including MMP8 and VEGF were elevated in LR- and EV-treated but not MSC-treated mice.

CONCLUSIONS

In conclusion, MSC EVs could be a potential cell-free therapy targeting endotheliopathy after HS/T via preservation of the vascular endothelial barrier in multiple organs early after injury. Further research is needed to better understand the immunomodulatory effects of these products following HS/T and to move toward translating these therapies into clinical studies.

Regulation of Vascular Endothelial Integrity by Mesenchymal Stem Cell Extracellular Vesicles after Hemorrhagic Shock and Trauma

BACKGROUND

Patients with hemorrhagic shock and trauma (HS/T) are vulnerable to the endotheliopathy of trauma (EOT), characterized by vascular barrier dysfunction, inflammation, and coagulopathy. Cellular therapies such as mesenchymal stem cells (MSCs) and MSC extracellular vesicles (EVs) have been proposed as potential therapies targeting the EOT. In this study we investigated the effects of MSCs and MSC EVs on endothelial and epithelial barrier integrity in vitro and in vivo in a mouse model of HS/T. This study addresses systemic effects of HS/T on multiorgan EOT in HS/T model.

METHODS

In vitro, pulmonary endothelial cell (PEC) and Caco-2 intestinal epithelial cell monolayers were treated with control media, MSC conditioned media (CM), or MSC EVs in varying doses and subjected to a thrombin or hydrogen peroxide (H2O2) challenge, respectively. Monolayer permeability was evaluated with a cell impedance assay, and intercellular junction integrity was evaluated with immunofluorescent staining. In vivo, a mouse model of HS/T was used to evaluate the effects of lactated Ringer's (LR), MSCs, and MSC EVs on endothelial and epithelial intercellular junctions in the lung and small intestine as well as on plasma inflammatory biomarkers.

RESULTS

MSC EVs and MSC CM attenuated permeability and preserved intercellular junctions of the PEC monolayer in vitro, whereas only MSC CM was protective of the Caco-2 epithelial monolayer. In vivo, both MSC EVs and MSCs mitigated the loss of endothelial adherens junctions in the lung and small intestine, though only MSCs had a protective effect on epithelial tight junctions in the lung. Several plasma biomarkers including MMP8 and VEGF were elevated in LR- and EV-treated but not MSC-treated mice.

CONCLUSIONS

In conclusion, MSC EVs could be a potential cell-free therapy targeting endotheliopathy after HS/T via preservation of the vascular endothelial barrier in multiple organs early after injury. Further research is needed to better understand the immunomodulatory effects of these products following HS/T and to move toward translating these therapies into clinical studies.

Investigational Therapies for Gunshot Wounds to the Spine: A Narrative Review

STUDY DESIGN

This was a narrative review.

OBJECTIVE

The objective of this study was to review the standards of care and triage protocol for gunshot wounds to the spine, highlighting innovative future treatment options that may be implemented in patients with spinal cord injury (SCI).

SUMMARY OF BACKGROUND DATA

With the increased availability of firearms among the United States population, gunshot wounds to the spine are becoming a clinically relevant and devastating issue. Such injuries result in severe and diverse complications. SCIs due to gunshot wounds are the leading cause of morbidity and mortality, as they often result in complete or incomplete paraplegia. Current standards of care focus on preventing further damage rather than total cure or treatment of SCI.

METHODS

A literature review was performed on the standards of care, triage protocol, associated conditions, current therapeutic options, and innovative treatment options for patients with gunshot wounds to the spine.

RESULTS

The general standards of care for spinal gunshot wounds involve maintaining or renewal of mechanical spinal steadiness and neurological activity while limiting complications of treatment. Current treatment options include management of mean arterial pressure goals, drug therapies consisting of antibiotics, and surgical approaches. With recent innovations in molecular biology and cell transplantation, potentially new and promising treatment options for patients with SCI exist. These options include cell transplantation therapies, platelet-rich plasma administration, exosomal treatments, and mitochondrial-targeted therapeutics. Stem cell transplantation is promising, as several clinical studies have been completed. However, loss-to-follow-up, lack of long-term evaluation, and questionable randomization has limited the use of stem cells in the standard of care practice. Although not studied on human models to a gunshot wound, exosomal and mitochondrial-based treatment options have been studied both in vitro and in animal models with SCI.

