Exploring pericyte and cardiac stem cell secretome unveils new tactics for drug discovery

Paracrine Responses of Cardiosphere-Derived Cells to Cytokines and TLR Ligands: A Comparative Analysis

Cardiosphere-derived cells (CDCs) are currently being evaluated in clinical trials as a potential therapeutic tool for regenerative medicine. The effectiveness of transplanted CDCs is largely attributed to their ability to release beneficial soluble factors to enhance therapeutic effects. An emerging area of research is the pretreatment of stem cells, including CDCs, with various cytokines to improve their therapeutic properties. This strategy aims to enhance their survival, proliferation, differentiation, and paracrine activities after transplantation. In our study, we investigated the differential effects of various cytokines and TLR ligands on the secretory phenotype of human CDCs. Using a magnetic bead-based immunoassay, we analyzed the CDCs-conditioned media for 41 cytokines and growth factors and detected the presence of 21 cytokines. We found that CDC incubation with lipopolysaccharide, a TLR4 ligand, and the cytokine combination of TNF/IFN significantly increased the secretion of most of the cytokines detected. Specifically, we observed an increased secretion and gene expression of IP10, MCP3, IL8, and VEGFA. In contrast, the TLR3 ligand polyinosinic-polycytidylic acid and TGF-beta had minimal effects on CDC cytokine secretion. Additionally, TNF/IFN, but not LPS, enhanced ICAM1 expression. Our findings offer new insights into the role of cytokines in potentially modulating the biology and regenerative potential of CDCs.

Microvessels derived from hiPSCs are a novel source for angiogenesis and tissue regeneration

The establishment of effective vascularization represents a key challenge in regenerative medicine. Adequate sources of vascular cells and intact vessel fragments have not yet been explored. We herein examined the potential application of microvessels induced from hiPSCs for rapid angiogenesis and tissue regeneration. Microvessels were generated from human pluripotent stem cells (iMVs) under a defined induction protocol and compared with human adipose tissue-derived microvessels (ad-MVs) to illustrate the similarity and differences of the alternative source. Then, the therapeutic effect of iMVs was detected by transplantation in vivo. The renal ischemia-reperfusion model and skin damage model were applied to explore the potential effect of vascular cells derived from iMVs (iMVs-VCs). Besides, the subcutaneous transplantation model and muscle injury model were established to explore the ability of iMVs for angiogenesis and tissue regeneration. The results revealed that iMVs had remarkable similarities to natural blood vessels in structure and cellular composition, and were potent for vascular formation and self-organization. The infusion of iMVs-VCs promoted tissue repair in the renal and skin damage model through direct contribution to the reconstruction of blood vessels and modulation of the immune microenvironment. Moreover, the transplantation of intact iMVs could form a massive perfused blood vessel and promote muscle regeneration at the early stage. The infusion of iMVs-VCs could facilitate the reconstruction and regeneration of blood vessels and modulation of the immune microenvironment to restore structures and functions of damaged tissues. Meanwhile, the intact iMVs could rapidly form perfused vessels and promote muscle regeneration. With the advantages of abundant sources and high angiogenesis potency, iMVs could be a candidate source for vascularization units for regenerative medicine.

Artificial Scaffolds in Cardiac Tissue Engineering

Cardiovascular diseases are a leading cause of death worldwide. Current treatments directed at heart repair have several disadvantages, such as a lack of donors for heart transplantation or non-bioactive inert materials for replacing damaged tissue. Because of the natural lack of regeneration of cardiomyocytes, new treatment strategies involve stimulating heart tissue regeneration. The basic three elements of cardiac tissue engineering (cells, growth factors, and scaffolds) are described in this review, with a highlight on the role of artificial scaffolds. Scaffolds for cardiac tissue engineering are tridimensional porous structures that imitate the extracellular heart matrix, with the ability to promote cell adhesion, migration, differentiation, and proliferation. In the heart, there is an important requirement to provide scaffold cellular attachment, but scaffolds also need to permit mechanical contractility and electrical conductivity. For researchers working in cardiac tissue engineering, there is an important need to choose an adequate artificial scaffold biofabrication technique, as well as the ideal biocompatible biodegradable biomaterial for scaffold construction. Finally, there are many suitable options for researchers to obtain scaffolds that promote cell–electrical interactions and tissue repair, reaching the goal of cardiac tissue engineering.

