Mesenchymal stromal cells form vascular tubes when placed in fibrin sealant and accelerate wound healing in vivo

Human umbilical cord mesenchymal stem cells combined with porcine small intestinal submucosa promote the healing of full-thickness skin injury in SD rats

Aim: To assess the therapeutic potential of human umbilical cord mesenchymal stem cells (hUCMSCs) combined with porcine small intestinal submucosa (SIS) on full-thickness skin injuries in rats. Methods: We established full-thickness skin injury models in Sprague-Dawley rats, dividing them into blank control, SIS, hUCMSCs and hUCMSCs combined with SIS. We monitored wound healing, scores and area, and analyzed inflammatory cells, microvessel density and collagen fibers after 12 days. Results: The blank group showed no healing, forming a scar of 0.6 × 0.5 cm2, while SIS and hUCMSCs groups exhibited incomplete healing with 0.4 × 0.5 cm2 scabs. Wound healing was significantly better in the hUCMSCs combined with the SIS group. Conclusion: Local application of hUCMSCs combined with SIS enhances full-thickness skin injury wound healing in rats.

Treatment of cytokine release syndrome-induced vascular endothelial injury using mesenchymal stem cells

Cytokine release syndrome (CRS) is an acute systemic inflammatory reaction in which hyperactivated immune cells suddenly release a large amount of cytokines, leading to exaggerated inflammatory responses, multiple organ dysfunction, and even death. Although palliative treatment strategies have significantly reduced the overall mortality, novel targeted treatment regimens with superior therapy efficacy are urgently needed. Vascular endothelial cells (ECs) are important target cells of systemic inflammation, and their destruction is considered to be the initiating event underlying many serious complications of CRS. Mesenchymal stem/stromal cells (MSCs) are multipotent cells with self-renewing differentiation capacity and immunomodulatory properties. MSC transplantation can effectively suppress the activation of immune cells, reduce the bulk release of cytokines, and repair damaged tissues and organs. Here, we review the molecular mechanisms underlying CRS-induced vascular endothelial injury and discuss potential treatments using MSCs. Preclinical studies demonstrate that MSC therapy can effectively repair endothelium damage and thus reduce the incidence and severity of ensuing CRS-induced complications. This review highlights the therapeutic role of MSCs in fighting against CRS-induced EC damage, and summarizes the possible therapeutic formulations of MSCs for improved efficacy in future clinical trials.

Biological scaffold as potential platforms for stem cells: Current development and applications in wound healing

Wound repair is a complex challenge for both clinical practitioners and researchers. Conventional approaches for wound repair have several limitations. Stem cell-based therapy has emerged as a novel strategy to address this issue, exhibiting significant potential for enhancing wound healing rates, improving wound quality, and promoting skin regeneration. However, the use of stem cells in skin regeneration presents several challenges. Recently, stem cells and biomaterials have been identified as crucial components of the wound-healing process. Combination therapy involving the development of biocompatible scaffolds, accompanying cells, multiple biological factors, and structures resembling the natural extracellular matrix (ECM) has gained considerable attention. Biological scaffolds encompass a range of biomaterials that serve as platforms for seeding stem cells, providing them with an environment conducive to growth, similar to that of the ECM. These scaffolds facilitate the delivery and application of stem cells for tissue regeneration and wound healing. This article provides a comprehensive review of the current developments and applications of biological scaffolds for stem cells in wound healing, emphasizing their capacity to facilitate stem cell adhesion, proliferation, differentiation, and paracrine functions. Additionally, we identify the pivotal characteristics of the scaffolds that contribute to enhanced cellular activity.

Fibrin Stiffness Regulates Phenotypic Plasticity of Metastatic Breast Cancer Cells

The extracellular matrix (ECM)-regulated phenotypic plasticity is crucial for metastatic progression of triple negative breast cancer (TNBC). While ECM faithful cell-based models are available for in situ and invasive tumors, such as cell aggregate cultures in reconstituted basement membrane and in collagenous gels, there are no ECM faithful models for metastatic circulating tumor cells (CTCs). Such models are essential to represent the stage of metastasis where clinical relevance and therapeutic opportunities are significant. Here, CTC-like DU4475 TNBC cells are cultured in mechanically tunable 3D fibrin hydrogels. This is motivated, as in circulation fibrin aids CTC survival by forming a protective coating reducing shear stress and immune cell-mediated cytotoxicity and promotes several stages of late metastatic processes at the interface between circulation and tissue. This work shows that fibrin hydrogels support DU4475 cell growth, resulting in spheroid formation. Furthermore, increasing fibrin stiffness from 57 to 175 Pa leads to highly motile, actin and tubulin containing cellular protrusions, which are associated with specific cell morphology and gene expression patterns that markedly differ from basement membrane or suspension cultures. Thus, mechanically tunable fibrin gels reveal specific matrix-based regulation of TNBC cell phenotype and offer scaffolds for CTC-like cells with better mechano-biological properties than liquid.

LPS-pretreatment adipose-derived mesenchymal stromal cells promote wound healing in diabetic rats by improving angiogenesis

Mesenchymal stem cells (MSCs) play a key role in wound healing, and the advantages of pretreated MSCs in wound healing have previously been reported. In the present study, we investigated the impact of LPS pretreated human adipose-derived MSCs on skin wound healing in diabetic rats. We found that some improvements occurred through improving angiogenesis. Then, we scrutinized the impact of lipopolysaccharide (LPS) treatment on human adipose-derived MSCs in a high-glucose (HG) medium, as an in vitro diabetic model. In vivo findings revealed significant improvements in epithelialization and angiogenesis of diabetic wounds which received LPS pre-MSCs. Particularly, LPS pre-MSCs-treated diabetic wounds reached considerably higher percentages of wound closure. Also, the granulation tissue of these wounds had higher pronounced epithelialization and more vascularization compared with PBS-treated and MSCs-treated diabetic ones by CD31, VEGF, CD90, collagen 1, and collagen 3 immunostaining. Western-blots analyses indicated that LPS pre-MSCs led to the upregulation of vascular endothelial growth factor (VEGF) and DNMT1. In addition, significantly higher cell viability (proliferation/colonie), and elevated VEGF and DNMT1 protein expression were observed when MSCs were treated with LPS (10 ng/ml, 6 h) in HG culture media. Based on these findings, it is suggested that LPS pre-MSCs could promote wound repair and skin regeneration, in some major processes, via the improvement of cellular behaviors of MSCs in the diabetic microenvironment. The beneficial advantages of LPS treated with mesenchymal stem cells on wound healing may lead to establishing a novel approach as an alternative therapeutic procedure to cure chronic wounds in diabetic conditions.

