Rebuilding the damaged heart: the potential of cytokines and growth factors in the treatment of ischemic heart disease

Mesenchymal stem cell secretome: A promising therapeutic strategy for erectile dysfunction?

Objective

The secretome, comprising bioactive chemicals released by mesenchymal stem cells (MSCs), holds therapeutic promise in regenerative medicine. This review aimed to explore the therapeutic potential of the MSC secretome in regenerative urology, particularly for treating erectile dysfunction (ED), and to provide an overview of preclinical and clinical research on MSCs in ED treatment and subsequently to highlight the rationales, mechanisms, preclinical investigations, and therapeutic potential of the MSC secretome in this context.

Methods

The review incorporated an analysis of preclinical and clinical research involving MSCs in the treatment of ED. Subsequently, it delved into the existing knowledge regarding the MSC secretome, exploring its therapeutic potential. The methods included a comprehensive examination of relevant literature to discern the processes underlying the therapeutic efficacy of the MSC secretome.

Results

Preclinical research indicated the effectiveness of the MSC secretome in treating various models of ED. However, the precise mechanisms of its therapeutic efficacy remain unknown. The review provided insights into the anti-inflammatory, pro-angiogenic, and trophic properties of the MSC secretome. It also discussed potential advantages, such as avoiding issues related to cellular therapy, including immunogenicity, neoplastic transformation, and cost.

Conclusion

This review underscores the significant therapeutic potential of the MSC secretome in regenerative urology, particularly for ED treatment. While preclinical studies demonstrate promising outcomes, further research is essential to elucidate the specific mechanisms underlying the therapeutic efficacy before clinical application. The review concludes by discussing future perspectives and highlighting the challenges associated with the clinical translation of the MSC secretome in regenerative urology.

Modulating the release of bioactive molecules of human mesenchymal stromal cell secretome: Heparinization of hyaluronic acid-based hydrogels

An amine derivative of hyaluronic acid (HA) was crosslinked to obtain a 3D dried sponge. The sponge was subsequently rehydrated using secretome from human mesenchymal stromal cells (MSCs), resulting in the formation of a hydrogel. The release kinetics analysis demonstrated that the hydrogel effectively sustained secretome release, with 70% of the initially loaded wound-healing-associated cytokines being released over a 12-day period. Tuning the hydrogel properties through heparin crosslinking resulted in a biomaterial with a distinct mechanism of action. Specifically, the presence of heparin enhanced water uptake capacity of the hydrogel and increased its sensitivity to enzymatic degradation. Notably, the heparin crosslinking also led to a significant retention of cytokines within the hydrogel matrix. Overall, the secretome-rehydrated HA hydrogel holds promise as a versatile device for regenerative medicine applications: the non-heparinized hydrogel may function as a biomaterial with low reabsorption rates, sustaining the release of bioactive molecules contained in MSC secretome. In contrast, the heparinized hydrogel may serve as a depot of bioactive molecules with faster reabsorption rates. Given its patch-like characteristic, the HA-based hydrogel appears suitable as topical treatment for external organs, such as the skin.

Mesenchymal Stem Cell Conditioned Medium Modulates Inflammation in Tenocytes: Complete Conditioned Medium Has Superior Therapeutic Efficacy than Its Extracellular Vesicle Fraction

Tendinopathy, a prevalent overuse injury, lacks effective treatment options, leading to a significant impact on quality of life and socioeconomic burden. Mesenchymal stem/stromal cells (MSCs) and their secretome, including conditioned medium (CM) and extracellular vesicles (EVs), have shown promise in tissue regeneration and immunomodulation. However, it remains unclear which components of the secretome contribute to their therapeutic effects. This study aimed to compare the efficacy of CM, EVs, and the soluble protein fraction (PF) in treating inflamed tenocytes. CM exhibited the highest protein and particle concentrations, followed by PF and EVs. Inflammation significantly altered gene expression in tenocytes, with CM showing the most distinct separation from the inflamed control group. Treatment with CM resulted in the most significant differential gene expression, with both upregulated and downregulated genes related to inflammation and tissue regeneration. EV treatment also demonstrated a therapeutic effect, albeit to a lesser extent. These findings suggest that CM holds superior therapeutic efficacy compared with its EV fraction alone, emphasizing the importance of the complete secretome in tendon injury treatment.

Human umbilical cord mesenchymal stem cells conditioned medium exerts anti-tumor effects on KGN cells in a cell density-dependent manner through activation of the Hippo pathway

BACKGROUND

The conditioned medium from human umbilical cord mesenchymal stem cells (UCMSCs-CM) provides a new cell-free therapy for tumors due to its unique secretome. However, there are many contradictory reports about the effect of UCMSCs-CM on tumor cells. The loss of contact inhibition is a common characteristic of tumor cells. A relationship between the effect of UCMSCs-CM on tumor cells and contact inhibition in tumor cells is rarely concerned. Whether the effect of UCMSCs-CM on tumor cells is affected by cell density? Here, we explored the effect of UCMSCs-CM on granulosa tumor cell line (KGN) cells at low or high density.

METHODS

Growth curve and CCK8 assay were used to assess cell proliferation and viability. Scratch wound and matrigel invasion assay were implicated to detect cell motility of KGN cells. UCMSCs-CM effects on cell cycle, apoptosis and pathway-related proteins were investigated by flow cytometry, TUNEL assay, western blot and immunofluorescence analysis respectively.

RESULTS

In growth curve analysis, before KGN cells proliferated into confluence, UCMSCs-CM had no effect on cell proliferation. However, once the cells proliferate to contact each other, UCMSCs-CM significantly inhibited proliferation. Meanwhile, when KGN cells were implanted at high density, UCMSCs-CM could induce cell cycle arrest at G1 phase, inhibit cell migration, invasion and promote apoptosis. While it had no similar effect on KGN cells implanted at low density. In mechanism, the UCMSCs-CM treatment activated the Hippo pathway when KGN cells were implanted at high density. Consistently, the MST1/2 inhibitor, XMU-MP-1, inhibited the activation of the Hippo pathway induced by UCMSCs-CM treatment and accordingly declined the anti-tumor effect of UCMSCs-CM on KGN cells.

