Marrow Stromal Cells for Cell-Based Therapy: The Role of Antiinflammatory Cytokines in Cellular Cardiomyoplasty

Research and application of hydrogel-encapsulated mesenchymal stem cells in the treatment of myocardial infarction

Myocardial infarction (MI) stands out as a highly lethal disease that poses a significant threat to global health. Worldwide, heart failure resulting from MI remains a leading cause of human mortality. Mesenchymal stem cell (MSC) therapy has emerged as a promising therapeutic approach, leveraging its intrinsic healing properties. Nevertheless, pervasive issues, including a low cell retention rate, suboptimal survival rate, and incomplete differentiation of MSCs, present formidable challenges for further research. The introduction and advancement of biomaterials have offered a novel avenue for the exploration of MSC therapy in MI, marking considerable progress thus far. Notably, hydrogels, among the representative biomaterials, have garnered extensive attention within the biomedical field. This review delves into recent advancements, specifically focusing on the application of hydrogels to augment MSC therapy for cardiac tissue regeneration in MI.

Amniotic stromal stem cell-loaded hydrogel repairs cardiac tissue in infarcted rat hearts via paracrine mediators

The use of stem cells to repair the heart after a myocardial infarction (MI) remains promising, yet clinical trials over the past 20 years suggest that cells fail to integrate into the native tissue, resulting in limited improvements in cardiac function. Here, we demonstrate the cardioprotective potential of a composite inserting human amniotic stromal mesenchymal stem cells (ASMCs) in a chitosan and hyaluronic acid (C/HA) based hydrogel in a rat MI model. Mechanical characterization of the C/HA platform indicated a swift elastic conversion at 40°C and a rapid sol-gel transition time at 37°C. Cell viability assay presented active and proliferating AMSCs in the C/HA. The ASMCs + C/HA injected composite significantly increased left ventricular ejection fraction, fractional shortening, and neovessel formation. The encapsulated AMSCs were abundantly detected in the infarcted myocardium 6 weeks post-administration and co-expressed cardiac proteins and notably proliferative markers. Proteomic profiling revealed that extracellular vesicles released from hypoxia preconditioned ASMCs contained proteins involved in cytoprotection, angiogenesis, cardiac differentiation and non-canonical Wnt-signaling. Independent activation of non-canonical Wnt-signaling pathways in ASMCs induced cardiogenesis. Despite a low injected cellular density at baseline, the encapsulated AMSCs were abundantly retained and increased cardiac function. Furthermore, the C/HA hydrogel provided an active milieu for the AMSCs to proliferate, co-express cardiac proteins, and induce new vessel formation. Hence, this novel composite of AMSCs + C/HA scaffold is a conceivable candidate that could restore cardiac function and reduce remodeling.

Perceived relationship support moderates the association of contextual stress with inflammation among African Americans

We followed 402 African American young adults from ages 24 to 29, a period of emerging committed relationships, to examine the association of contextual stress (CS), for example, experiences of financial strain, victimization, and racial discrimination, with inflammation, and to test predictions that greater perceived relationship warmth and support (PRWS) at age 29 would moderate the association between earlier CS and inflammation, using a multiplex assessment of cytokines to construct an index of the ratio between predominantly proinflammatory cytokines versus predominantly anti-inflammatory cytokines. CS experienced at age 24 was associated with greater inflammation at age 29 in the full sample (b = .112, p = .004). PRWS at age 29 moderated the association of earlier CS with inflammation (b = -.114, p = .011), but there was no significant main effect of PRWS (b = -.053, p = .265). Finally, using an internal moderator approach, we compared the association of CS with inflammation among those not in a committed relationship to those in more or less supportive relationships, showing a significant and stronger association of CS with inflammation for those with low PRWS (-1 SD; b = .182, p < .001), a weaker and nonsignificant association of CS with inflammation among those with higher PRWS (+1 SD; b = -.002, p = .975), and an intermediate and nonsignificant association of CS with inflammation among those with no committed romantic relationship (b = .077, p = .227). Results were robust to number of cytokines included in the inflammation index. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Immunomodulatory plasticity of mesenchymal stem cells: a potential key to successful solid organ transplantation

