How to Improve the Survival of Transplanted Mesenchymal Stem Cell in Ischemic Heart? Stem Cells Int. 2016;2016:9682757. [PMID: 26681958 PMCID: PMC4670674 DOI: 10.1155/2016/9682757]

Human mesenchymal stromal cells and derived extracellular vesicles: Translational strategies to increase their proangiogenic potential for the treatment of cardiovascular disease

Mesenchymal stromal cells (MSCs) offer great potential for the treatment of cardiovascular diseases (CVDs) such as myocardial infarction and heart failure. Studies have revealed that the efficacy of MSCs is mainly attributed to their capacity to secrete numerous trophic factors that promote angiogenesis, inhibit apoptosis, and modulate the immune response. There is growing evidence that MSC‐derived extracellular vesicles (EVs) containing a cargo of lipids, proteins, metabolites, and RNAs play a key role in this paracrine mechanism. In particular, encapsulated microRNAs have been identified as important positive regulators of angiogenesis in pathological settings of insufficient blood supply to the heart, thus opening a new path for the treatment of CVD. In the present review, we discuss the current knowledge related to the proangiogenic potential of MSCs and MSC‐derived EVs as well as methods to enhance their biological activities for improved cardiac tissue repair. Increasing our understanding of mechanisms supporting angiogenesis will help optimize future approaches to CVD intervention.

Exosomes from SIRT1-Overexpressing ADSCs Restore Cardiac Function by Improving Angiogenic Function of EPCs

Acute myocardial infarction (AMI) is one of the leading causes of mortality in cardiovascular diseases. The aim of this study was to investigate whether exosomes from Sirtuin 1 (SIRT1)-overexpressing adipose-derived stem cells (ADSCs) had a protective effect on AMI. The expression of C-X-C chemokine receptor type 7 (CXCR7) was significantly downregulated in peripheral blood endothelial progenitor cells (EPCs) from AMI patients (AMI-EPCs) compared with that in healthy donors, which coincided with impaired tube formation. The exosomes from SIRT1 overexpression in ADSCs (ADSCs-SIRT1-Exos) increased the expression of C-X-C motif chemokine 12 (CXCL12) and nuclear factor E2 related factor 2 (Nrf2) in AMI-EPCs, which promoted migration and tube formation of AMI-EPCs, and overexpression of CXCR7 helped AMI-EPCs to restore the function of cell migration and tube formation. Moreover, CXCR7 was downregulated in the myocardium of AMI mice, and knockout of CXCR7 exacerbated AMI-induced impairment of cardiovascular function. Injection of ADSCs-SIRT1-Exos increased the survival and promoted the recovery of myocardial function with reduced infarct size and post-AMI left ventricular remodeling, induced vasculogenesis, and decreased AMI-induced myocardial inflammation. These findings showed that ADSCs-SIRT1-Exos may recruit EPCs to the repair area and that this recruitment may be mediated by Nrf2/CXCL12/CXCR7 signaling.

Mesenchymal Stem Cell/Multipotent Stromal Cell Augmentation of Wound Healing: Lessons from the Physiology of Matrix and Hypoxia Support

Cutaneous wounds requiring tissue replacement are often challenging to treat and result in substantial economic burden. Many of the challenges inherent to therapy-mediated healing are due to comorbidities of disease and aging that render many wounds as chronic or nonhealing. Repeated failure to resolve chronic wounds compromises the reserve or functioning of localized reparative cells. Transplantation of mesenchymal stem cells/multipotent stromal cells (MSCs) has been proposed to augment the reparative capacity of resident cells within the wound bed to overcome stalled wound healing. However, MSCs face a variety of challenges within the wound micro-environment that curtail their survival after transplantation. MSCs are naturally pro-angiogenic and proreparative, and thus numerous techniques have been attempted to improve their survival and efficacy after transplantation, many with little impact. These setbacks have prompted researchers to re-examine the normal wound bed physiology, resulting in new approaches to MSC transplantation using extracellular matrix proteins and hypoxia preconditioning. These studies have also led to new insights on associated intracellular mechanisms, particularly autophagy, which play key roles in further regulating MSC survival and paracrine signaling. This review provides a brief overview of cutaneous wound healing with discussion on how extracellular matrix proteins and hypoxia can be utilized to improve MSC retention and therapeutic outcome.

Shattering barriers toward clinically meaningful MSC therapies

More than 1050 clinical trials are registered at FDA.gov that explore multipotent mesenchymal stromal cells (MSCs) for nearly every clinical application imaginable, including neurodegenerative and cardiac disorders, perianal fistulas, graft-versus-host disease, COVID-19, and cancer. Several companies have or are in the process of commercializing MSC-based therapies. However, most of the clinical-stage MSC therapies have been unable to meet primary efficacy end points. The innate therapeutic functions of MSCs administered to humans are not as robust as demonstrated in preclinical studies, and in general, the translation of cell-based therapy is impaired by a myriad of steps that introduce heterogeneity. In this review, we discuss the major clinical challenges with MSC therapies, the details of these challenges, and the potential bioengineering approaches that leverage the unique biology of MSCs to overcome the challenges and achieve more potent and versatile therapies.

Applied Bioengineering in Tissue Reconstruction, Replacement, and Regeneration

IMPACT STATEMENT

The use of autologous tissue in the reconstruction of tissue defects has been the gold standard. However, current standards still face many limitations and complications. Improving patient outcomes and quality of life by addressing these barriers remain imperative. This article provides historical perspective, covers the major limitations of current standards of care, and reviews recent advances and future prospects in applied bioengineering in the context of tissue reconstruction, replacement, and regeneration.

Experimental Single-Platform Approach to Enhance the Functionalization of Magnetically Targetable Cells

Magnetic guidance shows promise as a strategy for improving the delivery and performance of cell therapeutics. However, clinical translation of magnetically guided cell therapy requires cell functionalization protocols that provide adequate magnetic properties in balance with unaltered cell viability and biological function. Existing methodologies for characterizing cells functionalized with magnetic nanoparticles (MNP) produce aggregate results, both distorted and unable to reflect variability in either magnetic or biological properties within a preparation. In the present study, we developed an inverted-plate assay allowing determination of these characteristics using a single-platform approach, and applied this method for a comparative analysis of two loading protocols providing highly uniform vs. uneven MNP distribution across cells. MNP uptake patterns remarkably different between the two protocols were first shown by fluorimetry carried out in a well-scan mode on endothelial cells (EC) loaded with BODIPY558/568-labeled MNP. Using the inverted-plate assay we next demonstrated that, in stark contrast to unevenly loaded cells, more than 50% of uniformly functionalized EC were captured within 5 min over a broad range of MNP doses. Furthermore, magnetically captured cells exhibited unaltered viability, substrate attachment, and proliferation rates. Conducted in parallel, magnetophoretic mobility studies corroborated the markedly superior guidance capacity of uniformly functionalized cells, confirming substantially faster cell capture kinetics on a clinically relevant time scale. Taken together, these results emphasize the importance of optimizing cell preparation protocols with regard to loading uniformity as key to efficient site-specific delivery, engraftment, and expansion of the functionalized cells, essential for both improving performance and facilitating translation of targeted cell therapeutics.

