Preserving prostaglandin E2 level prevents rejection of implanted allogeneic mesenchymal stem cells and restores postinfarction ventricular function

Prostaglandin E2 Induces YAP1 and Agrin Through EP4 in Neonatally-Derived Islet-1+ Stem Cells

Prostaglandin E2 (PGE2) has recently gained attention in the field of regenerative medicine because of the beneficial effects of this molecule on stem cell proliferation and migration. Furthermore, PGE2 has the ability to mitigate immune rejection and fibrosis. In the colon and kidney, PGE2 induces YAP1, a transcription factor critical for cardiac regeneration. Establishing a similar connection in stem cells that can be transplanted in the heart could lead to the development of more effective therapeutics. In this report, we identify the effects of PGE2 on neonatal Islet-1+ stem cells. These stem cells synthesize PGE2, which functions by stimulating the transcription of the extracellular matrix protein Agrin. Agrin upregulates YAP1. Consequently, both YAP1 and Agrin are induced by PGE2 treatment. Our study shows that PGE2 upregulated the expression of both YAP1 and Agrin in Islet-1+ stem cells through the EP4 receptor and stimulated proliferation using the same mechanisms. PGE2 administration further elevated the expression of stemness markers and the matrix metalloproteinase MMP9, a key regulator of remodeling in the extracellular matrix post-injury. The expression of PGE2 in neonatal Islet-1+ cells is a factor which contributes to improving the functional efficacy of these cells for cardiac repair.

Stem cell therapy for cardiac regeneration: past, present, and future

Cardiac disorders remain the leading cause of mortality worldwide. Current clinical strategies, including drug therapy, surgical interventions, and organ transplantation offer limited benefits to patients without regenerating the damaged myocardium. Over the past decade, stem cell therapy has generated a keen interest owing to its unique self-renewal and immune privileged characteristics. Furthermore, the ability of stem cells to differentiate into specialized cell types, has made them a popular therapeutic tool against various diseases. This comprehensive review provides an overview of therapeutic potential of different types of stem cells in reference to cardiovascular diseases. Furthermore, it sheds light on the advantages and limitations associated with each cell type. An in-depth analysis of the challenges associated with stem cell research and the hurdles for its clinical translation and their possible solutions have also been elaborated upon. It examines the controversies surrounding embryonic stem cells and the emergence of alternative approaches, such as the use of induced pluripotent stem cells for cardiac therapeutic applications. Overall, this review serves as a valuable resource for researchers, clinicians, and policymakers involved in the field of regenerative medicine, guiding the development of safe and effective stem cell-based therapies to revolutionize patient care.

Enhancing Immunomodulatory Function of Mesenchymal Stromal Cells by Hydrogel Encapsulation

Mesenchymal stromal cells (MSCs) showcase remarkable immunoregulatory capabilities in vitro, positioning them as promising candidates for cellular therapeutics. However, the process of administering MSCs and the dynamic in vivo environment may impact the cell-cell and cell-matrix interactions of MSCs, consequently influencing their survival, engraftment, and their immunomodulatory efficacy. Addressing these concerns, hydrogel encapsulation emerges as a promising solution to enhance the therapeutic effectiveness of MSCs in vivo. Hydrogel, a highly flexible crosslinked hydrophilic polymer with a substantial water content, serves as a versatile platform for MSC encapsulation. Demonstrating improved engraftment and heightened immunomodulatory functions in vivo, MSCs encapsulated by hydrogel are at the forefront of advancing therapeutic outcomes. This review delves into current advancements in the field, with a focus on tuning various hydrogel parameters to elucidate mechanistic insights and elevate functional outcomes. Explored parameters encompass hydrogel composition, involving monomer type, functional modification, and co-encapsulation, along with biomechanical and physical properties like stiffness, viscoelasticity, topology, and porosity. The impact of these parameters on MSC behaviors and immunomodulatory functions is examined. Additionally, we discuss potential future research directions, aiming to kindle sustained interest in the exploration of hydrogel-encapsulated MSCs in the realm of immunomodulation.

Allogeneic Mesenchymal Stem Cells After In Vivo Transplantation: A Review

Autologous mesenchymal stem cells (MSCs) are ideal for tissue regeneration because of their ability to circumvent host rejection, but their procurement and processing present logistical and time-sensitive challenges. Allogeneic MSCs provide an alternative cell-based therapy capable of positively affecting all human organ systems, and can be readily available. Extensive research has been conducted in the treatment of autoimmune, degenerative, and inflammatory diseases with such stem cells, and has demonstrated predominantly safe outcomes with minimal complications. Nevertheless, continued clinical trials are necessary to ascertain optimal harvest and transplant techniques.

Stem cells derived exosomes and biomaterials to modulate autophagy and mend broken hearts

Autophagy maintains cellular homeostasis and plays a crucial role in managing pathological conditions including ischemic myocardial injury leading to heart failure (HF). Despite treatments, no intervention can replace lost cardiomyocytes. Stem cell therapy offers potential for post-myocardial infarction repair but struggles with poor cell retention due to immune rejection. In the search for effective therapies, stem cell-derived extracellular vesicles (EVs), especially exosomes, have emerged as promising tools. These tiny bioactive molecule carriers play vital roles in intercellular communication and tissue engineering. They offer numerous therapeutic benefits including modulating immune responses, promoting tissue repair, and boosting angiogenesis. Additionally, biomaterials provide a conducive 3D microenvironment for cell, exosome, and biomolecule delivery, and enhance heart muscle strength, making it a comprehensive cardiac repair strategy. In this regard, the current review delves into the intricate application of extracellular vesicles (EVs) and biomaterials for managing autophagy in the heart muscle during cardiac injury. Central to our investigation is the exploration of how these elements interact within the context of cardiac repair and regeneration. Additionally, this review also casts light on the formidable challenges that plague this field, such as the issues of safety, efficacy, controlled delivery, and acceptance of these therapeutic strategies for effective clinical translation. Addressing these challenges is crucial for unlocking the full therapeutic potential of EV and biomaterial-based therapies and ensuring their successful translation from bench to bedside.

The Role of COX-2 and PGE2 in the Regulation of Immunomodulation and Other Functions of Mesenchymal Stromal Cells

The ability of MSCs to modulate the inflammatory environment is well recognized, but understanding the molecular mechanisms responsible for these properties is still far from complete. Prostaglandin E2 (PGE2), a product of the cyclooxygenase 2 (COX-2) pathway, is indicated as one of the key mediators in the immunomodulatory effect of MSCs. Due to the pleiotropic effect of this molecule, determining its role in particular intercellular interactions and aspects of cell functioning is very difficult. In this article, the authors attempt to summarize the previous observations regarding the role of PGE2 and COX-2 in the immunomodulatory properties and other vital functions of MSCs. So far, the most consistent results relate to the inhibitory effect of MSC-derived PGE2 on the early maturation of dendritic cells, suppressive effect on the proliferation of activated lymphocytes, and stimulatory effect on the differentiation of macrophages into M2 phenotype. Additionally, COX-2/PGE2 plays an important role in maintaining the basic life functions of MSCs, such as the ability to proliferate, migrate and differentiate, and it also positively affects the formation of niches that are conducive to both hematopoiesis and carcinogenesis.