Cell-Free Treatments: A New Generation of Targeted Therapies for Treatment of Ischemic Heart Disease

Although recent progress in medicine has substantially reduced cardiovascular diseases (CVDs)-related mortalities, current therapeutics have failed miserably to be beneficial for all patients with CVDs. A wide array of evidence suggests that newly-introduced cell-free treatments (CFTs) have more reliable results in the improvement of cardiac function. The main regeneration activity of CFTs protocols is based on bypassing cells and using paracrine factors. In this article, we aim to compare various stem cell secretomes, a part of a CFTs strategy, to generalize their effective clinical outcomes for patients with CVDs. Data for this review article were collected from 70 published articles (original, review, randomized clinical trials (RCTs), and case reports/series studies done on human and animals) obtained from Cochrane, Science Direct, PubMed, Scopus, Elsevier, and Google Scholar) from 2015 to April 2020 using six keywords. Full-text/full-length articles, abstract, section of book, chapter, and conference papers in English language were included. Studies with irrelevant/insufficient/data, or undefined practical methods were excluded. CFTs approaches involved in growth factors (GFs); gene-based therapies; microRNAs (miRNAs); extracellular vesicles (EVs) [exosomes (EXs) and microvesicles (MVs)]; and conditioned media (CM). EXs and CM have shown more remarkable results than stem cell therapy (SCT). GF-based therapies have useful results as well as side effects like pathologic angiogenesis. Cell source, cell's aging and CM affect secretomes. Genetic manipulation of stem cells can change the secretome's components. Growing progression to end stage heart failure (HF), propounds CFTs as an advantageous method with practical and clinical values for replacement of injured myocardium, and induction of neovascularization. To elucidate the secrets behind amplifying the expansion rate of cells, increasing life-expectancy, and improving quality of life (QOL) for patients with ischemic heart diseases (IHDs), collaboration among cell biologist, basic medical scientists, and cardiologists is highly recommended.

Cardiac regeneration following myocardial infarction: the need for regeneration and a review of cardiac stromal cell populations used for transplantation

Myocardial infarction is a leading cause of death globally due to the inability of the adult human heart to regenerate after injury. Cell therapy using cardiac-derived progenitor populations emerged about two decades ago with the aim of replacing cells lost after ischaemic injury. Despite early promise from rodent studies, administration of these populations has not translated to the clinic. We will discuss the need for cardiac regeneration and review the debate surrounding how cardiac progenitor populations exert a therapeutic effect following transplantation into the heart, including their ability to form de novo cardiomyocytes and the release of paracrine factors. We will also discuss limitations hindering the cell therapy field, which include the challenges of performing cell-based clinical trials and the low retention of administered cells, and how future research may overcome them.

The Effect of miRNA-Modified Exosomes in Animal Models of Spinal Cord Injury: A meta-Analysis

Background: Spinal cord injury (SCI) is currently not completely curable. Exosomes have been widely used in preclinical studies of spinal cord injury. Here, in this meta-analysis, we focused on evaluating the overall efficacy of therapies based on miRNA-modified exosomes on functional recovery in animal models of SCI. Methods: PubMed, embase and Web of Science library databases were searched. Relevant literature was included, and the random effects model was used to assess the overall effect of the intervention, with outcomes expressed as SMD. The primary outcome included motor function scores. Risk of bias (ROB) was assessed using the ROB tool of the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE). R version 4.1.1software and Review Manager software were used for meta-analysis. Results: A total of 11 preclinical studies were included. The meta-analysis revealed that miRNA-modified exosome therapy was effective in improving motor function scores compared with exosomes alone or control therapy (standardized mean difference: 4.21; 95% confidence interval: 3.39-5.04). There was significant asymmetry in the funnel plot, and trim-and-fill analysis revealed four unpublished studies of motor scores. The quality of all included studies was evaluated with SYRCLE's ROB tool. The SCI model, administration time and dose had an impact on the effect of the treatment. Conclusion: MiRNA-modified exosomes have shown great potential in the treatment of SCI. Moreover, the efficacy of miRNA-modified exosomes was superior to that of exosomes alone.