A novel role of vitronectin in promoting survival of mesenchymal stem cells under serum deprivation stress

Background

Due to their immunomodulatory and trophic support functions, mesenchymal stem cells (MSCs) are promising in the field of cell-based regenerative medicine. However, MSC survival post-transplantation is challenged by various microenvironment stress factors. Here, we investigated the role of vitronectin (VTN) in the survival strategy of MSCs under serum deprivation stress condition.

Methods

Proliferation kinetics and cell adhesion of MSCs under serum deprivation were determined from population doublings and cell-matrix de-adhesion studies, respectively. mRNA and protein expression levels of VTN were confirmed by qRT-PCR and Western blotting, respectively. Immunofluorescence technique revealed distribution of VTN under serum deprivation stress. siRNA and inhibitor-based studies were performed to confirm the role and regulation of VTN. Apoptosis and cell cycle status of MSCs were assessed using flow cytometric analysis.

Results

Subjecting MSCs to serum deprivation led to significant increase in cell spread area and cell-matrix adhesion. An upregulation of VTN expression was noted with an arrest in G0/G1 phase of cell cycle and no appreciable apoptotic change. Pro-survival PI3kinase pathway inhibition led to further increase in VTN expression with no apoptotic change. siRNA-mediated inhibition of VTN resulted in reversal in G0/G1 cell cycle arrest and a marked increase in apoptosis, suggesting a role of VTN in preventing serum deprivation-induced apoptotic cell death. In addition, p65 knockdown resulted in downregulation of VTN establishing an association between NF-κβ pathway and VTN.

Conclusions

VTN was identified as a survival factor in providing protection from serum deprivation-induced apoptosis in MSCs.

The therapeutic potential of mesenchymal stem cells for cardiovascular diseases

Mesenchymal stem cells (MSCs) are derived from a wide range of sources and easily isolated and cultured. MSCs have the capacity for in vitro amplification and self-renewal, low immunogenicity and immunomodulatory properties, and under certain conditions, MSCs can be differentiated into a variety of cells. In the cardiovascular system, MSCs can protect the myocardium by reducing the level of inflammation, promoting the differentiation of myocardial cells around infarct areas and angiogenesis, increasing apoptosis resistance, and inhibiting fibrosis, which are ideal qualities for cardiovascular repair. Preclinical studies have shown that MSCs can be transplanted and improve cardiac repair, but challenges, such as their low rate of migration to the ischemic myocardium, low tissue retention, and low survival rate after transplantation, remain. This article reviews the potential and methods of MSC transplantation in the treatment of cardiovascular diseases (CVDs) and the challenges of the clinical use of MSCs.

Current Status and Future Prospects of Genome-Scale Metabolic Modeling to Optimize the Use of Mesenchymal Stem Cells in Regenerative Medicine

Mesenchymal stem cells are a promising source for externally grown tissue replacements and patient-specific immunomodulatory treatments. This promise has not yet been fulfilled in part due to production scaling issues and the need to maintain the correct phenotype after re-implantation. One aspect of extracorporeal growth that may be manipulated to optimize cell growth and differentiation is metabolism. The metabolism of MSCs changes during and in response to differentiation and immunomodulatory changes. MSC metabolism may be linked to functional differences but how this occurs and influences MSC function remains unclear. Understanding how MSC metabolism relates to cell function is however important as metabolite availability and environmental circumstances in the body may affect the success of implantation. Genome-scale constraint based metabolic modeling can be used as a tool to fill gaps in knowledge of MSC metabolism, acting as a framework to integrate and understand various data types (e.g., genomic, transcriptomic and metabolomic). These approaches have long been used to optimize the growth and productivity of bacterial production systems and are being increasingly used to provide insights into human health research. Production of tissue for implantation using MSCs requires both optimized production of cell mass and the understanding of the patient and phenotype specific metabolic situation. This review considers the current knowledge of MSC metabolism and how it may be optimized along with the current and future uses of genome scale constraint based metabolic modeling to further this aim.

Urodynamic Parameters in Spinal Cord Injury-Induced Neurogenic Bladder Rats after Stem Cell Transplantation: A Narrative Review

Neurogenic bladder (NGB) secondary to spinal cord injury (SCI) is accompanied with several complications such as urinary tract deterioration, urinary incontinence, and consequently lower quality of life (QoL), significant morbidities, and occasionally death. Current therapeutic methods have some side effects and there is no treatment for the upper urinary tract injuries. Stem cell therapy is a promising method for treating this condition. However, the best timing and the best route of its transplantation have not yet been determined. Animal models of SCI, especially in rats, are the most commonly used method for evaluating the efficacy of cell therapy in NGB improvement, and the most common assessment method is the urodynamic studies (UDS). However, there are variations in the range of UDS parameters among the published studies. The current review aimed to discuss the effect of stem cell transplantation on bladder dysfunction recovery based on urodynamic parameters after SCI in rats. For this purpose, the cell source, doses, the route of administration, and the complete UDS equipment and its parameters were summarized in SCI models in rats. In some urodynamic test results, to some extent, an improvement in the lower urinary system function was observed in each treatment group. However, this improvement was far from full functional recovery. The average cell dose was about 1 million cells in every injected site. In most studies, the stem cells (SCs) were transplanted 9 days after the injury using PE-50 and PE-60. Many researchers have recommended further experimental and clinical studies to confirm this treatment modality.

Cell sheet tissue engineering for scaffold-free three-dimensional (3D) tissue reconstruction

Three-dimensional (3D) reconstruction of highly functional tissues is of great importance in advancing the clinical benefit of tissue engineering and regenerative medicine. In the last quarter century, many studies have found that by engineering a 3D microenvironment that resembles the in vivo tissue condition, cells exhibit behaviors and functions that reflect those of native tissue. Biomaterial scaffolds are a central technology for providing 3D microenvironments in vitro, and, in conjunction with diverse design and cell seeding advents, have produced highly functional and complex 3D tissues. Here, we describe a new approach to creating 3D cell-dense tissue-like constructs without a biomaterial scaffold. Cell sheet technology with cell sheet layering strategies generates highly cell dense, engineered tissue capable of direct crosstalk with the tissue-engraftment surface, in addition to paracrine-mediated signaling. In this chapter, we will introduce methods of reconstructing 3D tissue using cell sheet technology and the advantages of a scaffold-free design.

Phenotypic traits of mesenchymal stem cell sheets fabricated by temperature-responsive cell culture plate: structural characteristics of MSC sheets

Background

In most stem cell therapy strategies reported to date, stem cells are introduced to damaged tissue sites to repair and regenerate the original tissue structure and function. MSC therapeutic efficacies are inconsistent, largely attributed to transplanted MSC difficulties both in engrafting at tissue sites and in retaining their therapeutic functions from suspension formulations. MSC functional components, including cell adhesion and cell–cell junction proteins, and ECM that contribute to essential cellular therapeutic effects, are damaged or removed by proteolytic enzymes used in stem cell harvesting strategies from culture. To overcome these limitations, methods to harvest and transplant cells without disrupting critical stem cell functions are required. Cell sheet technology, exploiting temperature-responsive cell culture surfaces, permits cell harvest without cell protein damage. This study is focused on phenotypic traits of MSC sheets structurally and functionally to understand therapeutic benefits of cell sheets.