Stem Cell-Mediated Angiogenesis in Skin Tissue Engineering and Wound Healing

The timely management of skin wounds has been an unmet clinical need for centuries. While there have been several attempts to accelerate wound healing and reduce the cost of hospitalisation and the healthcare burden, there remains a lack of efficient and effective wound healing approaches. In this regard, stem cell‐based therapies have garnered an outstanding position for the treatment of both acute and chronic skin wounds. Stem cells of different origins (e.g., embryo‐derived stem cells) have been utilised for managing cutaneous lesions; specifically, mesenchymal stem cells (MSCs) isolated from foetal (umbilical cord) and adult (bone marrow) tissues paved the way to more satisfactory outcomes. Since angiogenesis plays a critical role in all four stages of normal wound healing, recent therapeutic approaches have focused on utilising stem cells for inducing neovascularisation. In fact, stem cells can promote angiogenesis via either differentiation into endothelial lineages or secreting pro‐angiogenic exosomes. Furthermore, particular conditions (e.g., hypoxic environments) can be applied in order to boost the pro‐angiogenic capability of stem cells before transplantation. For tissue engineering and regenerative medicine applications, stem cells can be combined with specific types of pro‐angiogenic biocompatible materials (e.g., bioactive glasses) to enhance the neovascularisation process and subsequently accelerate wound healing. As such, this review article summarises such efforts emphasising the bright future that is conceivable when using pro‐angiogenic stem cells for treating acute and chronic skin wounds.

Inhibition of post-surgery tumour recurrence via a sprayable chemo-immunotherapy gel releasing PD-L1 antibody and platelet-derived small EVs

Background

Melanoma is the most serious type of skin cancer, and surgery is an effective method to treat melanoma. Unfortunately, local residual micro-infiltrated tumour cells and systemic circulating tumour cells (CTCs) are significant causes of treatment failure, leading to tumour recurrence and metastasis.

Methods

Small EVs were isolated from platelets by differential centrifugation, and doxorubicin-loaded small EVs (PexD) was prepared by mixing small EVs with doxorubicin (DOX). PexD and an anti-PD-L1 monoclonal antibody (aPD-L1) were co-encapsulated in fibrin gel. The synergistic antitumour efficacy of the gel containing PexD and aPD-L1 was assessed both in vitro and in vivo.

Results

Herein, we developed an in situ-formed bioresponsive gel combined with chemoimmunotherapeutic agents as a drug reservoir that could effectively inhibit both local tumour recurrence and tumour metastasis. In comparison with a DOX solution, PexD could better bind to tumour cells, induce more tumour immunogenic cell death (ICD) and promote a stronger antitumour immune response. PexD could enter the blood circulation through damaged blood vessels to track and eliminate CTCs. The concurrent release of aPD-L1 at the tumour site could impair the PD-1/PD-L1 pathway and restore the tumour-killing effect of cytotoxic T cells. This chemoimmunotherapeutic strategy triggered relatively strong T cell immune responses, significantly improving the tumour immune microenvironment.

Conclusion

Our findings indicated that the immunotherapeutic fibrin gel could “awaken” the host innate immune system to inhibit both local tumour recurrence post-surgery and metastatic potential, thus, it could serve as a promising approach to prevent tumour recurrence.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01270-7.

Autologous Adipose-Derived Stem Cell (Adsc) Transplantation In The Management Of Chronic Wounds

Our aim is to characterize chronic wound response to autologous adipose-derived stem cell (ADSC) sheet transplantation. A pilot descriptive longitudinal study was conducted at the Wound Healing Center of the Vietnam National Burn Hospital from July 1, 2019 to August 30, 2020. Thirty patients with 38 chronic wounds were enrolled in the study and were grafted with autologous ADSC sheets on the wound bed. Wound edges, wound bed, wound size and structure using H&E staining, ultrastructure changes by transmission electron microscope at the time of transplantation and at the first, second and third week of follow-up were observed. Results indicated that after ADSC sheet transplantation, the structure and ultrastructure of chronic wounds had improved. The extracellular matrix (ECM), neo-vascular, fibroblast and collagen fibers proliferated and arranged side by side at the dermis layer. Fibroblast proliferated and increased secretion of collagen. Keratinocytes proliferated and immigrated in the epidermis layer. After three weeks of autologous ADSC sheet transplantation, epithelial cells covered 90% of the wound surface. Neo-vascular, fibroblast and collagen proliferation increased weekly. The image of lymphocyte infiltration in connective tissues decreased. Wound size reduced significantly compared to before the experiment, wound beds were cleaner and filled with granulation tissue. Re-epithelialization appeared at the wound edge and throughout the wound. Wound measurements were statistically significant at the second and third weeks after starting treatment (week 2: 12.8±11.56 cm2 [range: 1-47.42 cm2], p<0.05; week 3: 7.44 ± 5.68 cm2 [range: 0.45- 20.10 cm2], p<0.001), indicating autologous ADSC treatment enhanced healing of chronic wounds. In conclusion, ADSCs have a beneficial effect on cutaneous regeneration and chronic wound healing.

Injectable Human Hair Keratin-Fibrinogen Hydrogels for Engineering 3D Microenvironments to Accelerate Oral Tissue Regeneration

Traumatic injury of the oral cavity is atypical and often accompanied by uncontrolled bleeding and inflammation. Injectable hydrogels have been considered to be promising candidates for the treatment of oral injuries because of their simple formulation, minimally invasive application technique, and site-specific delivery. Fibrinogen-based hydrogels have been widely explored as effective materials for wound healing in tissue engineering due to their uniqueness. Recently, an injectable foam has taken the spotlight. However, the fibrin component of this biomaterial is relatively stiff. To address these challenges, we created keratin-conjugated fibrinogen (KRT-FIB). This study aimed to develop a novel keratin biomaterial and assess cell-biomaterial interactions. Consequently, a novel injectable KRT-FIB hydrogel was optimized through rheological measurements, and its injection performance, swelling behavior, and surface morphology were investigated. We observed an excellent cell viability, proliferation, and migration/cell-cell interaction, indicating that the novel KRT-FIB-injectable hydrogel is a promising platform for oral tissue regeneration with a high clinical applicability.