Intracoronary Delivery of Porcine Cardiac Progenitor Cells Overexpressing IGF-1 and HGF in a Pig Model of Sub-Acute Myocardial Infarction

Human cardiac progenitor cells (hCPC) are considered a good candidate in cell therapy for ischemic heart disease, demonstrating capacity to improve functional recovery after myocardial infarction (MI), both in small and large preclinical animal models. However, improvements are required in terms of cell engraftment and efficacy. Based on previously published reports, insulin-growth factor 1 (IGF-1) and hepatocyte growth factor (HGF) have demonstrated substantial cardioprotective, repair and regeneration activities, so they are good candidates to be evaluated in large animal model of MI. We have validated porcine cardiac progenitor cells (pCPC) and lentiviral vectors to overexpress IGF-1 (co-expressing eGFP) and HGF (co-expressing mCherry). pCPC were transduced and IGF1-eGFP^pos and HGF-mCherry^pos populations were purified by cell sorting and further expanded. Overexpression of IGF-1 has a limited impact on pCPC expression profile, whereas results indicated that pCPC-HGF-mCherry cultures could be counter selecting high expresser cells. In addition, pCPC-IGF1-eGFP showed a higher cardiogenic response, evaluated in co-cultures with decellularized extracellular matrix, compared with native pCPC or pCPC-HGF-mCherry. In vivo intracoronary co-administration of pCPC-IGF1-eGFP and pCPC-HFG-mCherry (1:1; 40 × 10⁶/animal), one week after the induction of an MI model in swine, revealed no significant improvement in cardiac function.

Adipose-derived stem cell secretome as a cell-free product for cutaneous wound healing

Chronic wounds continue to be a substantial public health concern contributing to both humanistic and economic burden worldwide. The magnitude of chronic wounds as a global healthcare crisis is likely to increase due to the rising geriatric and diabetic population, demanding novel therapeutic approaches that can restore the functionality of the skin at a reduced cost. Stem cell therapy has been widely acknowledged as a promising strategy for the repair of damaged tissues due to its regenerative potential. This potential attributes to a concoction of bioactive molecules secreted by the stem cells, collectively called the secretome, that mediates paracrine and autocrine functions. Among the stem cell types, adipose tissue-derived mesenchymal stem cells (ADMSCs) have been receiving increased attention for its ease of isolation, abundance in tissue and notable impact on improving chronic wound healing. Owing to the reported advantages of cell-free preparations like the secretome over cellular products, developing secretome as a ready-to-use product for wound healing applications seems promising. In this review, we discuss the functional benefits of adipose stem cell secretome in wound healing, the techniques to enrich the secretome and the recommendations for the scale-up and commercialization of secretome products.

Bioengineering Technologies for Cardiac Regenerative Medicine

Cardiac regenerative medicine faces big challenges such as a lack of adult cardiac stem cells, low turnover of mature cardiomyocytes, and difficulty in therapeutic delivery to the injured heart. The interaction of bioengineering and cardiac regenerative medicine offers innovative solutions to this field. For example, cell reprogramming technology has been applied by both direct and indirect routes to generate patient-specific cardiomyocytes. Various viral and non-viral vectors have been utilized for gene editing to intervene gene expression patterns during the cardiac remodeling process. Cell-derived protein factors, exosomes, and miRNAs have been isolated and delivered through engineered particles to overcome many innate limitations of live cell therapy. Protein decoration, antibody modification, and platelet membranes have been used for targeting and precision medicine. Cardiac patches have been used for transferring therapeutics with better retention and integration. Other technologies such as 3D printing and 3D culture have been used to create replaceable cardiac tissue. In this review, we discuss recent advancements in bioengineering and biotechnologies for cardiac regenerative medicine.

