Mesenchymal stem cells pretreated with delivered Hph-1-Hsp70 protein are protected from hypoxia-mediated cell death and rescue heart functions from myocardial injury

Therapeutic applications of mesenchymal/medicinal stem/signaling cells preconditioned with external factors: Are there more efficient approaches to utilize their regenerative potential?

Mesenchymal/medicinal stem/signaling cells (MSCs) have emerged as a promising treatment option for various disorders. However, the donor's age, advanced stage of disease, and prolonged in vitro expansion often diminish the innate regenerative potential of MSCs. Besides that, the absence of MSCs' comprehensive "pre-admission testing" can result in the injection of cells with reduced viability and function, which may negatively affect the overall outcome of MSC-based therapies. It is, therefore, essential to develop effective strategies to improve the impaired biological performance of MSCs. This review focuses on the comprehensive characterization of various methods of external MSCs stimulation (hypoxia, heat shock, caloric restriction, acidosis, 3D culture, and application of extracellular matrix) that augment their medicinal potential. To emphasize the significance of MSCs priming, we summarize the effects of individual and combined preconditioning approaches, highlighting their impact on MSCs' response to either physiological or pathological conditions. We further investigate the synergic action of exogenous factors to maximize MSCs' therapeutic potential. Not to omit the field of tissue engineering, the application of pretreated MSCs seeded on scaffolds is discussed as well.

Transcriptomics Demonstrates Significant Biological Effect of Growing Stem Cells on RGD-Cotton Scaffold

Stem cell therapy provides a viable alternative treatment for degenerated or damaged tissue. Stem cells have been used either alone or in conjunction with an artificial scaffold. The latter provides a structural advantage by enabling the cells to thrive in three-dimensional (3D) settings, closely resembling the natural in vivo environments. Previously, we disclosed the development of a 3D scaffold made from cotton, which was conjugated with arginyl-glycyl-aspartic acid (RGD), to facilitate the growth and proliferation of mesenchymal stem cells (MSCs). This scaffold allowed the MSCs to adhere and proliferate without compromising their viability or their stem cell markers. A comprehensive analysis investigation of the molecular changes occurring in MSCs adhering to the cotton fibers will contribute to the advancement of therapy. The objective of this study is to analyze the molecular processes occurring in the growth of MSCs on a cotton-RGD conjugated-based scaffold by examining their gene expression profiles. To achieve this, we conducted an experiment where MSCs were seeded with and without the scaffold for a duration of 48 h. Subsequently, cells were collected for RNA extraction, cDNA synthesis, and whole-transcriptomic analysis performed on both populations. Our analysis revealed several upregulated and downregulated differently expressed genes in the MSCs adhering to the scaffold compared with the control cells. Through gene ontology analysis, we were able to identify enriched biological processes, molecular functions, pathways, and protein-protein interactions in these differentially expressed genes. Our data suggest that the scaffold may have the potential to enhance osteogenesis in the MSCs. Furthermore, our results indicate that the scaffold does not induce oxidative stress, inflammation, or aging in the MSCs. These findings provide valuable insights for the application of MSCs in tissue engineering and regenerative medicine.

The Effect of Adipose-Derived Mesenchymal Stem Cells on Peripheral Nerve Damage in a Rodent Model

Peripheral nerve damage is a significant clinical problem with limited therapeutic options. Adipose-derived mesenchymal stem cells (ADSCs) have emerged as a promising therapeutic approach due to their regenerative potential. However, the underlying mechanisms by which ADSCs promote peripheral nerve regeneration remain unclear. In this study, we investigated the role of syndecan-1 and heat shock protein 70 (HSP-70) in mediating the regenerative effects of ADSCs on peripheral nerves. ADSCs were characterized and isolated from the adipose tissue of rats. In vitro experiments were conducted to evaluate the ability of ADSCs to secrete syndecan-1 and HSP-70 in response to stress conditions. To evaluate the therapeutic potential of ADSCs, rats with sciatic nerve injuries were treated with ADSCs and assessed for functional recovery, nerve regeneration, and changes in syndecan-1 and HSP-70 levels. Regeneration was evaluated with Electromyography (EMG) histology. The results showed that ADSCs could secrete syndecan-1 and HSP-70 in response to stress conditions. Furthermore, ADSC treatment significantly improved functional recovery and nerve regeneration and increased syndecan-1 and HSP-70 levels in the injured nerve. On the other hand, ADSCs make improvements histologically through the influence of Nerve growth factor (NGF), Malondialdehyde (MDA), and EMG.

Cell-penetrating peptide-mediated delivery of therapeutic peptides/proteins to manage the diseases involving oxidative stress, inflammatory response and apoptosis

OBJECTIVES

Peptides and proteins represent great potential for modulating various cellular processes including oxidative stress, inflammatory response, apoptosis and consequently the treatment of related diseases. However, their therapeutic effects are limited by their inability to cross cellular barriers. Cell-penetrating peptides (CPPs), which can transport cargoes into the cell, could resolve this issue, as would be discussed in this review.

KEY FINDINGS

CPPs have been successfully exploited in vitro and in vivo for peptide/protein delivery to treat a wide range of diseases involving oxidative stress, inflammatory processes and apoptosis. Their in vivo applications are still limited due to some fundamental issues of CPPs, including nonspecificity, proteolytic instability, potential toxicity and immunogenicity.

SUMMARY

Totally, CPPs could potentially help to manage the diseases involving oxidative stress, inflammatory response and apoptosis by delivering peptides/proteins that could selectively reach proper intracellular targets. More studies to overcome related CPP limitations and confirm the efficacy and safety of this strategy are needed before their clinical usage.

Secretome of Mesenchymal Stem Cells from Consecutive Hypoxic Cultures Promotes Resolution of Lung Inflammation by Reprogramming Anti-Inflammatory Macrophages

The secretome from hypoxia-preconditioned mesenchymal stem cells (MSCs) has been shown to promote resolution of inflammation and alleviate acute lung injury (ALI) through its immunomodulatory function. However, the effects of consecutive hypoxic culture on immunomodulatory function of the MSCs secretome are largely unclarified. Here, we intend to investigate the effects of consecutive hypoxia on therapeutic efficacy of conditioned medium derived from MSCs (MSCs-CM) in alleviating ALI. Human umbilical cord-derived MSCs (UC-MSCs) were consecutively cultured in 21% O₂ (Nor-MSCs) or in 1% O₂ (Hypo-MSCs) from passage 0. Their conditioned medium (Nor-CM and Hypo-CM respectively) was collected and administered into ALI models. Our findings confirmed that Hypo-MSCs exhibited increased proliferation ability and decreased cell senescence compared with Nor-MSCs. Consecutive hypoxia promoted UC-MSCs to secrete immunomodulatory cytokines, such as insulin-like growth factor 1(IGF1), IL10, TNFα-stimulated gene 6(TSG6), TGFβ, and prostaglandin E2 (PGE2). Both Nor-CM and Hypo-CM could effectively limit lung inflammation, promote efferocytosis and modulate anti-inflammatory polarization of lung macrophages in ALI models. Moreover, the effects of Hypo-CM were more potent than Nor-CM. Taken together, our findings indicate that consecutive hypoxic cultures could not only promote both proliferation and quality of UC-MSCs, but also enhance the therapeutic efficacy of their secretome in mitigating lung inflammation by promoting efferocytosis and anti-inflammatory polarization of macrophages.