CONCLUSION

Newly emerging molecular and cellular therapy modalities for SCI contribute to the recovery process and may be utilized in conjunction with the current modalities for better outcomes.

A Limited Role for AMD3100 Induced Stem Cell Mobilization for Modulation of Thoracic Trauma Outcome

ABSTRACT

Thoracic trauma is a major cause of mortality due to the associated inflammatory acute respiratory distress syndrome and morbidity due to impaired tissue regeneration. Trauma-induced lung inflammation is characterized by the early recruitment of cells with pro- or anti-inflammatory activity to the lung. Therapeutic interventions reducing the level of tissue inflammation may result in decreased tissue damage and improved healing and recovery. Stem cells might be able to improve trauma outcome via immunomodulation or by enhancing tissue regeneration.Here, we describe the migratory dynamics of murine mesenchymal, hematopoietic and endothelial stem and progenitor cells (SPCs) as well as mature inflammatory cells (monocytes, neutrophils, lymphocytes) to peripheral blood (PB) and lung tissue between 0.2 and 48 h post-blunt chest trauma (TXT). We demonstrate that the kinetics of immune cell and SPC distribution upon trauma are both cell-type and tissue-dependent. We identified a transient, early increase in the number of inflammatory cells in PB and lung at 2 h post-TXT and a second wave of infiltrating SPCs in lungs by 48 h after TXT induction, suggesting a role for SPCs in tissue remodeling after the initial inflammatory phase. Cxcl12/Cxcr4 blockade by AMD3100 within the first 6 h after TXT, while inducing a strong and coordinated mobilization of SPCs and leukocytes to PB and lung tissue, did not significantly affect TXT associated inflammation or tissue damage as determined by inflammatory cytokine levels, plasma markers for organ function, lung cell proliferation and survival, and myofibroblast/fibroblast ratio in the lung. Further understanding the dynamics of the distribution of endogenous SPCs and inflammatory cells will therefore be indispensable for stem cell-based or immunomodulation therapies in trauma.

Mesenchymal stem cell extracellular vesicles mitigate vascular permeability and injury in the small intestine and lung in a mouse model of hemorrhagic shock and trauma

BACKGROUND

Hemorrhagic shock and trauma (HS/T)-induced gut injury may play a critical role in the development of multi-organ failure. Novel therapies that target gut injury and vascular permeability early after HS/T could have substantial impacts on trauma patients. In this study, we investigate the therapeutic potential of human mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (MSC EVs) in vivo in HS/T in mice and in vitro in Caco-2 human intestinal epithelial cells.

METHODS

In vivo, using a mouse model of HS/T, vascular permeability to a 10-kDa dextran dye and histopathologic injury in the small intestine and lungs were measured among mice. Groups were (1) sham, (2) HS/T + lactated Ringer's (LR), (3) HS/T + MSCs, and (4) HS/T + MSC EVs. In vitro, Caco-2 cell monolayer integrity was evaluated by an epithelial cell impedance assay. Caco-2 cells were pretreated with control media, MSC conditioned media (CM), or MSC EVs, then challenged with hydrogen peroxide (H2O2).

RESULTS

In vivo, both MSCs and MSC EVs significantly reduced vascular permeability in the small intestine (fluorescence units: sham, 456 ± 88; LR, 1067 ± 295; MSC, 765 ± 258; MSC EV, 715 ± 200) and lung (sham, 297 ± 155; LR, 791 ± 331; MSC, 331 ± 172; MSC EV, 303 ± 88). Histopathologic injury in the small intestine and lung was also attenuated by MSCs and MSC EVs. In vitro, MSC CM but not MSC EVs attenuated the increased permeability among Caco-2 cell monolayers challenged with H2O2.

CONCLUSION

Mesenchymal stem cell EVs recapitulate the effects of MSCs in reducing vascular permeability and injury in the small intestine and lungs in vivo, suggesting MSC EVs may be a potential cell-free therapy targeting multi-organ dysfunction in HS/T. This is the first study to demonstrate that MSC EVs improve both gut and lung injury in an animal model of HS/T.