Methods/results

This study verified cleaved cellular proteins (vinculin, fibronectin, laminin, integrin β-1, and connexin 43) and increased apoptotic cell death produced under standard trypsin harvesting treatment in a time-dependent manner. However, MSC sheets produced without trypsin using only temperature-controlled sheet harvest from culture plastic exhibited intact cellular structures. Also, MSCs harvested using enzymatic treatment (i.e., chemical disruption) showed higher pYAP expression compared to MSC sheets.

Conclusion

Retention of cellular structures such as ECM, cell–cell junctions, and cell–ECM junctions is correlated with human umbilical cord mesenchymal stem cell (hUC-MSC) survival after detachment from cell culture surfaces. Retaining these proteins intact in MSC cultures using cell sheet technology is proposed to enhance stem cell survival and their function in stem cell-based therapy.

Bone marrow mesenchymal stem cells overexpressing GATA-4 improve cardiac function following myocardial infarction

INTRODUCTION

The present study aimed to examine whether GATA-4 overexpressing bone marrow mesenchymal stem cells can improve cardiac function in a murine myocardial infarction model compared with bone marrow mesenchymal stem cells alone.

METHODS

A lentiviral-based transgenic system was used to generate bone mesenchymal stem cells which stably expressed GATA-4 (GATA-4-bone marrow mesenchymal stem cells). Apoptosis and the myogenic phenotype of the bone marrow mesenchymal stem cells were measured using Western blot and immunofluorescence assays co-cultured with cardiomyocytes. Cardiac function, bone marrow mesenchymal stem cell homing, cardiac cell apoptosis, and vessel number following transplantation were assessed, as well as the expression of c-Kit.

RESULTS

In GATA-4-bone marrow mesenchymal stem cells-cardiomyocyte co-cultures, expression of myocardial-specific antigens, cTnT, connexin-43, desmin, and α-actin was increased compared with bone marrow mesenchymal stem cells alone. Caspase 8 and cytochrome C expression was lower, and the apoptotic rate was significantly lower in GATA-4 bone marrow mesenchymal stem cells. Cardiac function following myocardial infarction was also increased in the GATA-4 bone marrow mesenchymal stem cell group as demonstrated by enhanced ejection fraction and left ventricular fractional shortening. Analysis of the cardiac tissue revealed that the GATA-4 bone marrow mesenchymal stem cell group had a greater number of DiR-positive cells suggestive of increased homing and/or survival. Transplantation with GATA-4-bone marrow mesenchymal stem cells significantly increased the number of blood vessels, decreased the proportion of apoptotic cells, and increased the mean number of cardiac c-kit-positive cells.

CONCLUSION

GATA-4 overexpression in bone marrow mesenchymal stem cells exerts anti-apoptotic effects by targeting cytochrome C and Fas pathways, promotes the aggregation of bone marrow mesenchymal stem cells in cardiac tissue, facilitates angiogenesis, and effectively mobilizes c-kit-positive cells following myocardial infarction, leading to the improvement of cardiac function after MI.

Platelet-Rich Plasma Improves the Wound Healing Potential of Mesenchymal Stem Cells through Paracrine and Metabolism Alterations

Chronic and acute nonhealing wounds represent a major public health problem, and replacement of cutaneous lesions by the newly regenerated skin is challenging. Mesenchymal stem cells (MSC) and platelet-rich plasma (PRP) were separately tested in the attempt to regenerate the lost skin. However, these treatments often remained inefficient to achieve complete wound healing. Additional studies suggested that PRP could be used in combination with MSC to improve the cell therapy efficacy for tissue repair. However, systematic studies related to the effects of PRP on MSC properties and their ability to rebuild skin barrier are lacking. We evaluated in a mouse exhibiting 4 full-thickness wounds, the skin repair ability of a treatment combining human adipose-derived MSC and human PRP by comparison to treatment with saline solution, PRP alone, or MSC alone. Wound healing in these animals was measured at day 3, day 7, and day 10. In addition, we examined in vitro and in vivo whether PRP alters in MSC their proangiogenic properties, their survival, and their proliferation. We showed that PRP improved the efficacy of engrafted MSC to replace lost skin in mice by accelerating the wound healing processes and ameliorating the elasticity of the newly regenerated skin. In addition, we found that PRP treatment stimulated in vitro, in a dose-dependent manner, the proangiogenic potential of MSC through enhanced secretion of soluble factors like VEGF and SDF-1. Moreover, PRP treatment ameliorated the survival and activated the proliferation of in vitro cultured MSC and that these effects were accompanied by an alteration of the MSC energetic metabolism including oxygen consumption rate and mitochondrial ATP production. Similar observations were found in vivo following combined administration of PRP and MSC into mouse wounds. In conclusion, our study strengthens that the use of PRP in combination with MSC might be a safe alternative to aid wound healing.

Combining ECM Hydrogels of Cardiac Bioactivity with Stem Cells of High Cardiomyogenic Potential for Myocardial Repair

Tissue engineering exploring the combination of scaffolds and seeding cells was proposed as a promising strategy for myocardial repair. However, the therapeutic outcomes varied greatly due to different selection of scaffolds and seeding cells. Herein, the potential of combining bioactive extracellular matrix (ECM) hydrogels and high cardiomyogenic seeding cells was explored for myocardial repair in vitro and in vivo. Temperature-sensitive ECM hydrogels were prepared from decellularized rat hearts, and cardiomyogenic seeding cells were isolated from brown adipose (brown adipose-derived stem cells (BADSCs)). The in vitro studies demonstrated that ECM hydrogel significantly supported the proliferation and cardiomyogenic differentiation of BADSCs. Importantly, the function and maturation of BADSC-derived cardiomyocytes were also promoted as evidenced by Ca²⁺ transient's measurement and protein marker expression. After myocardial transplantation, the combination of BADSCs and ECM hydrogels significantly preserved cardiac function and chamber geometry compared with BADSCs or ECM hydrogels alone. Meanwhile, the ECM hydrogel also enhanced BADSC engraftment and myocardial regeneration in vivo. These results indicated that heart-derived ECM hydrogels exerted significant influence on the fate of cardiomyogenic cells toward benefiting myocardial repair, which may explain the enhanced stem cell therapy by the scaffold. Collectively, it indicated that the combination of ECM hydrogel and the cardiomyogenic cells may represent a promising strategy for cardiac tissue engineering.

Three-Dimensional Spheroid Formation of Cryopreserved Human Dental Follicle-Derived Stem Cells Enhances Pluripotency and Osteogenic Induction Properties

Background

Enhancement and maintenance of the stemness of mesenchymal stem cells (MSCs) is one of the most important factors contributing to the successful in vivo therapeutic application of these cells. In this regard, three-dimensional (3D) spheroid formation has been developed as reliable method for increasing the pluripotency of MSCs. Moreover, using a new protocol, we have previously shown that dental tissues of extracted wisdom teeth can be effectively cryopreserved for subsequent use as a source of autologous stem cells. The main purpose of this study is to analyze the stemness and in vitro osteogenic differentiation potential of 3D spheroid dental MSCs compared with conventional mono-layer cultured MSCs.