CONCLUSIONS

The effect of UCMSCs-CM on tumor cells is affected by cell density. UCMSCs-CM exerted anti-tumor effect on KGN cells by activating Hippo pathway to restore contact inhibition. Our results suggest that UCMSCs-CM is a promising therapeutic candidate for GCT treatment.

Notch Signaling-Modified Mesenchymal Stem Cell Patch Improves Left Ventricular Function via Arteriogenesis Induction in a Rat Myocardial Infarction Model

For ischemic cardiomyopathy (ICM) with limited therapeutic options, the induction of arteriogenesis has the potential to improve cardiac function through major restoration of blood flow. We hypothesized that transplantation of a Notch signaling-modified mesenchymal stem cell (SB623 cell) patch would induce angiogenesis and arteriogenesis in ischemic lesions, leading to improvement of left ventricular (LV) function in a rat ICM model. Two weeks after the induction of ischemia, SB623 cell patch transplantation into ICM rats (SB group, n = 10) or a sham operation (no-treatment group, n = 10) was performed. The LV ejection fraction was significantly improved at 6 weeks after SB623 cell patch transplantation (P < 0.001). Histological findings revealed that the number of von Willebrand factor (vWF)-positive capillary vessels (P < 0.01) and alpha smooth muscle actin (αSMA)- and vWF-positive arterioles with a diameter greater than 20 µm (P = 0.002) was significantly increased in the SB group, suggesting the induction of angiogenesis and arteriogenesis. Moreover, rat cardiomyocytes treated with SB623 cell patch transplantation showed upregulation of ephrin-B2 (P = 0.03) and EphB4 (P = 0.01) gene expression, indicating arteriogenesis induction. In conclusion, SB623 cell patch transplantation improved LV function by inducing angiogenesis and arteriogenesis in a rat ICM model.

Healing the Broken Hearts: A Glimpse on Next Generation Therapeutics

Cardiovascular diseases are the leading cause of death worldwide, accounting for 32% of deaths globally and thus representing almost 18 million people according to WHO. Myocardial infarction, the most prevalent adult cardiovascular pathology, affects over half a million people in the USA according to the last records of the AHA. However, not only adult cardiovascular diseases are the most frequent diseases in adulthood, but congenital heart diseases also affect 0.8–1.2% of all births, accounting for mild developmental defects such as atrial septal defects to life-threatening pathologies such as tetralogy of Fallot or permanent common trunk that, if not surgically corrected in early postnatal days, they are incompatible with life. Therefore, both congenital and adult cardiovascular diseases represent an enormous social and economic burden that invariably demands continuous efforts to understand the causes of such cardiovascular defects and develop innovative strategies to correct and/or palliate them. In the next paragraphs, we aim to briefly account for our current understanding of the cellular bases of both congenital and adult cardiovascular diseases, providing a perspective of the plausible lines of action that might eventually result in increasing our understanding of cardiovascular diseases. This analysis will come out with the building blocks for designing novel and innovative therapeutic approaches to healing the broken hearts.

Activation of the sigma-1 receptor exerts cardioprotection in a rodent model of chronic heart failure by stimulation of angiogenesis

Background

Angiogenesis plays a critical role on post-infarction heart failure (PIHF), the presence of which facilitates additional blood supply to maintain the survival of residual cardiomyocytes. The sigma-1 receptor (S1R) has been substantiated to stimulate angiogenesis, with the effect on a model of PIHF remaining unknown.

Aims

This study aims to investigate the effects of S1R on PIHF and the underlying mechanisms involved.

Methods

Rats were implemented left anterior descending artery ligation followed by rearing for 6 weeks to induce a phenotype of heart failure. Daily intraperitoneal injection of S1R agonist or antagonist for 5 weeks was applied from 2nd week after surgery. The effects exerted by S1R were detected by echocardiography, hemodynamic testing, western blot, Sirius red dyeing, ELISA, immunohistochemistry and fluorescence. We also cultured HUVECs to verify the mechanisms in vitro.

Results

Stimulation of S1R significantly ameliorated the cardiac function resulted from PIHF, in addition to the observation of reduced fibrosis in the peri-infarct region and the apoptosis of residual cardiomyocytes, which were associated with augmentation of microvascular density in peri-infarct region through activation of the JAK2/STAT3 pathway. We also indicated that suppression of JAK2/STAT3 pathway by specific inhibitor in vitro reversed the pro-angiogenic effects of S1R on HUVECs, which further confirmed that angiogenesis, responsible for PIHF amelioration, by S1R stimulation was in a JAK2/STAT3 pathway-dependent manner.

Conclusion

S1R stimulation improved PIHF-induced cardiac dysfunction and ventricular remodeling through promoting angiogenesis by activating the JAK2/STAT3 pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00517-1.

Fabrication of Tβ4-Exosome-releasing artificial stem cells for myocardial infarction therapy by improving coronary collateralization

Currently, stem cell transplantations in cardiac repair are limited owing to disadvantages, such as immunological rejection and poor cell viability. Although direct injection of exosomes can have a curative effect similar to that of stem cell transplantation, high clearance hinders its application in clinical practice. Previous reports suggested that induction of coronary collateralization can be a desired method of adjunctive therapy for someone who had missed the optimal operation time to attenuate myocardial ischemia. In this study, to mimic the paracrine and biological activity of stem cells, we developed artificial stem cells that can continuously release Tβ4-exosomes (Tβ4-ASCs) by encapsulating specific exosomes within microspheres using microfluidics technology. The results show that Tβ4-ASCs can greatly promote coronary collateralization in the periphery of the myocardial infarcted area, and its therapeutic effect is superior to that of directly injecting the exosomes. In addition, to better understand how it works, we demonstrated that the Tβ4-ASC-derived exosomes can enhance the angiogenic capacity of coronary endothelial cells (CAECs) via the miR-17-5p/PHD3/Hif-1α pathway. In brief, as artificial stem cells, Tβ4-ASCs can constantly release functional exosomes and stimulate the formation of collateral circulation after myocardial infarction, providing a feasible and alternative method for clinical revascularization.