Therapeutic Applications of Stem Cells and Extracellular Vesicles in Emergency Care: Futuristic Perspectives

Regenerative medicine (RM) is an interdisciplinary field that aims to repair, replace or regenerate damaged or missing tissue or organs to function as close as possible to its physiological architecture and functions. Stem cells, which are undifferentiated cells retaining self-renewal potential, excessive proliferation and differentiation capacity into offspring or daughter cells that form different lineage cells of an organism, are considered as an important part of the RM approaches. They have been widely investigated in preclinical and clinical studies for therapeutic purposes. Extracellular vesicles (EVs) are the vital mediators that regulate the therapeutic effects of stem cells. Besides, they carry various types of cargo between cells which make them a significant contributor of intercellular communication. Given their role in physiological and pathological conditions in living cells, EVs are considered as a new therapeutic alternative solution for a variety of diseases in which there is a high unmet clinical need. This review aims to summarize and identify therapeutic potential of stem cells and EVs in diseases requiring acute emergency care such as trauma, heart diseases, stroke, acute respiratory distress syndrome and burn injury. Diseases that affect militaries or societies including acute radiation syndrome, sepsis and viral pandemics such as novel coronavirus disease 2019 are also discussed. Additionally, featuring and problematic issues that hamper clinical translation of stem cells and EVs are debated in a comparative manner with a futuristic perspective. Graphical Abstract.

Immunotherapeutic options for inflammation in trauma

BACKGROUND

Surgical management of trauma in the last 20 years has evolved in parallel with the military's experience in the current conflicts. Therapies such as widespread tourniquet use, empiric administration of fresh frozen plasma, and airborne intensive care units had been viewed skeptically but are now common practice. There is an opportunity to expand the envelope of care even further through similarly innovative approaches and varied avenues of research.

RESULTS

As the molecular biology of trauma is elucidated, research methodologies must also be developed to capitalize on innovative approaches to resuscitation. Blood component therapy and control of bleeding remain as the fundamental concepts in trauma care. The inflammo-immune response to injury, however, plays an increasingly recognized role in recovery of organ function. Perhaps the inflammatory cascade of trauma can be manipulated to extend the treatment envelope of at risk trauma patients.In trauma, the additional challenge of delivering effective treatment, often required very early after injury, necessitates the development of treatments to be implemented on the front lines of trauma care that are cost-effective, portable, and environmentally stable. Future conflicts may not offer ready access to high-level surgical care; therefore, resuscitative therapies will be needed for wounded service members because they are evacuated to the surgeon. Manipulation of the inflammatory response to trauma may offer a solution. As our understanding of the immune response continues to develop, the potential for improved outcomes for the wounded expands.

CONCLUSION

A review of basic concepts in immunology is necessary to appreciate any potential impact of immunotherapeutic approaches to trauma and inflammation. An overview of current options will focus on outcome benefits of available therapies and suggest possible areas for future investigation. Quantitative approaches will leverage basic science to identify high-yield strategies to improve care of the injured combatant.

LEVEL OF EVIDENCE

Review, level III.

Neglected No More: Emerging Cellular Therapies in Traumatic Injury

Traumatic injuries are a leading cause of death and disability in both military and civilian populations. Given the complexity and diversity of traumatic injuries, novel and individualized treatment strategies are required to optimize outcomes. Cellular therapies have potential benefit for the treatment of acute or chronic injuries, and various cell-based pharmaceuticals are currently being tested in preclinical studies or in clinical trials. Cellular therapeutics may have the ability to complement existing therapies, especially in restoring organ function lost due to tissue disruption, prolonged hypoxia or inflammatory damage. In this article we highlight the current status and discuss future directions of cellular therapies for the treatment of traumatic injury. Both published research and ongoing clinical trials are discussed here.

Use of multiple potency assays to evaluate human mesenchymal stromal cells

BACKGROUND

There is broad interest in the use of cell therapies and cell products for treatment of a variety of diseases and problems. Of interest to the military, cellular therapies have the potential to confer tremendous benefit for treatment of both acute and chronic injuries. Although many different cell therapy products are currently under investigation, mesenchymal stromal cells (MSCs) are good candidates, based on their ability to respond to inflammation, limit vascular permeability, and modulate immune responses to injury. Although a large number of clinical trials utilize MSCs or their products, there is no firm consensus defining the characteristics and activities of a good MSC product. Here, we test multiple human MSCs in several assays designed to test potency, to determine if functionally relevant differences between MSCs can be defined using in vitro assays, allowing identification of superior MSC products for preclinical or clinical testing.

METHODS

Human MSCs derived from several tissue sources (adipose, bone marrow, umbilical cord) were evaluated for their ability to respond to inflammatory signaling by upregulating indoleamine-2,3-dioxygenase and TSG6, suppress lymphocyte proliferation, alter the polarization of macrophages, and affect tube formation by endothelial cells.