Methods

In this study, MSC-characterized stem cells were isolated and cultured from long-term cryopreserved dental follicles (hDFSCs), and then 2D hDFSCs were cultured under 3D spheroid-forming conditions using a newly designed microchip dish. The spheroids (3D hDFSCs) thus produced were investigated and characterized with respect to stemness, MSC marker expression, apoptosis, cell cycle analysis, extracellular matrix (ECM) production, and osteogenic and adipogenic differentiation properties.

Results

In terms of MSC and senescence markers, spheroid cells showed no difference when compared with 2D hDFSCs; however, 3D hDFSCs were observed to have a higher proportion of cell cycle arrest and a larger number of apoptotic cells. Moreover, spheroids showed substantially increased levels of pluripotency marker (early transcription factors) and ECM protein expression. Compared with 2D hDFSCs, there was also a notable enhancement in the osteogenic induction potential of spheroids, although no differences were observed with respect to in vitro adipogenesis.

Conclusion

To the best of our knowledge, this is the first study to demonstrate the application of a spheroid culture system for dental follicle-derived stem cells using a microchip dish. Although further studies are needed, including in vivo transplantation, the results obtained in this study indicate that spheroid hDFSCs derived from cryopreserved dental follicle tissues could be used as a valuable source of autologous stem cells for bone tissue regeneration.

Optimization and Characterization of Calcium Phosphate Transfection in Mesenchymal Stem Cells

IMPACT STATEMENT

Mesenchymal stem cells (MSCs) are a promising tool for cell therapy, and gene-modified MSCs further expand their applications. To take full advantage of MSCs as a therapeutic approach, developing effective gene transfer methods is critical. Calcium phosphate transfection is well-established and safe, but the protocols need to be optimized according to different cell types. Currently, there is no optimized protocol for MSCs. This study optimized the protocol of calcium phosphate transfection for MSCs and highlighted the importance of serum during the process of transfection. More interestingly, the behavior of gene overexpression in MSCs in the in vivo environment was verified.

O-cyclic phytosphingosine-1-phosphate stimulates HIF1α-dependent glycolytic reprogramming to enhance the therapeutic potential of mesenchymal stem cells

O-cyclic phytosphingosine-1-phosphate (cP1P) is a novel chemically synthesized sphingosine metabolite derived from phytosphingosine-1-phosphate. Although structurally similar to sphingosine-1-phosphate (S1P), its biological properties in stem cells remain to be reported. We investigated the effect of cP1P on the therapeutic potential of mesenchymal stem cells (MSCs) and their regulatory mechanism. We found that, under hypoxia, cP1P suppressed MSC mitochondrial dysfunction and apoptosis. Metabolic data revealed that cP1P stimulated glycolysis via the upregulation of glycolysis-related genes. cP1P-induced hypoxia-inducible factor 1 alpha (HIF1α) plays a key role for MSC glycolytic reprogramming and transplantation efficacy. The intracellular calcium-dependent PKCα/mammalian target of the rapamycin (mTOR) signaling pathway triggered by cP1P regulated HIF1α translation via S6K1, which is critical for HIF1 activation. Furthermore, the cP1P-activated mTOR pathway induced bicaudal D homolog 1 expression, leading to HIF1α nuclear translocation. In conclusion, cP1P enhances the therapeutic potential of MSC through mTOR-dependent HIF1α translation and nuclear translocation.

Inflammation in myocardial injury: mesenchymal stem cells as potential immunomodulators

Ischemic heart disease is a growing worldwide epidemic. Improvements in medical and surgical therapies have reduced early mortality after acute myocardial infarction and increased the number of patients living with chronic heart failure. The irreversible loss of functional cardiomyocytes puts these patients at significant risk of ongoing morbidity and mortality after their index event. Recent evidence suggests that inflammation is a key mediator of postinfarction adverse remodeling in the heart. In this review, we discuss the cardioprotective and deleterious effects of inflammation and its mediators during acute myocardial infarction. We also explore the role of mesenchymal stem cell therapy to limit secondary injury and promote myocardial healing after myocardial infarction.

Decellularized extracellular matrix gelloids support mesenchymal stem cell growth and function in vitro

Volumetric muscle loss (VML) injuries are irrecoverable due to a significant loss of regenerative elements, persistent inflammation, extensive fibrosis, and functional impairment. When used in isolation, previous stem cell and biomaterial-based therapies have failed to regenerate skeletal muscle at clinically relevant levels. The extracellular matrix (ECM) microenvironment is crucial for the viability, stemness, and differentiation of stem cells. Decellularized-ECM (D-ECM) scaffolds are at the forefront of ongoing research to develop a viable therapy for VML. Due to the retention of key ECM components, D-ECM scaffolds provide an excellent substrate for the adhesion and migration of several cell types. Mesenchymal stem cells (MSCs) possess regenerative and immunomodulatory properties and are currently under investigation in clinical trials for a wide range of medical conditions. However, a major limitation to the use of MSCs in clinical applications is their poor viability at the site of transplantation. In this study, we have fabricated spherical scaffolds composed of gelatin and skeletal muscle D-ECM for the adhesion and delivery of MSCs to the site of VML injury. These spherical scaffolds termed "gelloids" supported MSC survival, expansion, trophic factor secretion, immunomodulation, and myogenic protein expression in vitro. Future studies would determine the therapeutic efficacy of this approach in a murine model of VML injury.

Magnetic resonance imaging of stem cell-macrophage interactions with ferumoxytol and ferumoxytol-derived nanoparticles

"Off the shelf" allogeneic stem cell transplants and stem cell nano-composites are being used for the treatment of degenerative bone diseases. However, major and minor histocompatibility antigens of therapeutic cell transplants can be recognized as foreign and lead to their rejection by the host immune system. If a host immune response is identified within the first week post-transplant, immune modulating therapies could be applied to prevent graft failure and support engraftment. Ferumoxytol (Feraheme™) is an FDA approved iron oxide nanoparticle preparation for the treatment of anemia in patients. Ferumoxytol can be used "off label" as an magnetic resonance (MR) contrast agent, as these nanoparticles provide measurable signal changes on magnetic resonance imaging (MRI). In this focused review article, we will discuss three methods to localize and identify innate immune responses to stem cell transplants using ferumoxytol-enhanced MRI, which are based on tracking stem cells, tracking macrophages or detecting mediators of cell death: (a) monitor MRI signal changes of ferumoxytol-labeled stem cells in the presence or absence of innate immune responses, (b) monitor influx of ferumoxytol-labeled macrophages into stem cell implants, and (c) monitor apoptosis of stem cell implants with caspase-3 activatable nanoparticles. These techniques can detect transplant failure at an early stage, when immune-modulating interventions can potentially preserve the viability of the cell transplants and thereby improve bone and cartilage repair outcomes. Approaches 1 and 2 are immediately translatable to clinical practice. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging Nanotechnology Approaches to Biology > Cells at the Nanoscale Diagnostic Tools > Biosensing.