Suppressing Pyroptosis Augments Post-Transplant Survival of Stem Cells and Cardiac Function Following Ischemic Injury

The acute demise of stem cells following transplantation significantly compromises the efficacy of stem cell-based cell therapeutics for infarcted hearts. As the stem cells transplanted into the damaged heart are readily exposed to the hostile environment, it can be assumed that the acute death of the transplanted stem cells is also inflicted by the same environmental cues that caused massive death of the host cardiac cells. Pyroptosis, a highly inflammatory form of programmed cell death, has been added to the list of important cell death mechanisms in the damaged heart. However, unlike the well-established cell death mechanisms such as necrosis or apoptosis, the exact role and significance of pyroptosis in the acute death of transplanted stem cells have not been explored in depth. In the present study, we found that M1 macrophages mediate the pyroptosis in the ischemia/reperfusion (I/R) injured hearts and identified miRNA-762 as an important regulator of interleukin 1β production and subsequent pyroptosis. Delivery of exogenous miRNA-762 prior to transplantation significantly increased the post-transplant survival of stem cells and also significantly ameliorated cardiac fibrosis and heart functions following I/R injury. Our data strongly suggest that suppressing pyroptosis can be an effective adjuvant strategy to enhance the efficacy of stem cell-based therapeutics for diseased hearts.

LRP5 Regulates HIF-1α Stability via Interaction with PHD2 in Ischemic Myocardium

Low-density lipoprotein receptor-related protein 5 (LRP5) has been studied as a co-receptor for Wnt/β-catenin signaling. However, its role in the ischemic myocardium is largely unknown. Here, we show that LRP5 may act as a negative regulator of ischemic heart injury via its interaction with prolyl hydroxylase 2 (PHD2), resulting in hypoxia-inducible factor-1α (HIF-1α) degradation. Overexpression of LRP5 in cardiomyocytes promoted hypoxia-induced apoptotic cell death, whereas LRP5-silenced cardiomyocytes were protected from hypoxic insult. Gene expression analysis (mRNA-seq) demonstrated that overexpression of LRP5 limited the expression of HIF-1α target genes. LRP5 promoted HIF-1α degradation, as evidenced by the increased hydroxylation and shorter stability of HIF-1α under hypoxic conditions through the interaction between LRP5 and PHD2. Moreover, the specific phosphorylation of LRP5 at T1492 and S1503 is responsible for enhancing the hydroxylation activity of PHD2, resulting in HIF-1α degradation, which is independent of Wnt/β-catenin signaling. Importantly, direct myocardial delivery of adenoviral constructs, silencing LRP5 in vivo, significantly improved cardiac function in infarcted rat hearts, suggesting the potential value of LRP5 as a new target for ischemic injury treatment.

Interaction of head and neck squamous cell carcinoma cells and mesenchymal stem cells under hypoxia and normoxia

Mesenchymal stem cells (MSCs) exhibit strong tropism towards tumor tissue. While MSCs generally surround tumors, they can also infiltrate tumors and thereby influence their proliferation. Interactions between MSCs and tumor cells are usually tested under normoxia, but the majority of solid tumors, including head and neck squamous cell carcinoma (HNSCC), are also characterized by hypoxic areas. Hence, the present study aimed to assess the interaction between MSCs and tumor cells under hypoxic conditions. MSCs were cultivated under normoxia and hypoxia, and conditioned media were used to cultivate the HNSCC cell line FaDu. The cell cycle distribution and viability of MSCs and the proliferation of FaDu cells were analyzed under normoxia and hypoxia, and changes in cytokine levels in the conditioned media were evaluated. No cell cycle changes were observed for MSCs after 24 h of cultivation under hypoxia, but the cell viability had declined. Hypoxia also led to a decrease in the proliferation of FaDu cells; however, FaDu cells proliferated faster after 48 h under hypoxia compared with normoxic conditions. This effect was reversed after incubation under normoxia for 72 h and hypoxia for 72 h. While these changes constituted a trend, these differences were not statistically significant. A cytokine assay showed an increase in interleukin (IL)-6 in the hypoxic medium. Overall, the results indicated that there was an interaction between MSCs and tumor cells. The presence or absence of oxygen seemed to influence the functionality of MSCs and their protumorigenic properties, in which IL-6 was identified as a potential mediator. Since MSCs are a component of the tumor stroma, further in vitro and in vivo studies are needed to investigate this interaction in order to develop novel approaches for tumor therapy.

Heat Shock Proteins and their Protective Roles in Stem Cell Biology

Stem cells (SCs) are discovered long back but the idea that SCs possess therapeutic potential came up just a few decades back. In a past decade stem cell therapy is highly emerged and displayed tremendous potential for the treatment of a wide range of diseases and disorders such as blindness and vision impairment, type I diabetes, infertility, HIV, etc. SCs are very susceptible to destruction after transplantation into the host because of the inability to sustain elevated stress conditions inside the damaged tissue/organ. Heat shock proteins (HSPs) are molecular chaperones/stress proteins expressed in response to stress (elevated temperature, harmful chemicals, ischemia, viruses, etc) inside a living cell. HSPs protect the cell from damage by assisting in the proper folding of cellular proteins. This review briefly summarises different types of HSPs, their classification, cellular functions as well as the role of HSPs in regulating SC self-renewal and survival in the transplanted host. Applications of HSP modulated SCs in regenerative medicine and for the treatment of ischemic heart disease, myocardial infarction (MI), osteoarthritis, ischemic stroke, spinocerebellar ataxia type 3 (SCA3), leukemia, hepatic ischemia-reperfusion injury, Graft-versus-host disease (GVHD) and Parkinson's disease (PD) are discussed. In order to provide potential insights in understanding molecular mechanisms related to SCs in vertebrates, correlations between HSPs and SCs in cnidarians and planarians are also reviewed. There is a need to advance research in order to validate the use of HSPs for SC therapy and establish effective treatment strategies.

Targeted Delivery of Recombinant Heat Shock Protein 27 to Cardiomyocytes Promotes Recovery from Myocardial Infarction

Ischemic heart disease, especially myocardial infarction (MI), is the leading cause of death worldwide. Apoptotic mechanisms are thought to play a significant role in cardiomyocyte death after MI. Increased production of heat shock proteins (Hsps) in cardiomyocytes is a normal response to promote tolerance and to reduce cell damage. Hsp27 is considered to be a therapeutic option for the treatment of ischemic heart disease due to its protective effects on hypoxia-induced apoptosis. Despite its antiapoptotic effects, the lack of strategies to deliver Hsp27 to the heart tissue in vivo limits its clinical applicability. In this study, we utilized an antibody against the angiotensin II type 1 (AT1) receptor, which is expressed immediately after ischemia/reperfusion in the heart of MI rats. To achieve cardiomyocyte-targeted Hsp27 delivery after ischemia/reperfusion, we employed the immunoglobulin-binding dimer ZZ, a modified domain of protein A, in conjunction with the AT1 receptor antibody. Using the AT1 receptor antibody, we achieved systemic delivery of ZZ-TAT-GFP fusion protein into the heart of MI rats. This approach enabled selective delivery of Hsp27 to cardiomyocytes, rescued cells from apoptosis, reduced the area of fibrosis, and improved cardiac function in the rat MI model, thus suggesting its applicability as a cardiomyocyte-targeted protein delivery system to inhibit apoptosis induced by ischemic injury.

Current Trend and Pro-survival Approaches for Augmenting Stem Cell Viability

BACKGROUND

Stem cells are of two types: embryonic and adult stem cells and they act as a repair system by replenishing body tissue. Stem cells differentiate into different types of cells, such as neural, hematopoietic, adipose, etc. and are used for the treatment of various conditions like myocardial infarction, spinal cord injury, Parkinson's disease and diabetes.

METHODS

This article focuses on recent research development that addresses the viability issues of stem cells. The efficiency of transplanted stem cells reduces due to conditions like hypoxia, inflammation, nutrient deprivation, immunogenicity, extracellular matrix loss on delivery and mechanical stress.

RESULTS

To increase the viability of stem cells, techniques like scaffolds of stem cells with hydrogel or alginate, pre-conditioning, different routes of administration and encapsulation, are implemented.

CONCLUSION

For the protection of stem cells against apoptosis, different pathways, namely Phosphoinositide 3-Kinase (PI3K/AKT), Hypoxia-Inducible Factor (HIF1), Mitogen-Activated Protein Kinases (MAPK) and Hippo, are discussed.