RESULTS

All MSCs tested displayed activity in the functional assays utilized, but differences in potency were observed in each assay.

CONCLUSION

The indoleamine-2,3-dioxygenase enzyme activity assay represents a simple way to screen multiple samples. The mixed lymphocyte reaction and monocyte assays used to test interactions between MSCs and immune cells are more involved but give direct information on immunomodulation potential. The endothelial cell tube formation assay is relatively simple to perform but a large number of images must be generated and analyzed. However, it tests a functional activity other than immunomodulation and, therefore, adds another facet to MSC evaluation.

Down-Regulation of miR-301a-3p Reduces Burn-Induced Vascular Endothelial Apoptosis by potentiating hMSC-Secreted IGF-1 and PI3K/Akt/FOXO3a Pathway

Vascular endothelium dysfunction plays a pivotal role in the initiation and progression of multiple organ dysfunction. The mesenchymal stem cell (MSC) maintains vascular endothelial barrier survival via secreting bioactive factors. However, the mechanism of human umbilical cord MSC (hMSC) in protecting endothelial survival remains unclear. Here, we found IGF-1 secreted by hMSC suppressed severe burn-induced apoptosis of human umbilical vein endothelial cells (HUVECs) and alleviated the dysfunction of vascular endothelial barrier and multiple organs in severely burned rats. Severe burn repressed miR-301a-3p expression, which directly regulated IGF-1 synthesis and secretion in hMSC. Down-regulation of miR-301a-3p decreased HUVECs apoptosis, stabilized endothelial barrier permeability, and subsequently protected against multiple organ dysfunction in vivo. Additionally, miR-301a-3p negatively regulated PI3K/Akt/FOXO3 signaling through IGF-1. Taken together, our study highlights the protective function of IGF-1 against the dysfunction of multiple organs negatively regulated by miR-301a-3p, which may provide the theoretical foundation for further clinical application of hMSC.

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IGF-1 secreted by hMSC suppressed severe burn-induced apoptosis of HUVECs

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miR-301a-3p directly regulated IGF-1 synthesis and secretion in hMSC

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DomiR-301a-3p protected against multiple organ dysfunction

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miR-301a-3p regulated PI3K/Akt/FOXO3 signaling through hMSC-secreted IGF-1

Mesenchymal stromal cell and bone marrow concentrate therapies for musculoskeletal indications: a concise review of current literature

The interest on applying mesenchymal stromal cells (MSCs) in orthopedic disorders has risen tremendously in the last years due to scientific successes in preclinical in vitro and animal model studies. In a wide range of diseases and injuries of the musculoskeletal system, MSCs are currently under evaluation, but so far have found access to clinical use only in few cases. The current assignment is to translate the acquired knowledge into clinical practice. Therefore, this review aims at presenting a synopsis of the up-to-date status of the use of MSCs and MSC related cell products in musculoskeletal indications. Clinical studies were included, whereas preclinical and animal study data not have been considered. Most studies published so far investigate the final outcome applying bone marrow derived MSCs. In fewer trials the use of adipose tissue derived MSCs and allogenic MSCs was investigated in different applications. Although the reported results are equivocal in the current literature, the vast majority of the studies shows a benefit of MSC based therapies depending on the cell sources and the indication in clinical use. In summary, the clinical use of MSCs in patients in orthopedic indications has been found to be safe. Standardized protocols and clear definitions of the mechanisms of action and the mode and timing of application as well as further coordinated research efforts will be necessary for finally adding MSC based therapies in standard operating procedures and guidelines for the clinicians treating orthopedic disorders.

Application of Bone Marrow-Derived Mesenchymal Stem Cells for Muscle Healing After Contusion Injury in Mice

BACKGROUND

Skeletal muscle injuries are very common in sports medicine. Conventional therapies have limited clinical efficacy. New treatment methods should be developed to allow athletes to return to play with better function.

PURPOSE

To evaluate the in vitro differentiation potential of bone marrow-derived mesenchymal stem cells and the in vivo histologic and physiologic effects of mesenchymal stem cell therapy on muscle healing after contusion injury.

STUDY DESIGN

Controlled laboratory study.