Future applications of 3D bioprinting: A promising technology for treating recessive dystrophic epidermolysis bullosa

Three-dimensional (3D) bioprinting is a rapidly developing technology that has the potential to initiate a paradigm shift in the treatment of skin wounds arising from burns, ulcers and genodermatoses. Recessive dystrophic epidermolysis bullosa (RDEB), a severe form of epidermolysis bullosa, is a rare genodermatosis that results in mechanically induced blistering of epithelial tissues that leads to chronic wounds. Currently, there is no cure for RDEB, and effective treatment is limited to protection from trauma and extensive bandaging. The care of chronic wounds and burns significantly burdens the healthcare system, further illustrating the dire need for more beneficial wound care. However, in its infancy, 3D bioprinting offers therapeutic potential for wound healing and could be a breakthrough technology for the treatment of rare, incurable genodermatoses like RDEB. This viewpoint essay outlines the promise of 3D bioprinting applications for treating RDEB, including skin regeneration, a delivery system for gene-edited cells and small molecules, and disease modelling. Although the future of 3D bioprinting is encouraging, there are many technical challenges to overcome-including optimizing bioink and cell source-before this approach can be widely implemented in clinical practice.

Ultrafast in-situ forming halloysite nanotube-doped chitosan/oxidized dextran hydrogels for hemostasis and wound repair

A series of halloysite nanotube (HNT)-doped chitosan (CS)/oxidized dextran (ODEX) adhesive hydrogels were developed through a Schiff base reaction. The resultant CS/ODEX/HNT hydrogels could not only form in situ on wounds within only 1 s when injected, but could also adapt to wounds of different shapes and depths after injection. We established four rat and rabbit hemorrhage models and demonstrated that the hydrogels are better than the clinically used gelatin sponge for reducing hemostatic time and blood loss, particularly in arterial and deep noncompressible bleeding wounds. Moreover, the natural antibacterial features of CS and ODEX provided the hydrogels with strong bacteria-killing effects. Consequently, they significantly promoted methicillin-resistant Staphylococcus aureus -infected-wound repair compared to commercial gelatin sponge and silver-alginate antibacterial wound dressing. Hence, our multifunctional hydrogels with facile preparation process and utilization procedure could potentially be used as first-aid biomaterials for rapid hemostasis and infected-wound repair in emergency injury events.

Cellular human tissue-engineered skin substitutes investigated for deep and difficult to heal injuries

Wound healing is an important function of skin; however, after significant skin injury (burns) or in certain dermatological pathologies (chronic wounds), this important process can be deregulated or lost, resulting in severe complications. To avoid these, studies have focused on developing tissue-engineered skin substitutes (TESSs), which attempt to replace and regenerate the damaged skin. Autologous cultured epithelial substitutes (CESs) constituted of keratinocytes, allogeneic cultured dermal substitutes (CDSs) composed of biomaterials and fibroblasts and autologous composite skin substitutes (CSSs) comprised of biomaterials, keratinocytes and fibroblasts, have been the most studied clinical TESSs, reporting positive results for different pathological conditions. However, researchers' purpose is to develop TESSs that resemble in a better way the human skin and its wound healing process. For this reason, they have also evaluated at preclinical level the incorporation of other human cell types such as melanocytes, Merkel and Langerhans cells, skin stem cells (SSCs), induced pluripotent stem cells (iPSCs) or mesenchymal stem cells (MSCs). Among these, MSCs have been also reported in clinical studies with hopeful results. Future perspectives in the field of human-TESSs are focused on improving in vivo animal models, incorporating immune cells, designing specific niches inside the biomaterials to increase stem cell potential and developing three-dimensional bioprinting strategies, with the final purpose of increasing patient's health care. In this review we summarize the use of different human cell populations for preclinical and clinical TESSs under research, remarking their strengths and limitations and discuss the future perspectives, which could be useful for wound healing purposes.

Engineering a Chemically Defined Hydrogel Bioink for Direct Bioprinting of Microvasculature

Vascularizing printed tissues is a critical challenge in bioprinting. While protein-based hydrogel bioinks have been successfully used to bioprint microvasculature, their compositions are ill-defined and subject to batch variation. Few studies have focused on engineering proangiogenic bioinks with defined properties to direct endogenous microvascular network formation after printing. Here, a peptide-functionalized alginate hydrogel bioink with defined mechanical, rheological, and biochemical properties is developed for direct bioprinting of microvascularized tissues. An integrin-binding peptide (RGD) and a vascular endothelial growth factor-mimetic peptide with a protease-sensitive linker are conjugated onto a biodegradable alginate to synergistically promote vascular morphogenesis and capillary-scale endothelial tube formation. Partial ionic crosslinking before printing converts the otherwise unprintable hydrogel into a viscoelastic bioink with excellent printability and cytocompatibility. We use the bioink to fabricate a compartmentalized vascularized tissue construct, wherein we observe pericyte-endothelial cell colocalization and angiogenic sprouting across a tissue interface, accompanied by deposition of fibronectin and collagen in vascular and tissue components, respectively. This study provides a tunable and translational "off-the-shelf" hydrogel bioink with defined composition for vascularized bioprinting.

Biofunctionalized fibrin gel co-embedded with BMSCs and VEGF for accelerating skin injury repair

Rapid and effective repair of epithelial tissue is desirable for improving the success rate of operation and reducing postoperative complications. Hydrogel is a widely studied wound repair material, especially as a wound dressing for damaged epithelial tissue. Based on the catalytic effect of thrombin on fibrinogen, in this study, a three-dimensional fibrin gel which of adequate epithelial cell compatibility was constructed by using thrombin and fibrinogen under the cross-linking action of calcium ion. Immunofluorescence staining and hematoxylin-eosin (H&E) staining showed that bone marrow mesenchymal stem cell (BMSC) was embedded in fibrin gel. Furthermore, vascular endothelial growth factor (VEGF) was used to induce BMSC to differentiate into CD31+ and vWF+ endothelial cell (EC) in fibrin gel. The results showed that the fibrin gel surface may effectively promote the adhesion and proliferation of EC and smooth muscle cell (SMC). After 15 days of culture, it was found that the BMSC embedded in the hydrogel had differentiated into EC. The results of in vivo skin wound experiment in rats further proved that the fibrin gel containing BMSC could promote wound healing and repair, and showed the potential to promote neovascularization at the injured site. The construction method of hydrogel materials proposed in this study has potential application value in the field of regenerative medicine.