DISCUSSION

Activation of the PI3K/AKT pathway decreases the concentration of apoptotic factors, while the HIF pathway protects stem cells against the micro-environment of tissue (hypoxia).

Ticagrelor Enhances Release of Anti-Hypoxic Cardiac Progenitor Cell-Derived Exosomes Through Increasing Cell Proliferation In Vitro

Despite the widespread clinical use of cardioprotection by long-term direct antagonism of P2Y12 receptor, underlying mechanisms are unclear. Here, we identify how release of pro-survival exosomes from human cardiac-derived mesenchymal progenitor cells (hCPCs) is regulated by clinically relevant dose of ticagrelor (1 μM), an oral selective and reversible non-thienopyridine P2Y₁₂ inhibitor. Ticagrelor-induced enhancement of exosome levels is related to increased mitotic activity of hCPCs. We show a drug-response threshold above which the effects on hCPCs are lost due to higher dose of ticagrelor and larger adenosine levels. While it is known that pan-Aurora kinase inhibitor halts cell proliferation through dephosphorylation of histone H3 residue Ser10, we demonstrate that it also prevents ticagrelor-induced effects on release of cardiac progenitor cell-derived exosomes delivering anti-apoptotic HSP70. Indeed, sustained pre-treatment of cardiomyocytes with exosomes released from explant-derived hCPCs exposed to low-dose ticagrelor attenuated hypoxia-induced apoptosis through acute phosphorylation of ERK42/44. Our data indicate that ticagrelor can be leveraged to modulate release of anti-hypoxic exosomes from resident hCPCs.

Silk fibroin scaffolds potentiate immunomodulatory function of human mesenchymal stromal cells

Although mesenchymal stromal cells (MSCs) show great potential for use in regenerative medicine, their therapeutic efficacy remains limited because of their low adaptation efficiency and viability observed in clinical trials. To potentiate the adaptation and survival efficiency of MSCs after administration in vivo, silk fibroin nanofibers (SFNs) were applied as a scaffold. SFNs are biocompatible, biodegradable polymers with tunable architectures and mechanical properties. Treatment with interferon (IFN)-γ for 18 h increased the expression of immunomodulatory functional cytokines, IDO and COX2 in MSCs. Further, the MSCs grown on SFN sheets showed enhanced IDO1 and COX2 expression following IFN-γ treatment. MSCs showed significantly greater migratory ability on SFN sheets than on glass surfaces or PLGA control sheets. Though IFN-γ treatment slightly reduced the migration ability of MSCs cultured on glass or poly(lactic-co-glycolic acid) (PLGA) nanofiber sheets, it did not alter MSC motility on SFN sheets. Furthermore, MSCs cultured on SFN sheets dramatically suppressed TNF-α secretion from lipopolysaccharide-activated murine splenocytes, suggesting that the immunomodulatory function of MSCs was enhanced by the SFN sheets. Taken together, these data demonstrate that SFN sheets potentiate the reparative and regenerative properties of MSCs.

CD90low MSCs modulate intratumoral immunity to confer antitumor activity in a mouse model of ovarian cancer

Both anti-tumoral and pro-tumoral effects of mesenchymal stem cells (MSCs) in preclinical treatment of ovarian cancer have been controversially demonstrated. In this study, we profiled the phenotypes of mouse compact bone-derived MSCs (CB-MSCs) and bone marrow-derived MSCs (BM-MSCs) and found that CB-MSCs expressed lower CD90 compared to BM-MSCs. We examined gene expression of immune regulating cytokines of CB-MSCs in 2D and 3D culture and under stimulation with TLR4 agonist LPS or immune activator VIC-008. Our data showed that when CB-MSCs were cultured in simulated in vivo 3D condition, CD90 expression was further decreased. Moreover, gene expressions of immune activating cytokines IL-12, IL-21, IFNγ and a pro-inflammatory cytokine CXCL10 in CB-MSCs were increased in 3D culture whereas gene expression of anti-inflammatory cytokines IL-10 and CCL5 were downregulated. Stimulation of CB-MSCs by LPS or VIC-008 presented similar profile of the cytokine gene expressions to that in 3D culture which might benefit the anti-tumor efficacy of CD90low MSCs. The anti-tumor effects of CD90low CB-MSCs alone or in combination with VIC-008 were evaluated in a syngeneic orthotopic mouse model of ovarian cancer. Treatment that combines CB-MSCs and VIC-008 significantly decreased tumor growth and prolonged mouse survival. This was associated with the increase of activated anti-tumoral CD4+ and CD8+ T cells and the decrease of Treg cells in the tumor microenvironment. Taken together, our study demonstrates the synergistic anti-tumoral efficacy by application of CB-MSCs combined with immune activator VIC-008 and provides new insight into CD90low MSCs as a new anti-tumor arsenal.

Multiple Combination of Angelica gigas Extract and Mesenchymal Stem Cells Enhances Therapeutic Effect

Alternative medicines attract attention because stroke is rarely expected to make a full recovery with the most advanced medical technology. Angelica gigas (AG) is a well-known herbal medicine as a neuroprotective agent. The present study introduced mesenchymal stem cells (MSCs) to identify for the advanced treatment of the cerebrovascular disease. The objective of this research is validation of the enhanced effects of multiple combined treatment of AG extract with MSCs on stroke through angiogenesis. Our results confirmed that AG extract with MSCs improved the neovascularization increasing expression of angiogenesis-regulated molecules. The changes of brain and the behavioral ability showed the increased effects of AG extract with MSCs. As a result, AG extract and MSCs may synergistically increase the therapeutic potential by enhancing neovascularization. This mixed approach provides a new experimental protocol of herbal medicine therapy for the treatment of a variety of diseases including stroke, trauma, and spinal cord injury.

Priming stem cells with protein kinase C activator enhances early stem cell-chondrocyte interaction by increasing adhesion molecules

BACKGROUND

Osteoarthritis (OA) can be defined as degradation of articular cartilage of the joint, and is the most common degenerative disease. To regenerate the damaged cartilage, different experimental approaches including stem cell therapy have been tried. One of the major limitations of stem cell therapy is the poor post-transplantation survival of the stem cells. Anoikis, where insufficient matrix support and adhesion to extracellular matrix causes apoptotic cell death, is one of the main causes of the low post-transplantation survival rate of stem cells. Therefore, enhancing the initial interaction of the transplanted stem cells with chondrocytes could improve the therapeutic efficacy of stem cell therapy for OA. Previously, protein kinase C activator phorbol 12-myristate 13-acetate (PMA)-induced increase of mesenchymal stem cell adhesion via activation of focal adhesion kinase (FAK) has been reported. In the present study, we examine the effect PMA on the adipose-derived stem cells (ADSCs) adhesion and spreading to culture substrates, and further on the initial interaction between ADSC and chondrocytes.

RESULTS

PMA treatment increased the initial adhesion of ADSC to culture substrate and cellular spreading with increased expression of adhesion molecules, such as FAK, vinculin, talin, and paxillin, at both RNA and protein level. Priming of ADSC with PMA increased the number of ADSCs attached to confluent layer of cultured chondrocytes compared to that of untreated ADSCs at early time point (4 h after seeding).

CONCLUSION

Taken together, the results of this study suggest that priming ADSCs with PMA can increase the initial interaction with chondrocytes, and this proof of concept can be used to develop a non-invasive therapeutic approach for treating OA. It may also accelerate the regeneration process so that it can relieve the accompanied pain faster in OA patients. Further in vivo studies examining the therapeutic effect of PMA pretreatment of ADSCs for articular cartilage damage are required.