Porous composite hydrogels with improved MSC survival for robust epithelial sealing around implants and M2 macrophage polarization

The application of mesenchymal stem cell (MSC)-based therapy is expected to make a significant contribution to the improvement of epithelial sealing around implants. However, there is currently no optimal MSC delivery biomaterial for clinical application in peri-implant epithelium (PIE) integration. In this study, we show that injectable photo-cross-linkable porous gelatin methacryloyl (GelMA)/silk fibroin glycidyl methacrylate (SilMA) hydrogels encapsulating gingival tissue-derived MSCs (GMSCs) are a simple and practical approach for re-epithelization applications. The hydrogels played a prominent role in supporting the proliferation, survival, and spread of GMSCs. Moreover, it was found that GMSCs-laden Porous GelMA/SilMA hydrogels could significantly upregulate the hemidesmosomes (HDs)-related genes and proteins expression and promote M2 polarization while inhibiting M1 polarization in vitro. Based on a rat model of early implant placement, application of the MSC-loaded hydrogels could enhance the protein expression of LAMA3 and BP180 (COL17A1) at the implant-PIE interface and reduce horseradish peroxidase (HRP) penetration between the implants and PIE. Noticeably, hydrogel-based MSC therapy contributed to augmenting M2 macrophage infiltration at two time points in the gingival connective tissue around implants. These findings demonstrated that GMSCs-laden Porous GelMA/SilMA hydrogels could facilitate epithelial sealing around implants and M2-polarized macrophages and may be a novel and facile therapeutic strategy for implant-PIE integration. STATEMENT OF SIGNIFICANCE: In the case of poor integration between the implant and gingival epithelium, peri-implantitis can develop, which is one of the main causes of implant failure. While stem cell therapy has tremendous potential for addressing this issue, poor cell survival and engraftment compromise the effectiveness of the therapy. Due to the excellent modifiable and tunable properties of gelatin and silk fibroin, injectable photo-cross-linkable porous hydrogels were developed using gelatin methacryloyl (GelMA) and silk fibroin glycidyl methacrylate (SilMA) as delivery vehicles for gingiva-derived MSCs (GMSCs). Porous GelMA/SilMA not only enhanced the proliferation and viability of GMSCs but also promoted their immunomodulatory capability for favorable epithelial sealing around implants. Overall, GMSCs-seeded porous hydrogels could be promising strategies for re-epithelization treatment.

Engineering of human mesenchymal stem cells resistant to multiple natural killer subtypes

Mesenchymal stem cells (MSCs) as a therapeutic promise are often quickly cleared by innate immune cells of the host including natural killer (NK) cells. Efforts have been made to generate immune-escaping human embryonic stem cells (hESCs) where T cell immunity is evaded by defecting β-2-microglobulin (B2M), a common unit for human leukocyte antigen (HLA) class I, and NK cells are inhibited via ectopic expression of HLA-E or -G. However, NK subtypes vary among recipients and even at different pathologic statuses. It is necessary to dissect and optimize the efficacy of the immune-escaping cells against NK subtypes. Here, we first generated B2M knockout hESCs and differentiated them to MSCs (EMSCs) and found that NK resistance occurred with B2M^-/- EMSCs expressing HLA-E and -G only when they were transduced via an inducible lentiviral system in a dose-dependent manner but not when they were inserted into a safe harbor. HLA-E and -G expressed at high levels together in transduced EMSCs inhibited three major NK subtypes, including NKG2A⁺/LILRB1⁺, NKG2A⁺/LILRB1^-, and NKG2A^-/LILRB1⁺, which was further potentiated by IFN-γ priming. Thus, this study engineers MSCs with resistance to multiple NK subtypes and underscores that dosage matters when a transgene is used to confer a novel effect to host cells, especially for therapeutic cells to evade immune rejection.

Neuroprotection and Axonal Regeneration Induced by Bone Marrow Mesenchymal Stromal Cells Depend on the Type of Transplant

Mesenchymal stromal cell (MSC) therapy to treat neurodegenerative diseases has not been as successful as expected in some preclinical studies. Because preclinical research is so diverse, it is difficult to know whether the therapeutic outcome is due to the cell type, the type of transplant or the model of disease. Our aim here was to analyze the effect of the type of transplant on neuroprotection and axonal regeneration, so we tested MSCs from the same niche in the same model of neurodegeneration in the three transplantation settings: xenogeneic, syngeneic and allogeneic. For this, bone marrow mesenchymal stromal cells (BM-MSCs) isolated from healthy human volunteers or C57/BL6 mice were injected into the vitreous body of C57/BL6 mice (xenograft and syngraft) or BALB/c mice (allograft) right after optic nerve axotomy. As controls, vehicle matched groups were done. Retinal anatomy and function were analyzed in vivo by optical coherence tomography and electroretinogram, respectively. Survival of vision forming (Brn3a⁺) and non-vision forming (melanopsin⁺) retinal ganglion cells (RGCs) was assessed at 3, 5 and 90 days after the lesion. Regenerative axons were visualized by cholera toxin β anterograde transport. Our data show that grafted BM-MSCs did not integrate in the retina but formed a mesh on top of the ganglion cell layer. The xenotransplant caused retinal edema, detachment and folding, and a significant decrease of functionality compared to the murine transplants. RGC survival and axonal regeneration were significantly higher in the syngrafted retinas than in the other two groups or vehicle controls. Melanopsin⁺RGCs, but not Brn3a⁺RGCs, were also neuroprotected by the xenograft. In conclusion, the type of transplant has an impact on the therapeutic effect of BM-MSCs affecting not only neuronal survival but also the host tissue response. Our data indicate that syngrafts may be more beneficial than allografts and, interestingly, that the type of neuron that is rescued also plays a significant role in the successfulness of the cell therapy.

An overview of mesenchymal stem cells and their potential therapeutic benefits in cancer therapy

There has been increased interest in using stem cells for regenerative medicine and cancer therapy in the past decade. Mesenchymal stem cells (MSCs) are among the most studied stem cells due to their unique characteristics, such as self-renewal and developmental potency to differentiate into numerous cell types. MSC use has fewer ethical challenges compared with other types of stem cells. Although a number of studies have reported the beneficial effects of MSC-based therapies in treating various diseases, their contribution to cancer therapy remains controversial. The behaviour of MSCs is determined by the interaction between intrinsic transcriptional genes and extrinsic environmental factors. Numerous studies continue to emerge, as there is no denying the potential of MSCs to treat a wide variety of human afflictions. Therefore, the present review article provided an overview of MSCs and their differences compared with embryonic stem cells, and described the molecular mechanisms involved in maintaining their stemness. In addition, the article examined the therapeutic application of stem cells in the field of cancer. The present article also discussed the current divergent roles of MSCs in cancer therapy and the future potential in this field.

Rational Design of Immunomodulatory Hydrogels for Chronic Wound Healing

With all the advances in tissue engineering for construction of fully functional skin tissue, complete regeneration of chronic wounds is still challenging. Since immune reaction to the tissue damage is critical in regulating both the quality and duration of chronic wound healing cascade, strategies to modulate the immune system are of importance. Generally, in response to an injury, macrophages switch from pro-inflammatory to an anti-inflammatory phenotype. Therefore, controlling macrophages' polarization has become an appealing approach in regenerative medicine. Recently, hydrogels-based constructs, incorporated with various cellular and molecular signals, have been developed and utilized to adjust immune cell functions in various stages of wound healing. Here, the current state of knowledge on immune cell functions during skin tissue regeneration is first discussed. Recent advanced technologies used to design immunomodulatory hydrogels for controlling macrophages' polarization are then summarized. Rational design of hydrogels for providing controlled immune stimulation via hydrogel chemistry and surface modification, as well as incorporation of cell and molecules, are also dicussed. In addition, the effects of hydrogels' properties on immunogenic features and the wound healing process are summarized. Finally, future directions and upcoming research strategies to control immune responses during chronic wound healing are highlighted.

Role of prostaglandin E2 in tissue repair and regeneration

Tissue regeneration following injury from disease or medical treatment still represents a challenge in regeneration medicine. Prostaglandin E2 (PGE2), which involves diverse physiological processes via E-type prostanoid (EP) receptor family, favors the regeneration of various organ systems following injury for its capabilities such as activation of endogenous stem cells, immune regulation, and angiogenesis. Understanding how PGE2 modulates tissue regeneration and then exploring how to elevate the regenerative efficiency of PGE2 will provide key insights into the tissue repair and regeneration processes by PGE2. In this review, we summarized the application of PGE2 to guide the regeneration of different tissues, including skin, heart, liver, kidney, intestine, bone, skeletal muscle, and hematopoietic stem cell regeneration. Moreover, we introduced PGE2-based therapeutic strategies to accelerate the recovery of impaired tissue or organs, including 15-hydroxyprostaglandin dehydrogenase (15-PGDH) inhibitors boosting endogenous PGE2 levels and biomaterial scaffolds to control PGE2 release.