Extemporaneous Preparation of Injectable and Enzymatically Degradable 3D Cell Culture Matrices from an Animal-Component-Free Recombinant Protein Based on Human Collagen Type I

Injectable hydrogels are considered important to realize safe and effective minimally invasive therapy. Although animal-derived natural polymers are well studied, they typically lack injectability and fail to eliminate the potential risks of immunogenic reactions or unknown pathogen contamination. Despite extensive research activities to explore ideal injectable hydrogels, such state-of-the-art technology remains inaccessible to non-specialists. In this article, the design of a new injectable hydrogel platform that can be extemporaneously prepared from commercially available animal-component-free materials is described. The hydrogels can be prepared simply by mixing mutually reactive aqueous solutions without necessitating specialized knowledge or equipment. Their solidification time can be adjusted by choosing proper buffer conditions from immediate to an extended period of time, that is, few or several tens of minutes depending on the concentration of polymeric components, which not only provides injectability, but enables 3D encapsulation of cells. Mesenchymal stromal/stem cells can be encapsulated and cultured in the hydrogels at least for 2 weeks by traditional cell culture techniques, and retrieved by collagenase digestion with cell viability of approximately 80%. This hydrogel platform accelerates future cell-related research activities.

Empowering Mesenchymal Stem Cells for Ocular Degenerative Disorders

Multipotent mesenchymal stem cells (MSCs) have been employed in numerous pre-clinical and clinical settings for various diseases. MSCs have been used in treating degenerative disorders pertaining to the eye, for example, age-related macular degeneration, glaucoma, retinitis pigmentosa, diabetic retinopathy, and optic neuritis. Despite the known therapeutic role and mechanisms of MSCs, low cell precision towards the targeted area and cell survivability at tissue needing repair often resulted in a disparity in therapeutic outcomes. In this review, we will discuss the current and feasible strategy options to enhance treatment outcomes with MSC therapy. We will review the application of various types of biomaterials and advances in nanotechnology, which have been employed on MSCs to augment cellular function and differentiation for improving treatment of visual functions. In addition, several modes of gene delivery into MSCs and the types of associated therapeutic genes that are important for modulation of ocular tissue function and repair will be highlighted.

Melatonin preconditioning of bone marrow-derived mesenchymal stem cells promotes their engraftment and improves renal regeneration in a rat model of chronic kidney disease

Bone marrow-derived mesenchymal stem cells (BMMSCs) transplantation has shown to be effective in treating chronic kidney disease. However, the effectiveness of this strategy is constrained by low homing and survival rate of transplanted cells in the injured organs. Therefore, developing strategies to improve homing and cell survival rate and therapeutic potential in cell-based therapies seems necessary. The purpose of this study is to evaluate the effect of pretreating BMMSCs with melatonin (MT) on the prosurvival and renoprotective of transplanted cells into the irreversible model of unilateral ureteral obstruction. Adult male Sprague-Dawley rats were randomized into four groups: Sham, UUO, UUO + BMMSCs, and UUO + BMMSCs + MT. The results of our study demonstrated that preconditioning with MT enhanced homing of BMMSCs into the injured kidney. MT reduced the number of TUNEL positive transplanted cells in the UUO + BMMSCs + MT group. The UUO + BMMSCs + MT group showed lower expressions of TGF-β1, α-SMA and TNF-α at both gene and protein levels but higher expression of E-cadherin compared with the UUO + BMMSCs group. In addition, MT preconditioned BMMSCs ameliorated basement membrane disruption and histological status of injured renal tubules and also reduced fibrosis in damaged kidneys. In conclusion, our results show that stem cells pretreated by MT may represent a feasible approach for improving the beneficial effects of stem cell therapy and significantly enhance their survival after transplantation to the injured kidney.

Unveiling Mesenchymal Stromal Cells' Organizing Function in Regeneration

Regeneration is a fundamental process attributed to the functions of adult stem cells. In the last decades, delivery of suspended adult stem cells is widely adopted in regenerative medicine as a leading means of cell therapy. However, adult stem cells cannot complete the task of human body regeneration effectively by themselves as far as they need a receptive microenvironment (the niche) to engraft and perform properly. Understanding the mechanisms underlying mammalian regeneration leads us to an assumption that improved outcomes of cell therapy require a specific microenvironment that is generated in damaged areas prior to stem cell delivery. To a certain extent, it may be achieved by the delivery of mesenchymal stromal cells (MSCs), not in dispersed form, but rather in self-organized cell sheets (CS) ⁻ tissue-like structures comprised of viable cells and microenvironment components: extracellular matrix and soluble factors deposited in the matrix. In this review, we highlight the potential role of MSCs as regeneration organizers and speculate that this function emerges in CS. This concept shifts our understanding of the therapeutic mechanism underlying a widely known CS-based delivery method for regenerative medicine.

Nucleic acid delivery to mesenchymal stem cells: a review of nonviral methods and applications

Background

Mesenchymal stem cells (MSCs) are multipotent stem cells that can be isolated and expanded from many tissues, and are being investigated for use in cell therapies. Though MSC therapies have demonstrated some success, none have been FDA approved for clinical use. MSCs lose stemness ex vivo, decreasing therapeutic potential, and face additional barriers in vivo, decreasing therapeutic efficacy. Culture optimization and genetic modification of MSCs can overcome these barriers. Viral transduction is efficient, but limited by safety concerns related to mutagenicity of integrating viral vectors and potential immunogenicity of viral antigens. Nonviral delivery methods are safer, though limited by inefficiency and toxicity, and are flexible and scalable, making them attractive for engineering MSC therapies.

Main text

Transfection method and nucleic acid determine efficiency and expression profile in transfection of MSCs. Transfection methods include microinjection, electroporation, and nanocarrier delivery. Microinjection and electroporation are efficient, but are limited by throughput and toxicity. In contrast, a variety of nanocarriers have been demonstrated to transfer nucleic acids into cells, however nanocarrier delivery to MSCs has traditionally been inefficient. To improve efficiency, plasmid sequences can be optimized by choice of promoter, inclusion of DNA targeting sequences, and removal of bacterial elements. Instead of DNA, RNA can be delivered for rapid protein expression or regulation of endogenous gene expression. Beyond choice of nanocarrier and nucleic acid, transfection can be optimized by priming cells with media additives and cell culture surface modifications to modulate barriers of transfection. Media additives known to enhance MSC transfection include glucocorticoids and histone deacetylase inhibitors. Culture surface properties known to modulate MSC transfection include substrate stiffness and specific protein coating. If nonviral gene delivery to MSCs can be sufficiently improved, MSC therapies could be enhanced by transfection for guided differentiation and reprogramming, transplantation survival and directed homing, and secretion of therapeutics. We discuss utilized delivery methods and nucleic acids, and resulting efficiency and outcomes, in transfection of MSCs reported for such applications.

Conclusion

Recent developments in transfection methods, including nanocarrier and nucleic acid technologies, combined with chemical and physical priming of MSCs, may sufficiently improve transfection efficiency, enabling scalable genetic engineering of MSCs, potentially bringing effective MSC therapies to patients.

Stem cells technology: a powerful tool behind new brain treatments

Stem cell research has recently become a hot research topic in biomedical research due to the foreseen unlimited potential of stem cells in tissue engineering and regenerative medicine. For many years, medicine has been facing intense challenges, such as an insufficient number of organ donations that is preventing clinicians to fulfill the increasing needs. To try and overcome this regrettable matter, research has been aiming at developing strategies to facilitate the in vitro culture and study of stem cells as a tool for tissue regeneration. Meanwhile, new developments in the microfluidics technology brought forward emerging cell culture applications that are currently allowing for a better chemical and physical control of cellular microenvironment. This review presents the latest developments in stem cell research that brought new therapies to the clinics and how the convergence of the microfluidics technology with stem cell research can have positive outcomes on the fields of regenerative medicine and high-throughput screening. These advances will bring new translational solutions for drug discovery and will upgrade in vitro cell culture to a new level of accuracy and performance. We hope this review will provide new insights into the understanding of new brain treatments from the perspective of stem cell technology especially regarding regenerative medicine and tissue engineering.