METHODS

Bone marrow cells were flushed from both femurs of 5-week-old C57BL/6 mice to establish immortalized mesenchymal stem cell lines. A total of 36 mice aged 8 to 10 weeks were used to develop a muscle contusion model and were divided into 6 groups (6 mice/group) on the basis of the different dosages of IM2 cells to be injected (0, 1.25 × 10⁵, and 2.5 × 10⁵ cells with/without F-127 in 100 μL of phosphate-buffered saline). Histological analysis of muscle regeneration was performed, and the fast-twitch and tetanus strength of the muscle contractions was measured 28 days after muscle contusion injury, after injections of different doses of mesenchymal stem cells with or without the F-127 scaffold beginning 14 days after contusion injury.

RESULTS

The mesenchymal stem cell-treated muscles exhibited numerous regenerating myofibers. All the groups treated with mesenchymal stem cells (1.25 × 10⁵ cells, 2.5 × 10⁵ cells, 1.25 × 10⁵ cells plus F-127, and 2.5 × 10⁵ cells plus F-127) exhibited a significantly higher number of regenerating myofibers (mean ± SD: 111.6 ± 14.77, 133.4 ± 21.44, 221.89 ± 32.65, and 241.5 ± 25.95, respectively) as compared with the control group and the control with F-127 (69 ± 18.79 and 63.2 ± 18.98). The physiologic evaluation of fast-twitch and tetanus strength did not reveal differences between the age-matched uninjured group and the groups treated with various doses of mesenchymal stem cells 28 days after contusion. Significant differences were found between the control group and the groups treated with various doses of mesenchymal stem cells after muscle contusion.

CONCLUSION

Mesenchymal stem cell therapy increased the number of regenerating myofibers and improved fast-twitch and tetanus muscle strength in a mouse model of muscle contusion. However, the rapid decay of transplanted mesenchymal stem cells suggests a paracrine effect of this action. Treatment with mesenchymal stem cells at various doses combined with the F-127 scaffold is a potential therapy for a muscle contusion.

CLINICAL RELEVANCE

Mesenchymal stem cell therapy has an effect on sports medicine because of its effects on myofiber regeneration and muscle strength after contusion injury.

Freeze-Dried Extracellular Vesicles From Adipose-Derived Stem Cells Prevent Hypoxia-Induced Muscle Cell Injury

Cellular therapies have tremendous potential for the successful treatment of major extremity wounds in the combat setting, however, the challenges associated with transplanting stem cells in the prolonged field care (PFC) environment are a critical barrier to progress in treating such injuries. These challenges include not only production and storage but also transport and handling issues. Our goal is to develop a new strategy utilizing extracellular vesicles (EVs) secreted by stem cells that can resolve many of these issues and prevent ischemic tissue injury. While EVs can be preserved by freezing or lyophilization, both processes result in decrease in their bioactivity. Here, we describe optimized procedures for EVs production, isolation, and lyophilization from primary human adipose-derived stem cells (hADSCs). We compared two isolation approaches that were ultrafiltration (UF) using a tangential fluid filtration (TFF) system and differential ultracentrifugation (UC). We also optimized EVs lyophilization in conjunction with trehalose and polyvinylpyrrolidone 40 (PVP40) as lyoprotectants. Bioactivity of EVs was assessed based on reversal of hypoxia-induced muscle cell injury. To this end, primary human myoblasts were subjected to hypoxic conditions for 6 h, and then treated with hADSC-derived EVs at a concentration of 50 μg/mL. Subsequently, muscle cell viability and toxicity were evaluated using MTS and LDH assays, respectively. Overall, nanoparticle tracking data indicated that UF/TFF yields threefold more particles than UC. Lyophilization of EVs resulted in a significantly reduced number of particles, which could be attenuated by adding lyoprotections to the freeze-drying solution. Furthermore, EVs isolated by UF/TFF and freeze-dried in the presence of trehalose significantly increased viability (P < 0.0193). Taken together, our findings suggest that the isolation and preservation methods presented in this study may enhance therapeutic applications of EVs.

Human primary fibroblasts perform similarly to MSCs in assays used to evaluate MSC safety and potency

BACKGROUND

Cellular therapeutic agents may benefit trauma patients by modulating the immune response to injury, and by reducing inflammation and vascular leakage. Administration of allogeneic mesenchymal stromal cells (MSCs) shows some benefit in preclinical and clinical trials, but less testing has been performed with other cell types. Human primary fibroblasts (FBs) were compared to MSCs in assays designed to evaluate MSCs to determine if these assays actually evaluate properties unique to MSCs or whether related cell types perform similarly.