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Inspired by the paracrine of stem cells, we fabricated artificial stem cells (Tβ4-ASCs) by loading engineered Tβ4-exosomes with microspheres using microfluidics technology.

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Tβ4-ASCs stimulate the formation of coronary collateralization in myocardial infarcted area through a slowly sustained release of engineered Tβ4-exosomes.

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Tβ4-ASCs improve coronary collateralization via the miR-17-5p/PHD3/Hif-1α signaling pathway.

Study on Mechanism of Invigorating Qi and Promoting Blood Circulation in Treatment of Angiogenesis after Myocardial Infarction Using Network Pharmacology

Objective

This article aims to explore the impact and mechanism of invigorating qi and promoting blood circulation (IQPBC) on angiogenesis after myocardial infarction (AMI) by using network pharmacology approach.

Methods

First, IQPBC was searched on the traditional Chinese medicine systems pharmacology database and analysis platform (TCMSP), and the main active ingredients and targets of IQPBC were screened and obtained. Second, by virtue of GeneCards and Online Mendelian Inheritance in Man (OMIM) databases, the targets related to AMI are screened and then obtained. Then, the intersection targets between IQPBC and AMI can be obtained by using online tool Venny 2.1.0. Third, based on the STRING database, the interaction of target proteins is established and some key targets can be analyzed and obtained. Finally, the IQPBC-AMI interaction network is constructed by using Cytoscape, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses are executed by DAVID and OmicShare databases.

Results

143 intersection targets between IQPBC and AMI are obtained. Besides, key active ingredients, namely, quercetin, tanshinone, kaempferol, and luteolin, are shown. Furthermore, AKT1, VEGFA, STAT3, HIF-1α, and other 10 key targets are obtained. A total of 752 enrichment results are acquired by using GO analysis. KEGG pathway enrichment analysis shows 241 signaling pathways, focusing on cancer, fluid shear stress and atherosclerosis, and TNF and PI3K/AKT signaling pathways.

Conclusion

This article studies the potential targets and signaling pathways of IQPBC drugs acting on AMI via the network pharmacology approach, which better illustrates the effect and mechanism, and provides some good ideas for the following mechanism research studies.

Enhancing myocardial repair with CardioClusters

Cellular therapy to treat heart failure is an ongoing focus of intense research, but progress toward structural and functional recovery remains modest. Engineered augmentation of established cellular effectors overcomes impediments to enhance reparative activity. Such 'next generation' implementation includes delivery of combinatorial cell populations exerting synergistic effects. Concurrent isolation and expansion of three distinct cardiac-derived interstitial cell types from human heart tissue, previously reported by our group, prompted design of a 3D structure that maximizes cellular interaction, allows for defined cell ratios, controls size, enables injectability, and minimizes cell loss. Herein, mesenchymal stem cells (MSCs), endothelial progenitor cells (EPCs) and c-Kit⁺ cardiac interstitial cells (cCICs) when cultured together spontaneously form scaffold-free 3D microenvironments termed CardioClusters. scRNA-Seq profiling reveals CardioCluster expression of stem cell-relevant factors, adhesion/extracellular-matrix molecules, and cytokines, while maintaining a more native transcriptome similar to endogenous cardiac cells. CardioCluster intramyocardial delivery improves cell retention and capillary density with preservation of cardiomyocyte size and long-term cardiac function in a murine infarction model followed 20 weeks. CardioCluster utilization in this preclinical setting establish fundamental insights, laying the framework for optimization in cell-based therapeutics intended to mitigate cardiomyopathic damage.

Mechanical Cues Regulating Proangiogenic Potential of Human Mesenchymal Stem Cells through YAP-Mediated Mechanosensing

Stem cells secrete trophic factors that induce angiogenesis. These soluble factors are promising candidates for stem cell-based therapies, especially for cardiovascular diseases. Mechanical stimuli and biophysical factors presented in the stem cell microenvironment play important roles in guiding their behaviors. However, the complex interplay and precise role of these cues in directing pro-angiogenic signaling remain unclear. Here, a platform is designed using gelatin methacryloyl hydrogels with tunable rigidity and a dynamic mechanical compression bioreactor to evaluate the influence of matrix rigidity and mechanical stimuli on the secretion of pro-angiogenic factors from human mesenchymal stem cells (hMSCs). Cells cultured in matrices mimicking mechanical elasticity of bone tissues in vivo show elevated secretion of vascular endothelial growth factor (VEGF), one of representative signaling proteins promoting angiogenesis, as well as increased vascularization of human umbilical vein endothelial cells (HUVECs) with a supplement of conditioned media from hMSCs cultured across different conditions. When hMSCs are cultured in matrices stimulated with a range of cyclic compressions, increased VEGF secretion is observed with increasing mechanical strains, which is also in line with the enhanced tubulogenesis of HUVECs. Moreover, it is demonstrated that matrix stiffness and cyclic compression modulate secretion of pro-angiogenic molecules from hMSCs through yes-associated protein activity.

Decellularized Human Dermal Matrix as a Biological Scaffold for Cardiac Repair and Regeneration

The complex and highly organized environment in which cells reside consists primarily of the extracellular matrix (ECM) that delivers biological signals and physical stimuli to resident cells. In the native myocardium, the ECM contributes to both heart compliance and cardiomyocyte maturation and function. Thus, myocardium regeneration cannot be accomplished if cardiac ECM is not restored. We hypothesize that decellularized human skin might make an easily accessible and viable alternate biological scaffold for cardiac tissue engineering (CTE). To test our hypothesis, we decellularized specimens of both human skin and human myocardium and analyzed and compared their composition by histological methods and quantitative assays. Decellularized dermal matrix was then cut into 600-μm-thick sections and either tested by uniaxial tensile stretching to characterize its mechanical behavior or used as three-dimensional scaffold to assess its capability to support regeneration by resident cardiac progenitor cells (hCPCs) in vitro. Histological and quantitative analyses of the dermal matrix provided evidence of both effective decellularization with preserved tissue architecture and retention of ECM proteins and growth factors typical of cardiac matrix. Further, the elastic modulus of the dermal matrix resulted comparable with that reported in literature for the human myocardium and, when tested in vitro, dermal matrix resulted a comfortable and protective substrate promoting and supporting hCPC engraftment, survival and cardiomyogenic potential. Our study provides compelling evidence that dermal matrix holds promise as a fully autologous and cost-effective biological scaffold for CTE.

