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

Inter- and Intra-donor variability in bone marrow-derived mesenchymal stromal cells: implications for clinical applications

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) are attractive as a therapeutic modality in multiple disease conditions characterized by inflammation and vascular compromise. Logistically they are advantageous because they can be isolated from adult tissue sources, such as bone marrow (BM). The phase 2a START clinical trial determined BM-MSCs to be safe in patients with moderate-to-severe acute respiratory distress syndrome (ARDS). Herein, we examine a subset of the clinical doses of MSCs generated for the phase 2a START trial from three unique donors (1-3), where one of the donors' donated BM on two separate occasions (donor 3 and 3W).

METHODS

The main objective of this study was to correlate properties of the cells from the four lots with plasma biomarkers from treated patients and relevant to ARDS outcomes. To do this we evaluated MSC donor lots for (i) post-thaw viability, (ii) growth kinetics, (iii) metabolism, (iv) surface marker expression, (v) protein expression, (vi) immunomodulatory ability and (vii) their functional effects on regulating endothelial cell permeability.

RESULTS

MSC-specific marker expression and protection of thrombin-challenged endothelial barrier permeability was similar among all four donor lots. Inter and intra-donor variability was observed in all the other in vitro assays. Furthermore, patient plasma ANG-2 and protein C levels at 6 hours post-transfusion were correlated to cell viability in an inter- and intra-donor dependent manner.

CONCLUSIONS

These findings highlight the potential of donor dependent (inter-) and collection dependent (intra-) effects in patient biomarker expression.

Evaluating Thera-101 as a Low-Volume Resuscitation Fluid in a Model of Polytrauma

Traumatic brain injury (TBI) and hemorrhage remain challenging to treat in austere conditions. Developing a therapeutic to mitigate the associated pathophysiology is critical to meet this treatment gap, especially as these injuries and associated high mortality are possibly preventable. Here, Thera-101 (T-101) was evaluated as low-volume resuscitative fluid in a rat model of TBI and hemorrhage. The therapeutic, T-101, is uniquely situated as a TBI and hemorrhage intervention. It contains a cocktail of proteins and microvesicles from the secretome of adipose-derived mesenchymal stromal cells that can act on repair and regenerative mechanisms associated with poly-trauma. T-101 efficacy was determined at 4, 24, 48, and 72 h post-injury by evaluating blood chemistry, inflammatory chemo/cytokines, histology, and diffusion tensor imaging. Blood chemistry indicated that T-101 reduced the markers of liver damage to Sham levels while the levels remained elevated with the control (saline) resuscitative fluid. Histology supports the potential protective effects of T-101 on the kidneys. Diffusion tensor imaging showed that the injury caused the most damage to the corpus callosum and the fimbria. Immunohistochemistry suggests that T-101 may mitigate astrocyte activation at 72 h. Together, these data suggest that T-101 may serve as a potential field deployable low-volume resuscitation therapeutic.

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.

Flow Cytometric Analysis of Hematopoietic Populations in Rat Bone Marrow. Impact of Trauma and Hemorrhagic Shock

Severe injury and hemorrhagic shock (HS) result in multiple changes to hematopoietic differentiation, which contribute to the development of immunosuppression and multiple organ failure (MOF). Understanding the changes that take place during the acute injury phase may help predict which patients will develop MOF and provide potential targets for therapy. Obtaining bone marrow from humans during the acute injury phase is difficult so published data are largely derived from peripheral blood samples, which infer bone marrow changes that reflect the sustained inflammatory response. This preliminary and opportunistic study investigated leucopoietic changes in rat bone marrow 6 h following traumatic injury and HS. Terminally anesthetized male Porton Wistar rats were allocated randomly to receive a sham operation (cannulation with no injury) or femoral fracture and HS. Bone marrow cells were flushed from rat femurs and immunophenotypically stained with specific antibody panels for lymphoid (CD45R, CD127, CD90, and IgM) or myeloid (CD11b, CD45, and RP-1) lineages. Subsequently, cell populations were fluorescence-activated cell sorted for morphological assessment. Stage-specific cell populations were identified using a limited number of antibodies, and leucopoietic changes were determined 6 h following trauma and HS. Myeloid subpopulations could be identified by varying levels CD11b expression, CD45, and RP-1. Trauma and HS resulted in a significant reduction in total CD11b + myeloid cells including both immature (RP-1(-)) and mature (RP-1+) granulocytes. Multiple B-cell lymphoid subsets were identified. The total percentage of CD90+ subsets remained unchanged following trauma and HS, but there was a reduction in the numbers of maturing CD90(-) cells suggesting movement into the periphery. © 2019 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

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.

Mesenchymal stromal cell plasticity and the tumor microenvironment

Mesenchymal stem cells or mesenchymal stromal cells (MSCs) are a multipotent, heterogeneous population of cells that play a critical role in wound healing and tissue regeneration. MSCs, found in the tumor microenvironment, support tumor growth through the production of angiogenic factors, growth factors and extracellular matrix proteins. They also have immunomodulatory properties, and since they produce indoleamine 2,3-dioxygenase (IDO), prostaglandin E2 (PGE2) and transforming growth factor β (TGF-β), they have been thought to have primarily immunosuppressive effects. However, their role in the tumor microenvironment is complex and demonstrates plasticity depending on location, stimulatory factors and environment. The presence of melanoma-activated tumor-infiltrating lymphocytes (TILs) has been shown to produce pro-inflammatory changes with TH1 (type 1T helper)-like phenotype in MSCs via activated-TIL released cytokines such as interferon γ (IFN-γ), tumor necrosis factor α (TNF-α) and interleukin-1α (IL-1α), while simultaneously producing factors, such as IDO1, which have been traditionally associated with immunosuppression. Similarly, the combination of IFN-γ and TNF-α polarizes MSCs to a primarily TH1-like phenotype with the expression of immunosuppressive factors. Ultimately, further studies are encouraged and needed for a greater understanding of the role of MSCs in the tumor microenvironment and to improve cancer immunotherapy.