Effects of Cardiotoxins on Cardiac Stem and Progenitor Cell Populations

As research and understanding of the cardiotoxic side-effects of anticancer therapy expands further and the affected patient population grows, notably the long-term survivors of childhood cancers, it is important to consider the full range of myocardial cell types affected. While the direct impacts of these toxins on cardiac myocytes constitute the most immediate damage, over the longer term, the myocardial ability to repair, or adapt to this damage becomes an ever greater component of the disease phenotype. One aspect is the potential for endogenous myocardial repair and renewal and how this may be limited by cardiotoxins depleting the cells that contribute to these processes. Clear evidence exists of new cardiomyocyte formation in adult human myocardium, along with the identification in the myocardium of endogenous stem/progenitor cell populations with pro-regenerative properties. Any effects of cardiotoxins on either of these processes will worsen long-term prognosis. While the role of cardiac stem/progenitor cells in cardiomyocyte renewal appears at best limited (although with stronger evidence of this process in response to diffuse cardiomyocyte loss), there are strong indications of a pro-regenerative function through the support of injured cell survival. A number of recent studies have identified detrimental impacts of anticancer therapies on cardiac stem/progenitor cells, with negative effects seen from both long-established chemotherapy agents such as, doxorubicin and from newer, less overtly cardiotoxic agents such as tyrosine kinase inhibitors. Damaging impacts are seen both directly, on cell numbers and viability, but also on these cells' ability to maintain the myocardium through generation of pro-survival secretome and differentiated cells. We here present a review of the identified impacts of cardiotoxins on cardiac stem and progenitor cells, considered in the context of the likely role played by these cells in the maintenance of myocardial tissue homeostasis.

Emerging Role of Pericytes and Their Secretome in the Heart

Pericytes, as mural cells covering microvascular capillaries, play an essential role in vascular remodeling and maintaining vascular functions and blood flow. Pericytes are crucial participants in the physiological and pathological processes of cardiovascular disease. They actively interact with endothelial cells, vascular smooth muscle cells (VSMCs), fibroblasts, and other cells via the mechanisms involved in the secretome. The secretome of pericytes, along with diverse molecules including proinflammatory cytokines, angiogenic growth factors, and the extracellular matrix (ECM), has great impacts on the formation, stabilization, and remodeling of vasculature, as well as on regenerative processes. Emerging evidence also indicates that pericytes work as mesenchymal cells or progenitor cells in cardiovascular regeneration. Their capacity for differentiation also contributes to vascular remodeling in different ways. Previous studies primarily focused on the roles of pericytes in organs such as the brain, retina, lung, and kidney; very few studies have focused on pericytes in the heart. In this review, following a brief introduction of the origin and fundamental characteristics of pericytes, we focus on pericyte functions and mechanisms with respect to heart disease, ending with the promising use of cardiac pericytes in the treatment of ischemic heart failure.

Cell augmentation strategies for cardiac stem cell therapies

Myocardial infarction (MI) has been the primary cause of death in developed countries, resulting in a major psychological and financial burden for society. Current treatments for acute MI are directed toward rapid restoration of perfusion to limit damage to the myocardium, rather than promoting tissue regeneration and subsequent contractile function recovery. Regenerative cell therapies (CTs), in particular those using multipotent stem cells (SCs), are in the spotlight for treatment post‐MI. Unfortunately, the efficacy of CTs is somewhat limited by their poor long‐term viability, homing, and engraftment to the myocardium. In response, a range of novel SC‐based technologies are in development to provide additional cellular modalities, bringing CTs a step closer to the clinic. In this review, the current landscape of emerging CTs and their augmentation strategies for the treatment post‐MI are discussed. In doing so, we highlight recent advances in cell membrane reengineering via genetic modifications, recombinant protein immobilization, and the utilization of soft biomimetic scaffold interfaces.

Harnessing nerve-muscle cell interactions for biomaterials-based skeletal muscle regeneration

Nerve cells secrete neurotrophic factors that play a critical role in neuronal survival, proliferation, and regeneration. However, their role in regulating myoblast behavior and skeletal muscle repair remains largely unexplored. In the present study, we investigated the effects of PC12 secreted signaling factors in modulating C2C12 myoblast behavior under physiologically relevant conditions. We showed that PC12 conditioned media modulated myoblast proliferation and differentiation in both 2D culture and 3D aligned electrospun fiber scaffold system in a dose-dependent manner. We further developed a biomimetic, tunable hydrogel consisting of hyaluronic acid, chondroitin sulfate, and polyethylene glycol as a 3D matrix encapsulating PC12 cells. The hydrogel-encapsulated PC12 cells promoted survival and proliferation of myoblasts in co-culture. Further proteomics analysis identified a total of 2,088 proteins from the secretome of the encapsulated PC12 cells and revealed the biological role and overlapping functions of nerve-secreted proteins for skeletal muscle regeneration, potentially through regulating myoblast behavior, nerve function, and angiogenesis. These experiments provide insights into the nerve-muscle interactions and pave the way for developing advanced biomaterials strategies incorporating nerve cell secretome for accelerated skeletal muscle regeneration.