Bioactive Scaffolds in Stem Cell-Based Therapies for Myocardial Infarction: a Systematic Review and Meta-Analysis of Preclinical Trials

The use of bioactive scaffolds in conjunction with stem cell therapies for cardiac repair after a myocardial infarction shows significant promise for clinical translation. We performed a systematic review and meta-analysis of preclinical trials that investigated the use of bioactive scaffolds to support stem cell-aided cardiac regeneration, in comparison to stem cell treatment alone. Cochrane Library, Medline, Embase, PubMed, Scopus, Web of Science, and grey literature were searched through April 23, 2020 and 60 articles were included in the final analysis. The overall effect size observed in scaffold and stem cell-treated small animals compared to stem cell-treated controls for ejection fraction (EF) was 7.98 [95% confidence interval (CI): 6.36, 9.59] and for fractional shortening (FS) was 5.50 [95% CI: 4.35, 6.65] in small animal models. The largest improvements in EF and FS were observed when hydrogels were used (MD = 8.45 [95% CI: 6.46, 10.45] and MD = 5.76 [95% CI: 4.46, 7.05], respectively). Subgroup analysis revealed that cardiac progenitor cells had the largest effect size for FS, and was significant from pluripotent, mesenchymal and endothelial stem cell types. In large animal studies, the overall improvement of EF favoured the use of stem cell-embedded scaffolds compared to direct injection of cells (MD = 10.49 [95% CI: 6.30, 14.67]). Significant publication bias was present in the small animal trials for EF and FS. This study supports the use of bioactive scaffolds to aid in stem cell-based cardiac regeneration. Hydrogels should be further investigated in larger animal models for clinical translation.

Human Fallopian Tube - Derived Mesenchymal Stem Cells Inhibit Experimental Autoimmune Encephalomyelitis by Suppressing Th1/Th17 Activation and Migration to Central Nervous System

Mesenchymal stem cells comprise a natural reservoir of undifferentiated cells within adult tissues. Given their self-renewal, multipotency, regenerative potential and immunomodulatory properties, MSCs have been reported as a promising cell therapy for the treatment of different diseases, including neurodegenerative and autoimmune diseases. In this study, we investigated the immunomodulatory properties of human tubal mesenchymal stem cells (htMSCs) using the EAE model. htMSCs were able to suppress dendritic cells activation downregulating antigen presentation-related molecules, such as MHCII, CD80 and CD86, while impairing IFN-γ and IL-17 and increasing IL-10 and IL-4 secretion. It further correlated with milder disease scores when compared to the control group due to fewer leukocytes infiltrating the CNS, specially Th1 and Th17 lymphocytes, associated with increased IL-10 secreting Tr1 cells. Conversely, microglia were less activated and infiltrating mononuclear cells secreted higher levels of IL-4 and IL-10 and expressed reduced chemokine receptors as CCR4, CCR6 and CCR8. qPCR of the spinal cords revealed upregulation of indoleamine-2,3-dioxygenase (IDO) and brain derived neurotrophic factor (BDNF). Taken together, here evidenced the potential of htMSCs as an alternative for the treatment of inflammatory, autoimmune or neurodegenerative diseases.

The Expanding Armamentarium of Innovative Bioengineered Strategies to Augment Cardiovascular Repair and Regeneration

Cardiovascular disease remains the leading cause of death worldwide. While clinical trials of cell therapy have demonstrated largely neutral results, recent investigations into the mechanisms of natural myocardial regeneration have demonstrated promising new intersections between molecular, cellular, tissue, biomaterial, and biomechanical engineering solutions. New insight into the crucial role of inflammation in natural regenerative processes may explain why previous efforts have yielded only modest degrees of regeneration. Furthermore, the new understanding of the interdependent relationship of inflammation and myocardial regeneration have catalyzed the emergence of promising new areas of investigation at the intersection of many fields.

Metformin impairs homing ability and efficacy of mesenchymal stem cells for cardiac repair in streptozotocin-induced diabetic cardiomyopathy in rats

Bone marrow-derived mesenchymal stem cells (BM-MSCs) have demonstrated potential in treating diabetic cardiomyopathy. However, patients with diabetes are on multiple drugs and there is a lack of understanding of how transplanted stem cells would respond in presence of such drugs. Metformin is an AMP kinase (AMPK) activator, the widest used antidiabetic drug. In this study, we investigated the effect of metformin on the efficacy of stem cell therapy in a diabetic cardiomyopathy animal model using streptozotocin (STZ) in male Wistar rats. To comprehend the effect of metformin on the efficacy of BM-MSCs, we transplanted BM-MSCs (1 million cells/rat) with or without metformin. Our data demonstrate that transplantation of BM-MSCs prevented cardiac fibrosis and promoted angiogenesis in diabetic hearts. However, metformin supplementation downregulated BM-MSC-mediated cardioprotection. Interestingly, both BM-MSCs and metformin treatment individually improved cardiac function with no synergistic effect of metformin supplementation along with BM-MSCs. Investigating the mechanisms of loss of efficacy of BM-MSCs in the presence of metformin, we found that metformin treatment impairs homing of implanted BM-MSCs in the heart and leads to poor survival of transplanted cells. Furthermore, our data demonstrate that metformin-mediated activation of AMPK is responsible for poor homing and survival of BM-MSCs in the diabetic heart. Hence, the current study confirms that a conflict arises between metformin and BM-MSCs for treating diabetic cardiomyopathy. Approximately 10% of the world population is diabetic to which metformin is prescribed very commonly. Hence, future cell replacement therapies in combination with AMPK inhibitors may be more effective for patients with diabetes.NEW & NOTEWORTHY Metformin treatment reduces the efficacy of mesenchymal stem cell therapy for cardiac repair during diabetic cardiomyopathy. Stem cell therapy in diabetics may be more effective in combination with AMPK inhibitors.

Cardiac Cell Therapy for Heart Repair: Should the Cells Be Left Out?

Cardiovascular disease (CVD) is still the leading cause of death worldwide. Coronary artery occlusion, or myocardial infarction (MI) causes massive loss of cardiomyocytes. The ischemia area is eventually replaced by a fibrotic scar. From the mechanical dysfunctions of the scar in electronic transduction, contraction and compliance, pathological cardiac dilation and heart failure develops. Once end-stage heart failure occurs, the only option is to perform heart transplantation. The sequential changes are termed cardiac remodeling, and are due to the lack of endogenous regenerative actions in the adult human heart. Regenerative medicine and biomedical engineering strategies have been pursued to repair the damaged heart and to restore normal cardiac function. Such strategies include both cellular and acellular products, in combination with biomaterials. In addition, substantial progress has been made to elucidate the molecular and cellular mechanisms underlying heart repair and regeneration. In this review, we summarize and discuss current therapeutic approaches for cardiac repair and provide a perspective on novel strategies that holding potential opportunities for future research and clinical translation.

Role of prostaglandin E2 in allogeneic mesenchymal stem cell therapy for cardiac repair

Ischemic heart disease is among the primary causes of cardiovascular-related deaths worldwide. Conventional treatments including surgical interventions and medical therapies aid in preventing further damage to heart muscle but are unable to provide a permanent solution. In recent years, stem cell therapy has emerged as an attractive alternative to restore damaged myocardium after myocardial injury. Allogeneic (donor-derived) mesenchymal stem cells (MSCs) have shown great promise in preclinical and clinical studies, making them the most widely accepted candidates for cardiac cell therapy. MSCs promote cardiac repair by modulating host immune system and secreting various soluble factors, of which prostaglandin E2 (PGE2) is an important one. PGE2 plays a significant role in regulating cardiac remodeling following myocardial injury. In this review, we provide an overview of allogeneic MSCs as candidates for myocardial regeneration with a focus on the role of the PGE2/cyclooxygenase-2 (COX2) pathway in mediating these effects.