Colloidal Surface Engineering: Growth of Layered Double Hydroxides with Intrinsic Oxidase-Mimicking Activities to Fight Against Bacterial Infection in Wound Healing

Colloidal surface engineering is of particular importance to impart modular functionalities to the colloidal systems. Here, a layer of Mn/Ni layered hydroxides (Mn/Ni(OH)_x LDHs) can be successfully coated on various colloidal particles, such as silica spheres, silica rods, ferrite nanocrystal supraparticles, as well as FeOOH nanorods. Such layered hydroxides have intrinsic oxidase-mimetic activities, as demonstrated by catalytic oxidation of tetramethyl benzidine in the presence of oxygen. Furthermore, Mn/Ni(OH)_x LDHs structure seems to capture bacteria (both Gram positive and Gram negative) and exhibit antibacterial properties in vitro. Moreover, local delivery of Mn/Ni-LDH structure fights against infection and reverses delayed wound healing procedures in mice models. Importantly, such hierarchical structures may have strong adhesive properties to the bacteria, which may maximize the contact between Mn/Ni(OH)_x LDHs and the bacteria's surface. Overall, the present versatile colloidal surface engineering strategy will bring new insights in the field of antibiotics for its high efficiency toward antibacterial activity.

Resident mesenchymal vascular progenitors modulate adaptive angiogenesis and pulmonary remodeling via regulation of canonical Wnt signaling

Adaptive angiogenesis is necessary for tissue repair, however, it may also be associated with the exacerbation of injury and development of chronic disease. In these studies, we demonstrate that lung mesenchymal vascular progenitor cells (MVPC) modulate adaptive angiogenesis via lineage trace, depletion of MVPC, and modulation of β-catenin expression. Single cell sequencing confirmed MVPC as multipotential vascular progenitors, thus, genetic depletion resulted in alveolar simplification with reduced adaptive angiogenesis. Following vascular endothelial injury, Wnt activation in MVPC was sufficient to elicit an emphysema-like phenotype characterized by increased MLI, fibrosis, and MVPC driven adaptive angiogenesis. Lastly, activation of Wnt/β-catenin signaling skewed the profile of human and murine MVPC toward an adaptive phenotype. These data suggest that lung MVPC drive angiogenesis in response to injury and regulate the microvascular niche as well as subsequent distal lung tissue architecture via Wnt signaling.

Fibrin-based Bioinks: New Tricks from an Old Dog

For the past 10 years, the main efforts of most bioprinting research teams have focused on creating new bioink formulations, rather than inventing new printing set-up concepts. New tissue-specific bioinks with good printability, shape fidelity, and biocompatibility are based on "old" (well-known) biomaterials, particularly fibrin. While the interest in fibrin-based bioinks is constantly growing, it is essential to provide a framework of material's properties and trends. This review aims to describe the fibrin properties and application in three-dimensional bioprinting and provide a view on further development of fibrin-based bioinks.

Mesenchymal Regulation of the Microvascular Niche in Chronic Lung Diseases

The adult lung is comprised of diverse vascular, epithelial, and mesenchymal progenitor cell populations that reside in distinct niches. Mesenchymal progenitor cells (MPCs) are intimately associated with both the epithelium and the vasculature, and new evidence is emerging to describe their functional roles in these niches. Also emerging, following lineage analysis and single cell sequencing, is a new understanding of the diversity of mesenchymal cell subpopulations in the lung. However, several gaps in knowledge remain, including how newly defined MPC lineages interact with cells in the vascular niche and the role of adult lung MPCs during lung repair and regeneration following injury, especially in chronic lung diseases. Here we summarize how the current evidence on MPC regulation of the microvasculature during tissue homeostasis and injury may inform studies on understanding their role in chronic lung disease pathogenesis or repair. © 2019 American Physiological Society. Compr Physiol 9:1431-1441, 2019.

Silkworm Silk Matrices Coated with Functionalized Spider Silk Accelerate Healing of Diabetic Wounds

Complex cutaneous wounds like diabetic foot ulcers represent a critical clinical challenge and demand a large-scale and low-cost strategy for effective treatment. Herein, we use a rabbit animal model to investigate efficacy of bioactive wound dressings made up of silk biomaterials. Nanofibrous mats of Antheraea assama silkworm silk fibroin (AaSF) are coated with various recombinant spider silk fusion proteins through silk-silk interactions to fabricate multifunctional wound dressings. Two different types of spider silk coatings are used to compare their healing efficiency: FN-4RepCT (contains a cell binding motif derived from fibronectin) and Lac-4RepCT (contains a cationic antimicrobial peptide from lactoferricin). AaSF mats coated with spider silk show accelerated wound healing properties in comparison to the uncoated mats. Among the spider silk coated variants, dual coating of FN-4RepCT and Lac-4RepCT on top of AaSF mat demonstrated better wound healing efficiency, followed by FN-4RepCT and Lac-4RepCT single coated counterparts. The in vivo study also reveals excellent skin regeneration by the functionalized silk dressings in comparison to commercially used Duoderm dressing and untreated wounds. The spider silk coatings demonstrate early granulation tissue development, re-epithelialization, and efficient matrix remodelling of wounds. The results thus validate potential of bioactive silk matrices in faster repair of diabetic wounds.

Acellular and cellular approaches to improve diabetic wound healing

Chronic diabetic wounds represent a huge socioeconomic burden for both affected individuals and the entire healthcare system. Although the number of available treatment options as well as our understanding of wound healing mechanisms associated with diabetes has vastly improved over the past decades, there still remains a great need for additional therapeutic options. Tissue engineering and regenerative medicine approaches provide great advantages over conventional treatment options, which are mainly aimed at wound closure rather than addressing the underlying pathophysiology of diabetic wounds. Recent advances in biomaterials and stem cell research presented in this review provide novel ways to tackle different molecular and cellular culprits responsible for chronic and nonhealing wounds by delivering therapeutic agents in direct or indirect ways. Careful integration of different approaches presented in the current article could lead to the development of new therapeutic platforms that can address multiple pathophysiologic abnormalities and facilitate wound healing in patients with diabetes.