The Role of MSC Therapy in Attenuating the Damaging Effects of the Cytokine Storm Induced by COVID-19 on the Heart and Cardiovascular System

The global pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19) has led to 47 m infected cases and 1. 2 m (2.6%) deaths. A hallmark of more severe cases of SARS-CoV-2 in patients with acute respiratory distress syndrome (ARDS) appears to be a virally-induced over-activation or unregulated response of the immune system, termed a "cytokine storm," featuring elevated levels of pro-inflammatory cytokines such as IL-2, IL-6, IL-7, IL-22, CXCL10, and TNFα. Whilst the lungs are the primary site of infection for SARS-CoV-2, in more severe cases its effects can be detected in multiple organ systems. Indeed, many COVID-19 positive patients develop cardiovascular complications, such as myocardial injury, myocarditis, cardiac arrhythmia, and thromboembolism, which are associated with higher mortality. Drug and cell therapies targeting immunosuppression have been suggested to help combat the cytokine storm. In particular, mesenchymal stromal cells (MSCs), owing to their powerful immunomodulatory ability, have shown promise in early clinical studies to avoid, prevent or attenuate the cytokine storm. In this review, we will discuss the mechanistic underpinnings of the cytokine storm on the cardiovascular system, and how MSCs potentially attenuate the damage caused by the cytokine storm induced by COVID-19. We will also address how MSC transplantation could alleviate the long-term complications seen in some COVID-19 patients, such as improving tissue repair and regeneration.

Promotion of Proangiogenic Secretome from Mesenchymal Stromal Cells via Hierarchically Structured Biodegradable Microcarriers

Adipose-derived mesenchymal stromal cells (AdMSC) release numerous soluble factors capable of stimulating angiogenesis. Improved methods for delivering these cells to maximize their potency are now sought that ideally they retain viable cells in the target tissue while promoting the secretion of angiogenic factors. Substrate surface topography is a parameter that can be used to manipulate the behavior of AdMSC but challenges exist with translating this parameter into materials compatible with minimally invasive delivery into tissues for in situ delivery of the angiogenic secretome. The current study investigates three compositions of hierarchically structured, porous biodegradable microcarriers for the culture of AdMSC and the influence of their surface topographies on the angiogenic secretome. All three compositions perform well as cell microcarriers in xeno-free conditions. The attached AdMSC retain their capacity for subsequent trilineage differentiation. The secretome of AdMSC attached to the microcarriers consists of multiple proangiogenic factors, including significantly elevated levels of vascular endothelial growth factor, which stimulates angiogenesis in vitro. The unique properties of hierarchically structured, porous biodegradable microcarriers investigated in this study offer a radically transformative approach for achieving targeted in vivo delivery of AdMSC and enhancing the potency of their proangiogenic activity to induce neovascularization in ischemic tissue.

The secretome from embryonic stem cell cardiomyogenesis: Same signals, different cellular feedbacks

Ischemic heart diseases are a global health problem that requires the search for alternative therapies to the current treatments. Thus, an understanding of how cardiomyogenic signals can affect cellular behavior would allow us to create strategies to improve the cell recovery in damaged tissues. In this study, we aimed to evaluate the effects of the conditioned medium (CM), collected at different time points during in vitro cardiomyogenesis of human embryonic stem cells (hESCs), to direct cell behavior. We assayed different cell types to demonstrate noncytotoxic effects from the collected CM and that the CM obtained at initial time points of cardiomyogenic differentiation could promote the cell proliferation. Otherwise, the secretome derived from cardiac committed cells during cardiomyogenesis was unable to improve angiogenesis or migration in endothelial cells, and ineffective to stimulate the differentiation of cardioblasts or increase the differentiation efficiency of hESC. Therefore, we demonstrated that the effectiveness of the CM response varies depending on the cell type and the differentiation step of hESC-derived cardiomyocytes.

Generation of Cardiomyocytes From Vascular Adventitia-Resident Stem Cells

RATIONALE

Regeneration of lost cardiomyocytes is a fundamental unresolved problem leading to heart failure. Despite several strategies developed from intensive studies performed in the past decades, endogenous regeneration of heart tissue is still limited and presents a big challenge that needs to be overcome to serve as a successful therapeutic option for myocardial infarction.