Organ transplantation remains to be a treatment of choice for patients suffering from irreversible organ failure. Immunosuppressive (IS) drugs employed to maintain the allograft have shown excellent short-term graft survival, but, their long-term use could contribute to immunological and non-immunological risk factors, resulting in graft dysfunctionalities. Upcoming IS regimes have highlighted the use of cell-based therapies, which can eliminate the risk of drug-borne toxicities while maintaining efficacy of the treatment. Mesenchymal stem cells (MSCs) have been considered as an invaluable cell type, owing to their unique immunomodulatory properties, which makes them desirable for application in transplant settings, where hyper-activation of the immune system is evident. The immunoregulatory potential of MSCs holds true for preclinical studies while achieving it in clinical studies continues to be a challenge. Understanding the biological factors responsible for subdued responses of MSCs in vivo would allow uninhibited use of this therapy for countless conditions. In this review, we summarize the variations in the preclinical and clinical studies utilizing MSCs, discuss the factors which might be responsible for variability in outcome and propose the advancements likely to occur in future for using this as a "boutique/personalised therapy" for patient care.

A Tumor Necrosis Factor-α and Hypoxia-Induced Secretome Therapy for Myocardial Repair

BACKGROUND

Poor viability and retention of transplanted bone marrow mesenchymal stem cells (BM-MSC) remains an obstacle in promoting healing after myocardial infarction (MI). This study aimed to understand the migratory, angiogenic, and cardioprotective effects induced by tumor necrosis factor (TNF)-α and hypoxia through rat BM-MSC (rBM-MSC) paracrine secretions, collectively referred to as secretome, after MI.

METHODS

Secretome from rBM-MSC cultures treated with various combinations of H9c2 cardiomyoblast-conditioned medium, TNF-α, and hypoxia was initially collected. Immunocytochemistry, Western blot analyses, and transwell cell migration assays were conducted. In vivo, echocardiography was performed on rats with induced MI after their treatment with TNF-α and hypoxia-induced secretome.

RESULTS

Immunocytochemistry confirmed the presence of TNF receptors 1 and 2 on rBM-MSCs. Western blot analyses of rBM-MSCs treated with TNF-α and hypoxia showed an overall increasing trend in the expression of antiinflammatory proteins and angiogenic and migratory cytokines (transforming growth factor-β, fibroblast growth factor-2, angiopoietin-2, vascular endothelial growth factor-1). In addition, the TNF-α and hypoxia-induced secretome significantly increased the in vitro rBM-MSCs migration. In the rat MI model, the rats treated with the TNF-α and hypoxia-induced secretome had a significantly higher left ventricular fractional shortening than the control group.

CONCLUSIONS

Our data suggest that after MI, rBM-MSCs secrete paracrine factors in response to TNF-α and hypoxia that work together to manipulate the microenvironment and decrease inflammation. In addition, these signaling factors trigger angiogenic and migratory effects at the site of the infarct to promote myocardial healing and improve the cardiac function.

Cardioprotective activity of placental growth factor combined with oral supplementation of l-arginine in a rat model of acute myocardial infarction

OBJECTIVE

Exogenous administration of placental growth factor (PlGF) stimulates angiogenesis and improves ventricular remodeling after acute myocardial infarction (AMI), and supplementation with l-arginine ameliorates endothelial function. The objective of the present study was to compare the cardioprotective effects of combination therapy of PlGF and l-arginine with those of direct administration of PlGF alone in a rat model of AMI.

MATERIALS AND METHODS

Fifty male Sprague Dawley rats were randomly divided into five groups: sham group, normal saline group, l-arginine group, PlGF group, and combination group (PlGF + l-arginine). An AMI rat model was established by ligation of the left anterior descending of coronary arteries. After 4 weeks of postligation treatment, cardiac function, scar area, angiogenesis and arteriogenesis, myocardial endothelial nitric oxide synthase (eNOS) and collagen I protein content, and plasma concentration of brain natriuretic peptide (BNP) were studied. Echocardiography, Masson's staining, immunohistochemical analyses, Western blot, and enzyme-linked immunosorbent assay were performed.

RESULTS

Left ventricular ejection fraction (LVEF), left ventricular fraction shortening (LVFS), and capillary and arteriole densities were higher in the PlGF group than in the normal saline group (P<0.01). Scar area, collagen I protein content, and plasma concentration of BNP were decreased in the PlGF group (P<0.01). Myocardial eNOS protein level was elevated in the l-arginine group and PlGF + l-arginine group (P<0.01). Compared with the PlGF group, LVEF, LVFS, myocardial eNOS, and capillary and arteriole densities were higher in the combination group (P<0.01). Scar area, content of collagen I protein, and plasma concentration of BNP were reduced in the combination group (P<0.01).