Hypoxia-induced downregulation of cyclooxygenase 2 leads to the loss of immunoprivilege of allogeneic mesenchymal stem cells

Allogeneic mesenchymal stem cells (MSCs) from young and healthy donors are reported to hold the potential to treat several immunological and degenerative disorders. However, recent data from animal studies and clinical trials demonstrate that immunogenicity and poor survival of transplanted MSCs impaired the efficacy of cells for regenerative applications. It is reported that initially immunoprivileged under in vitro conditions, MSCs are targeted by the host immune system after transplantation in the ischemic tissues in vivo. We performed in vitro (in MSCs) and in vivo (in the rat model of myocardial infarction [MI]) studies to elucidate the mechanisms responsible for the change in the immunophenotype of MSCs from immunoprivileged to immunogenic under ischemic conditions. We have recently reported that a soluble factor prostaglandin E2 (PGE2) preserves the immunoprivilege of allogeneic MSCs. In the current study, we found that PGE2 levels, which were elevated during normoxia, decreased in MSCs following exposure to hypoxia. Further, we found that proteasome-mediated degradation of cyclooxygenase-2 (COX2, rate-limiting enzyme in PGE2 biosynthesis) in hypoxic MSCs is responsible for PGE2 decrease and loss of immunoprivilege of MSCs. While investigating the mechanisms of COX2 degradation in hypoxic MSCs, we found that in normoxic MSCs, COP9 signalosome subunit 5 (CSN5) binds to COX2 and prevents its degradation by the proteasome. However, exposure to hypoxia leads to a decrease in CSN5 levels and its binding to COX2, rendering COX2 protein susceptible to proteasome-mediated degradation. This subsequently causes PGE2 downregulation and loss of immunoprivilege of MSCs. Maintaining COX2 levels in MSCs preserves immunoprivilege in vitro and improves the survival of transplanted MSCs in a rat model of MI. These data provide novel mechanistic evidence that PGE2 is downregulated in hypoxic MSCs which is responsible for the post-transplantation rejection of allogeneic MSCs. Therefore, our data suggest that the new strategies that target CSN5-COX2 signaling may improve survival and utility of transplanted allogeneic MSCs in the ischemic heart.

Hypoxia-induced increase in Sug1 leads to poor post-transplantation survival of allogeneic mesenchymal stem cells

Allogeneic mesenchymal stem cells (MSCs) from young and healthy donors are immunoprivileged and have the potential to treat numerous degenerative diseases. However, recent reviews of clinical trials report poor long-term survival of transplanted cells in the recipient that turned down the enthusiasm regarding MSC therapies. Increasing evidence now confirm that though initially immunoprivileged, MSCs eventually become immunogenic after transplantation in the ischemic or hypoxic environment of diseased tissues and are rejected by the host immune system. We performed in vitro (in rat and human cells) and in vivo (in a rat model) investigations to understand the mechanisms of the immune switch in the phenotype of MSCs. The immunoprivilege of MSCs is preserved by the absence of cell surface immune antigen, major histocompatibility complex II (MHC-II) molecule. We found that the ATPase subunit of 19S proteasome "Sug1" regulates MHC-II biosynthesis in MSCs. Exposure to hypoxia upregulates Sug1 in MSCs and its binding to class II transactivator (CIITA), a coactivator of MHC-II transcription. Sug1 binding to CIITA in hypoxic MSCs promotes the acetylation and K63 ubiquitination of CIITA leading to its activation and translocation to the nucleus, and ultimately MHC-II upregulation. In both rat and human MSCs, knocking down Sug1 inactivated MHC-II and preserved immunoprivilege even following hypoxia. In a rat model of myocardial infarction, transplantation of Sug1-knockdown MSCs in ischemic heart preserved immunoprivilege and improved the survival of transplanted cells. Therefore, the current study provides novel mechanisms of post-transplantation loss of immunoprivilege of MSCs. This study may help in facilitating better planning for future clinical trials.

Mesenchymal Stem Cells: A New Generation of Therapeutic Agents as Vehicles in Gene Therapy

In recent years, mesenchymal stem cells (MSCs) as a new tool for therapeutic gene delivery in clinics have attracted much attention. Their advantages cover longer lifespan, better isolation, and higher transfection efficiency and proliferation rate. MSCs are the preferred approach for cell-based therapies because of their in vitro self-renewal capacity, migrating especially to tumor tissues, as well as anti-inflammatory and immunomodulatory properties. Therefore, they have considerable efficiency in genetic engineering for future clinical applications in cancer gene therapy and other diseases. For improving therapeutic efficiency, targeted therapy of cancers can be achieved through the sustained release of therapeutic agents and functional gene expression induction to the intended tissues. The development of a new vector in gene therapy can improve the durability of a transgene expression. Also, the safety of the vector, if administered systemically, may resolve several problems, such as durability of expression and the host immune response. Currently, MSCs are prominent candidates as cell vehicles for both preclinical and clinical trials due to the secretion of therapeutic agents in several cancers. In the present study, we discuss the status of gene therapy in both viral and non-viral vectors along with their limitations. Throughout this study, the use of several nano-carriers for gene therapy is also investigated. Finally, we critically discuss the promising advantages of MSCs in targeted gene delivery, tumor inhibition and their utilization as the gene carriers in clinical situations.

Hypoxia-induced shift in the phenotype of proteasome from 26S toward immunoproteasome triggers loss of immunoprivilege of mesenchymal stem cells

Allogeneic mesenchymal stem cells (MSCs) are immunoprivileged and are being investigated in phase I and phase II clinical trials to treat different degenerative and autoimmune diseases. In spite of encouraging outcome of initial trials, the long-term poor survival of transplanted cells in the host tissue has declined the overall enthusiasm. Recent analyses of allogeneic MSCs based studies confirm that after transplantation in the hypoxic or ischemic microenvironment of diseased tissues, MSCs become immunogenic and are rejected by recipient immune system. The immunoprivilege of MSCs is preserved by absence or negligible expression of cell surface antigen, human leukocyte antigen (HLA)-DRα. We found that in normoxic MSCs, 26S proteasome degrades HLA-DRα and maintains immunoprivilege of MSCs. The exposure to hypoxia leads to inactivation of 26S proteasome and formation of immunoproteasome in MSCs, which is associated with upregulation and activation of HLA-DRα, and as a result, MSCs become immunogenic. Furthermore, inhibition of immunoproteasome formation in hypoxic MSCs preserves the immunoprivilege. Therefore, hypoxia-induced shift in the phenotype of proteasome from 26S toward immunoproteasome triggers loss of immunoprivilege of allogeneic MSCs. The outcome of the current study may provide molecular targets to plan interventions to preserve immunoprivilege of allogeneic MSCs in the hypoxic or ischemic environment.

Syngeneic Mesenchymal Stem Cells Reduce Immune Rejection After Induced Pluripotent Stem Cell-Derived Allogeneic Cardiomyocyte Transplantation

Avoiding immune rejection after allogeneic induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) transplantation is a concern. However, mesenchymal stem cells (MSCs) can suppress immune rejection. To determine whether MSC co-transplantation can reduce immune rejection after allogeneic iPSC-CM transplantation, the latter cell type, harbouring a luciferase transgene, was subcutaneously transplanted alone or together with syngeneic MSCs into BALB/c mice. Bioluminescence imaging revealed that MSC co-transplantation significantly improved graft survival (day 7: iPSC-CMs alone 34 ± 5%; iPSC-CMs with MSCs, 61 ± 7%; P = 0.008). MSC co-transplantation increased CD4 + CD25 + FOXP3 + regulatory T cell numbers, apoptotic CD8-positive T cells, and IL-10 and TGF-beta expression at the implantation site. Analysis using a regulatory T cell depletion model indicated that enhanced regulatory T cell populations in the iPSC-CM with MSC group partially contributed to the extended iPSC-CM survival. Further, MSCs affected activated lymphocytes directly through cell–cell contact, which reduced the CD8/CD4 ratio, the proportion of Th1-positive cells among CD4-positive cells, and the secretion of several inflammation-related cytokines. Syngeneic MSC co-transplantation might thus control allogeneic iPSC-CM rejection by mediating immune tolerance via regulatory T cells and cell–cell contact with activated lymphocytes; this approach has promise for cardiomyogenesis-based therapy using allogeneic iPSC-CMs for severe heart failure.