OBJECTIVE

One of the essential prerequisites for cardiac regeneration is the identification of endogenous cardiomyocyte progenitors and their niche that can be targeted by new therapeutic approaches. In this context, we hypothesized that the vascular wall, which was shown to harbor different types of stem and progenitor cells, might serve as a source for cardiac progenitors.

METHODS AND RESULTS

We describe generation of spontaneously beating mouse aortic wall-derived cardiomyocytes without any genetic manipulation. Using aortic wall-derived cells (AoCs) of WT (wild type), αMHC (α-myosin heavy chain), and Flk1 (fetal liver kinase 1)-reporter mice and magnetic bead-associated cell sorting sorting of Flk1⁺ AoCs from GFP (green fluorescent protein) mice, we identified Flk1⁺CD (cluster of differentiation) 34⁺Sca-1 (stem cell antigen-1)-CD44^- AoCs as the population that gives rise to aortic wall-derived cardiomyocytes. This AoC subpopulation delivered also endothelial cells and macrophages with a particular accumulation within the aortic wall-derived cardiomyocyte containing colonies. In vivo, cardiomyocyte differentiation capacity was studied by implantation of fluorescently labeled AoCs into chick embryonic heart. These cells acquired cardiomyocyte-like phenotype as shown by αSRA (α-sarcomeric actinin) expression. Furthermore, coronary adventitial Flk1⁺ and CD34⁺ cells proliferated, migrated into the myocardium after mouse myocardial infarction, and expressed Isl-1⁺ (insulin gene enhancer protein-1) indicative of cardiovascular progenitor potential.

CONCLUSIONS

Our data suggest Flk1⁺CD34⁺ vascular adventitia-resident stem cells, including those of coronary adventitia, as a novel endogenous source for generating cardiomyocytes. This process is essentially supported by endothelial cells and macrophages. In summary, the therapeutic manipulation of coronary adventitia-resident cardiac stem and their supportive cells may open new avenues for promoting cardiac regeneration and repair after myocardial infarction and for preventing heart failure.

Human Bone Marrow Mesenchymal Stem Cell Conditioned Medium Promotes Wound Healing in Deep Second-Degree Burns in Male Rats

Burn wound treatment is difficult and one of the most challenging problems in the clinic. Researchers have examined the applications of mesenchymal stem cells as a cell-based therapy for skin regeneration. But the role of human bone marrow mesenchymal stem cell conditioned medium (hBM-MSC-CM) in the treatment of burn injury remains unclear. This research aims at detecting whether hBM-MSC-CM can increase the wound healing of deep second-degree burns in male rats. In this study, 32 adult male rats per each time point were randomly divided into four groups: (1) control group, (2) sham group (DMEM), (3) common treatment group (CT), and (4) conditioned media group (CM). A 3 × 3 cm circular burn was created on the back of the rats. On postsurgical days 7, 15, and 28, the wound closure area of each wound was measured and then the skin samples were removed and analyzed using stereological methods. Wound closure area was significantly increased in the CM and CT groups on the 15th and the 28th day after burn injury compared to the control and DMEM groups. The stereological parameters and immunohistochemistry analysis of the wounds revealed significantly improved healing in the CM group compared to the control and other groups. It is concluded that these findings indicate that hBM-MSC-CM promotes skin wound healing by increasing cell proliferation, regulating collagen synthesis and collagen composition, and inducing angiogenesis at the injury site.

SDF-1α promotes repair of myocardial ischemic necrosis zones in rats

OBJECTIVE

To explore the repair effect of stromal cell-derived factor-1α (SDF-1α) on myocardial ischemic necrosis zones.

METHODS

Lentivirus (LV-SDF-1α-GFP) containing SDF-1α target gene was established, the separated and cultured neonatal rat cardiac fibroblasts were transfected, and caudal intravenous injection of isoproterenol was conducted to prepare a rat model of myocardial ischemia. Small animal ultrasound was used to evaluate the effect on cardiac functions. Morphology and immunofluorescence were used to observe the change of ischemic necrosis zones and expressions of stem cellular markers c-kit, CD34, nkx2.5, and nanog, and a quantitative analysis was performed.