CONCLUSION

Exogenous administration of PlGF stimulates angiogenesis and improves cardiac function. l-arginine increases the expression of the eNOS protein. PlGF and l-arginine have a more pronounced, synergistic protective effect on myocardial protection compared with that of exogenous PlGF therapy alone.

Viral-mediated fusion of mesenchymal stem cells with cells of the infarcted heart hinders healing via decreased vascularization and immune modulation

Cell fusion can occur between mesenchymal stem cells (MSCs) transplanted to improve cardiac function and cells of the recipient. The therapeutic benefit or detriment of resultant cell hybrids is unknown. Here we augment fusion of transplanted MSCs with recipient cardiac cell types via viral fusogens to determine how cardiac function is impacted. Using a Cre/LoxP-based luciferase reporter system coupled to biophotonic imaging and echocardiography, we found that augmenting fusion with the vesicular stomatitis virus glycoprotein (VSVG) increased the amount of fusion in the recipient mouse heart, but led to diminished cardiac function. Specifically, MSCs transfected with VSVG (MSC-VSVG) had the lowest mean fold increase in fractional area change (FAC) and cardiac output (CO). Although the amount of fusion detected had a strong positive correlation (Pearson) with fractional area change and cardiac output at day 7, this effect was lost by day 28. The decrease in cardiac function seen with MSC-VSVG treatment versus MSC alone or sham treatment was associated with decreased MSC retention, altered immune cell responsiveness and reduced vascularization in the heart. This outcome garners consideration in the context of cellular transplantation to damaged tissues, those with viral infection or other microenvironmental conditions that might promote fusion.

Tracking fusion of human mesenchymal stem cells after transplantation to the heart

Evidence suggests that transplanted mesenchymal stem cells (MSCs) can aid recovery of damaged myocardium caused by myocardial infarction. One possible mechanism for MSC-mediated recovery is reprogramming after cell fusion between transplanted MSCs and recipient cardiac cells. We used a Cre/LoxP-based luciferase reporter system coupled to biophotonic imaging to detect fusion of transplanted human pluripotent stem cell-derived MSCs to cells of organs of living mice. Human MSCs, with transient expression of a viral fusogen, were delivered to the murine heart via a collagen patch. At 2 days and 1 week later, living mice were probed for bioluminescence indicative of cell fusion. Cell fusion was detected at the site of delivery (heart) and in distal tissues (i.e., stomach, small intestine, liver). Fusion was confirmed at the cellular scale via fluorescence in situ hybridization for human-specific and mouse-specific centromeres. Human cells in organs distal to the heart were typically located near the vasculature, suggesting MSCs and perhaps MSC fusion products have the ability to migrate via the circulatory system to distal organs and engraft with local cells. The present study reveals previously unknown migratory patterns of delivered human MSCs and associated fusion products in the healthy murine heart. The study also sets the stage for follow-on studies to determine the functional effects of cell fusion in a model of myocardial damage or disease.

SIGNIFICANCE

Mesenchymal stem cells (MSCs) are transplanted to the heart, cartilage, and other tissues to recover lost function or at least limit overactive immune responses. Analysis of tissues after MSC transplantation shows evidence of fusion between MSCs and the cells of the recipient. To date, the biologic implications of cell fusion remain unclear. A newly developed in vivo tracking system was used to identify MSC fusion products in living mice. The migratory patterns of fusion products were determined both in the target organ (i.e., the heart) and in distal organs. This study shows, for the first time, evidence of fusion products at sites distal from the target organ and data to suggest that migration occurs via the vasculature. These results will inform and improve future, MSC-based therapeutics.