STUDY DESIGN AND METHODS

MSC-related surface marker expression, tissue factor, and human leukocyte antigen-D related were evaluated by flow cytometry, and in vitro adipogenic and osteogenic differentiation potential were determined. Procoagulant activity was determined by thromboelastography. Two potency assays correlated with immunomodulation potential were utilized: the mixed lymphocyte reaction and indoleamine 2,3-dioxygenase enzyme activity assays.

RESULTS

Human primary FBs performed similarly to MSCs in assays designed to evaluate MSC characteristics and potency. Although similar for MSC-positive cell surface marker expression, FBs did not show robust adipose differentiation and expressed some level of markers not expected on MSCs.

CONCLUSIONS

Human primary FBs are very similar to human MSCs, at least in assays currently used to evaluate MSC potency. Preclinical and clinical testing are required to determine if FBs show similar activity to MSCs in vivo. If FBs show inferior activity in vivo, development of new MSC-specific potency assays will be necessary to evaluate properties relevant to their unique clinical benefits.

Human-induced pluripotent stem cells derived hematopoietic progenitor cells for treatment of hematopoietic failure among trauma hemorrhagic shock patients

Hematopoietic failure (HF) has been observed in trauma hemorrhagic shock (T/HS) patients. Multiple factors are involved. Elevated serum levels of cytokines, catecholamine, granulocyte colony stimulating factor, peripheral blood hematopoietic progenitor cells (HPCs) and decreased expression of erythropoietin receptor are associated with HF among T/HS. HF leads to anaemia, susceptibility to infection, sepsis and multi-organ failure. There is a lack of molecular understanding of HF and its potential therapeutic strategies. Cell-based therapy has ability to modulate the production of inflammatory cytokines, vascular dysfunction, tissue damage and apoptosis. Human-induced pluripotent stem cells (iPSC) derived HPCs may have the ability to restore HF in T/HS. Autologous cell-based iPSC have great promises for various diseases such as Alzheimer's disease, Parkinson's disease, cardiovascular disease, diabetes, amyotrophic lateral sclerosis, and spinal cord injury without ethical concerns. Similarly, treatment with iPSC derived hematopoietic stem cells can used for the treatment of HF among T/HS and may also improve the outcome. Here, we review the potential of human iPSC derived HSC to reversed HF following T/HS.

Barriers to clinical research in trauma

As with all areas of medicine, high-quality clinical research is essential to improving the care of trauma patients. This research is crucial in developing evidence-based treatments that decrease cost, decrease morbidity, and improve mortality. Trauma continues to extract a significant toll on society and is the single largest cause of years of life lost in the United States. The need to conduct high-quality clinical research in trauma is not disputed. However, significant challenges and barriers unique to the field of trauma make performing this research more difficult. It is critical to be aware of these challenges and barriers to performing clinical research involving trauma patients so these challenges can be accounted for and solutions implemented to minimize their impact on research. This review will focus on the barriers and challenges that are encountered while performing clinical research in trauma.

Regenerative medicine and war: a front-line focus for UK defence

The recent prolonged conflicts in Iraq and Afghanistan saw the advancement of deployed trauma care to a point never before seen in war. The rapid translation of lessons from combat casualty care research, facilitated by an appetite for risk, contributed to year-on-year improvements in care of the injured. These paradigms, however, can only ever halt the progression of damage. Regenerative medicine approaches, in contrast, hold a truly disruptive potential to go beyond the cessation of damage from blast or ballistic trauma, to stimulate its reversal, and to do so from a very early point following injury. The internationally distributed and, in parts austere environments in which operational medical care is delivered provide an almost unique challenge to the development and translation of regenerative medicine technologies. In parallel, however, an inherent appetite for risk means that Defence will always be an early adopter. In focusing our operational priorities for regenerative medicine, the authors conducted a review of the current research landscape in the UK and abroad and sought wide clinical opinion. Our priorities are all applicable very far forward in the patient care pathway, and are focused on three broad and currently under-researched areas, namely: (a) blood, as an engineered tissue; (b) the mechanobiology of deep tissue loss and mechanobiological approaches to regeneration, and; (c) modification of the endogenous response. In focusing on these areas, we hope to engender the development of regenerative solutions for improved functional recovery from injuries sustained in conflict.