RESULTS

The established LV-SDF-1α-GFP was used to transfect myocardial fibroblasts which presented GFP green fluorescent expression and could secrete SDF-1α. The small animal ultrasound system showed that rat cardiac functions of the lentivirus group and cell group were improved to different degrees, myocardial ischemic necrosis zones of lentivirus group and cell group were reduced, and differences had statistical significances (P<0.05). Immunofluorescence showed that expressions of stem cellular markers c-kit, CD34, nkx2.5 and nanog in myocardial tissue ischemic zones in both the lentivirus group and cell group increased, and differences through inter-group comparison had statistical significances (P<0.05).

CONCLUSION

SDF-1α can promote migration and proliferation of stem cells into the myocardial ischemic necrosis zone, participate in repair of the myocardial necrosis zone, and improve cardiac function.

Dose-dependent improvement of cardiac function in a swine model of acute myocardial infarction after intracoronary administration of allogeneic heart-derived cells

BACKGROUND

Allogeneic cardiac-derived progenitor cells (CPC) without immunosuppression could provide an effective ancillary therapy to improve cardiac function in reperfused myocardial infarction. We set out to perform a comprehensive preclinical feasibility and safety evaluation of porcine CPC (pCPC) in the infarcted porcine model, analyzing biodistribution and mid-term efficacy, as well as safety in healthy non-infarcted swine.

METHODS

The expression profile of several pCPC isolates was compared with humans using both FACS and RT-qPCR. ELISA was used to compare the functional secretome. One week after infarction, female swine received an intracoronary (IC) infusion of vehicle (CON), 25 × 10⁶ pCPC (25 M), or 50 × 10⁶ pCPC (50 M). Animals were followed up for 10 weeks using serial cardiac magnetic resonance imaging to assess functional and structural remodeling (left ventricular ejection fraction (LVEF), systolic and diastolic volumes, and myocardial salvage index). Statistical comparisons were performed using Kruskal-Wallis and Mann-Whitney U tests. Biodistribution analysis of ¹⁸F-FDG-labeled pCPC was also performed 4 h after infarction in a different subset of animals.

RESULTS

Phenotypic and functional characterization of pCPC revealed a gene expression profile comparable to their human counterparts as well as preliminary functional equivalence. Left ventricular functional and structural remodeling showed significantly increased LVEF 10 weeks after IC administration of 50 M pCPC, associated to the recovery of left ventricular volumes that returned to pre-infarction values (LVEF at 10 weeks was 42.1 ± 10.0% in CON, 46.5 ± 7.4% in 25 M, and 50.2 ± 4.9% in 50 M, p < 0.05). Infarct remodeling was also improved following pCPC infusion with a significantly higher myocardial salvage index in both treated groups (0.35 ± 0.20 in CON; 0.61 ± 0.20, p = 0.04, in 25 M; and 0.63 ± 0.17, p = 0.01, in 50 M). Biodistribution studies demonstrated cardiac tropism 4 h after IC administration, with substantial myocardial retention of pCPC-associated tracer activity (18% of labeled cells in the heart), and no obstruction of coronary flow, indicating their suitability as a cell therapy product.

CONCLUSIONS

IC administration of allogeneic pCPC at 1 week after acute myocardial infarction is feasible, safe, and associated with marked structural and functional benefit. The robust cardiac tropism of pCPC and the paracrine effects on left ventricle post-infarction remodeling established the preclinical bases for the CAREMI clinical trial (NCT02439398).

Pericytes in the Heart

Mural cells known as pericytes envelop the endothelial layer of microvessels throughout the body and have been described to have tissue-specific functions. Cardiac pericytes are abundantly found in the heart, but they are relatively understudied. Currently, their importance is emerging in cardiovascular homeostasis and dysfunction due to their pleiotropism. They are known to play key roles in vascular tone and vascular integrity as well as angiogenesis. However, their dysfunctional presence and/or absence is critical in the mechanisms that lead to cardiac pathologies such as myocardial infarction, fibrosis, and thrombosis. Moreover, they are targeted as a therapeutic potential due to their mesenchymal properties that could allow them to repair and regenerate a damaged heart. They are also sought after as a cell-based therapy based on their healing potential in preclinical studies of animal models of myocardial infarction. Therefore, recognizing the importance of cardiac pericytes and understanding their biology will lead to new therapeutic concepts.