The harsh microenvironment in infarcted heart accelerates transplanted bone marrow mesenchymal stem cells injury: the role of injured cardiomyocytes-derived exosomes

Stem cell therapy can be used to repair and regenerate damaged hearts tissue; nevertheless, the low survival rate of transplanted cells limits their therapeutic efficacy. Recently, it has been proposed that exosomes regulate multiple cellular processes by mediating cell survival and communication among cells. The following study investigates whether injured cardiomyocytes-derived exosomes (cardiac exosomes) affect the survival of transplanted bone marrow mesenchymal stem cells (BMSCs) in infarcted heart. To mimic the harsh microenvironment in infarcted heart that the cardiomyocytes or transplanted BMSCs encounter in vivo, cardiomyocytes conditioned medium and cardiac exosomes collected from H₂O₂-treated cardiomyocytes culture medium were cultured with BMSCs under oxidative stress in vitro. Cardiomyocytes conditioned medium and cardiac exosomes significantly accelerated the injury of BMSCs induced by H₂O₂; increased cleaved caspase-3/caspase-3 and apoptotic percentage, and decreased the ratio of Bcl-2/Bax and cell viability in those cells. Next, we explored the role of cardiac exosomes in the survival of transplanted BMSCs in vivo by constructing a Rab27a knockout (KO) mice model by a transcription activator-like effector nuclease (TALEN) genome-editing technique; Rab27a is a family of GTPases, which has critical role in secretion of exosomes. Male mouse GFP-modified BMSCs were implanted into the viable myocardium bordering the infarction in Rab27a KO and wild-type female mice. The obtained results showed that the transplanted BMSCs survival in infarcted heart was increased in Rab27a KO mice by the higher level of Y-chromosome Sry DNA, GFP mRNA, and the GFP fluorescence signal intensity. To sum up, these findings revealed that the injured cardiomyocytes-derived exosomes accelerate transplanted BMSCs injury in infarcted heart, thus highlighting a new mechanism underlying the survival of transplanted cells after myocardial infarction.

Concise Review: Optimized Strategies for Stem Cell-Based Therapy in Myocardial Repair: Clinical Translatability and Potential Limitation

Ischemic heart diseases (IHDs) remain major public health problems with high rates of morbidity and mortality worldwide. Despite significant advances, current therapeutic approaches are unable to rescue the extensive and irreversible loss of cardiomyocytes caused by severe ischemia. Over the past 16 years, stem cell-based therapy has been recognized as an innovative strategy for cardiac repair/regeneration and functional recovery after IHDs. Although substantial preclinical animal studies using a variety of stem/progenitor cells have shown promising results, there is a tremendous degree of skepticism in the clinical community as many stem cell trials do not confer any beneficial effects. How to accelerate stem cell-based therapy toward successful clinical application attracts considerate attention. However, many important issues need to be fully addressed. In this Review, we have described and compared the effects of different types of stem cells with their dose, delivery routes, and timing that have been routinely tested in recent preclinical and clinical findings. We have also discussed the potential mechanisms of action of stem cells, and explored the role and underlying regulatory components of stem cell-derived secretomes/exosomes in myocardial repair. Furthermore, we have critically reviewed the different strategies for optimizing both donor stem cells and the target cardiac microenvironments to enhance the engraftment and efficacy of stem cells, highlighting their clinical translatability and potential limitation. Stem Cells 2018;36:482-500.

Overexpressing microRNA-150 attenuates hypoxia-induced human cardiomyocyte cell apoptosis by targeting glucose-regulated protein-94

MicroRNA (miR)-150 has been demonstrated to protect the heart from ischemic injury. However, the protective effect of miR-150 in hypoxia-injured cardiomyocytes remains unclear. The present study aimed to investigate the target gene of miR-150 and the underlying molecular mechanisms of miR-150 in hypoxia-induced cardiomyocyte apoptosis. Using the hypoxia model of human cardiomyocytes (HCMs) in vitro, it was demonstrated that miR-150 was markedly inhibited in HCMs after hypoxia treatment. Overexpressing miR-150 significantly decreased hypoxia-induced HCM death and apoptosis. In addition, GRP94 was revealed to be a direct target of miR-150. Additionally, GRP94 was demonstrated to be involved in hypoxia-induced HCM apoptosis, and the protein expression levels of GRP94 were increased in HCMs in the presence of hypoxia. These findings demonstrated that miR-150 is involved in hypoxia-mediated gene regulation and apoptosis in HCMs. Furthermore, GRP94 knockout increased the cell viability of hypoxia-impaired HCMs with miR-150 mimic or miR-150 inhibitor transfection. In conclusion, miR-150 may serve a protective role in cardiomyocyte hypoxia injury, and the underlying mechanism was mediated, at least partially, by inhibiting GRP94 expression. These findings may provide a novel insight for the therapy of hypoxia-induced myocardial I/R injury.

Heat-Shock Protein 70 Overexpression in Adipose-Derived Stem Cells Enhances Fat Graft Survival

BACKGROUND

Autologous fat grafting is a prevalent technique used for soft-tissue augmentation; however, the poor survival rate of the grafted tissue remains a drawback of this method. Although adipose-derived stem cells (ASCs) are an attractive candidate for enhancing graft retention, the poor posttransplantation viability of these cells limits their application. Here we investigated whether overexpression of the antiapoptotic protein heat-shock protein 70 (Hsp70) could enhance ASCs' therapeutic potential for fat transplant survival.

METHODS

Recombinant adenoviral vectors were used to overexpress Hsp70 in ASCs isolated from a healthy woman. The Hsp70 expression was assessed by quantitative real-time polymerase chain reaction and Western blot analyses. The adipose tissue granules aspirated from another woman were mixed with ASCs expressing green fluorescent protein (GFP)-tagged Hsp70 (group A) or GFP alone (group B), untreated ASCs (group C), and phosphate-buffered saline (group D). Fat mixtures were then injected subcutaneously into the backs of nude mice, and graft survival was compared after 3 months.

RESULTS

Adipose-derived stem cells transduced with recombinant adenoviral vectors exhibited significantly increased Hsp70 expression in vitro. Meanwhile, weight retention analyses demonstrated that fat grafts using the group A cell population exhibited significantly higher survival rates than the other treatment groups in vivo. Moreover, histological analyses revealed that fat grafts containing GFP-Hsp70-expressing ASCs yielded significantly lower levels of tissue fibrosis and fat cysts/vacuoles, higher capillary densities, and increased numbers of viable adipocytes than the control groups.

CONCLUSIONS

Our data indicate that Hsp70 overexpression enhances the efficacy of ASC therapy by improving the survival and quality of the transplanted fat tissues.

Selaginella bryopteris Aqueous Extract Improves Stability and Function of Cryopreserved Human Mesenchymal Stem Cells

The effective long-term cryopreservation of human mesenchymal stem cells (MSCs) is an essential prerequisite step and represents a critical approach for their sustained supply in basic research, regenerative medicine, and tissue engineering applications. Therefore, attempts have been made in the present investigation to formulate a freezing solution consisting of a combination of Selaginella bryopteris water-soluble extract with and without dimethyl sulfoxide (Me₂SO) for the efficient long-term storage of human umbilical cord blood- (hUCB-) derived MSCs. The cryopreservation experiment using the formulated freezing solution was further performed with hUCB MSCs in a controlled rate freezer. A significant increase in postthaw cell viability and cell attachment of MSCs was achieved with freezing medium containing Selaginella bryopteris water extract along with 10% Me₂SO as compared to the freezing medium containing Me₂SO (10% v/v) alone. Furthermore, the decreasing apoptotic events and reactive oxygen species production along with increasing expression of heat shock proteins also confirmed the beneficial effect of Selaginella bryopteris water extract. The beneficial effect of Selaginella bryopteris water extract was validated by its ability to render postpreservation high cell viability. In conclusion, the formulated freezing solution has been demonstrated to be effective for the standardization of cryopreservation protocol for hMSCs.