The right ventricular fibroblast secretome drives cardiomyocyte dedifferentiation

RATIONALE

In virtually all models of heart failure, prognosis is determined by right ventricular (RV) function; thus, understanding the cellular mechanisms contributing to RV dysfunction is critical. Whole organ remodeling is associated with cell-specific changes, including cardiomyocyte dedifferentiation and activation of cardiac fibroblasts (Cfib) which in turn is linked to disorganization of cytoskeletal proteins and loss of sarcomeric structures. However, how these cellular changes contribute to RV function remains unknown. We've previously shown significant organ-level RV dysfunction in a large animal model of pulmonary hypertension (PH) which was not mirrored by reduced function of isolated cardiomyocytes. We hypothesized that factors produced by the endogenous Cfib contribute to global RV dysfunction by generating a heterogeneous cellular environment populated by dedifferentiated cells.

OBJECTIVE

To determine the effect of Cfib conditioned media (CM) from the PH calf (PH-CM) on adult rat ventricular myocytes (ARVM) in culture.

METHODS AND RESULTS

Brief exposure (<2 days) to PH-CM results in rapid, marked dedifferentiation of ARVM to a neonatal-like phenotype exhibiting spontaneous contractile behavior. Dedifferentiated cells maintain viability for over 30 days with continued expression of cardiomyocyte proteins including TnI and α-actinin yet exhibit myofibroblast characteristics including expression of α-smooth muscle actin. Using a bioinformatics approach to identify factor(s) that contribute to dedifferentiation, we found activation of the PH Cfib results in a unique transcriptome correlating with factors both in the secretome and with activated pathways in the dedifferentiated myocyte. Further, we identified upregulation of periostin in the Cfib and CM, and demonstrate that periostin is sufficient to drive cardiomyocyte dedifferentiation.

CONCLUSIONS

These data suggest that paracrine factor(s) released by Cfib from the PH calf signal a phenotypic transformation in a population of cardiomyocytes that likely contributes to RV dysfunction. Therapies targeting this process, such as inhibition of periostin, have the potential to prevent RV dysfunction.

Efficacy and safety of stem cell therapy in patients with dilated cardiomyopathy: a systematic appraisal and meta-analysis

BACKGROUND

The clinical significance of stem cell therapy in the treatment of dilated cardiomyopathy remains unclear. This systemic appraisal and meta-analysis aimed to assess the efficacy and safety of stem cell therapy in patients with dilated cardiomyopathy. After searching the PubMed, Embase, and Cochrane library databases until November 2017, we conducted a meta-analysis to evaluate the efficacy and safety of stem cell therapy in patients with dilated cardiomyopathy.

METHODS

The weighted mean difference (WMD), standard mean difference (SMD), relative risk (RR), and 95% confidence interval (CI) were summarized in this meta-analysis. Both fixed effects and random effects models were used to combine the data. Sensitivity analyses were conducted to evaluate the impact of an individual dataset on the pooled results.

RESULTS

A total of eight randomized controlled trials, which involved 531 participants, met the inclusion criteria in this systematic appraisal and meta-analysis. Our meta-analysis showed that stem cell therapy improves left ventricular ejection fraction (SMD = 1.09, 95% CI 0.29 to 1.90, I2 = 92%) and reduces left ventricular end-systolic volume (SMD = - 0.36, 95% CI - 0.61 to - 0.10, I2 = 20.5%) and left ventricular end-diastolic chamber size (SMD = - 0.48, 95% CI - 0.89 to - 0.07, I2 = 64.8%) in patients with dilated cardiomyopathy. However, stem cell therapy has no effect on mortality (RR = 0.72, 95% CI 0.50 to 1.02, I2 = 30.2%) and 6-min-walk test (WMD = 51.52, 95% CI - 24.52 to 127.55, I2 = 94.8%).

CONCLUSIONS

This meta-analysis suggests that stem cell therapy improves left ventricular ejection fraction and reduces left ventricular end-systolic volume and left ventricular end-diastolic chamber size in patients with dilated cardiomyopathy. However, future well-designed large studies might be necessary to clarify the effect of stem cell therapy in patients with dilated cardiomyopathy.

The mesenchymal stem cell secretome: A new paradigm towards cell-free therapeutic mode in regenerative medicine

Mesenchymal Stem Cells (MSCs) have been shown to be a promising candidate for cell-based therapy. The therapeutic potential of MSCs, towards tissue repair and wound healing is essentially based on their paracrine effects. Numerous pre-clinical and clinical studies of MSCs have yielded encouraging results. Further, these cells have been shown to be relatively safe for clinical applications. MSCs harvested from numerous anatomical locations including the bone marrow, adipose tissue, Wharton's jelly of the umbilical cord etc., display similar immunophenotypic profiles. However, there is a large body of evidence showing that MSCs secrete a variety of biologically active molecules such as growth factors, chemokines, and cytokines. Despite the similarity in their immunophenotype, the secretome of MSCs appears to vary significantly, depending on the age of the host and niches where the cells reside. Thus, by implication, proteomics-based profiling suggests that the therapeutic potential of the different MSC populations must also be different. Analysis of the secretome points to its influence on varied biological processes such as angiogenesis, neurogenesis, tissue repair, immunomodulation, wound healing, anti-fibrotic and anti-tumour for tissue maintenance and regeneration. Though MSC based therapy has been shown to be relatively safe, from a clinical standpoint, the use of cell-free infusions can altogether circumvent the administration of viable cells for therapy. Understanding the secretome of in vitro cultured MSC populations, by the analysis of the corresponding conditioned medium, will enable us to evaluate its utility as a new therapeutic option. This review will focus on the accumulating evidence that points to the therapeutic potential of the conditioned medium, both from pre-clinical and clinical studies. Finally, this review will emphasize the importance of profiling the conditioned medium for assessing its potential for cell-free therapy therapy.