Effects of hypoxia on the immunomodulatory properties of human gingiva-derived mesenchymal stem cells

The environment of bone marrow mesenchymal stem cells (MSCs) is hypoxic, which plays an important role in maintaining their self-renewal potential and undifferentiated state. MSCs have been proven to possess immunomodulatory properties and have been used clinically to treat autoimmune diseases. Here, we tested the effects of hypoxia on the immunomodulatory properties of MSCs and examined its possible underlying mechanisms. We found that hypoxic stimulation promoted the immunomodulatory properties of human gingiva-derived mesenchymal stem cells (hGMSCs) by enhancing the suppressive effects of hGMSCs on peripheral blood mononuclear cells (PBMCs). The proliferation of PBMCs was significantly inhibited, while the apoptosis of PBMCs was increased, which was associated with the Fas ligand (FasL) expression of hGMSCs. The in vivo study showed that systemically infused hGMSCs could enhance skin wound repair, and 24-h hypoxic stimulation significantly promoted the reparative capacity of hGMSCs. For mechanism, hGMSC treatment inhibited the local inflammation of injured skin by suppressing the inflammatory cells, reducing the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α), and increasing anti-inflammatory cytokine interleukin-10 (IL-10), which was promoted by hypoxia. Hypoxia preconditioning may be a good optimizing method to promote the potential of MSCs for the future cell-based therapy.

Cardioprotective activity of placental growth factor in a rat model of acute myocardial infarction: nanoparticle-based delivery versus direct myocardial injection

Background

To comparatively evaluate the cardioprotective activity of placental growth factor (PGF) delivered through direct injection and a nanoparticle-based system respectively and to study the underlying mechanisms in a rat model of acute myocardial infarction (AMI).

Methods

Poly lactic-co-glycolic acid (PLGA)-based PGF-carrying nanoparticles (PGF-PLGA_NPs) were created. The mean size and morphology of particles were analyzed with particle size analyzer and transmission electronic microscopy (TEM). Encapsulation efficiency and sustained-release dose curve were analyzed by ELISA. Sprague-Dawley rats were randomized into four groups (n = 10). While animals in the first group were left untreated as controls, those in the other 3 groups underwent surgical induction of AMI, followed by treatment with physiological saline, PGF, and PGF-PLGA_NPs, respectively. Cardiac function was evaluated by transthoracic echocardiography at 4 weeks after treatment. At 6 weeks, rats were sacrificed, infarction size was analyzed with Masson trichrome staining, and protein contents of TIMP-2, MT1-MMP and MMP-2 at the infarction border were determined by immunohistochemistry and western blotting analysis.

Results

PGF was released for at least 15 days, showing successful preparation of PGF-PLGA_NPs. Coronary artery ligation successfully induced AMI. Compared to physiological saline control, PGF, injected to the myocardium either as a nude molecule or in a form of nanoparticles, significantly reduced infarction size, improved cardiac function, and elevated myocardial expression of TIMP-2, MT1-MMP, and MMP-2 (P < 0.05). The effect of PGF-PLGA_NPs was more pronounced than that of non-encapsulated PGF (P < 0.05).

Conclusion

Target PGF delivery to myocardium may improve cardiac function after AMI in rats. PLGA-based nanoparticles appear to be a better approach to delivery PGF. PGF exerts its cardioprotective effect at least partially through regulating metalloproteinase-mediated myocardial tissue remodeling.

Chemokine contribution in stem cell engraftment into the infarcted myocardium

Modern life styles have made cardiovascular disease the leading cause of morbidity and mortality worldwide. Although current treatments substantially ameliorate patients’ prognosis after MI, they cannot restore the affected tissue or entirely re-establish organ function. Therefore, the main goal of modern cardiology should be to design strategies to reduce myocardial necrosis and optimize cardiac repair following MI. Cell-based therapy was considered a novel and potentially new strategy in regenerative medicine; however, its clinical implementation has not yielded the expected results. Chemokines seem to increase the efficiency of cell-therapy and may represent a reliable method to be exploited in the future. This review surveys current knowledge of cell therapy and highlights key insights into the role of chemokines in stem cell engraftment in infarcted myocardium and their possible clinical implications.

Recent advancements in tissue engineering for stem cell-based cardiac therapies

Advances in cardiac tissue engineering have recently focused on utilizing stem cells to regenerate infarcted and scarred myocardium. Due to their proliferative nature and tremendous potential for differentiation, stem cells are presently being investigated for clinical applications. Unfortunately, limiting factors such as massive cell death and poor retention have hampered clinical outcomes. Consequently, the development of an efficient delivery system for stem cells to the target site is essential. The use of innovative tissue engineering techniques has opened up new horizons within the field of cellular cardiomyoplasty. This paper will present a comprehensive overview of the recent advancements in stem cell technology destined for myocardial tissue repair. In addition, the multidisciplinary approach to tissue engineering presented here will provide the reader with insight into the clinical realization of cellular cardiomyoplasty.