Application of Ti3 C2 MXene Quantum Dots for Immunomodulation and Regenerative Medicine

Inflammation is tightly linked to tissue injury. In regenerative medicine, immune activation plays a key role in rejection of transplanted stem cells and reduces the efficacy of stem cell therapies. Next-generation smart biomaterials are reported to possess multiple biologic properties for tissue repair. Here, the first use of 0D titanium carbide (Ti₃ C₂ ) MXene quantum dots (MQDs) for immunomodulation is presented with the goal of enhancing material-based tissue repair after injury. MQDs possess intrinsic immunomodulatory properties and selectively reduce activation of human CD4⁺ IFN-γ⁺ T-lymphocytes (control 87.1 ± 2.0%, MQDs 68.3 ± 5.4%) while promoting expansion of immunosuppressive CD4⁺ CD25⁺ FoxP3⁺ regulatory T-cells (control 5.5 ± 0.7%, MQDs 8.5 ± 0.8%) in a stimulated lymphocyte population. Furthermore, MQDs are biocompatible with bone marrow-derived mesenchymal stem cells and induced pluripotent stem cell-derived fibroblasts. Finally, Ti₃ C₂ MQDs are incorporated into a chitosan-based hydrogel to create a 3D platform with enhanced physicochemical properties for stem cell delivery and tissue repair. This composite hydrogel demonstrates increased conductivity while maintaining injectability and thermosensitivity. These findings suggest that this new class of biomaterials may help bridge the translational gap in material and stem cell-based therapies for tissue repair and treatment of inflammatory and degenerative diseases.

High throughput screening reveals no significant changes in protein synthesis, processing, and degradation machinery during passaging of mesenchymal stem cells

Increasing reports of successful and safe application of bone marrow derived mesenchymal stem cells (BM-MSCs) for cell therapy are pouring in from numerous studies. However poor survival of transplanted cells in the recipient has impaired the benefits of BM-MSCs based therapies. Therefore cell product preparation procedures pertaining to MSC therapy need to be optimized to improve the survival of transplanted cells. One of the important ex vivo procedures in the preparation of cells for therapy is passaging of BM-MSCs to ensure a suitable number of cells for transplantation, which may affect the turnover of proteins involved in regulation of cell survival and (or) death pathways. In the current study, we investigated the effect of an increase in passage number of BM-MSCs in cell culture on the intracellular protein turnover (protein synthesis, processing, and degradation machinery). We performed proteomic analysis of BM-MSCs at different passages. There was no significant difference observed in the ribosomal, protein processing, and proteasomal pathways related proteins in BM-MSCs with an increase in passage number from P3 to P7. Therefore, expansion of MSCs in the cell culture in clinically relevant passages (Passage 3–7) does not affect the quality of MSCs in terms of intracellular protein synthesis and turnover.

Cell-cell contact with proinflammatory macrophages enhances the immunotherapeutic effect of mesenchymal stem cells in two abortion models

Mesenchymal stem cells (MSCs), which are pluripotent cells with immunomodulatory properties, have been considered good candidates for the therapy of several immune disorders, such as inflammatory bowel diseases, concanavalin A-induced liver injury, and graft-versus-host disease. The embryo is a natural allograft to the maternal immune system. A successful pregnancy depends on the timely extinction of the inflammatory response induced by embryo implantation, followed by the switch to a tolerant immune microenvironment in both the uterus and the system. Excessive infiltration of immune cells and serious inflammatory responses are triggers for embryo rejection, which results in miscarriage. Here, we demonstrated that adoptive transfer of MSCs could prevent fetal loss in a lipopolysaccharide (LPS)-induced abortion model and immune response-mediated spontaneous abortion model. The immunosuppressive MSCs alleviated excessive inflammation by inhibiting CD4⁺T cell proliferation and promoting the decidual macrophage switch to M2 in a tumor necrosis factor-stimulated gene-6 (TSG-6)-dependent manner. Cell-to-cell contact with proinflammatory macrophages increased the TSG-6 production by the MSCs, thereby enhancing the suppressive regulation of T cells and macrophages. Moreover, proinflammatory macrophages in contact with the MSCs upregulated the expression of CD200 on the stem cells and facilitated the reprogramming of macrophages towards an anti-inflammatory skew through the interaction of CD200 with CD200R on proinflammatory macrophages. Therefore, the results demonstrate that a TSG-6-mediated paracrine effect, reinforced by cell-to-cell contact between MSCs and proinflammatory macrophages, is involved in the mechanism of MSC-mediated abortion relief through the induction of immune tolerance. Our study also indicates the potential application of MSCs in clinical recurrent miscarriages.

Hypoxia-induced 26S proteasome dysfunction increases immunogenicity of mesenchymal stem cells

Bone marrow-derived allogeneic (donor derived) mesenchymal stem cells (MSCs) are immunoprivileged and are considered to be prominent candidates for regenerative therapy for numerous degenerative diseases. Even though the outcome of initial allogeneic MSCs based clinical trials was encouraging, the overall enthusiasm, of late, has dimmed down. This is due to failure of long-term survival of transplanted cells in the recipient. In fact, recent analyses of allogeneic MSC-based studies demonstrated that cells after transplantation turned immunogenic and were subsequently rejected by host immune system. The current study reveals a novel mechanism of immune switch in MSCs. We demonstrate that hypoxia, a common denominator of ischemic tissues, induces an immune shift in MSCs from immunoprivileged to immunogenic state. The immunoprivilege of MSCs is preserved by downregulation or the absence of major histocompatibility complex class II (MHC-II) molecules. We found that 26S proteasome-mediated intracellular degradation of MHC-II helps maintain the absence of MHC-II expression on cell surface in normoxic MSCs and preserves their immunoprivilege. The exposure to hypoxia leads to dissociation of 19S and 20S subunits, and inactivation of 26S proteasome. This prevented the degradation of MHC-II and, as a result, the MSCs became immunogenic. Furthermore, we found that hypoxia-induced decrease in the levels of a chaperon protein HSP90α is responsible for inactivation of 26S proteasome. Maintaining HSP90α levels in hypoxic MSCs preserved the immunoprivilege of MSCs. Therefore, hypoxia-induced inactivation of 26S proteasome assembly instigates loss of immunoprivilege of allogeneic mesenchymal stem cells. Maintaining 26S proteasome activity in mesenchymal stem cells preserves their immunoprivilege.