Implications of scar structure and mechanics for post-infarction cardiac repair and regeneration

Regenerating cardiac muscle lost during a heart attack is a topic of broad interest and enormous potential impact. One promising approach is to regenerate or re-engineer new myocardium in situ, at the site of damage, by injecting cells, growth factors, and other materials, or by reprogramming aspects of the normal wound healing process. A wide variety of strategies have been explored, from promoting angiogenesis to injection of a variety of different progenitor cell types, to re-engineering resident cells to produce key growth factors or even transdifferentiate into myocytes. Despite substantial progress and continued promise, clinical impact of this work has fallen short of expectations. One contributing factor may be that many efforts focus primarily on generating cardiomyocytes, with less attention to re-engineering the extracellular matrix (ECM). Yet the role of the ECM is particularly crucial to consider following myocardial infarction, which leads to rapid formation of a collagen-rich scar. This review combines a brief summary of current efforts to regenerate cardiomyocytes with what is currently known about the structure and mechanics of post-infarction scar, with the goal of identifying principles that can guide efforts to produce new myocytes embedded in an extracellular environment that facilitates their differentiation, maintenance, and function.

Autologous bone marrow stem cell therapy for patients undergoing coronary artery bypass grafting: A meta-analysis of 14 randomized controlled trials

Autologous bone marrow stem cell (BMSC) therapy is a novel option for regenerative therapy in patients with ischemic heart disease. The aim of the present meta-analysis was to evaluate the effectiveness of BMSCs combined with coronary artery bypass grafting (CABG). The PubMed, Cochrane Library, EMBASE and Web of Science databases were searched from inception to November 22, 2017 for randomized controlled trials on BMSC therapy combined with CABG. Finally, 14 trials with a total of 596 participants were included. Data were analyzed using a random-effects model. Compared with the control group, the BMSC therapy group exhibited an improvement in the left ventricular (LV) ejection fraction from baseline to follow-up [mean difference (MD)=4.36%; 95% confidence interval (CI): 1.90–6.81%; P<0.01]. Analysis of the pooled results revealed non-significant differences in the LV end-diastolic volume (MD=−6.27 ml; 95% CI: −22.34 to 9.80 ml; P=0.44), LV end-diastolic volume index (MD=−15.11 ml/m²; 95% CI: −31.53 to 1.30 ml/m²; P=0.07), LV end-systolic volume (MD=−11.52 ml; 95% CI: −26.97 to 3.93 ml; P=0.14) and LV end-systolic volume index (MD=−16.56 ml/m²; 95% CI: −37.75 to 4.63 ml/m²; P=0.13) between the BMSC and CABG alone groups. Therefore, autologous BMSC therapy for patients undergoing CABG appears to be associated with an improvement in LV function compared with CABG alone.

Mesenchymal stem cells facilitate cardiac differentiation in Sox2-expressing cardiac C-kit cells in coculture

Stem cell therapy offers hope to reconstitute injured myocardium and salvage heart from failing. A recent approach using combinations of derived Cardiac-derived c-kit expressing cells (CCs) and mesenchymal stem cells (MSCs) in transplantation improved infarcted hearts with a greater functional outcome, but the effects of MSCs on CCs remain to be elucidated. We used a novel two-step protocol to clonogenically amplify colony forming c-kit expressing cells from 4- to 6-week-old C57BL/6N mice. This method yielded highly proliferative and clonogenic CCs with an average population doubling time of 17.2 ± 0.2, of which 80% were at the G1 phase. We identified two distinctly different CC populations based on its Sox2 expression, which was found to inversely related to their nkx2.5 and gata4 expression. To study CCs after MSC coculture, we developed micron-sized particles of iron oxide-based magnetic reisolation method to separate CCs from MSCs for subsequent analysis. Through validation using the sex and species mismatch CC-MSC coculture method, we confirmed that the purity of the reisolated cells was greater than 85%. In coculture experiment, we found that MSCs prominently enhanced Ctni and Mef2c expressions in Sox2 ^pos CCs after the induction of cardiac differentiation, and the level was higher than that of conditioned medium Sox2 ^pos CCs. However, these effects were not found in Sox2 ^neg CCs. Immunofluorescence labeling confirmed the presence of cardiac-like cells within Sox2 ^pos CCs after differentiation, identified by its cardiac troponin I and α-sarcomeric actinin expressions. In conclusion, this study shows that MSCs enhance CC differentiation toward cardiac myocytes. This enhancement is dependent on CC stemness state, which is determined by Sox2 expression.

Nanogel Tectonics for Tissue Engineering: Protein Delivery Systems with Nanogel Chaperones

Amphiphilic polysaccharide self-assembled (SA) nanogels are promising protein carriers owing to their chaperone-like activity that allows them to nanoencapsulate proteins within their polymer networks. The chaperoning function is an important concept that has led to breakthroughs in the development of effective protein drug delivery systems by stabilizing formulations and controlling the quality of unstable proteins. Recently, nanogel-tectonic materials that integrate SA nanogels as building blocks have been designed as new hydrogel biomaterials. This article describes recent progress and applications of SA nanogel tectonic materials as protein delivery systems for tissue engineering.