Cellular cardiomyoplasty: current state of the field

Cellular cardiomyoplasty employs stem cell therapy to regenerate myocardium. Characterized by their potential for proliferation, differentiation and capacity for self-renewal, stem cells are ideally suited for use in regenerative medicine. Supplementing traditional therapeutic modalities aimed at the palliation of congestive heart failure, cellular cardiomyoplasty is an innovative approach aimed at producing functional, viable myocardium following an acute infarction. The primary focus is to prevent the onset of congestive heart failure; however, potential applications aimed at reversing ischemic heart disease are concurrently in development. After decades of research, cellular cardiomyoplasty has moved beyond traditional in vitro and animal models; it is currently being implemented in clinical trials. Despite this monumental advance, certain limitations remain inherent in this process, preventing stem cell therapy from reaching its full potential. On a cellular level, stem cell retention and viability postimplantation continues to be problematic. Solutions under investigation include pioneering advances in cell delivery, in vitro pretreatment, and tissue engineering. Moreover, questions surrounding optimal cell type and cellular mechanisms concerning cellular cardiomyoplasty remain unanswered. Clarification of these issues is essential to ensure continued progression of this new technology. Stem cell therapy has been highly successful within the in vitro and in vivo environment. However, as clinical trials abound, cellular cardiomyoplasty must transition from an experimental concept to an effective therapeutic treatment. This process is hindered by discordance between scientific accrue and practical applicability. This review will provide a comprehensive summary of current innovations on cellular cardiomyoplasty, and future prospects. There will be a particular emphasis on the clinical aspects of stem cell therapy in an attempt to bridge the gap between science and medicine. Overcoming this barrier will render cellular cardiomyoplasty accessible to patients on a global basis.

Genipin-Cross-Linked Microencapsulated Human Adipose Stem Cells Augment Transplant Retention Resulting in Attenuation of Chronically Infarcted Rat Heart Fibrosis and Cardiac Dysfunction

Stem cell transplantation has been widely acknowledged for their immense potential in regenerative medicine. In these procedures, the implanted cells need to maintain both their viability and functional properties for effective therapeutic outcomes. This has long been a subject of major concern and intensive studies. Microencapsulation of stem cells within polymeric microcapsules can be an efficient approach to achieve this goal, particularly for heart diseases. This study reports the use of biocompatible, fluorogenic genipin-cross-linked alginate chitosan (GCAC) microcapsules in delivery of human adipose stem cells (hASCs) with an aim to increase the implant retention in the infarcted myocardium for maximum clinical benefits. In vitro results show, under hypoxic conditions, the microencapsulated cells overexpressed significantly higher amount of biologically active vascular endothelial growth factor (VEGF). We investigated on the in vivo potential using immunocompetent female rats after induction of myocardial infarction. For this, animal groups ( n = 8) received empty control microcapsules, 1.5 × 106 free male hASCs, or 1.5 × 106 microencapsulated male hASCs. Results show significant retention (3.5 times higher) of microencapsulated hASCs compared to free hASCs after 10 weeks of transplantation. Microencapsulated hASCs showed significantly attenuated infarct size compared to free hASCs and empty microcapsule group (21.6% ± 1.1% vs. 27.2% ± 3.1% vs. 33.3% ± 3.2%; p < 0.05), enhanced vasculogenesis, and improved cardiac function (fractional shortening: 24.2% ± 2.1% vs. 19.1% ± 0.5% vs. 12.0% ± 4.0%; p < 0.05). These data suggest that microencapsulated hASCs can contribute significantly to the improvement in cardiac functions. Their greater retentions exhibit reduced fibrosis and cardiac dysfunction in experimental animals. However, further research is needed to fully comprehend the underlying biological and immunological effects of microencapsulated hASCs, which jointly play important roles in cardiac repair.