Proliferative Cells From Kaposiform Lymphangiomatosis Lesions Resemble Mesenchyme Stem Cell-like Pericytes Defective in Vessel Formation

Kaposiform lymphangiomatosis (KLA) is a vascular anomaly featuring lymphatic expansion. It has no known cause, no effective treatment, and is associated with high morbidity. Proliferative cells from 3 KLA patient lesions were characterized relative to adiopose-derived mesenchyme stem cells (ADSCs) and cells derived from a patient with the related disease kaposiform hemangioendothelioma (KHE). KLA cells variably expressed markers of mesenchyme stem cells (CD73, CD90, CD105, CD146) and lacked endothelial cell markers (CD31, CD34) as determined by flow cytometry. They expressed markers of vascular pericytes (neural/glial antigen 2, alpha-smooth muscle actin, platelet-derived growth factor-beta receptor, and CXCL12) as determined by quantitative reverse transcription polymerase chain reaction. Lesion cells transcribed vascular markers VEGFC and VEGFD, as well as VCAM-1, the latter of which was confirmed by flow cytometry, consistent with angiogenic MSC-like pericytes. Furthermore, conditioned medium from each was shown to promote the proliferation of growth factor-starved lymphatic endothelial cells. Unlike kaposiform hemangioendothelioma-derived MSC-like pericytes and ADSCs, KLA isolates were defective in support of vascular network formation in co-cultures with either vascular or lymphatic endothelial cells. Genetic analysis by whole exome sequencing revealed novel variant alleles in 2 populations of KLA cells (BAD, TSC1) that may bear on aberrant pericyte growth and function.

Extracellular vesicle-mimetic nanovesicles transport LncRNA-H19 as competing endogenous RNA for the treatment of diabetic wounds

Diabetic wounds, one of the most enervating complications of diabetes mellitus, affect millions of people worldwide annually. Vascular insufficiency, caused by hyperglycemia, is one of the primary causes and categories of diabetic impaired wound healing. Recently, long noncoding RNA (LncRNA)-H19, which is significantly decreased in diabetes and may be crucial in triggering angiogenesis, has attracted increasing interest. The possible relationship between the decrease of LncRNA-H19 and the impairment of angiogenesis in diabetes could involve impairment of the insulin-phosphatidylinositol 3-kinase (PI3K)-Akt pathway via the interdiction of LncRNA-H19. Thus, a therapeutic strategy utilizing LncRNA-H19 delivery is feasible. In this study, we investigated the possibility of using high-yield extracellular vesicle-mimetic nanovesicles (EMNVs) as an effective nano-drug delivery system for LncRNA, and studied the function of EMNVs with a high content of LncRNA-H19 (^H19EMNVs). The results, which were exciting, showed that ^H19EMNVs had a strong ability to neutralize the regeneration-inhibiting effect of hyperglycemia, and could remarkably accelerate the healing processes of chronic wounds. Our results suggest that bioengineered EMNVs can serve as a powerful instrument to effectively deliver LncRNA and will be an extremely promising multifunctional drug delivery system in the immediate future.

Concise Review: Using Fat to Fight Disease: A Systematic Review of Nonhomologous Adipose-Derived Stromal/Stem Cell Therapies

The objective of this Review is to describe the safety and efficacy of adipose stem/stromal cells (ASC) and stromal vascular fraction (SVF) in treating common diseases and the next steps in research that must occur prior to clinical use. Pubmed, Ovid Medline, Embase, Web of Science, and the Cochrane Library were searched for articles about use of SVF or ASC for disease therapy published between 2012 and 2017. One meta-analysis, 2 randomized controlled trials, and 16 case series were included, representing 844 human patients. Sixty-nine studies were performed in preclinical models of disease. ASCs improved symptoms, fistula healing, remission, and recurrence rates in severe cases of inflammatory bowel disease. In osteoarthritis, ASC and SVF improved symptom-related, functional, radiographic, and histological scores. ASC and SVF were also shown to improve clinical outcomes in ischemic stroke, multiple sclerosis, myocardial ischemia, chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, chronic liver failure, glioblastoma, acute kidney injury, and chronic skin wounds. These effects were primarily paracrine in nature and mediated through reduction of inflammation and promotion of tissue repair. In the majority of human studies, autologous ASC and SVF from liposuction procedures were used, minimizing the risk to recipients. Very few serious, treatment-related adverse events were reported. The main adverse event was postprocedural pain. SVF and ASC are promising therapies for a variety of human diseases, particularly for patients with severe cases refractory to current medical treatments. Further randomized controlled trials must be performed to elaborate potential safety and efficacy prior to clinical use. Stem Cells 2018;36:1311-1328.

Engineered Microvasculature in PDMS Networks Using Endothelial Cells Derived from Human Induced Pluripotent Stem Cells

In this study, we used a polydimethylsiloxane (PDMS)-based platform for the generation of intact, perfusion-competent microvascular networks in vitro. COMSOL Multiphysics, a finite-element analysis and simulation software package, was used to obtain simulated velocity, pressure, and shear stress profiles. Transgene-free human induced pluripotent stem cells (hiPSCs) were differentiated into partially arterialized endothelial cells (hiPSC-ECs) in 5 d under completely chemically defined conditions, using the small molecule glycogen synthase kinase 3β inhibitor CHIR99021 and were thoroughly characterized for functionality and arterial-like marker expression. These cells, along with primary human umbilical vein endothelial cells (HUVECs), were seeded in the PDMS system to generate microvascular networks that were subjected to shear stress. Engineered microvessels had patent lumens and expressed VE-cadherin along their periphery. Shear stress caused by flowing medium increased the secretion of nitric oxide and caused endothelial cells s to align and to redistribute actin filaments parallel to the direction of the laminar flow. Shear stress also caused significant increases in gene expression for arterial markers Notch1 and EphrinB2 as well as antithrombotic markers Kruppel-like factor 2 (KLF-2)/4. These changes in response to shear stress in the microvascular platform were observed in hiPSC-EC microvessels but not in microvessels that were derived from HUVECs, which indicated that hiPSC-ECs may be more plastic in modulating their phenotype under flow than are HUVECs. Taken together, we demonstrate the feasibly of generating intact, engineered microvessels in vitro, which replicate some of the key biological features of native microvessels.