In situ cardiac regeneration by using neuropeptide substance P and IGF-1C peptide eluting heart patches

Cardiovascular diseases cause huge socio-economic burden worldwide. Although a mammalian myocardium has its own limited healing capability, scaffold materials capable of releasing stem cell recruiting/engrafting factors may facilitate the regeneration of the infarcted myocardium. The aim of this research was to develop cardiac patches capable of simultaneously eluting substance P (SP) and insulin-like growth factor-1C (IGF-1C) peptide. Polycaprolactone/collagen type 1-based patches with or without SP and IGF-1C peptide were fabricated by co-electrospinning, which exhibited nanofibrous morphology. SP and IGF-1C/SP patches recruited significantly higher numbers of bone marrow-mesenchymal stem cells than that of the negative control and patch-only groups in vitro. The developed patches were transplanted in an infarcted myocardium for up to 14 days. Mice underwent left anterior descending artery ligation and received one of the following treatments: (i) sham, (ii) saline, (iii) patch-only, (iv) IGF-1C patch, (v) SP patch and (vi) IGF-1C/SP patch. SP and IGF-1C/SP patch-treated groups exhibited better heart function and attenuated adverse cardiac remodeling than that of the saline, patch-only and individual peptide containing cardiac patches. SP patch and IGF-1C/SP patch-treated groups also showed higher numbers of CD31-positive vessels and isolectin B4-positive capillaries than that of other groups. IGF-1C/SP-treated group also showed thicker left ventricular wall in comparison to the saline and patch-only groups. Moreover, IGF-1C/SP patches recruited significantly higher numbers of CD29-positive cells and showed less numbers of Tunel-positive cells compared with the other groups. These data suggest that SP and IGF-1C peptides may act synergistically for in situ tissue repair.

Bioprocessing of Mesenchymal Stem Cells and Their Derivatives: Toward Cell-Free Therapeutics

Mesenchymal stem cells (MSCs) have attracted tremendous research interest due to their ability to repair tissues and reduce inflammation when implanted into a damaged or diseased site. These therapeutic effects have been largely attributed to the collection of biomolecules they secrete (i.e., their secretome). Recent studies have provided evidence that similar effects may be produced by utilizing only the secretome fraction containing extracellular vesicles (EVs). EVs are cell-derived, membrane-bound vesicles that contain various biomolecules. Due to their small size and relative mobility, they provide a stable mechanism to deliver biomolecules (i.e., biological signals) throughout an organism. The use of the MSC secretome, or its components, has advantages over the implantation of the MSCs themselves: (i) signals can be bioengineered and scaled to specific dosages, and (ii) the nonliving nature of the secretome enables it to be efficiently stored and transported. However, since the composition and therapeutic benefit of the secretome can be influenced by cell source, culture conditions, isolation methods, and storage conditions, there is a need for standardization of bioprocessing parameters. This review focuses on key parameters within the MSC culture environment that affect the nature and functionality of the secretome. This information is pertinent to the development of bioprocesses aimed at scaling up the production of secretome-derived products for their use as therapeutics.

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.

VEGF-B electrotransfer mediated gene therapy induces cardiomyogenesis in a rat model of cardiac ischemia

Atherosclerosis induced myocardial infarction (MI) continues to be a major public health concern. Regenerative therapies that restore cardiac muscle cells are largely absent. The rate of cardiomyogenesis in adults is insufficient to compensate for MI damage. In this study, we explored the capacity of a gene therapy approach to promote cardiomyogenesis. We hypothesized that VEGF-B, critical during fetal heart development, could promote cardiomyogenesis in adult ischemic hearts. Gene electrotransfer (GET), a physical method of in vivo gene delivery, was adapted to the rat model of MI. Favorable pulsing parameters were then used for delivery of pVEGF-B and compared to a sham control in terms of infarct size, cardiomyocyte proliferation and presence of new cardiomyocytes. Ki67 immunoreactivity was used for proliferation analysis. Newly synthetized DNA was labeled with BrdU to identify new cells post-infarction. Cardiac troponin co-localization indicated proliferating and new cardiomyocytes histologically. Eight weeks post-treatment, GET pVEGF-B treated hearts had significantly smaller infarcts than the sham control group (p < 0.04). Proliferating and new cardiomyocytes were only present in the GET of pVEGF-B group, and absent in the controls. In summary, GET pVEGF-B promoted cardiomyogenesis post-MI, demonstrating for the first time direct evidence of myocardial regeneration post-infarction.

Important signals regulating coronary artery angiogenesis

Angiogenesis is a complex process of budding, the formation of new blood vessels from pre-existing microvessels, via migration, proliferation and survival. Vascular angiogenesis factors include different classes of molecules that have a fundamental role in blood vessel formation. Numerous inducers of angiogenesis, such as the members of the vascular endothelial growth factor (VEGF) family, basic fibroblast growth factor (bFGF), angiopoietin (Ang), hepatocyte growth factor (HGF), and hypoxia inducible factor-1 (HIF-1), have an important role in angiogenesis. However, VEGF, platelet-derived growth factor (PDGF), and transforming growth factor β (TGF-β) expression appear to be important in intraplaque angiogenesis. Interaction and combined effects between growth factors is essential in endothelial cell migration, proliferation, differentiation, and endothelial cell-cell communication that ultimately lead to the microvessel formation. Since VEGF has a key role during angiogenesis; it may be considered as a good therapeutic target in the clinic. The essential function of several angiogenic factors involved in coronary angiogenesis and intraplaque angiogenesis in atherosclerosis are carefully considered along with the use of angiogenic factors in clinical practice.

Paracrine Mechanisms of Mesenchymal Stem Cells in Tissue Repair

Tissue regeneration from transplanted mesenchymal stromal cells (MSC) either through transdifferentiation or cell fusion was originally proposed as the principal mechanism underlying their therapeutic action. However, several studies have now shown that both these mechanisms are very inefficient. The low MSC engraftment rate documented in injured areas also refutes the hypothesis that MSC repair tissue damage by replacing cell loss with newly differentiated cells. Indeed, despite evidence of preferential homing of MSC to the site of myocardial ischemia, exogenously administered MSC show poor survival and do not persist in the infarcted area. Therefore, it has been proposed that the functional benefits observed after MSC transplantation in experimental models of tissue injury might be related to the secretion of soluble factors acting in a paracrine fashion. This hypothesis is supported by pre-clinical studies demonstrating equal or even improved organ function upon infusion of MSC-derived conditioned medium (MSC-CM) compared with MSC transplantation. Identifying key MSC-secreted factors and their functional role seems a reasonable approach for a rational design of nextgeneration MSC-based therapeutics. Here, we summarize the major findings regarding both different MSC-mediated paracrine actions and the identification of paracrine mediators.