Directed Fusion of Mesenchymal Stem Cells with Cardiomyocytes via VSV-G Facilitates Stem Cell Programming

Mesenchymal stem cells (MSCs) spontaneously fuse with somatic cells in vivo, albeit rarely, and the fusion products are capable of tissue-specific function (mature trait) or proliferation (immature trait), depending on the microenvironment. That stem cells can be programmed, or somatic cells reprogrammed, in this fashion suggests that stem cell fusion holds promise as a therapeutic approach for the repair of damaged tissues, especially tissues not readily capable of functional regeneration, such as the myocardium. In an attempt to increase the frequency of stem cell fusion and, in so doing, increase the potential for cardiac tissue repair, we expressed the fusogen of the vesicular stomatitis virus (VSV-G) in human MSCs. We found VSV-G expressing MSCs (vMSCs) fused with cardiomyocytes (CMs) and these fusion products adopted a CM-like phenotype and morphology in vitro. In vivo, vMSCs delivered to damaged mouse myocardium via a collagen patch were able to home to the myocardium and fuse to cells within the infarct and peri-infarct region of the myocardium. This study provides a basis for the investigation of the biological impact of fusion of stem cells with CMs in vivo and illustrates how viral fusion proteins might better enable such studies.

Perspectives on mesenchymal stem cells: tissue repair, immune modulation, and tumor homing

Mesenchymal stem cells (MSCs) or MSC-like cells have been identified in a variety of different tissues that share molecular expression profiles and biological functions but also retain a unique differentiation preference depending on their tissue origins. MSCs play beneficial roles in the healing of damaged tissue by directly differentiating to many different resident cell types and/or by secreting several trophic factors that aid tissue repair. Aside from MSCs' reparative stem cell function, they drive immune responses toward immunosuppression and anti-inflammation. This novel function of MSCs opens up new avenues for clinical development of MSC immune-therapeutics to treat uncontrollable, life threatening, severe, chronic inflammation and autoimmune disease. Unexpectedly high rates of MSCs' tumor homing capacity and their tumor supporting capability have also been noted in tumor-bearing animal models. In this review, we will discuss MSCs' basic cell biology and perspectives on MSCs in terms of tissue repair, immune modulation, and tumor homing.

Intramyocardial sustained delivery of placental growth factor using nanoparticles as a vehicle for delivery in the rat infarct model

BACKGROUND

Acute myocardial ischemia results in scar formation with ventricular dilatation and eventually heart failure. Placental growth factor (PlGF) is reported to stimulate angiogenesis and improve cardiac function. In this study, it was hypothesized that intramyocardial injection of PlGF contained in nanoparticles can be released at the site of action for an extended time period as a sustained slow-release protective mechanism that accelerates myocardial recovery in a rat model of ischemic cardiomyopathy.

METHODS

PlGF-loaded chitosan-alginate nanoparticles were injected into an acute myocardial infarction model in rats (n = 10 per group). Transthoracic echocardiography was performed at different time intervals. Enzyme-linked immunosorbent assay was used to measure the serum cytokines levels at 8 weeks. Hearts were stained with Masson's trichrome for scar area analysis. Immunofluorostaining was performed to evaluate the extent of myocardial angiogenesis at the infarction border. PlGF enzyme-linked immunosorbent assay was used to measure the in vitro release kinetics of PlGF-loaded nanoparticles.

RESULTS

At 8 weeks after coronary ligation, hearts that were treated with PlGF-loaded chitosan-alginate nanoparticles had significant increases in left-ventricular function (P < 0.01), vascular density (P < 0.01), and in the serum level of the anti-inflammatory cytokine interleukin-10 (P < 0.05). There was significant decrease in scar area formation (P < 0.05) and in serum levels of the proinflammatory cytokines tumor necrosis factor-alpha and interleukin-6 (P < 0.01). In vitro PlGF-release kinetic studies showed a sustained release of PlGF from the particles over a 120-hour period.

CONCLUSION

The use of nanoparticles as a vehicle for PlGF delivery, as opposed to the direct injection of the growth factor after acute myocardial infarction, can provide sustained slow-release PlGF therapy, enhancing the positive effects of the growth factor in the setting of acute myocardial ischemia.

Superior therapeutic potential of young bone marrow mesenchymal stem cells by direct intramyocardial delivery in aged recipients with acute myocardial infarction: in vitro and in vivo investigation

Introduction. Bone-marrow-derived mesenchymal stem cells (MSCs) have been studied for treatment of myocardial infarction (MI). Since MSCs from older donors show quantitative and qualitative senescent changes, we hypothesized that a better outcome may be achieved if aged recipients are given MSCs obtained from young donors, rather than using their own autologous MSCs. Methods. In vitro studies compared properties of young and old MSCs. Aged rats randomized into 3 groups underwent coronary artery ligations and were then injected with either old (O) or young (Y) MSCs, or ligation alone. Echocardiography evaluated ejection fractions (EF). At 16 weeks, scar deposition was analyzed. Results. Old MSCs exhibited decreased cell viability, proliferation, and differentiation potentials. EF significantly improved early in both cell therapy groups (P < .05). However, at later stages of the study, group Y showed significantly better function which correlated with decreased scar deposition. Conclusions. The significant difference between young and old cells indicates the possible advantage for allotransplanting MSCs from young donors to elderly patients with MI.