Chronic stress induces CD99, suppresses autophagy, and affects spontaneous adipogenesis in human bone marrow stromal cells

BACKGROUND

Bone marrow-derived mesenchymal stromal cells (MSCs) are multipotent cells with a high constitutive level of autophagy and low expression of CD99. Under certain conditions, MSCs may develop tumorigenic properties. However, these transformation-induced conditions are largely unknown. Recently, we have identified an association between Hsp70, a main participant in cellular stress response and tumorigenesis, and CD99. Preliminary observations had revealed upregulation of both proteins in stressed long-term cultured MSCs. And so we hypothesized that CD99 is implicated in stress-induced mechanisms of cellular transformation in MSCs. Hence, we investigated the effects of prolonged stress on MSCs and the role of CD99 and autophagy in their survival.

METHODS

Human telomerase reverse transcriptase (hTERT) overexpressing immortalized MSCs and primary bone marrow stromal cells were used to investigate the influence of long-term serum deprivation and hypoxia on growth and differentiation of MSCs. Cell proliferation and apoptosis were evaluated using flow cytometry, differentiation capabilities of MSCs were assessed by immunohistochemical staining followed by microscopic examination. CD99, Hsp70 expression were analyzed using flow cytometry, western blotting, and reverse transcriptase polymerase chain reaction. Autophagy was explored with specific inhibitors using cell morphology examination and western blotting.

RESULTS

Chronic stress factors are able to change the morphology of MSCs and to inhibit spontaneous differentiation into adipocyte lineage. Furthermore, CD99 elevation and downregulation of p53 and p21 accompanied defective autophagy, which is usually associated with tumor formation. We found that inhibition of autophagy by chloroquine promoted cell detachment and modulated CD99 expression level whereas incorporation of CD99 recombinant protein into the cells suppressed autophagy.

CONCLUSIONS

Obtained results provide a model for chronic stress-induced transformation of MSCs via CD99 and may therefore be highly relevant to mesenchymal tumorigenesis.

SRT1720 promotes survival of aged human mesenchymal stem cells via FAIM: a pharmacological strategy to improve stem cell-based therapy for rat myocardial infarction

SIRT1 has been proved to rejuvenate and improve the therapeutic efficacy of aged rat mesenchymal stem cells (MSCs). Herein, we investigate the protective effect of pretreatment with SIRT1 activator SRT1720 on aged human MSCs (hMSCs). The optimized pretreatment condition for aged hMSCs was determined to be 0.5 μM SRT1720 for 24 h by monitoring the survival of aged hMSCs subjected to serum deprivation±hypoxia and±500 μM hydrogen peroxide (H₂O₂). Pretreatment with these conditions increased the survival of aged hMSCs 1 day (2.7-fold) and 3 days (1.9-fold) after being transplanted into a rat myocardial infarction (MI) model created by ligation of the left anterior descending (LAD) coronary artery. Transplantation with SRT1720 pretreated aged hMSCs achieved increased left ventricular ejection fraction (58.9±3.6 versus 52.8±5%) and angiogenesis with reduced fibrosis of rat hearts as compared to DMSO pretreated group 28 days following MI. Unbiased transcriptome analysis conducted on aged hMSCs under oxidative stress indicated the Fas apoptosis inhibitory molecule (FAIM) was significantly upregulated following SRT1720 pretreatment (14.9±0.2-folds). Moreover, the anti-apoptotic effect of SRT1720 was mitigated by FAIM knockdown with a small interfering RNA-targeted FAIM. These results indicated that pretreatment with SRT1720 improves survival of aged hMSCs, and enhances their therapeutic efficacy for rat myocardial infarction (MI). Upregulation of FAIM possibly involves in the mechanisms of the protective effects.

Acute Hypoxic Stress Affects Migration Machinery of Tissue O2-Adapted Adipose Stromal Cells

The ability of mesenchymal stromal (stem) cells (MSCs) to be mobilised from their local depot towards sites of injury and to participate in tissue repair makes these cells promising candidates for cell therapy. Physiological O₂ tension in an MSC niche in vivo is about 4-7%. However, most in vitro studies of MSC functional activity are performed at 20% O₂. Therefore, this study focused on the effects of short-term hypoxic stress (0.1% O₂, 24 h) on adipose tissue-derived MSC motility at tissue-related O₂ level. No significant changes in integrin expression were detected after short-term hypoxic stress. However, O₂ deprivation provoked vimentin disassembly and actin polymerisation and increased cell stiffness. In addition, hypoxic stress induced the downregulation of ACTR3, DSTN, MACF1, MID1, MYPT1, NCK1, ROCK1, TIAM1, and WASF1 expression, the products of which are known to be involved in leading edge formation and cell translocation. These changes were accompanied by the attenuation of targeted and nontargeted migration of MSCs after short-term hypoxic exposure, as demonstrated in scratch and transwell migration assays. These results indicate that acute hypoxic stress can modulate MSC function in their native milieu, preventing their mobilisation from sites of injury.

Stem cell-based therapy: Improving myocardial cell delivery

Stem cell-based therapies form an exciting new class of medicine that attempt to provide the body with the building blocks required for the reconstruction of damaged organs. However, delivering cells to the correct location, while preserving their integrity and functional properties, is a complex undertaking. These challenges have led to the development of a highly dynamic interdisciplinary research field, wherein medical, biological, and chemical sciences have collaborated to develop strategies to overcome the physiological barriers imposed on the cellular therapeutics. In this respect, improving the acute retention and subsequent survival of stem cells is key to effectively increase the effect of the therapy, while proper tissue integration is imperative for stem cells to functionally replace lost cells in damaged organs. In this review, we will use the heart as an example to highlight the current knowledge of therapeutic stem cell utilization, the existing pitfalls and limitations, and the approaches that have been developed to overcome them.

Response of Adipose Tissue-Derived Stromal Cells in Tissue-Related O2 Microenvironment to Short-Term Hypoxic Stress

A microenvironment low in O2 ('physiological' hypoxia) governs the functions of perivascular multipotent mesenchymal stromal cells, defining their involvement in tissue physiological homeostasis and regenerative remodelling. Acute hypoxic stress is considered as one of the important factors inducing tissue damage. Here, we evaluate the influence of short-term hypoxia (1% O2 for 24 h) on perivascular adipose tissue-derived cells (ASCs) permanently expanded in tissue-related O2 (5%) microenvironment. After hypoxic exposure, ASCs retained high viability, stromal cell morphology and mesenchymal phenotype (CD73+, CD90+, CD105+ and CD45-). Mild oxidative damage was unveiled as elevation of reactive oxygen species and thiobarbituric acid-active products, while no reduction in the activity of the antioxidant enzymes catalase and glutathione peroxidase and a 20% statistically significant increase in superoxide dismutase activity was detected. Expression of hypoxia-inducible factor (HIF)-1α and HIF-3α isoforms was differently regulated. HIF-1α displayed transient up-regulation, with maximum levels 30 min after acute hypoxic exposure, while HIF-3α was significantly up-regulated after 24 h. Up-regulation of ERK7, MEK1 and c-fos, and down-regulation of MKK6, p53, CCNA2, CCNB1 and CCNB2 were observed after 24 h of oxygen deprivation. Acute hypoxic exposure did not affect the gene expression of other mitogen-activated protein kinases (MAPKs) and MAPK kinases, MAPK/ERK kinase-interacting proteins, MAPK-activated transcription factors and scaffolding proteins. Significant stimulation of vascular endothelial growth factor α and interleukin-6 production was detected in ASC-conditioned medium. Thus, tissue O2-adapted ASCs are resistant to hypoxic stress, which can ensure their effective involvement in the regeneration of tissue damage under significant oxygen deprivation.

Endomicroscopy Will Track Injected Mesenchymal Stem Cells in Rat Colitis Models

BACKGROUND

Mesenchymal stem cells (MSCs) have demonstrated significant potentials for the treatment of inflammatory bowel disease. Clinical feasible methods to individually document the MSC recruitment to intestinal mucosa is lacking. Here, we proposed that endomicroscopy could noninvasively track MSCs in vivo at cellular resolution.

METHOD

Isolated Sprague Dawley rat MSC was characterized, fluorescently labeled, and imaged ex vivo using an endomicroscope. Then enhanced green fluorescent protein (eGFP)-labeled MSC was tracked in vivo, and acquired images were compared with immunofluorescence, immunohistology, and fluorescent in situ hybridization results.