Highly efficient local delivery of endothelial progenitor cells significantly potentiates angiogenesis and full-thickness wound healing

Wound therapy with a rapid healing performance remains a critical clinical challenge. Cellular delivery is considered to be a promising approach to improve the efficiency of healing, yet problems such as compromised cell viability and functionality arise due to the inefficient delivery. Here, we report the efficient delivery of endothelial progenitor cells (EPCs) with a bioactive nanofibrous scaffold (composed of collagen and polycaprolactone and bioactive glass nanoparticles, CPB) for enhancing wound healing. Under the stimulation of CPB nanofibrous system, the viability and angiogenic ability of EPCs were significantly enhanced through the activation of Hif-1α/VEGF/SDF-1α signaling. In vivo, CPB/EPC constructs significantly enhanced the formation of high-density blood vessels by greatly upregulating the expressions of Hif-1α, VEGF, and SDF-1α. Moreover, owing to the increased local delivery of cells and fast neovascularization within the wound site, cell proliferative activity, granulation tissue formation, and collagen synthesis and deposition were greatly promoted by CPB/EPC constructs resulting in rapid re-epithelialization and regeneration of skin appendages. As a result, the synergistic enhancement of wound healing was observed from CPB/EPC constructs, which suggests the highly efficient delivery of EPCs. CPB/EPC constructs may become highly competitive cell-based therapeutic products for efficient impaired wound healing application. This study may also provide a novel strategy to develop bioactive cell therapy constructs for angiogenesis-related regenerative medicine.

STATEMENT OF SIGNIFICANCE

This paper reported a highly efficient local delivery of EPCs using bioactive glass-based CPB nanofibrous scaffold for enhancing angiogenesis and wound regeneration. In vitro study showed that CPB can promote the proliferation, migration, and tube formation of EPCs through upregulation of the Hif-1α/VEGF/SDF-1α signaling pathway, indicating that the bioactivity and angiogenic ability of EPCs can be highly maintained and promoted by the CPB scaffold. Moreover, CPB/EPC constructs effectively stimulated the regeneration of diabetic wounds with satisfactory vascularization and better healing outcomes in a full-thickness wound model, suggesting that the highly efficient delivery of EPCs to wound site facilitates angiogenesis and further leads to wound healing. The high angiogenic capacity and excellent healing ability make CPB/EPC constructs highly competitive in cell-based therapeutic products for efficient wound repair application.

The effect of mesenchymal stem cells combined with platelet-rich plasma on skin wound healing

INTRODUCTION

Mesenchymal stem cells (MSCs) are multipotent stem cells that have the potential of proliferation, high self-renewal, and the potential of multilineage differentiation. The differentiation potential of the MSCs in vivo and in vitro has caused these cells to be regarded as potentially appropriate tools for wound healing. After the burn, trauma or removal of the tumor of wide wounds is developed. Although standard treatment for skin wounds is primary healing or skin grafting, they are not always practical mainly because of limited autologous skin grafting.

EVIDENCE ACQUISITIONS

Directory of Open Access Journals (DOAJ), Google Scholar, PubMed (NLM), LISTA (EBSCO), and Web of Science have been searched.

EVIDENCE SYNTHESIS

For clinical use of the MSCs in wound healing, two key issues should be taken into account: First, engineering biocompatible scaffolds clinical use of which leads to the least amount of side effects without any immunologic response and secondly, use of stem cells secretions with the least amount of clinical complications despite their high capability of healing damage.

CONCLUSION

In light of the MSCs' high capability of proliferation and multilineage differentiation as well as their significant role in modulating immunity, these cells can be used in combination with tissue engineering techniques. Moreover, the MSCs' secretions can be used in cell therapy to heal many types of wounds. The combination of MSCs and PRP aids wound healing which could potentially be used to promote wound healing.

Allogeneic Stem Cells Alter Gene Expression and Improve Healing of Distal Limb Wounds in Horses

Distal extremity wounds are a significant clinical problem in horses and humans and may benefit from mesenchymal stem cell (MSC) therapy. This study evaluated the effects of direct wound treatment with allogeneic stem cells, in terms of gross, histologic, and transcriptional features of healing. Three full-thickness cutaneous wounds were created on each distal forelimb in six healthy horses, for a total of six wounds per horse. Umbilical cord-blood derived equine MSCs were applied to each wound 1 day after wound creation, in one of four forms: (a) normoxic- or (b) hypoxic-preconditioned cells injected into wound margins, or (c) normoxic- or (d) hypoxic-preconditioned cells embedded in an autologous fibrin gel and applied topically to the wound bed. Controls were one blank (saline) injected wound and one blank fibrin gel-treated wound per horse. Data were collected weekly for 6 weeks and included wound surface area, thermography, gene expression, and histologic scoring. Results indicated that MSC treatment by either delivery method was safe and improved histologic outcomes and wound area. Hypoxic-preconditioning did not offer an advantage. MSC treatment by injection resulted in statistically significant increases in transforming growth factor beta and cyclooxygenase-2 expression at week 1. Histologically, significantly more MSC-treated wounds were categorized as pro-healing than pro-inflammatory. Wound area was significantly affected by treatment: MSC-injected wounds were consistently smaller than gel-treated or control wounds. In conclusion, MSC therapy shows promise for distal extremity wounds in horses, particularly when applied by direct injection into the wound margin. Stem Cells Translational Medicine 2018;7:98-108.

Human umbilical cord blood-derived mesenchymal stromal cells and small intestinal submucosa hydrogel composite promotes combined radiation-wound healing of mice

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) are a promising agent for treating impaired wound healing, and their therapeutic potential may be enhanced by employing extracellular matrix scaffolds as cell culture scaffolds or transplant cell carriers. Here, we evaluated the effect of human umbilical cord blood-derived (hUCB)-MSCs and a porcine small intestinal submucosa (SIS)-derived extracellular matrix scaffold in a combined radiation-wound mouse model of impaired wound healing.

METHODS

hUCB-MSCs and SIS hydrogel composite was applied to the excisional wound of whole-body irradiated mice. Assessment of wound closing and histological evaluation were performed in vivo. We also cultured hUCB-MSCs on SIS gel and examined the angiogenic effect of conditioned medium on irradiated human umbilical vein endothelial cells (HUVECs) in vitro.