Mesenchymal stem cell-derived extracellular vesicles attenuate pulmonary vascular permeability and lung injury induced by hemorrhagic shock and trauma

BACKGROUND

Mesenchymal stem cells (MSCs) have been shown to mitigate vascular permeability in hemorrhagic shock (HS) and trauma-induced brain and lung injury. Mechanistically, paracrine factors secreted from MSCs have been identified that can recapitulate many of the potent biologic effects of MSCs in animal models of disease. Interestingly, MSC-derived extracellular vesicles (EVs), contain many of these key soluble factors, and have therapeutic potential independent of the parent cells. In this study we sought to determine whether MSC-derived EVs (MSC EVs) could recapitulate the beneficial therapeutic effects of MSCs on lung vascular permeability induced by HS in mice.

METHODS

Mesenchymal stem cell EVs were isolated from human bone marrow-derived MSCs by ultracentrifugation. A mouse model of fixed pressure HS was used to study the effects of shock, shock + MSCs and shock + MSC EVs on lung vascular endothelial permeability. Mice were administered MSCs, MSC EVs, or saline IV. Lung tissue was harvested and assayed for permeability, RhoA/Rac1 activation, and for differential phosphoprotein expression. In vitro, human lung microvascular cells junctional integrity was evaluated by immunocytochemistry and endothelial cell impedance assays.

RESULTS

Hemorrhagic shock-induced lung vascular permeability was significantly decreased by both MSC and MSC EV infusion. Phosphoprotein profiling of lung tissue revealed differential activation of proteins and pathways related to cytoskeletal rearrangement and regulation of vascular permeability by MSCs and MSC EVs. Lung tissue from treatment groups demonstrated decreased activation of the cytoskeletal GTPase RhoA. In vitro, human lung microvascular cells, MSC CM but not MSC-EVs prevented thrombin-induced endothelial cell permeability as measured by electrical cell-substrate impedance sensing system and immunocytochemistry of VE-cadherin and actin.

CONCLUSION

Mesenchymal stem cells and MSC EVs modulate cytoskeletal signaling and attenuate lung vascular permeability after HS. Mesenchymal stem cell EVs may potentially be used as a novel "stem cell free" therapeutic to treat HS-induced lung injury.

The promise of mesenchymal stem cell therapy for acute respiratory distress syndrome

This review describes the current state of the science on mesenchymal stem cell (MSC) treatment for acute lung injury (ALI). The general characteristics, regenerative potential, and mechanism of action of MSCs are first presented. Next, particular emphasis is placed on the application of MSCs for the treatment of acute respiratory distress syndrome (ARDS) in preclinical and clinical studies. Finally, we discuss current challenges and future directions in the field presented from a clinician-researcher perspective. The objective of this work is to provide the readership with a current review of the literature discussing the hurdles and overall promise of MSCs as therapeutic interventions for the treatment of ARDS.

Procoagulant activity of human mesenchymal stem cells

BACKGROUND

Allogeneic mesenchymal stem cells (MSCs) show great potential for the treatment of military and civilian trauma based on their reduced immunogenicity and ability to modulate inflammation and immune function in the recipient. Although generally considered to be safe, MSCs express tissue factor (TF), a potent activator of coagulation. In the current study, we evaluated multiple MSC populations for tissue factor expression and procoagulant activity to characterize safety considerations for systemic use of MSCs in trauma patients who may have altered coagulation homeostasis.

METHODS

Multiple MSC populations derived from either human adipose tissue or bone marrow were expanded in the recommended stem cell media. Stem cell identity was confirmed using a well-characterized panel of positive and negative markers. Tissue factor expression on the cell surface was evaluated by flow cytometry with anti-CD142 antibody. Effects on blood coagulation were determined by thromboelastography and calibrated automated thrombogram assays using platelet-poor plasma or whole blood.

RESULTS

Mesenchymal stem cells express tissue factor on their surfaces and are procoagulant in the presence of blood or plasma. The adipose-derived MSCs (Ad-MSC) evaluated were more procoagulant and expressed more tissue factor than bone marrow MSCs (BM-MSCs), which showed a greater variability in TF expression. Bone marrow MSCs were identified that exhibited low procoagulant activity, whereas all Ad-MSCs examined exhibited high procoagulant activity. The percentage of cells in a given population expressing surface tissue factor correlates roughly with functional procoagulant activity. Mesenchymal stem cell tissue factor expression and procoagulant activity change over time in culture.