RESULTS

Endomicroscopy visualized clearly the eGFP-labeled or carboxyfluorescein succinimidyl ester-stained MSC ex vivo. Endomicroscopy using the FIVE1 system could track eGFP-labeled MSC with distinct in vivo features. Immunofluorescence, immunohistochemistry, and fluorescent in situ hybridization confirmed the presence of eGFP-positive cells. In vivo endomicroscopy could quantify the transplanted MSCs that homed to colonic mucosa of the recipient rat in multiple models, including the rat-to-rat allograft, human-to-rat xenograft, hypoxia-induced MSC, and busulfan immunosuppressed recipient rat models. After hypoxia induction, there was a trend of enhanced rat MSC homing to the inflamed mucosa as visualized by endomicroscopy (114.1 in hypoxia group versus 34.3 in other 3 groups combined, t = 2.14, P = 0.0644).

CONCLUSIONS

Endomicroscopy is a novel and promising tool to track transplanted MSCs to the colonic mucosa. This clinical available noninvasive cellular tracking method may provide new insight to individualize each recipient's regimen in the future.

Application and Progress of Combined Mesenchymal Stem Cell Transplantation in the Treatment of Ischemic Cardiomyopathy

Treatment of ischemic cardiomyopathy caused by myocardial infarction (MI) using mesenchymal stem cell (MSC) transplantation is a widely researched field, with promising clinical application. However, the low survival rate of transplanted cells has a severe impact on treatment outcome. Currently, research is focused on investigating the strategy of combining genetic engineering, tissue engineering materials, and drug/hypoxia preconditioning to improve ischemic cardiomyopathy treatment outcome using MSC transplantation treatment (MSCTT). This review discusses the application and progress of these techniques.

Periostin enhances adipose-derived stem cell adhesion, migration, and therapeutic efficiency in Apo E deficient mice with hind limb ischemia

Introduction

Therapeutic angiogenesis by transplantation of autologous/allogeneic adipose-derived stem cells (ADSCs) is a potential approach for severe ischemic diseases. However, poor viability, adhesion, migration and differentiation limit the therapeutic efficiency after the cells were transplanted into the targeted area. Periostin, an extracellular matrix protein, exhibits a critical role in wound repair as well as promotes cell adhesion, survival, and angiogenesis.

Method

ADSCs were obtained and genetically engineered with periostin gene (P-ADSCs). The viability, proliferation, migration, and apoptosis of P-ADSCs under hypoxia were analyzed. Moreover, P-ADSCs were implanted into Apo E deficient mice with hind limb ischemia. The Laser Doppler perfusion index, immunofluorescence, and histological pathology assay were tested to evaluate the therapeutic effects. The associated molecular mechanism of periostin on the proliferation, adhesion, migration, and differentiation of ADSCs was also analyzed.

Results

The in vitro studies have shown that periostin-transfected ADSCs (P-ADSCs) promoted viability, proliferation, and migration of ADSCs. Apoptosis of ADSCs was inhibited under hypoxic conditions. The Laser Doppler perfusion index was significantly higher in the P-ADSCs group compared with that in the ADSC and control groups after 4 weeks. Immunofluorescence and histological pathology assay showed that the P-ADSCs were in and around the ischemic sites, and some cells differentiated into capillaries and endothelium. Microvessel densities were significantly improved in P-ADSCs group compared with those in the control group. The molecular mechanisms that provide the beneficial effects of periostin were connected with the upregulated expression of integrinβ1/FAK/PI3K/Akt/eNOS signal pathway and the increased secretion of growth factors.

Conclusion

Overexpression of periostin by gene transfection on ADSCs promotes survival, migration, and therapeutic efficiency, which will bring new insights into the treatment of critical limb ischemia.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0126-x) contains supplementary material, which is available to authorized users.

Enhanced Healing of Rat Calvarial Bone Defects with Hypoxic Conditioned Medium from Mesenchymal Stem Cells through Increased Endogenous Stem Cell Migration via Regulation of ICAM-1 Targeted-microRNA-221

The use of conditioned medium from mesenchymal stem cells may be a feasible approach for regeneration of bone defects through secretion of various components of mesenchymal stem cells such as cytokines, chemokines, and growth factors. Mesenchymal stem cells secrete and accumulate multiple factors in conditioned medium under specific physiological conditions. In this study, we investigated whether the conditioned medium collected under hypoxic condition could effectively influence bone regeneration through enhanced migration and adhesion of endogenous mesenchymal stem cells. Cell migration and adhesion abilities were increased through overexpression of intercellular adhesion molecule-1 in hypoxic conditioned medium treated group. Intercellular adhesion molecule-1 was upregulated by microRNA-221 in mesenchymal stem cells because microRNAs are key regulators of various biological functions via gene expression. To investigate the effects in vivo, evaluation of bone regeneration by computed tomography and histological assays revealed that osteogenesis was enhanced in the hypoxic conditioned medium group relative to the other groups. These results suggest that behavioral changes of endogenous mesenchymal stem cells through microRNA-221 targeted-intercellular adhesion molecule-1 expression under hypoxic conditions may be a potential treatment for patients with bone defects.

Graphene oxide flakes as a cellular adhesive: prevention of reactive oxygen species mediated death of implanted cells for cardiac repair

Mesenchymal stem cell (MSC) implantation has emerged as a potential therapy for myocardial infarction (MI). However, the poor survival of MSCs implanted to treat MI has significantly limited the therapeutic efficacy of this approach. This poor survival is primarily due to reactive oxygen species (ROS) generated in the ischemic myocardium after the restoration of blood flow. ROS primarily causes the death of implanted MSCs by inhibiting the adhesion of the MSCs to extracellular matrices at the lesion site (i.e., anoikis). In this study, we proposed the use of graphene oxide (GO) flakes to protect the implanted MSCs from ROS-mediated death and thereby improve the therapeutic efficacy of the MSCs. GO can adsorb extracellular matrix (ECM) proteins. The survival of MSCs, which had adhered to ECM protein-adsorbed GO flakes and were subsequently exposed to ROS in vitro or implanted into the ischemia-damaged and reperfused myocardium, significantly exceeded that of unmodified MSCs. Furthermore, the MSC engraftment improved by the adhesion of MSCs to GO flakes prior to implantation enhanced the paracrine secretion from the MSCs following MSC implantation, which in turn promoted cardiac tissue repair and cardiac function restoration. This study demonstrates that GO can effectively improve the engraftment and therapeutic efficacy of MSCs used to repair the injury of ROS-abundant ischemia and reperfusion by protecting implanted cells from anoikis.

Activation of NRG1-ERBB4 signaling potentiates mesenchymal stem cell-mediated myocardial repairs following myocardial infarction

Mesenchymal stem cell (MSC) transplantation has achieved only modest success in the treatment of ischemic heart disease owing to poor cell viability in the diseased microenvironment. Activation of the NRG1 (neuregulin1)-ERBB4 (v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 4) signaling pathway has been shown to stimulate mature cardiomyocyte cell cycle re-entry and cell division. In this connection, we aimed to determine whether overexpression of ERBB4 in MSCs can enhance their cardio-protective effects following myocardial infarction. NRG1, MSCs or MSC-ERBB4 (MSC with ERBB4 overexpression), were transplanted into mice following myocardial infarction. Superior to that of MSCs and solely NRG1, MSC-ERBB4 transplantation significantly preserved heart functions accompanied with reduced infarct size, enhanced cardiomyocyte division and less apoptosis during early phase of infarction. The transduction of ERBB4 into MSCs indeed increased cell mobility and apoptotic resistance under hypoxic and glucose-deprived conditions via a PI3K/Akt signaling pathway in the presence of NRG1. Unexpectedly, introduction of ERBB4 into MSC in turn potentiates NRG1 synthesis and secretion, thus forming a novel NRG1-ERBB4-NRG1 autocrine loop. Conditioned medium of MSC-ERBB4 containing elevated NRG1, promoted cardiomyocyte growth and division, whereas neutralization of NRG1 blunted this proliferation. These findings collectively suggest that ERBB4 overexpression potentiates MSC survival in the infarcted heart, enhances NRG1 generation to restore declining NRG1 in the infarcted region and stimulates cardiomyocyte division. ERBB4 has an important role in MSC-mediated myocardial repairs.