Fractalkine is an independent predictor of mortality in patients with advanced heart failure

Immunological processes are implicated in the multifactorial pathophysiology of heart failure (HF). The multifunctional chemokine fractalkine (CX3CL1) promotes the extravasation of cytotoxic lymphocytes into tissues. We aimed to assess the prognostic value of fractalkine in HF. Fractalkine plasma levels were determined in 349 patients with advanced systolic HF (median 75 years, 66% male). During a median follow-up of 4.9 years (interquartile range: 4.6–5.2), 55.9% of patients died. Fractalkine was a significant predictor of all-cause mortality (p <0.001) with a hazard ratio of 2.78 (95% confidence interval: 1.95–3.95) for the third compared to the first tertile. This association remained significant after multivariable adjustment for demographics, clinical predictive variables and N-terminal pro-B-type natriuretic peptide (NT-proBNP, p=0.008). The predictive value of fractalkine did not significantly differ between patients with ischaemic and non-ischaemic HF aetiology (p=0.79). The predictive value of fractalkine tertiles was not significantly modified by tertiles of NT-proBNP (p=0.18) but was more pronounced in the first and third tertile of NT-proBNP. Fractalkine was also an independent predictor of cardiovascular mortality (p=0.015). Fractalkine levels were significantly lower in patients on angiotensin-converting enzyme inhibitor therapy (p <0.001). In conclusion, circulating fractalkine with its pro-inflammatory and immunomodulatory effects is an independent predictor of mortality in advanced HF patients. Fractalkine improves risk prediction beyond NTproBNP and might therefore help to identify high risk patients who need special care. Our data indicate the implication of immune modulation in HF pathology.

Hepatocyte growth factor: Molecular biomarker and player in cardioprotection and cardiovascular regeneration

The liver possesses impressive regenerative capacities. Grafts of embryonic liver explants and liver explant-conditioned media have been shown to enhance the mitotic activity of hepatocytes. Hepatocyte growth factor (HGF), also named scatter factor (SF), has been identified as a primary candidate in promoting and regulating liver regeneration. Although initially thought to be a liver-specific mitogen, HGF was later reported to have mitogenic, motogenic, morphogenic, and anti-apoptotic activities in various cell types. By promoting angiogenesis and inhibiting apoptosis, endogenous HGF may play an important role in cardioprotection as well as in the regeneration of endothelial cells and cardiomyocytes after myocardial infarction. Since serum concentration of HGF increases in the early phase of myocardial infarction and in heart failure, HGF may also play a key role as a prognostic and diagnostic biomarker of cardiovascular disease. Here we discuss the role of HGF as a biomarker and mediator in cardioprotection and cardiovascular regeneration.

Possible Muscle Repair in the Human Cardiovascular System

The regenerative potential of tissues and organs could promote survival, extended lifespan and healthy life in multicellular organisms. Niches of adult stemness are widely distributed and lead to the anatomical and functional regeneration of the damaged organ. Conversely, muscular regeneration in mammals, and humans in particular, is very limited and not a single piece of muscle can fully regrow after a severe injury. Therefore, muscle repair after myocardial infarction is still a chimera. Recently, it has been recognized that epigenetics could play a role in tissue regrowth since it guarantees the maintenance of cellular identity in differentiated cells and, therefore, the stability of organs and tissues. The removal of these locks can shift a specific cell identity back to the stem-like one. Given the gradual loss of tissue renewal potential in the course of evolution, in the last few years many different attempts to retrieve such potential by means of cell therapy approaches have been performed in experimental models. Here we review pathways and mechanisms involved in the in vivo repair of cardiovascular muscle tissues in humans. Moreover, we address the ongoing research on mammalian cardiac muscle repair based on adult stem cell transplantation and pro-regenerative factor delivery. This latter issue, involving genetic manipulations of adult cells, paves the way for developing possible therapeutic strategies in the field of cardiovascular muscle repair.

The Biological Basis for Cardiac Repair After Myocardial Infarction: From Inflammation to Fibrosis

In adult mammals, massive sudden loss of cardiomyocytes after infarction overwhelms the limited regenerative capacity of the myocardium, resulting in the formation of a collagen-based scar. Necrotic cells release danger signals, activating innate immune pathways and triggering an intense inflammatory response. Stimulation of toll-like receptor signaling and complement activation induces expression of proinflammatory cytokines (such as interleukin-1 and tumor necrosis factor-α) and chemokines (such as monocyte chemoattractant protein-1/ chemokine (C-C motif) ligand 2 [CCL2]). Inflammatory signals promote adhesive interactions between leukocytes and endothelial cells, leading to extravasation of neutrophils and monocytes. As infiltrating leukocytes clear the infarct from dead cells, mediators repressing inflammation are released, and anti-inflammatory mononuclear cell subsets predominate. Suppression of the inflammatory response is associated with activation of reparative cells. Fibroblasts proliferate, undergo myofibroblast transdifferentiation, and deposit large amounts of extracellular matrix proteins maintaining the structural integrity of the infarcted ventricle. The renin-angiotensin-aldosterone system and members of the transforming growth factor-β family play an important role in activation of infarct myofibroblasts. Maturation of the scar follows, as a network of cross-linked collagenous matrix is formed and granulation tissue cells become apoptotic. This review discusses the cellular effectors and molecular signals regulating the inflammatory and reparative response after myocardial infarction. Dysregulation of immune pathways, impaired suppression of postinfarction inflammation, perturbed spatial containment of the inflammatory response, and overactive fibrosis may cause adverse remodeling in patients with infarction contributing to the pathogenesis of heart failure. Therapeutic modulation of the inflammatory and reparative response may hold promise for the prevention of postinfarction heart failure.