Cytoprotective role of vitamin E in porcine adipose-tissue-derived mesenchymal stem cells against hydrogen-peroxide-induced oxidative stress

Survival of mesenchymal stem cells (MSCs) against oxidative stress and inflammation is vital for effective stem cell therapy. The reactive oxygen species (ROS) result in apoptosis and release of inflammatory mediators. Adipose-derived stem cells (ASCs) have shown promise for stem cell therapy owing to their anti-inflammatory and anti-oxidant activity. Previously, we showed the benefits of vitamin E against hydrogen peroxide (H₂O₂)-induced oxidative stress in rat bone marrow-derived MSCs. In this study, we aim to evaluate the effect of vitamin E treatment on porcine adipose-derived mesenchymal stem cells (pASCs) against H₂O₂-induced oxidative stress. The oxidative stress was induced by treating pASCs with 500 μM H₂O₂ with or without vitamin E. Viability of pASCs is enhanced after vitamin E treatment. In addition, reduced cellular toxicity, total NO level, PGE₂ production and caspase-3 activity were observed after vitamin E treatment. Gene expression analysis of vitamin E-treated pASCs showed down-regulated expression for the genes associated with oxidative stress and apoptosis, viz., NOS2, Casp3, p53, BAX, MDM2, NFκB, HIF1α and VEGF-A genes. On the other hand, expression of anti-apoptotic and survival genes was up-regulated, viz., BCL2, BCL2L1 and MCL1. Furthermore, phosphorylation of Akt was attenuated following vitamin E treatment. The findings of this study may help in developing effective stem cell therapy for the diseases characterized by the oxidative stress and inflammation.

Early passaging of mesenchymal stem cells does not instigate significant modifications in their immunological behavior

Background

Bone marrow-derived allogeneic mesenchymal stem cells (MSCs) from young healthy donors are immunoprivileged and their clinical application for regenerative medicine is under evaluation. However, data from preclinical and initial clinical trials indicate that allogeneic MSCs after transplantation provoke a host immune response and are rejected. In the current study, we evaluated the effect of an increase in passage number in cell culture on immunoprivilege of the MSCs. Since only limited numbers of MSCs can be sourced at a time from a donor, it is imperative to expand them in culture to meet the necessary numbers required for cell therapy. Presently, the most commonly used passages for transplantation include passages (P)3–7. Therefore, in this study we included clinically relevant passages, i.e., P3, P5, and P7, for evaluation.

Methods

The immunoprivilege of MSCs was assessed with the mixed leukocyte reaction assay, where rat MSCs were cocultured with peripheral blood leukocytes for 72 h. Leukocyte-mediated cytotoxicity, apoptosis (Bax/Bcl-xl ratio), leukocyte proliferation, and alterations in cellular bioenergetics in MSCs were assessed after the coculture. Furthermore, the expression of various oxidized phospholipids (oxidized phosphatidylcholine (ox-PC)) was analyzed in MSCs using a lipidomic platform. To determine if the ox-PCs were acting in tandem with downstream intracellular protein alterations, we performed proteome analysis using a liquid chromatography/mass spectrometry (LC/MS) proteomic platform.

Results

Our data demonstrate that MSCs were immunoprivileged at all three passages since coculture with leukocytes did not affect the survival of MSCs at P3, P5, and P7. We also found that, with an increase in the passage number of MSCs, leukocytes did not cause any significant effect on cellular bioenergetics (basal respiration rate, spare respiratory capacity, maximal respiration, and coupling efficiency). Interestingly, in our omics data, we detected alterations in some of the ox-PCs and proteins in MSCs at different passages; however, these changes were not significant enough to affect their immunoprivilege.

Conclusions

The outcome of this study demonstrates that an increase in passage number (from P3 to P7) in the cell culture does not have any significant effect on the immunoprivilege of MSCs.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0867-4) contains supplementary material, which is available to authorized users.

New strategies for improving stem cell therapy in ischemic heart disease

Stem cell therapy is a promising approach to the treatment of ischemic heart disease via replenishing cell loss after myocardial infarction. Both preclinical studies and clinical trials have indicated that cardiac function improved consistently, but very modestly after cell-based therapy. This mainly attributed to low cell survival rate, engraftment and functional integration, which became the major challenges to regenerative medicine. In recent years, several new cell types have been developed to regenerate cardiomyocytes and novel delivery approaches helped to increase local cell retention. New strategies, such as cell pretreatment, gene-based therapy, tissue engineering, extracellular vesicles application and immunologic regulation, have surged and brought about improved cell survival and functional integration leading to better therapeutic effects after cell transplantation. In this review, we summarize these new strategies targeting at challenges of cardiac regenerative medicine and discuss recent evidences that may hint their effectiveness in the future clinical settings.

Anti-Donor Immune Responses Elicited by Allogeneic Mesenchymal Stem Cells and Their Extracellular Vesicles: Are We Still Learning?

Mesenchymal stromal cells (MSC) have been used to treat a broad range of disease indications such as acute and chronic inflammatory disorders, autoimmune diseases, and transplant rejection due to their potent immunosuppressive/anti-inflammatory properties. The breadth of their usage is due in no small part to the vast quantity of published studies showing their ability to modulate multiple immune cell types of both the innate and adaptive immune response. While patient-derived (autologous) MSC may be the safer choice in terms of avoiding unwanted immune responses, factors including donor comorbidities may preclude these cells from use. In these situations, allogeneic MSC derived from genetically unrelated individuals must be used. While allogeneic MSC were initially believed to be immune-privileged, substantial evidence now exists to prove otherwise with multiple studies documenting specific cellular and humoral immune responses against donor antigens following administration of these cells. In this article, we will review recent published studies using non-manipulated, inflammatory molecule-activated (licensed) and differentiated allogeneic MSC, as well as MSC extracellular vesicles focusing on the immune responses to these cells and whether or not such responses have an impact on allogeneic MSC-mediated safety and efficacy.

Aging dysregulates D- and E-series resolvins to modulate cardiosplenic and cardiorenal network following myocardial infarction

Post-myocardial infarction (MI), overactive inflammation is the hallmark of aging, however, the mechanism is unclear. We hypothesized that excess influx of omega 6 fatty acids may impair resolution, thus impacting the cardiosplenic and cardiorenal network post-MI. Young and aging mice were fed on standard lab chow (LC) and excess fatty acid (safflower oil; SO)-enriched diet for 2 months and were then subjected to MI surgery. Despite similar infarct areas and left ventricle (LV) dysfunction post-MI, splenic mass spectrometry data revealed higher levels of arachidonic acid (AA) derived pro-inflammatory metabolites in young-SO, but minimal formation of docosanoids, D- and E- series resolvins in SO-fed aged mice. The aged mice receiving excess intake of fatty acids exhibit; 1) decreased lipoxygenases (5-,12-, and 15) in the infarcted LV; 2) lower levels of 14HDHA, RvD1, RvD5, protectin D1, 7(S)maresin1, 8-,11-,18-HEPE and RvE3 with high levels of tetranor-12-HETEs; 3) dual population of macrophages (CD11b^low/F480^high and CD11b^high/F480^high) with increased pro-inflammatory (CD11b⁺F4/80⁺Ly6C^hi) phenotype and; 4) increased kidney injury marker NGAL with increased expression of TNF-ɑ and IL-1β indicating MI-induced non-resolving response compared with LC-group. Thus, excess fatty acid intake magnifies the post-MI chemokine signaling and inflames the cardiosplenic and cardiorenal network towards a non-resolving microenvironment in aging.

Insights into cell-free therapeutic approach: Role of stem cell "soup-ernatant"

Current advances in medicine have revolutionized the field of regenerative medicine dramatically with newly evolved therapies for repair or replacement of degenerating or injured tissues. Stem cells (SCs) can be harvested from different sources for clinical therapeutics, which include fetal tissues, umbilical cord blood, embryos, and adult tissues. SCs can be isolated and differentiated into desired lineages for tissue regeneration and cell replacement therapy. However, several loopholes need to be addressed properly before this can be extended for large-scale therapeutic application. These include a careful approach for patient safety during SC treatments and tolerance of recipients. SC treatments are associated with a number of risk factors and require successful integration and survival of transplanted cells in the desired microenvironment with concurrent tissue regeneration. Recent studies have focused on developing alternatives that can replace the cell-based therapy using paracrine factors. The development of stem "cell free" therapies can be devoted mainly to the use of soluble factors (secretome), extracellular vesicles, and mitochondrial transfer. The present review emphasizes on the paradigms related to the use of SC-based therapeutics and the potential applications of a cell-free approach as an alternative to cell-based therapy in the area of regenerative medicine.