The Winding Road of Cardiac Regeneration-Stem Cell Omics in the Spotlight

Despite significant progress in treating ischemic cardiac disease and succeeding heart failure, there is still an unmet need to develop effective therapeutic strategies given the persistent high-mortality rate. Advances in stem cell biology hold great promise for regenerative medicine, particularly for cardiac regeneration. Various cell types have been used both in preclinical and clinical studies to repair the injured heart, either directly or indirectly. Transplanted cells may act in an autocrine and/or paracrine manner to improve the myocyte survival and migration of remote and/or resident stem cells to the site of injury. Still, the molecular mechanisms regulating cardiac protection and repair are poorly understood. Stem cell fate is directed by multifaceted interactions between genetic, epigenetic, transcriptional, and post-transcriptional mechanisms. Decoding stem cells' "panomic" data would provide a comprehensive picture of the underlying mechanisms, resulting in patient-tailored therapy. This review offers a critical analysis of omics data in relation to stem cell survival and differentiation. Additionally, the emerging role of stem cell-derived exosomes as "cell-free" therapy is debated. Last but not least, we discuss the challenges to retrieve and analyze the huge amount of publicly available omics data.

Melatonin protects mesenchymal stem cells from autophagy-mediated death under ischaemic ER-stress conditions by increasing prion protein expression

Object

The purpose of this study was to explore whether melatonin could protect mesenchymal stem cells (MSCs) against ischaemic injury, by inhibiting endoplasmic reticulum (ER) stress and autophagy both in vivo and in vitro.

Materials and Methods

To confirm the protective effect of melatonin against ER stress in MSCs, markers of cell viability, apoptosis and autophagy were analysed. To further investigate the regenerative effect of melatonin‐treated MSCs in ischaemic tissues, a murine hindlimb ischaemic model was established.

Results

Under oxidative stress conditions, treatment with melatonin suppressed the activation of ER stress–associated proteins and autophagy‐associated proteins acting through upregulation of cellular prion protein (PrP^C) expression. Consequently, inhibition of apoptotic cell death occurred. Melatonin also promoted the activation of MnSOD and catalase activities in MSCs. In a murine hindlimb ischaemia model, melatonin‐treated MSCs also enhanced the functional limb recovery as well as neovascularization. These beneficial effects of melatonin were all blocked by knock‐down of PrP^C expression.

Conclusion

Melatonin protects against ER stress/autophagy‐induced apoptotic cell death by augmenting PrP^C expression. Thus, melatonin‐treated MSCs could be a potential cell‐based therapeutic agent for ER stress–induced ischaemic diseases, and melatonin‐induced PrP^C might be a key molecule in ameliorating ER stress and autophagy.

Combinatorial Screening of Nanoclay-Reinforced Hydrogels: A Glimpse of the "Holy Grail" in Orthopedic Stem Cell Therapy?

Despite the promise of hydrogel-based stem cell therapies in orthopedics, a significant need still exists for the development of injectable microenvironments capable of utilizing the  regenerative potential of donor cells. Indeed, the quest for biomaterials that can direct stem cells into bone without the need of external factors has been the "Holy Grail" in orthopedic stem cell therapy for decades. To address this challenge, we have utilized a combinatorial approach to screen over 63 nanoengineered hydrogels made from alginate, hyaluronic acid, and two-dimensional nanoclays. Out of these combinations, we have identified a biomaterial that can promote osteogenesis in the absence of well-established differentiation factors such as bone morphogenetic protein 2 (BMP2) or dexamethasone. Notably, in our "hit" formulations we observed a 36-fold increase in alkaline phosphate (ALP) activity and a 11-fold increase in the formation of mineralized matrix, compared to the control hydrogel. This induced osteogenesis was further supported by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy. Additionally, the Montmorillonite-reinforced hydrogels exhibited high osteointegration as evident from the relatively stronger adhesion to the bone explants as compared to the control. Overall, our results demonstrate the capability of combinatorial and nanoengineered biomaterials to induce bone regeneration through osteoinduction of stem cells in a natural and differentiation-factor-free environment.

Therapeutic effects of a mesenchymal stem cell‑based insulin‑like growth factor‑1/enhanced green fluorescent protein dual gene sorting system in a myocardial infarction rat model

The present study was conducted in order to improve gene expression efficiency of insulin‑like growth factor‑1 (IGF‑1)‑transfected mesenchymal stem cells (MSCs) using a non‑viral carrier and a simplified method of dual gene selection. The therapeutic efficacy of this MSC‑based IGF‑1/enhanced green fluorescent protein (EGFP) dual gene sorting system was evaluated in a rat myocardial infarction (MI) model. IGF‑1 and EGFP genes were expressed in MSCs in vitro. The purity of dual gene‑expressing MSCs was 95.1% by fluorescence‑activated cell sorting. Transfected MSCs injected into rats were identified based on green fluorescence, with an increased signal intensity observed in rats injected with sorted cells, compared with unsorted cells. IGF‑1 expression levels were additionally increased in the sorted group, and decreases in infarct size, fibrotic area and fraction of apoptotic cells were observed. These results demonstrated that IGF‑1 overexpression protects against fibrosis and apoptosis in the myocardium and reduces infarct size following MI. Additionally, the present vector sorting system may potentially be applied to other types of stem cell‑based gene therapy.

Promotion of excisional wound repair by a menstrual blood-derived stem cell-seeded decellularized human amniotic membrane

This is the first study demonstrating the efficacy of menstrual blood-derived stem cell (MenSC) transplantation via decellularized human amniotic membrane (DAM), for the promotion of skin excisional wound repair. The DAM was seeded with MenSCs at the density of 3 × 10⁴ cells/cm² and implanted onto a rat's 1.50 × 1.50 cm² full-thickness excisional wound defect. The results of wound closure and histopathological examinations demonstrated that the MenSC-seeded DAM could significantly improve the wound healing compared with DAM-treatment. All in all, our data indicated that the MenSCs can be a potential source for cell-based therapies to regenerate skin injuries.

Hydrogel Biomaterials for Stem Cell Microencapsulation

Stem cell transplantation has been recognized as a promising strategy to induce the regeneration of injured and diseased tissues and sustain therapeutic molecules for prolonged periods in vivo. However, stem cell-based therapy is often ineffective due to low survival, poor engraftment, and a lack of site-specificity. Hydrogels can offer several advantages as cell delivery vehicles, including cell stabilization and the provision of tissue-like environments with specific cellular signals; however, the administration of bulk hydrogels is still not appropriate to obtain safe and effective outcomes. Hence, stem cell encapsulation in uniform micro-sized hydrogels and their transplantation in vivo have recently garnered great attention for minimally invasive administration and the enhancement of therapeutic activities of the transplanted stem cells. Several important methods for stem cell microencapsulation are described in this review. In addition, various natural and synthetic polymers, which have been employed for the microencapsulation of stem cells, are reviewed in this article.