RESULTS

hUCB-MSCs and SIS hydrogel composite treatment enhanced wound healing and angiogenesis in the wound site of mice. Conditioned medium from hUCB-MSCs cultured on SIS hydrogel promoted the chemotaxis of irradiated HUVECs more than their proliferation. The secretion of angiogenic growth factors hepatocyte growth factor, vascular endothelial growth factor-A and angiopoietin-1 from hUCB-MSCs was significantly increased by SIS hydrogel, with HGF being the predominant angiogenic factor of irradiated HUVECs.

CONCLUSIONS

Our results suggest that the wound healing effect of hUCB-MSCs is enhanced by SIS hydrogel via a paracrine factor-mediated recruitment of vascular endothelial cells in a combined radiation-wound mouse model.

Fibrin Tissue Sealant as an Adjunct to Cleft Palate Repair

PURPOSE

Fibrin glue is a common tissue sealant used to promote hemostasis, adhere tissues, and accelerate healing. Cleft palate repair can be technically challenging, creating dead space between tissue planes, and can be prone to complications such as would dehiscence or bleeding. The purpose of this study is to assess the role of fibrin glue as an adjunct to cleft palate repair. The authors hypothesize a beneficial impact on complication rates, including bleeding, dehiscence, and fistula formation, among others.

METHODS

Primary cleft palate repairs using fibrin glue were retrospectively analyzed. Demographic, intraoperative, perioperative, and postoperative data were combed for outcome variables. Complication rates were calculated in percentages and the results were compared to the published literature. Z-test statistics were performed for comparison.

RESULTS

A total of 45 patients, 21 females and 24 males, who underwent primary cleft palate repair with fibrin glue between 2011 and 2014, had sufficient data to be reviewed. There were no instances of bleeding, dehiscence, airway obstruction, infection, oronasal fistula, or return to the operating room in any patients. One patient exhibited mild postoperative coughing and secretions that resolved with conservative measures. Another patient displayed postoperative seizure activity due to a pre-existing condition. All complication rates in our fibrin glue series were lower than those reported without the use of fibrin glue. Overall complication rates with fibrin sealant are significantly lower than overall complication rates without.

CONCLUSION

Our data suggest that fibrin sealant is a beneficial adjunct to cleft palate repair. Its application is well-tolerated and the complication profile in our cohort was much less than the reported rates. The results of this preliminary study should be vetted with a prospective analysis involving a control group.

Determining the optimal protocol for preparing an acellular scaffold of tissue engineered small-diameter blood vessels

Although detergent-based decellularization protocols have been widely used to obtain a natural extracellular matrix (ECM) scaffold in tissue engineering, some key challenges still exist. To achieve an optimum natural decellularized scaffold for the construction of tissue-engineered small-diameter blood vessels (TEBV), porcine carotid arteries (PCAs) were decellularized by combining sodium dodecyl sulfate (SDS), sodium deoxycholate (SDC) and Triton X-100 (Triton) in different concentrations. Tissue samples were processed and their histological, biochemical and biomechanical characteristics were investigated. Results showed that only two methods 0.5% (SDS + SDC) and 1% (SDS + SDC) could completely remove of the cellular contents and preserve the native ECM architecture. Furthermore, 1% (SDS + SDC) based methods acquire preferable porosity and suitable mechanical strength. Residual Triton in the ECM scaffold holds intensive cytotoxity. In conclusion, 1%(SDS + SDC) based method can obtain a superior PCAs scaffold for the construction of TEBV. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 619-631, 2018.

Effect of Fibrin Packing on Managing Hepatic Hemorrhage and Liver Wound Healing in a Model of Liver Stab Wound in Rat

OBJECTIVE

To evaluate the effect of fibrin perihepatic packing on controlling liver hemorrhage and liver wound healing.

METHODS

In this animal experimental study, 20 adult male Sprague Dawley rats, weighing 200-220 g, were included. Stab wound injury was created by number 15 scalpel, so that bilateral liver capsules and liver tissue were cut, and acute bleeding was accrued. The animals were divided into 2 study groups: control (with a primary gauze packing treatment) and test group (with fibrin packing treatment). Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total serum bilirubin (TSB) levels were measured as a liver function test during the treatment period. Blood loss was calculated for estimation of hepatic hemorrhage during surgery. After four weeks, the liver wound repair was evaluated by sampling and Hematoxylin and Eosin staining (H&E).

RESULTS

In the test group, all of animals were alive (mortality rate= 0%). Significantly, ALT and AST levels were raised after surgery, followed by a decrease ALT (p=0.783) and AST (p=0.947) to the normal level during 4 days. Estimated blood loss was 2.89 ± 0.73 mL (about 19.65% of estimated blood volume). Hematocrit levels returned to the normal level (p=0.109) after 48 hours. In the control group, the mortality rate was 50% during 12h after surgery. ALT (p=0.773) and AST (p=0.853) were decreased to normal level during 6 days, and estimated blood loss was 4.98 ± 0.77 mL (about 32.98% of estimated blood volume) in the remaining animals. Moreover, hematocrit levels returned to the normal level (p=0.432) after 72 hours. Estimated blood loss in the test group was significantly less than control group (p<0.001). Total serum bilirubin levels were not significantly different from the normal level, before and after surgery in both groups. Histopathology sections from the post-hepatectomy specimens showed that the site of the previous incision was completely repaired, and a dense fibrous septum was observed in both groups.

CONCLUSION

The fibrin dressing was effective in preventing blood loss and saving lives after a liver stab injury and major internal bleeding in the animal model of rat.

In vivo vascularization of MSC-loaded porous hydroxyapatite constructs coated with VEGF-functionalized collagen/heparin multilayers

Rapid and adequate vascularization is vital to the long-term success of porous orbital enucleation implants. In this study, porous hydroxyapatite (HA) scaffolds coated with vascular endothelial growth factor (VEGF)-functionalized collagen (COL)/heparin (HEP) multilayers (porosity 75%, pore size 316.8 ± 77.1 μm, VEGF dose 3.39 ng/mm³) were fabricated to enhance vascularization by inducing the differentiation of mesenchymal stem cells (MSCs) to endothelial cells. The in vitro immunofluorescence staining, quantitative real-time polymerase chain reaction (qRT-PCR), and western blotting results demonstrated that the expression of the endothelial differentiation markers CD31, Flk-1, and von Willebrand factor (vWF) was significantly increased in the HA/(COL/HEP)₅/VEGF/MSCs group compared with the HA/VEGF/MSCs group. Moreover, the HA/(COL/HEP)₅ scaffolds showed a better entrapment of the MSCs and accelerated cell proliferation. The in vivo assays showed that the number of newly formed vessels within the constructs after 28 d was significantly higher in the HA/(COL/HEP)₅/VEGF/MSCs group (51.9 ± 6.3/mm²) than in the HA (26.7 ± 2.3/mm²) and HA/VEGF/MSCs (38.2 ± 2.4/mm²) groups. The qRT-PCR and western blotting results demonstrated that the HA/(COL/HEP)₅/VEGF/MSCs group also had the highest expression of CD31, Flk-1, and vWF at both the mRNA and protein levels.