Absence of NUCKS augments paracrine effects of mesenchymal stem cells-mediated cardiac protection

Bone marrow-derived mesenchymal stem cells (BM-MSCs) contribute to myocardial repair after myocardial infarction (MI) by secreting a panel of growth factors and cytokines. This study was to investigate the potential mechanisms of the nuclear casein kinase and cyclin-dependent kinase substrate 1 (NUCKS) in regulation of the profiles of BM-MSCs secretion and compare the therapeutic efficacy of NUCKS^-/-- and wide type-BM-MSCs (WT-BM-MSCs) on MI. The secretion profiles between NUCKS^-/-- and WT-BM-MSCs under hypoxia (1%O₂) were analyzed. Gene function analysis showed that compared with WT-BM-MSCs-conditioned medium (CdM), some genes over-presented in NUCKS^-/--BM-MSCs-CdM were closely associated with inflammatory response, regulation of cell proliferation, death, migration and secretion. Notably, VEGFa in NUCKS^-/--BM-MSCs-CdM was higher than that of WT-BM-MSCs-CdM. WT-BM-MSCs and NUCKS^-/--BM-MSCs were transplanted into the peri-infarct region in mice of MI. At 4 weeks after cell transplantation, NUCKS^-/-- or WT-BM-MSCs group significantly improved heart function and vessels density and reduced infarction size and apoptosis of cardiomyocytes. Furthermore, NUCKS^-/--BM-MSCs provided better cardioprotective effects than WT-BM-MSCs against MI. Our study demonstrates that depletion of NUCKS enhances the therapeutic efficacy of BM-MSCs for MI via regulating the secretion.

Concise Review: Fat and Furious: Harnessing the Full Potential of Adipose-Derived Stromal Vascular Fraction

Due to their capacity to self-renew, proliferate and generate multi-lineage cells, adult-derived stem cells offer great potential for use in regenerative therapies to stop and/or reverse degenerative diseases such as diabetes, heart failure, Alzheimer's disease and others. However, these subsets of cells can be isolated from different niches, each with differing potential for therapeutic applications. The stromal vascular fraction (SVF), a stem cell enriched and adipose-derived cell population, has garnered interest as a therapeutic in regenerative medicine due to its ability to secrete paracrine factors that accelerate endogenous repair, ease of accessibility and lack of identified major adverse effects. Thus, one can easily understand the rush to employ adipose-derived SVF to treat human disease. Perhaps faster than any other cell preparation, SVF is making its way to clinics worldwide, while critical preclinical research needed to establish SVF safety, efficacy and optimal, standardized clinical procedures are underway. Here, we will provide an overview of the current knowledge driving this phenomenon, its regulatory issues and existing studies, and propose potential unmapped applications. Stem Cells Translational Medicine 2017;6:1096-1108.

Immunogenicity of insulin-producing cells derived from human umbilical cord mesenchymal stem cells

Mesenchymal stem cells (MSCs) have been considered as hypo-immunogenic and immunosuppressive. However, a thorough understanding of the immunological properties after MSC differentiation in vitro and in vivo has not been reached. We asked whether it would be immunogenic after differentiation or influenced by the immune microenvironment after transplantation. In different disease models, the immunological changes of MSCs after differentiation greatly varied, with contradicting results. In order to clarify this, we used a modified four-step induction method to induce human umbilical cord MSCs (hUCMSCs) to differentiate into insulin-producing cells (IPCs), and investigate the immunological changes after differentiation and immune reactions after transplantation into diabetic mice. We found that the induced IPCs are hypo-immunogenic, lacking HLA-DR, CD40 and CD80 expression. Of note, we observed immune cell infiltration to peritoneal cavity and left kidney capsule after local transplantation of induced IPCs. This indicated that hUCMSC-derived IPCs maintained hypo-immunogenic in vitro, but became immunogenic after transplanting to the host, possibly due to the changes of immune microenvironment and thereafter immunological enhancement and immune cell infiltration.

VEGF-loaded microsphere patch for local protein delivery to the ischemic heart

BACKGROUND

Revascularization of the heart after myocardial infarction (MI) using growth factors delivered by hydrogel-based microspheres represents a promising therapeutic approach for cardiac regeneration. Microspheres have tuneable degradation properties and support the prolonged release of soluble factors. Cardiac patches provide mechanical restraint, preventing dilatation associated with ventricular remodelling.

METHODS

We combined these approaches and produced a compacted calcium-alginate microsphere patch, restrained by a chitosan sheet, to deliver vascular endothelial growth factor (VEGF) to the heart after myocardial injury in rats.

RESULTS

Microspheres had an average diameter of 3.2μm, were nonporous, and characterized by a smooth dimpled surface. Microsphere patches demonstrated prolonged in vitro release characteristics compared to non-compacted microspheres and VEGF supernatants obtained from patches maintained their bioactivity for the 5day duration of the study in vitro. In vivo, patches were assessed with magnetic resonance imaging following MI, and demonstrated 50% degradation 25.6days after implantation. Both VEGF^(-) and VEGF⁽⁺⁾ microsphere patch-treated hearts had better cardiac function than unpatched (chitosan sheet only) controls. However, VEGF⁽⁺⁾ microsphere-patched hearts had thicker scars characterized by higher capillary density in the border zone than did those treated with VEGF^(-) patches. VEGF was detected in the patches 4weeks post-implantation.

CONCLUSION

The condensed microsphere patch represents a new therapeutic platform for cytokine delivery and could be used as an adjuvant to current biomaterial and cell-based therapies to promote localized angiogenesis in the infarcted heart.

STATEMENT OF SIGNIFICANCE

Following a heart attack, a lack of blood flow to the heart results in loss of heart cells. Growth factors may facilitate growth of blood vessels and heart tissue repair and prevent the onset of heart failure. Determining a way to deliver these growth factors directly to the heart is vital. Here, we combined two biomaterial-based approaches to deliver vascular endothelial growth factor (VEGF) to rat hearts after heart attack: a microsphere for prolonged release of VEGF, and a cardiac patch for mechanical restraint to prevent heart dysfunction. The feasibility of this microsphere patch was demonstrated by surgically implanting it over the infarct region of the heart post-injury. VEGF-patched hearts had better blood vessel growth, tissue repair, and heart function.

Whole-Genome Expression Analysis and Signal Pathway Screening of Synovium-Derived Mesenchymal Stromal Cells in Rheumatoid Arthritis

Synovium-derived mesenchymal stromal cells (SMSCs) may play an important role in the pathogenesis of rheumatoid arthritis (RA) and show promise for therapeutic applications in RA. In this study, a whole-genome microarray analysis was used to detect differential gene expression in SMSCs from RA patients and healthy donors (HDs). Our results showed that there were 4828 differentially expressed genes in the RA group compared to the HD group; 3117 genes were upregulated, and 1711 genes were downregulated. A Gene Ontology analysis showed significantly enriched terms of differentially expressed genes in the biological process, cellular component, and molecular function domains. A Kyoto Encyclopedia of Genes and Genomes analysis showed that the MAPK signaling and rheumatoid arthritis pathways were upregulated and that the p53 signaling pathway was downregulated in RA SMSCs. Quantitative real-time polymerase chain reaction was applied to verify the expression variations of the partial genes mentioned above, and a western blot analysis was used to determine the expression levels of p53, p-JNK, p-ERK, and p-p38. Our study found that differentially expressed genes in the MAPK signaling, rheumatoid arthritis, and p53 signaling pathways may help to explain the pathogenic mechanism of RA and lead to therapeutic RA SMSC applications.

Allogeneic Mesenchymal Stromal Cells Transplanted Onto the Heart Surface Achieve Therapeutic Myocardial Repair Despite Immunologic Responses in Rats

Background

Transplantation of allogeneic mesenchymal stromal cells (MSCs) is a promising treatment for heart failure. We have shown that epicardial placement of cell sheets markedly increases donor cell survival and augments therapeutic effects compared with the current methods. Although immune rejection of intramyocardially injected allogeneic MSCs have been suggested, allogeneic MSCs transplanted on the heart surface (virtual space) may undergo different courses. This study aimed to elucidate immunologic response against epicardially placed allogeneic MSCs, rejection or acceptance of these cells, and their therapeutic effects for heart failure.