Mesenchymal stromal cells for cardiovascular disease

The fields of regenerative medicine and cellular therapy have been the subject of tremendous hype and hope. In particular, the perceived usage of somatic cells like mesenchymal stromal cells (MSCs) has captured the imagination of many. MSCs are a rare population of cells found in multiple regions within the body that can be readily expanded ex vivo and utilized clinically. Originally, it was hypothesized that transplantation of MSCs to sites of injury would lead to de novo tissue-specific differentiation and thereby replace damaged tissue. Now, it is generally agreed that MSC home to sites of injury and direct positive remodeling via the secretion of paracrine factors. Consequently, their clinical utilization has largely revolved around their abilities to promote neovascularization for ischemic disorders and modulate overly exuberant inflammatory responses for autoimmune and alloimmune conditions. One of the major issues surrounding the development of somatic cell therapies like MSCs is that despite evoking a positive response, long-term engraftment and persistence of these cells is rare. Consequently, very large cell doses need be administered for raising production, delivery, and efficacy issues. In this review, we will outline the field of MSC in the context of ischemia and discuss causes for their lack of persistence. In addition, some of the methodologies be used to enhance their therapeutic potential will be highlighted.

Exploitation of herpesvirus immune evasion strategies to modify the immunogenicity of human mesenchymal stem cell transplants

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent cells residing in the connective tissue of many organs and holding great potential for tissue repair. In culture, human MSCs (hMSCs) are capable of extensive proliferation without showing chromosomal aberrations. Large numbers of hMSCs can thus be acquired from small samples of easily obtainable tissues like fat and bone marrow. MSCs can contribute to regeneration indirectly by secretion of cytokines or directly by differentiation into specialized cell types. The latter mechanism requires their long-term acceptance by the recipient. Although MSCs do not elicit immune responses in vitro, animal studies have revealed that allogeneic and xenogeneic MSCs are rejected.

METHODOLOGY/PRINCIPAL FINDINGS

We aim to overcome MSC immune rejection through permanent down-regulation of major histocompatibility complex (MHC) class I proteins on the surface of these MHC class II-negative cells through the use of viral immune evasion proteins. Transduction of hMSCs with a retroviral vector encoding the human cytomegalovirus US11 protein resulted in strong inhibition of MHC class I surface expression. When transplanted into immunocompetent mice, persistence of the US11-expressing and HLA-ABC-negative hMSCs at levels resembling those found in immunodeficient (i.e., NOD/SCID) mice could be attained provided that recipients' natural killer (NK) cells were depleted prior to cell transplantation.

CONCLUSIONS/SIGNIFICANCE

Our findings demonstrate the potential utility of herpesviral immunoevasins to prevent rejection of xenogeneic MSCs. The observation that down-regulation of MHC class I surface expression renders hMSCs vulnerable to NK cell recognition and cytolysis implies that multiple viral immune evasion proteins are likely required to make hMSCs non-immunogenic and thereby universally transplantable.

Bone marrow stem cell derived paracrine factors for regenerative medicine: current perspectives and therapeutic potential

During the past several years, there has been intense research in the field of bone marrow-derived stem cell (BMSC) therapy to facilitate its translation into clinical setting. Although a lot has been accomplished, plenty of challenges lie ahead. Furthermore, there is a growing body of evidence showing that administration of BMSC-derived conditioned media (BMSC-CM) can recapitulate the beneficial effects observed after stem cell therapy. BMSCs produce a wide range of cytokines and chemokines that have, until now, shown extensive therapeutic potential. These paracrine mechanisms could be as diverse as stimulating receptor-mediated survival pathways, inducing stem cell homing and differentiation or regulating the anti-inflammatory effects in wounded areas. The current review reflects the rapid shift of interest from BMSC to BMSC-CM to alleviate many logistical and technical issues regarding cell therapy and evaluates its future potential as an effective regenerative therapy.