Chick tendon fibroblast transcriptome and shape depend on whether the cell has made its own collagen matrix

Collagen- and fibrin-based gels are extensively used to study cell behaviour. However, 2D–3D and collagen-fibrin comparisons of gene expression, cell shape and mechanotransduction, with an in vivo reference, have not been reported. Here we compared chick tendon fibroblasts (CTFs) at three stages of embryonic development with CTFs cultured in collagen- or fibrin-based tissue engineered constructs (TECs). CTFs synthesised their own collagen matrix in fibrin-based TECs and better recapitulated the gene expression, collagen fibril alignment and cell shape seen in vivo. In contrast, cells in 3D collagen gels exhibited a 2D-like morphology and expressed fewer of the genes expressed in vivo. Analysis of YAP/TAZ target genes showed that collagen gels desensitise mechanotransduction pathways. In conclusion, gene expression and cell shape are similar on plastic and 3D collagen whereas cells in 3D fibrin have a shape and transcriptome better resembling the in vivo situation. Implications for wound healing are discussed.

The Effect of Bone Marrow-Derived Mesenchymal Stem Cells and Their Conditioned Media Topically Delivered in Fibrin Glue on Chronic Wound Healing in Rats

Bone marrow-derived mesenchymal stem cells (BM-MSCs) represent a modern approach for management of chronic skin injuries. In this work, we describe BM-MSCs application versus their conditioned media (CM) when delivered topically admixed with fibrin glue to enhance the healing of chronic excisional wounds in rats. Fifty-two adult male rats were classified into four groups after induction of large-sized full-thickness skin wound: control group (CG), fibrin only group (FG), fibrin + MSCs group (FG + SCs), and fibrin + CM group (FG + CM). Healing wounds were evaluated functionally and microscopically. Eight days after injury, number of CD68+ macrophages infiltrating granulation tissue was considerably higher in the latter two groups. Although--later--none of the groups depicted a substantially different healing rate, the quality of regenerated skin was significantly boosted by the application of either BM-MSCs or their CM both (1) structurally as demonstrated by the obviously increased mean area percent of collagen fibers in Masson's trichrome-stained skin biopsies and (2) functionally as supported by the interestingly improved epidermal barrier as well as dermal tensile strength. Thus, we conclude that topically applied BM-MSCs and their CM-via fibrin vehicle--could effectively improve the quality of healed skin in chronic excisional wounds in rats, albeit without true acceleration of wound closure.

Human mesenchymal stromal cells decrease mortality after intestinal ischemia and reperfusion injury

BACKGROUND

Cellular therapy is a novel treatment option for intestinal ischemia. Bone marrow-derived mesenchymal stromal cells (BMSCs) have previously been shown to abate the damage caused by intestinal ischemia/reperfusion (I/R) injury. We therefore hypothesized that (1) human BMSCs (hBMSCs) would produce more beneficial growth factors and lower levels of proinflammatory mediators compared to differentiated cells, (2) direct application of hBMSCs to ischemic intestine would decrease mortality after injury, and (3) decreased mortality would be associated with an altered intestinal and hepatic inflammatory response.

METHODS

Adult hBMSCs and keratinocytes were cultured on polystyrene flasks. For in vitro experiments, cells were exposed to tumor necrosis factor, lipopolysaccharides, or 2% oxygen for 24 h. Supernatants were then analyzed for growth factors and chemokines by multiplex assay. For in vivo experiments, 8- to 12-wk-old male C57Bl6J mice were anesthetized and underwent a midline laparotomy. Experimental groups were exposed to temporary superior mesenteric artery occlusion for 60 min. Immediately after ischemia, 2 × 10(6) hBMSCs or keratinocytes in phosphate-buffered saline were placed into the peritoneal cavity. Animals were then closed and allowed to recover for 6 h (molecular/histologic analysis) or 7 d (survival analysis). After 6-h reperfusion, animals were euthanized. Intestines and livers were harvested and analyzed for inflammatory chemokines, growth factors, and histologic changes.

RESULTS

hBMSCs expressed higher levels of human interleukin (IL) 6, IL-8, vascular endothelial growth factor (VEGF), and epidermal growth factor and lower levels of IL-1, IL-3, IL-7, and granulocyte-monocyte colony-stimulating factor after stimulation. In vivo, I/R resulted in significant mortality (70% mortality), whereas application of hBMSCs after ischemia decreased mortality to 10% in a dose-dependent fashion (P = 0.004). Keratinocyte therapy offered no improvements in mortality above I/R. Histologic profiles were equivalent between ischemic groups, regardless of the application of hBMSCs or keratinocytes. Cellular therapy yielded significantly decreased murine intestinal levels of soluble activin receptor-like kinase 1, betacellulin, and endothelin, whereas increasing levels of eotaxin, monokine induced by gamma interferon (MIG), monocyte chemoattractant protein 1, IL-6, granulocyte colony-stimulating factor (G-CSF), and interferon gamma-induced protein 10 (IP-10) from ischemia were appreciated. hBMSC therapy yielded significantly higher expression of murine intestinal VEGF and lower levels of intestinal MIG compared to keratinocyte therapy. Application of hBMSCs after ischemia yielded significantly lower murine levels of hepatic MIG, IP-10, and G-CSF compared to keratinocyte therapy.

CONCLUSIONS

Human BMSCs produce multiple beneficial growth factors. Direct application of hBMSCs to the peritoneal cavity after intestinal I/R decreased mortality by 60%. Improved outcomes with hBMSC therapy were not associated with improved histologic profiles in this model. hBMSC therapy was associated with higher VEGF in intestines and lower levels of proinflammtory MIG, IP-10, and G-CSF in liver tissue after ischemia, suggesting that reperfusion with hBMSC therapy may alter survival by modulating the systemic inflammatory response to ischemia.