Methods and Results

At 4 weeks after coronary artery ligation, Lewis rats underwent epicardial placement of MSC sheets from syngeneic Lewis or allogeneic Fischer 344 rats or sham treatment. At days 3 and 10 after treatment, similar ratios (≈50% and 30%, respectively) of grafted MSCs survived on the heart surface in both MSC sheet groups. By day 28, survival of syngeneic MSCs was substantially reduced (8.9%); survival of allogeneic MSCs was more extensively reduced (0.2%), suggesting allorejection. Correspondingly, allogeneic MSCs were found to have evoked an immunologic response, albeit low level, as characterized by accumulation of CD4⁺ T cells and upregulation of interleukin 6. Despite this alloimmune response, the allogeneic MSC sheet achieved myocardial upregulation of reparative factors, enhanced repair of the failing myocardium, and improved cardiac function to the equivalent degree observed for the syngeneic MSC sheet.

Conclusions

Allogeneic MSCs placed on the heart surface evoked an immunologic response; however, this allowed sufficient early phase donor cell survival to induce equivalent therapeutic benefits to syngeneic MSCs. Further development of this approach toward clinical application is warranted.

Heterogeneous Differentiation of Human Mesenchymal Stem Cells in 3D Extracellular Matrix Composites

Extracellular matrix (ECM) proteins are structural elements of tissue and also potent signaling molecules. Previously, our laboratory showed that ECM of 2D coatings can trigger differentiation of bone marrow-derived mesenchymal stem cells (MSCs) into mesodermal lineages in an ECM-specific manner over 14 days, in some cases comparable to chemical induction. To test whether a similar effect was possible in a 3D, tissue-like environment, we designed a synthetic-natural biomaterial composite. The composite can present whole-molecule ECM proteins to cells, even those that do not spontaneously form hydrogels ex vivo, in 3D. To this end, we entrapped collagen type I, laminin-111, or fibronectin in ECM composites with MSCs and directly compared markers of mesodermal differentiation including cardiomyogenic (ACTC1), osteogenic (SPP1), adipogenic (PPARG), and chondrogenic (SOX9) in 2D versus 3D. We found the 3D condition largely mimicked the 2D condition such that the addition of type I collagen was the most potent inducer of differentiation to all lineages tested. One notable difference between 2D and 3D was pronounced adipogenic differentiation in 3D especially in the presence of exogenous collagen type I. In particular, PPARG gene expression was significantly increased ∼16-fold relative to chemical induction, in 3D and not in 2D. Unexpectedly, 3D engagement of ECM proteins also altered immunomodulatory function of MSCs in that expression of IL-6 gene was elevated relative to basal levels in 2D. In fact, levels of IL-6 gene expression in 3D composites containing exogenously supplied collagen type I or fibronectin were statistically similar to levels attained in 2D with tumor necrosis factor-α (TNF-α) stimulation and these levels were sustained over a 2-week period. Thus, this novel biomaterial platform allowed us to compare the biochemical impact of whole-molecule ECM proteins in 2D versus 3D indicating enhanced adipogenic differentiation and IL-6 expression of MSC in the 3D context. Exploiting the biochemical impact of ECM proteins on MSC differentiation and immunomodulation could augment the therapeutic utility of MSCs.

Immunotolerant Properties of Mesenchymal Stem Cells: Updated Review

Stem cell transplantation is a potential therapeutic option to regenerate damaged myocardium and restore function after infarct. Current research is focused on the use of allogeneic mesenchymal stem cells (MSCs) due to their unique immunomodulatory characteristics and ability to be harvested from young and healthy donors. Both animal and human studies support the immunoprivileged state of MSCs and even demonstrate improvements in cardiac function after transplantation. This research continues to be a topic of interest, as advances will ultimately enable the clinical use of these universal cells for therapy after a myocardial infarction. Updated in vitro, in vivo, and clinical trial studies are discussed in detail in the following review.

The challenges and promises of allogeneic mesenchymal stem cells for use as a cell-based therapy

Mesenchymal stem cells (MSCs) are ideal for cell-based therapy in various inflammatory diseases because of their immunosuppressive and tissue repair properties. Moreover, their immunosuppressive properties and low immunogenicity contribute to a reduced or weakened immune response elicited by the implantation of allogeneic MSCs compared with other cell types. Therefore, implantation of allogeneic MSCs may be a promising cell-based therapy. In this review, we first summarize the unique advantages of allogeneic MSCs for therapeutic applications. Second, we critically analyze the factors influencing their therapeutic effects, including administration routes, detection time-points, disease models, differentiation of MSCs in vivo, and timing and dosage of MSC administration. Finally, current approaches to allogeneic MSC application are discussed. In conclusion, allogeneic MSCs are a promising option because of their low immunogenicity and immunosuppressive and tissue repair capabilities. Further investigations are needed to enhance the consistency and efficacy of MSCs when used as a cell-based therapy in inflammatory diseases as well as for tissue repair.

Roles of microRNA-34a targeting SIRT1 in mesenchymal stem cells

Introduction

Mesenchymal stem cell (MSC)-based therapies have had positive outcomes both in animal models of cardiovascular diseases and in clinical patients. However, the number and function of MSCs decline during hypoxia and serum deprivation (H/SD), reducing their ability to contribute to endogenous injury repair. MicroRNA-34a (miR-34a) is originally identified as a TP53-targeted miRNA that modulates cell functions, including apoptosis, proliferation, and senescence via several signaling pathways, and hence is an appealing target for MSC-based therapy for myocardial infarction.

Methods

Bone marrow-derived MSCs were isolated from 60–80 g male donor rats. Expression levels of miR-34a were determined by qRT-PCR. The roles of miR-34a in regulating cell vitality, apoptosis and senescence were investigated using the cell counting kit (CCK-8) assay, flow cytometric analysis of Annexin V-FITC/PI staining and senescence-associated β-galactosidase (SA-β-gal) staining, respectively. The expression of silent information regulator 1 (SIRT1) and forkhead box class O 3a (FOXO3a) and of apoptosis- and senescence-associated proteins in MSCs were analyzed by western blotting.

Results

The results of the current study showed that miR-34a was significantly up-regulated under H/SD conditions in MSCs, while overexpression of miR-34a was significantly associated with increased apoptosis, impaired cell vitality and aggravated senescence. Moreover, we found that the mechanism underlying the proapoptotic function of miR-34a involves activation of the SIRT1/FOXO3a pathway, mitochondrial dysfunction and finally, activation of the intrinsic apoptosis pathway. Further study showed that miR-34a can also aggravate MSC senescence, an effect which was partly abolished by the reactive oxygen species (ROS) scavenger, N-acetylcysteine (NAC).

Conclusions

Our study demonstrates for the first time that miR-34a plays pro-apoptotic and pro-senescence roles in MSCs by targeting SIRT1. Thus, inhibition of miR-34a might have important therapeutic implications in MSC-based therapy for myocardial infarction.

Stem cell therapy for cardiac regeneration: hits and misses

Cardiac injury and loss of cardiomyocytes is a causative as well as a resultant condition of cardiovascular disorders, which are the leading cause of death throughout the world. This loss of cardiomyocytes cannot be completely addressed through the currently available drugs being administered, which mainly function only in relieving the symptoms. There is a huge potential being investigated for regenerative and cell replacement therapies through recruiting stem cells of various origins namely embryonic, reprogramming/induction, and adult tissue. These sources are being actively studied for translation to clinical scenarios. In this review, we attempt to discuss some of these promising scenarios, including the clinical trials and the obstacles that need to be overcome, and hope to address the direction in which stem cell therapy is heading.