Transplanted interleukin-4--secreting mesenchymal stromal cells show extended survival and increased bone mineral density in the murine femur

BACKGROUND

Mesenchymal stromal cell (MSC)-based therapy has great potential to modulate chronic inflammation and enhance tissue regeneration. Crosstalk between MSC-lineage cells and polarized macrophages is critical for bone formation and remodeling in inflammatory bone diseases. However, the translational application of this interaction is limited by the short-term viability of MSCs after cell transplantation.

METHODS

Three types of genetically modified (GM) MSCs were created: (1) luciferase-expressing reporter MSCs; (2) MSCs that secrete interleukin (IL)-4 either constitutively; and (3) MSCs that secrete IL-4 as a response to nuclear factor kappa-light-chain-enhancer of activated B cell (NFκB) activation. Cells were injected into the murine distal femoral bone marrow cavity. MSC viability and bone formation were examined in vivo. Cytokine secretion was determined in a femoral explant organ culture model.

RESULTS

The reporter MSCs survived up to 4 weeks post-implantation. No difference in the number of viable cells was found between high (2.5 × 10⁶) and low (0.5 × 10⁶) cell-injected groups. Injection of 2.5 × 10⁶ reporter MSCs increased local bone mineral density at 4 weeks post-implantation. Injection of 0.5 × 10⁶ constitutive IL-4 or NFκB-sensing IL-4-secreting MSCs increased bone mineral density at 2 weeks post-implantation. In the femoral explant organ culture model, LPS treatment induced IL-4 secretion in the NFκB-sensing IL-4-secreting MSC group and IL-10 secretion in all the femur samples. No significant differences in tumor necrosis factor (TNF)α and IL-1β secretion were observed between the MSC-transplanted and control groups in the explant culture.

DISCUSSION

Transplanted GM MSCs demonstrated prolonged cell viability when transplanted to a compatible niche within the bone marrow cavity. GM IL-4-secreting MSCs may have great potential to enhance bone regeneration in disorders associated with chronic inflammation.

Critical View on Mesenchymal Stromal Cells in Regenerative Medicine

SIGNIFICANCE

The belief in the potency of stem cells has resulted in the medical applications of numerous cell types for organ repair, often with the low adherence to methodological stringency. Such uncritical enthusiasm is mainly presented in the approaches employing so-called mesenchymal stem cells (MSC), for the treatment of numerous, unrelated conditions. However, it should be stressed that such broad clinical applications of MSC are mostly based on the belief that MSC can efficiently differentiate into multiple cell types, not only osteoblasts, chondrocytes and adipose cells. Recent Advances: Studies employing lineage tracing established more promising markers to characterize MSC identity and localization in vivo and confirmed the differences between MSC isolated from various organs. Furthermore, preclinical and clinical experiments proved that transdifferentiation of MSC is unlikely to contribute to repair of numerous tissues, including the heart. Therefore, the salvage hypotheses, like MSC fusion with cells in target organs or the paracrine mechanisms, were proposed to justify the widespread application of MSC and to explain transient, if any, effects.

CRITICAL ISSUES

The lack of standardization concerning the cells markers, their origin and particularly the absence of stringent functional characterization of MSC, leads to propagation of the worrying hype despite the lack of convincing therapeutic efficiency of MSC.

FUTURE DIRECTIONS

The adherence to rigorous methodological rules is necessary to prevent the application of procedures which can be dangerous for patients and scientific research on the medical application of stem cells. Antioxid. Redox Signal. 00, 000-000.

Stabilization of Hypoxia-Inducible Factor-1 Alpha Augments the Therapeutic Capacity of Bone Marrow-Derived Mesenchymal Stem Cells in Experimental Pneumonia

Bone marrow-derived mesenchymal stem cells (MSCs) have therapeutic effects in experimental models of lung injury. Hypoxia-inducible factor-1 alpha (HIF-1α) is a transcriptional regulator that influences cellular metabolism, energetics, and survival under hypoxic conditions. The current study investigated the effects of stabilizing HIF-1α on the therapeutic capacity of MSCs in an experimental mouse model of bacterial pneumonia. HIF-1α stabilization was achieved by the small molecule prolyl-hydroxlase inhibitor, AKB-4924 (Aerpio Therapeutics, Inc.), which blocks the pathway for HIF-1α degradation in the proteosome. In vitro, pre-treatment with AKB-4924 increased HIF-1α levels in MSCs, reduced the kinetics of their cell death when exposed to cytotoxic stimuli, and increased their antibacterial capacity. In vivo, AKB-4924 enhanced MSC therapeutic capacity in experimental pneumonia as quantified by a sustainable survival benefit, greater bacterial clearance from the lung, decreased lung injury, and reduced inflammatory indices. These results suggest that HIF-1α stabilization in MSCs, achieved ex vivo, may represent a promising approach to augment the therapeutic benefit of these cells in severe pneumonia complicated by acute lung injury.

Retention and Functional Effect of Adipose-Derived Stromal Cells Administered in Alginate Hydrogel in a Rat Model of Acute Myocardial Infarction

Background

Cell therapy for heart disease has been proven safe and efficacious, despite poor cell retention in the injected area. Improving cell retention is hypothesized to increase the treatment effect. In the present study, human adipose-derived stromal cells (ASCs) were delivered in an in situ forming alginate hydrogel following acute myocardial infarction (AMI) in rats.

Methods

ASCs were transduced with luciferase and tested for ASC phenotype. AMI was inducted in nude rats, with subsequent injection of saline (controls), 1 × 10⁶ ASCs in saline or 1 × 10⁶ ASCs in 1% (w/v) alginate hydrogel. ASCs were tracked by bioluminescence and functional measurements were assessed by magnetic resonance imaging (MRI) and ⁸²rubidium positron emission tomography (PET).

Results

ASCs in both saline and alginate hydrogel significantly increased the ejection fraction (7.2% and 7.8% at 14 days and 7.2% and 8.0% at 28 days, resp.). After 28 days, there was a tendency for decreased infarct area and increased perfusion, compared to controls. No significant differences were observed between ASCs in saline or alginate hydrogel, in terms of retention and functional salvage.

Conclusion

ASCs improved the myocardial function after AMI, but administration in the alginate hydrogel did not further improve retention of the cells or myocardial function.

Recent Progress in Stem Cell Modification for Cardiac Regeneration

During the past decades, stem cell-based therapy has acquired a promising role in regenerative medicine. The application of novel cell therapeutics for the treatment of cardiovascular diseases could potentially achieve the ambitious aim of effective cardiac regeneration. Despite the highly positive results from preclinical studies, data from phase I/II clinical trials are inconsistent and the improvement of cardiac remodeling and heart performance was found to be quite limited. The major issues which cardiac stem cell therapy is facing include inefficient cell delivery to the site of injury, accompanied by low cell retention and weak effectiveness of remaining stem cells in tissue regeneration. According to preclinical and clinical studies, various stem cells (adult stem cells, embryonic stem cells, and induced pluripotent stem cells) represent the most promising cell types so far. Beside the selection of the appropriate cell type, researchers have developed several strategies to produce “second-generation” stem cell products with improved regenerative capacity. Genetic and nongenetic modifications, chemical and physical preconditioning, and the application of biomaterials were found to significantly enhance the regenerative capacity of transplanted stem cells. In this review, we will give an overview of the recent developments in stem cell engineering with the goal to facilitate stem cell delivery and to promote their cardiac regenerative activity.