Exosomes from normal and diabetic human corneolimbal keratocytes differentially regulate migration, proliferation and marker expression of limbal epithelial cells

Limbal epithelial stem cells (LESC) maintenance requires communication between stem cells and neighboring stromal keratocytes. Extracellular vesicles (EVs) are important for intercellular communication in various stem cell niches. We explored the regulatory roles of limbal stromal cell (LSC)-derived exosomes (Exos), an EV sub-population, in limbal epithelial cells (LEC) in normal and diabetic limbal niche and determined differences in Exo cargos from normal and diabetic LSC. Wound healing and proliferation rates in primary normal LEC were significantly enhanced upon treatment by normal Exos (N-Exos), but not by diabetic Exos (DM-Exos). Western analysis showed increased Akt phosphorylation in wounded LECs and organ-cultured corneas treated with N-Exos, compared to untreated wounded cells and DM-Exos treated fellow corneas, respectively. N-Exos treated organ-cultured corneas showed upregulation of putative LESC markers, keratin 15 (K15) and Frizzled-7, compared to the DM-Exos treated fellow corneas. By next generation sequencing, we identified differentially expressed small RNAs including microRNAs in DM-Exos vs. N-Exos. Overall, N-Exos have greater effect on LEC proliferation and wound healing than DM-Exos, likely by activating Akt signaling. The small RNA differences in Exos from diabetic vs. normal LSC could contribute to the disease state. Our study suggests that exosomes may serve as novel therapeutic tools for diabetic cornea.

The pericyte secretome: Potential impact on regeneration

Personalized and regenerative medicine is an emerging therapeutic strategy that is based on cell biology and biomedical engineering used to develop biological substitutes to maintain normal function or restore damaged tissues and organs. The secretory capacities of different cell types are now explored as such possible therapeutic regenerative agents in a variety of diseases. A secretome can comprise chemokines, cytokines, growth factors, but also extracellular matrix components, microvesicles and exosomes as well as genetic material and may differ depending on the tissue and the stimulus applied to the cell. With regard to clinical applications, the secretome of mesenchymal stem cells (MSC) is currently the most widely explored. However, other cell types such as pericytes may have similar properties as MSC and the potential therapeutic possibilities of these cells are only just beginning to emerge. In this review, we will summarize the currently available data describing the secretome of pericytes and its potential implications for tissue regeneration, whereby we especially focus on brain pericytes as potential new target cell for neuroregeneration and brain repair.

Pericyte Secretome

The role of pericytes seems to extend beyond their known function in angiogenesis, fibrosis and wound healing, blood-brain barrier maintenance, and blood flow regulation. More and more data are currently accumulating indicating that pericytes, uniquely positioned at the interface between blood and parenchyma, secrete a large plethora of different molecules in response to microenvironmental changes. Their secretome is tissue-specific and stimulus-specific and includes pro- and anti-inflammatory factors, growth factors, and extracellular matrix as well as microvesicles suggesting the important role of pericytes in the regulation of immune response and immune evasion of tumors. However, the angiogenic and trophic secretome of pericytes indicates that their secretome plays a role in physiological homeostasis but possibly also in disease progression or could be exploited for regenerative processes in the future. This book chapter summarizes the current data on the secretory properties of pericytes from different tissues in response to certain pathological stimuli such as inflammatory stimuli, hypoxia, high glucose, and others and thereby aims to provide insights into the possible role of pericytes in these conditions.

Pericytes in Tissue Engineering

Pericytes have crucial roles in blood-brain barrier function, blood vessel function/stability, angiogenesis, endothelial cell proliferation/differentiation, wound healing, and hematopoietic stem cells maintenance. They can be isolated from fetal and adult tissues and have multipotential differentiation capacity as mesenchymal stem cells (MSCs). All of these properties make pericytes as preferred cells in the field of tissue engineering. Current developments have shown that tissue-engineered three-dimensional (3D) systems including multiple cell layers (or types) and a supporting biological matrix represent the in vivo environment better than those monolayers on plastic dishes. Tissue-engineered models are also more ethical and cheaper systems than animal models. This chapter describes the role of pericytes in tissue engineering for regenerative medicine.