Pretreatment of Adipose Derived Stem Cells with Curcumin Facilitates Myocardial Recovery via Antiapoptosis and Angiogenesis

The poor survival rate of transplanted stem cells in ischemic myocardium has limited their therapeutic efficacy. Curcumin has potent antioxidant property. This study investigates whether prior curcumin treatment protects stem cells from oxidative stress injury and improves myocardial recovery following cells transplantation. Autologous Sprague-Dawley rat adipose derived mesenchymal stem cells (ADSCs) were pretreated with or without curcumin. The hydrogen peroxide/serum deprivation (H2O2/SD) medium was used to mimic the ischemic condition in vitro. Cytoprotective effects of curcumin on ADSCs were evaluated. Curcumin pretreatment significantly increased cell viability and VEGF secretion, and decreased cell injury and apoptosis via regulation of PTEN/Akt/p53 and HO-1 signal proteins expression. The therapeutic potential of ADSCs implantation was investigated in myocardial ischemia-reperfusion injury (IRI) model. Transplantation of curcumin pretreated ADSCs not only resulted in better heart function, higher cells retention, and smaller infarct size, but also decreased myocardial apoptosis, promoted neovascularization, and increased VEGF level in ischemic myocardium. Together, priming of ADSCs with curcumin improved tolerance to oxidative stress injury and resulted in enhancement of their therapeutic potential of ADSCs for myocardial repair. Curcumin pretreatment is a promising adjuvant strategy for stem cells transplantation in myocardial restoration.

Cell adhesion and long-term survival of transplanted mesenchymal stem cells: a prerequisite for cell therapy

The literature provides abundant evidence that mesenchymal stem cells (MSCs) are an attractive resource for therapeutics and have beneficial effects in regenerating injured tissues due to their self-renewal ability and broad differentiation potential. Although the therapeutic potential of MSCs has been proven in both preclinical and clinical studies, several questions have not yet been addressed. A major limitation to the use of MSCs in clinical applications is their poor viability at the site of injury due to the harsh microenvironment and to anoikis driven by the loss of cell adhesion. To improve the survival of the transplanted MSCs, strategies to regulate apoptotic signaling and enhance cell adhesion have been developed, such as pretreatment with cytokines, growth factors, and antiapoptotic molecules, genetic modifications, and hypoxic preconditioning. More appropriate animal models and a greater understanding of the therapeutic mechanisms of MSCs will be required for their successful clinical application. Nevertheless, the development of stem cell therapies using MSCs has the potential to treat degenerative diseases. This review discusses various approaches to improving MSC survival by inhibiting anoikis.

The caspase-8 shRNA-modified mesenchymal stem cells improve the function of infarcted heart

The beneficial effects of mesenchymal stem cells (MSCs) in cardiac cell therapy are greatly limited due to poor survival after transplantation into ischemic hearts. Here, we investigated whether caspase 8 small hairpin RNA (shRNA) modification enhance human MSCs (hMSCs) survival and improve infarcted heart function. Recombinant adenovirus encoding pre-miRNA-155-designed caspase 8 shRNA was prepared to inhibit caspase 8 expression in hMSCs. The effect of caspase 8 shRNA modification on protecting hMSCs from apoptosis under the conditions of serum deprivation and hypoxia was tested by Annexin V/PI staining and caspase 8 activity assay. The caspase 8 shRNA-modified and superparamagnetic iron oxide (SPIO)-labeled hMSCs were injected into the border zone of the infarcted region of rat heart. Echocardiography and Masson trichrome staining were performed to assess heart function and cardiac fibrosis. Our results showed that adenovirus-mediated caspase 8 shRNA could efficiently inhibit caspase 8 expression in hMSCs. Knock-down of caspase 8 expression lead to inhibition of hMSCs apoptosis, reduction of caspase 8 activity and up-regulations of HGF, IGF-1 and Bcl-2. Transplantation of caspase 8 shRNA-modified hMSCs could significantly improve infracted heart function, attenuate cardiac fibrosis. Consistently, the rate of cardiomyocyte apoptosis and caspase 8 activity were significantly decreased, and the survival rate of transplanted hMSCs was markedly elevated in the myocardium receiving caspase 8 shRNA-modified hMSCs transplantation. Together, our findings implicated the therapeutic potential of caspase 8 shRNA-modified hMSCs in improving the infarcted heart function.

Mesenchymal stem cells and hypoxia: where are we?

Multipotent mesenchymal stromal cells (MSCs) are involved in the organization and maintenance of tissue integrity. MSCs have also attracted attention as a promising tool for cell therapy and regenerative medicine. However, their usage is limited due to cell impairment induced by an extremely harsh microenvironment during transplantation ex vivo. The microenvironment of MSCs in tissue depots is characterized by rather low oxygen consumption, demonstrating that MSCs might be quite resistant to oxygen limitation. However, accumulated data revealed that the response of MSCs to hypoxic conditions is rather controversial, demonstrating both damaging and ameliorating effects. Here, we make an attempt to summarize recent knowledge on the survival of MSCs under low oxygen conditions of varying duration and severity and to elucidate the mechanisms of MSC resistance/sensitivity to hypoxic impact.

Diabetic Mesenchymal Stem Cells Are Ineffective for Improving Limb Ischemia Due to Their Impaired Angiogenic Capability

The purpose of this study was to investigate the effects of diabetes on mesenchymal stem cells (MSCs) in terms of their angiogenic and therapeutic potential for repairing tissue ischemia. We culture-isolated MSCs from streptozotocin-induced diabetic rats (D-MSCs) and compared their proliferation, differentiation, and angiogenic effects with those from normal rats (N-MSCs). The angiogenic effects of MSCs were evaluated by real-time PCR, in vitro tube formation assay, and transplantation of the MSCs into a hindlimb ischemia model followed by laser Doppler perfusion imaging. The number of MSCs derived from diabetic rats was smaller, and their proliferation rate was slower than N-MSCs. Upon induction of differentiation, the osteogenic and angiogenic differentiation of D-MSCs were aberrant compared to N-MSCs. The expression of angiogenic factors was lower in D-MSCs than N-MSCs. D-MSCs cocultured with endothelial cells resulted in decreased tube formation compared to N-MSCs. D-MSCs were ineffective to improve hindlimb ischemia and showed lower capillary density and angiogenic gene expression in ischemic limbs than N-MSCs. D-MSCs have defective proliferation and angiogenic activities and are ineffective for repairing hindlimb ischemia. Newer measures are needed before MSCs can be employed as a source for autologous cell therapy.

Transplantation of SIRT1-engineered aged mesenchymal stem cells improves cardiac function in a rat myocardial infarction model

BACKGROUND

Previous studies have demonstrated that biological aging has a negative influence on the therapeutic effects of mesenchymal stem cells (MSCs)-based therapy. Using a rat myocardial infarction (MI) model, we tested the hypothesis that silent mating type information regulation 2 homolog 1 (SIRT1) may ameliorate the phenotype and improve the function of aged MSCs and thus enhance the efficacy of aged MSCs-based therapy.

METHODS

Sixty female rats underwent left anterior descending coronary artery ligation and were randomly assigned to receiving: intramyocardial injection of cell culture medium (DMEM group); SIRT1 overexpression vector-treated aged MSCs (SIRT1-aged MSCs group) obtained from aged male SD rats or empty vector-treated aged MSCs (vector-aged MSCs group). Another 20 sham-operated rats that underwent open-chest surgery without coronary ligation or any other intervention served as controls.