CONCLUSIONS

All MSC populations are not equivalent; care should be taken to select cells for clinical use that minimize potential safety problems and maximize chance of patient benefit. Adipose-derived MSCs seem more consistently procoagulant than BM-MSCs, presenting a potential safety concern for systemic administration in coagulopathic patients. Donor variation exists between different cell populations, and culture handling conditions may also determine coagulation activity. Cells must be routinely monitored during preparation to ensure that they retain the desired characteristics before patient administration.

A novel model of highly lethal uncontrolled torso hemorrhage in swine

INTRODUCTION

A reproducible, lethal noncompressible torso hemorrhage model is important to civilian and military trauma research. Current large animal models balancing clinical applicability with standardization and internal validity. As such, large animal models of trauma vary widely in the surgical literature, limiting comparisons. Our aim was to create and validate a porcine model of uncontrolled hemorrhage that maximizes reproducibility and standardization.

METHODS

Seven Yorkshire-cross swine were anesthetized, instrumented, and splenectomized. A simple liver tourniquet was applied before injury to prevent unregulated hemorrhage while creating a traumatic amputation of 30% of the liver. Release of the tourniquet and rapid abdominal closure following injury provided a standardized reference point for the onset and duration of uncontrolled hemorrhage. At the moment of death, the liver tourniquet was quickly reapplied to provide accurate quantification of intra-abdominal blood loss. Weight and volume of the resected and residual liver segments were measured. Hemodynamic parameters were recorded continuously throughout each experiment.

RESULTS

This liver injury was rapidly and universally lethal (11.2 ± 4.9 min). The volume of hemorrhage (35.8% ± 6% of total blood volume) and severity of uncontrolled hemorrhage (100% of animals deteriorated to a sustained mean arterial pressure <35 mmHg for 5 min) were consistent across all animals. Use of the tourniquet effectively halted preprocedure and postprocedure blood loss allowing for accurate quantification of amount of hemorrhage over a defined period. In addition, the tourniquet facilitated the creation of a consistent liver resection weight (0.0043 ± 0.0003 liver resection weight: body weight) and as a percentage of total liver resection weight (27% ± 2.2%).

CONCLUSIONS

This novel tourniquet-assisted noncompressible torso hemorrhage model creates a standardized, reproducible, highly lethal, and clinically applicable injury in swine. Use of the tourniquet allowed for consistent liver injury and precise control over hemorrhage. Recorded blood loss was similar across all animals. Improving reproducibility and standardization has the potential to offer improvements in large animal translational models of hemorrhage.

LEVEL OF EVIDENCE

Level I.

Major scientific lessons learned in the trauma field over the last two decades

John B Holcomb summarizes recent conceptual and practical advances in trauma care, in both military and civilian settings, and presents directions for future research.

Cellular therapies in trauma and critical care medicine: Looking towards the future

Shibani Pati and Todd Rasmussen summarize progress in preclinical research on cellular therapeutics for traumatic injury and its sequelae and discuss prospects for clinical translation.

Concise Review: Mesenchymal Stem (Stromal) Cells: Biology and Preclinical Evidence for Therapeutic Potential for Organ Dysfunction Following Trauma or Sepsis

Several experimental studies have provided evidence that bone-marrow derived mesenchymal stem (stromal) cells (MSC) may be effective in treating critically ill surgical patients who develop traumatic brain injury, acute renal failure, or the acute respiratory distress syndrome. There is also preclinical evidence that MSC may be effective in treating sepsis-induced organ failure, including evidence that MSC have antimicrobial properties. This review considers preclinical studies with direct relevance to organ failure following trauma, sepsis or major infections that apply to critically ill patients. Progress has been made in understanding the mechanisms of benefit, including MSC release of paracrine factors, transfer of mitochondria, and elaboration of exosomes and microvesicles. Regardless of how well they are designed, preclinical studies have limitations in modeling the complexity of clinical syndromes, especially in patients who are critically ill. In order to facilitate translation of the preclinical studies of MSC to critically ill patients, there will need to be more standardization regarding MSC production with a focus on culture methods and cell characterization. Finally, well designed clinical trials will be needed in critically ill patient to assess safety and efficacy. Stem Cells 2017;35:316-324.