Decellularized Matrices As Cell-Instructive Scaffolds to Guide Tissue-Specific Regeneration

Decellularized scaffolds are promising clinically translational biomaterials that can be applied to direct cell responses and promote tissue regeneration. Bioscaffolds derived from the extracellular matrix (ECM) of decellularized tissues can naturally mimic the complex extracellular microenvironment through the retention of compositional, biomechanical, and structural properties specific to the native ECM. Increasingly, studies have investigated the use of ECM-derived scaffolds as instructive substrates to recapitulate properties of the stem cell niche and guide cell proliferation, paracrine factor production, and differentiation in a tissue-specific manner. Here, we review the application of decellularized tissue scaffolds as instructive matrices for stem or progenitor cells, with a focus on the mechanisms through which ECM-derived scaffolds can mediate cell behavior to promote tissue-specific regeneration. We conclude that although additional preclinical studies are required, ECM-derived scaffolds are a promising platform to guide cell behavior and may have widespread clinical applications in the field of regenerative medicine.

Differentiation and Application of Induced Pluripotent Stem Cell–Derived Vascular Smooth Muscle Cells

Vascular smooth muscle cells (VSMCs) play a role in the development of vascular disease, for example, neointimal formation, arterial aneurysm, and Marfan syndrome caused by genetic mutations in VSMCs, but little is known about the mechanisms of the disease process. Advances in induced pluripotent stem cell technology have now made it possible to derive VSMCs from several different somatic cells using a selection of protocols. As such, researchers have set out to delineate key signaling processes involved in triggering VSMC gene expression to grasp the extent of gene regulatory networks involved in phenotype commitment. This technology has also paved the way for investigations into diseases affecting VSMC behavior and function, which may be treatable once an identifiable culprit molecule or gene has been repaired. Moreover, induced pluripotent stem cell–derived VSMCs are also being considered for their use in tissue-engineered blood vessels as they may prove more beneficial than using autologous vessels. Finally, while several issues remains to be clarified before induced pluripotent stem cell–derived VSMCs can become used in regenerative medicine, they do offer both clinicians and researchers hope for both treating and understanding vascular disease. In this review, we aim to update the recent progress on VSMC generation from stem cells and the underlying molecular mechanisms of VSMC differentiation. We will also explore how the use of induced pluripotent stem cell–derived VSMCs has changed the game for regenerative medicine by offering new therapeutic avenues to clinicians, as well as providing researchers with a new platform for modeling of vascular disease.

A Look into Stem Cell Therapy: Exploring the Options for Treatment of Ischemic Stroke

Neural stem cells (NSCs) offer a potential therapeutic benefit in the recovery from ischemic stroke. Understanding the role of endogenous neural stem and progenitor cells under normal physiological conditions aids in analyzing their effects after ischemic injury, including their impact on functional recovery and neurogenesis at the site of injury. Recent animal studies have utilized unique subsets of exogenous and endogenous stem cells as well as preconditioning with pharmacologic agents to better understand the best situation for stem cell proliferation, migration, and differentiation. These stem cell therapies provide a promising effect on stimulation of endogenous neurogenesis, neuroprotection, anti-inflammatory effects, and improved cell survival rates. Clinical trials performed using various stem cell types show promising results to their safety and effectiveness on reducing the effects of ischemic stroke in humans. Another important aspect of stem cell therapy discussed in this review is tracking endogenous and exogenous NSCs with magnetic resonance imaging. This review explores the pathophysiology of NSCs on ischemic stroke, stem cell therapy studies and their effects on neurogenesis, the most recent clinical trials, and techniques to track and monitor the progress of endogenous and exogenous stem cells.

Preconditioning with far-infrared irradiation enhances proliferation, cell survival, and migration of rat bone marrow-derived stem cells via CXCR4-ERK pathways

Far-infrared radiation (FIR) has been shown to exert positive effects on the cardiovascular system. However, the biological effects of FIR on bone marrow-derived stem cells (BMSCs) are not understood. In the present study, BMSCs were isolated from rat femur bone marrow and cultured in vitro. To investigate the effects of an FIR generator with an energy flux of 0.13 mW/cm² on rat BMSCs, survival of BMSCs was measured by crystal violet staining, and cell proliferation was additionally measured using Ez-Cytox cell viability, EdU, and Brd U assays. FIR preconditioning was found to significantly increase BMSC proliferation and survival against H₂O₂. The scratch and transwell migration assays showed that FIR preconditioning resulted in an increase in BMSC migration. qRT-PCR and Western blot analyses demonstrated that FIR upregulated Nanog, Sox2, c-Kit, Nkx2.5, and CXCR4 at both the mRNA and protein levels. Consistent with these observations, PD98059 (an ERK inhibitor) and AMD3100 (a CXCR4 inhibitor) prevented the activation of CXCR4/ERK and blocked the cell proliferation and migration induced by FIR. Overall, these findings provide the first evidence that FIR confers a real and significant benefit on the preconditioning of BMSCs, and might lead to novel strategies for improving BMSC therapy for cardiac ischemia.

Bone Marrow Aspirate Concentrate-Enhanced Marrow Stimulation of Chondral Defects

Mesenchymal stem cells (MSCs) from bone marrow play a critical role in osteochondral repair. A bone marrow clot forms within the cartilage defect either as a result of marrow stimulation or during the course of the spontaneous repair of osteochondral defects. Mobilized pluripotent MSCs from the subchondral bone migrate into the defect filled with the clot, differentiate into chondrocytes and osteoblasts, and form a repair tissue over time. The additional application of a bone marrow aspirate (BMA) to the procedure of marrow stimulation is thought to enhance cartilage repair as it may provide both an additional cell population capable of chondrogenesis and a source of growth factors stimulating cartilage repair. Moreover, the BMA clot provides a three-dimensional environment, possibly further supporting chondrogenesis and protecting the subchondral bone from structural alterations. The purpose of this review is to bridge the gap in our understanding between the basic science knowledge on MSCs and BMA and the clinical and technical aspects of marrow stimulation-based cartilage repair by examining available data on the role and mechanisms of MSCs and BMA in osteochondral repair. Implications of findings from both translational and clinical studies using BMA concentrate-enhanced marrow stimulation are discussed.

Restoring heart function and electrical integrity: closing the circuit

Cardiovascular diseases are the main cause of death in the world and are often associated with the occurrence of arrhythmias due to disruption of myocardial electrical integrity. Pathologies involving dysfunction of the specialized cardiac excitatory/conductive tissue are also common and constitute an added source of morbidity and mortality since current standard therapies withstand a great number of limitations. As electrical integrity is essential for a well-functioning heart, innovative strategies have been bioengineered to improve heart conduction and/or promote myocardial repair, based on: (1) gene and/or cell delivery; or (2) conductive biomaterials as tools for cardiac tissue engineering. Herein we aim to review the state-of-art in the area, while briefly describing the biological principles underlying the heart electrical/conduction system and how this system can be disrupted in heart disease. Suggestions regarding targets for future studies are also presented.