RESULTS

SIRT1-aged MSC group exhibited enhanced blood vessel density in the border zone of MI hearts, which was associated with reduced cardiac remodeling, leading to improved cardiac performance. Consistent with the in vivo data, our in vitro experiments also demonstrated that SIRT1 overexpression ameliorated aged MSCs senescent phenotype and recapitulated the pro-angiogenesis property of MSCs and conferred the anti-stress response capabilities, as indicated by increases in pro-angiogenic factors, angiopoietin 1 (Ang1) and basic fibroblast growth factor (bFGF), expressions and a decrease in anti-angiogenic factor thrombospondin-1 (TBS1) at mRNA levels, and increases in Bcl-2/Bax ratio at protein level.

CONCLUSIONS

Up-regulating SIRT1 expression could enhance the efficacy of aged MSCs-based therapy for MI as it relates to the amelioration of senescent phenotype and hence improved biological function of aged MSCs.

Mesenchymal stem cell survival in the infarcted heart is enhanced by lentivirus vector-mediated heat shock protein 27 expression

Mesenchymal stem cell (MSC) therapy offers the potential to promote recovery after myocardial infarction (MI). However, therapeutic efficacy may be limited by poor survival and retention of transplanted cells. A combination of gene and cell therapy has the capacity to prevent donor cell death and augment the reparative and regenerative effects of cell transfer. The present study investigates the effect of exogenous heat shock protein 27 (Hsp27) expression in MSCs in an in vitro model of ischemia and in an in vivo rat MI model and aims to determine if this could enhance the therapeutic benefit associated with cell delivery. Hsp27 overexpression by lentivirus vector modification resulted in increased MSC survival in vitro and in vivo. Furthermore, decreased apoptosis in the infarcted tissue and improved cardiac function was observed in the Hsp27 group, enhancing the therapeutic effect of MSCs. Together, these data demonstrate that ex vivo genetic modification-specifically Hsp27 overexpression-offers the possibility of enhancing the efficacy of MSC therapy in MI.

Optimization of the cardiovascular therapeutic properties of mesenchymal stromal/stem cells-taking the next step

Despite current treatment options, cardiac failure is associated with significant morbidity and mortality highlighting a compelling clinical need for novel therapeutic approaches. Based on promising pre-clinical data, stem cell therapy has been suggested as a possible therapeutic strategy. Of the candidate cell types evaluated, mesenchymal stromal/stem cells (MSCs) have been widely evaluated due to their ease of isolation and ex vivo expansion, potential allogeneic utility and capacity to promote neo-angiogenesis and endogenous cardiac repair. However, the clinical application of MSCs for mainstream cardiovascular use is currently hindered by several important limitations, including suboptimal retention and engraftment and restricted capacity for bona fide cardiomyocyte regeneration. Consequently, this has prompted intense efforts to advance the therapeutic properties of MSCs for cardiovascular disease. In this review, we consider the scope of benefit from traditional plastic adherence-isolated MSCs and the lessons learned from their conventional use in preclinical and clinical studies. Focus is then given to the evolving strategies aimed at optimizing MSC therapy, including discussion of cell-targeted techniques that encompass the preparation, pre-conditioning and manipulation of these cells ex vivo, methods to improve their delivery to the heart and innovative substrate-directed strategies to support their interaction with the host myocardium.

Low ATP level is sufficient to maintain the uncommitted state of multipotent mesenchymal stem cells

BACKGROUND

Multipotent mesenchymal stromal cells (MMSCs) are minimally differentiated precursors with great potential to transdifferentiate. These cells are quite resistant to oxygen limitation, suggesting that a hypoxic milieu can be physiological for MMSCs.

METHODS

Human MMSCs isolated from adipose tissue were grown at various oxygen concentrations. Alteration in cell immunophenotype was determined by flow cytometry after staining with specific antibodies. Concentrations of glucose and lactate were determined using the Biocon colorimetric test. Cellular respiration was assessed using oxygen electrode. The modes of cell death were analyzed by flow cytometry after staining with Annexin V and propidium iodide.

RESULTS

We found that permanent oxygen deprivation attenuated cellular ATP levels in these cells, diminishing mitochondrial ATP production but stimulating glycolytic ATP production. At the same time, permanent hypoxia did not affect MMSCs' viability, stimulated their proliferation and reduced their capacity to differentiate. Further, permanent hypoxia decreased spontaneous cell death by MMSCs.

CONCLUSIONS

Under hypoxic conditions glycolysis provides sufficient energy to maintain MMSCs in an uncommitted state.

GENERAL SIGNIFICANCE

These findings are of interest not only for scientific reasons, but also in practical terms. Oxygen concentration makes an essential contribution to MMSC physiology and should be taken into account in the setting of protocols for cellular therapy.

Stem cell recruitment after injury: lessons for regenerative medicine

Tissue repair and regeneration are thought to involve resident cell proliferation as well as the selective recruitment of circulating stem and progenitor cell populations through complex signaling cascades. Many of these recruited cells originate from the bone marrow, and specific subpopulations of bone marrow cells have been isolated and used to augment adult tissue regeneration in preclinical models. Clinical studies of cell-based therapies have reported mixed results, however, and a variety of approaches to enhance the regenerative capacity of stem cell therapies are being developed based on emerging insights into the mechanisms of progenitor cell biology and recruitment following injury. This article discusses the function and mechanisms of recruitment of important bone marrow-derived stem and progenitor cell populations following injury, as well as the emerging therapeutic applications targeting these cells.

Bone marrow mesenchymal stem cells for post-myocardial infarction cardiac repair: microRNAs as novel regulators

Transplantation of bone marrow-derived mesenchymal stem cells (MSCs) is safe and may improve cardiac function and structural remodelling in patients following myocardial infarction (MI). Cardiovascular cell differentiation and paracrine effects to promote endogenous cardiac regeneration, neovascularization, anti-inflammation, anti-apoptosis, anti-remodelling and cardiac contractility, may contribute to MSC-based cardiac repair following MI. However, current evidence indicates that the efficacy of MSC transplantation was unsatisfactory, due to the poor viability and massive death of the engrafted MSCs in the infarcted myocardium. MicroRNAs are short endogenous, conserved, non-coding RNAs and important regulators involved in numerous facets of cardiac pathophysiologic processes. There is an obvious involvement of microRNAs in almost every facet of putative repair mechanisms of MSC-based therapy in MI, such as stem cell differentiation, neovascularization, apoptosis, cardiac remodelling, cardiac contractility and arrhythmias, and others. It is proposed that therapeutic modulation of individual cardiovascular microRNA of MSCs, either mimicking or antagonizing microRNA actions, will hopefully enhance MSC therapeutic efficacy. In addition, MSCs may be manipulated to enhance functional microRNA expression or to inhibit aberrant microRNA levels in a paracrine manner. We hypothesize that microRNAs may be used as novel regulators in MSC-based therapy in MI and MSC transplantation by microRNA regulation may represent promising therapeutic strategy for MI patients in the future.

The promotion of cardiogenic differentiation of hMSCs by targeting epidermal growth factor receptor using microRNA-133a

Human bone marrow-derived mesenchymal stem cells (hMSCs) are an attractive candidate for cell therapy in heart disease. Low survival and incomplete electromechanical integration between resident cardiomyocytes and transplanted hMSCs remain unsolved. In order for an infarcted heart to tolerate transplantation, differentiation capacity in stem cells must be reinforced. In this study, we found that compound 56, an epidermal growth factor receptor (EGFR) inhibitor, promotes cardiogenic differentiation of hMSCs and the transplantation of hMSCs treated with compound 56 resulted in enhancement of heart functions. Furthermore, hMSCs transfected with microRNA-133a (miR-133a), which targets EGFR, were observed to express cardiac-specific markers. We also discovered that luciferase activity is exclusively decreased by targeting EGFR in hMSCs transfected with miR-133a mimic. These results suggest that EGFR plays a key role in the regulation of cardiogenic differentiation in hMSCs.