Multimodal Hydrogel-Based Platform To Deliver and Monitor Cardiac Progenitor/Stem Cell Engraftment

Retention and survival of transplanted cells are major limitations to the efficacy of regenerative medicine, with short-term paracrine signals being the principal mechanism underlying current cell therapies for heart repair. Consequently, even improvements in short-term durability may have a potential impact on cardiac cell grafting. We have developed a multimodal hydrogel-based platform comprised of a poly(ethylene glycol) network cross-linked with bioactive peptides functionalized with Gd(III) in order to monitor the localization and retention of the hydrogel in vivo by magnetic resonance imaging. In this study, we have tailored the material for cardiac applications through the inclusion of a heparin-binding peptide (HBP) sequence in the cross-linker design and formulated the gel to display mechanical properties resembling those of cardiac tissue. Luciferase-expressing cardiac stem cells (CSC-Luc2) encapsulated within these gels maintained their metabolic activity for up to 14 days in vitro. Encapsulation in the HBP hydrogels improved CSC-Luc2 retention in the mouse myocardium and hind limbs at 3 days by 6.5- and 12- fold, respectively. Thus, this novel heparin-binding based, Gd(III)-tagged hydrogel and CSC-Luc2 platform system demonstrates a tailored, in vivo detectable theranostic cell delivery system that can be implemented to monitor and assess the transplanted material and cell retention.

Fabrication of Synthetic Mesenchymal Stem Cells for the Treatment of Acute Myocardial Infarction in Mice

RATIONALE

Stem cell therapy faces several challenges. It is difficult to grow, preserve, and transport stem cells before they are administered to the patient. Synthetic analogs for stem cells represent a new approach to overcome these hurdles and hold the potential to revolutionize regenerative medicine.

OBJECTIVE

We aim to fabricate synthetic analogs of stem cells and test their therapeutic potential for treatment of acute myocardial infarction in mice.

METHODS AND RESULTS

We packaged secreted factors from human bone marrow-derived mesenchymal stem cells (MSC) into poly(lactic-co-glycolic acid) microparticles and then coated them with MSC membranes. We named these therapeutic particles synthetic MSC (or synMSC). synMSC exhibited a factor release profile and surface antigens similar to those of genuine MSC. synMSC promoted cardiomyocyte functions and displayed cryopreservation and lyophilization stability in vitro and in vivo. In a mouse model of acute myocardial infarction, direct injection of synMSC promoted angiogenesis and mitigated left ventricle remodeling.

CONCLUSIONS

We successfully fabricated a synMSC therapeutic particle and demonstrated its regenerative potential in mice with acute myocardial infarction. The synMSC strategy may provide novel insight into tissue engineering for treating multiple diseases.

Antagomir-92a impregnated gelatin hydrogel microsphere sheet enhances cardiac regeneration after myocardial infarction in rats

Introduction

We investigated whether attachment of gelatin hydrogel microsphere (GHM) sheet impregnated with antagomir-92a on the infarcted heart promotes angiogenesis and cardiomyogenesis, and improves cardiac function after myocardial infarction (MI) in rats.

Methods

GHM sheet impregnated with antagomir-92a, its scramble sequence antagomir-control sheet or the sheet alone was attached on the area at risk of MI after the left anterior descending coronary artery ligation. Bromodeoxyuridine (BrdU) was included in the sheet to trace proliferating cells.

Results

The antagomir-92a sheet significantly increased capillary density in the infarct border zone 14 days after MI compared to the antagomir-control sheet or the sheet alone, associated with an increase in endothelial cells incorporated with BrdU. The antagomir-92a sheet significantly increased cardiac stem cells incorporated with BrdU 3 days after MI in the infarct border zone. This was associated with an increase in cardiomyocytes incorporated with BrdU 14 days after MI. Scar area was significantly reduced by the antagomir-92a sheet compared to the antagomir-control sheet or the sheet alone (12.8 ± 1.3 vs 25.2 ± 2.2, 24.0 ± 1.7% LV area, respectively) 14 days after MI. LV dilatation was inhibited, and LV wall motion was improved 14 days after MI in rats with the antagomir-92a sheet compared to the antagomir-control sheet or the sheet alone.

Conclusions

These results suggest that attachment of the GHM sheet impregnated with antagomir-92a on the area at risk of MI enhances angiogenesis, promotes cardiomyogenesis, and ameliorates LV function.

Secretome from resident cardiac stromal cells stimulates proliferation, cardiomyogenesis and angiogenesis of progenitor cells

In the heart, tissue-derived signals play a central role on recruiting/activating stem cell sources to induce cardiac lineage specification for maintenance of tissue homeostasis and repair. Cardiac resident stromal cells (CRSCs) may play a pivotal role in cardiac repair throughout their secretome. Here, we performed the characterization of CRSCs and their secretome by analyzing the composition of their culture-derived extracellular matrix (ECM) and conditioned medium (CM) and by investigating their potential effect on adipose-derived stem cell (ADSC) and progenitor cell behavior. We confirmed that CRSCs are a heterogeneous cell population whose secretome is composed by proteins related to cellular growth, immune response and cardiovascular development and function. We also observed that CRSC secretome was unable to change the behavior of ADSCs, except for proliferation. Additionally, CM from CRSCs demonstrated the potential to drive proliferation and cardiac differentiation of H9c2 cells and also the ability to induce angiogenesis in vitro. Our data suggest that the CRSCs can be a source of important modulating signals for cardiac progenitor cell recruitment/activation.

Catheter-based Intramyocardial Injection of FGF1 or NRG1-loaded MPs Improves Cardiac Function in a Preclinical Model of Ischemia-Reperfusion

Cardiovascular protein therapeutics such as neuregulin (NRG1) and acidic-fibroblast growth factor (FGF1) requires new formulation strategies that allow for sustained bioavailability of the drug in the infarcted myocardium. However, there is no FDA-approved injectable protein delivery platform due to translational concerns about biomaterial administration through cardiac catheters. We therefore sought to evaluate the efficacy of percutaneous intramyocardial injection of poly(lactic-co-glycolic acid) microparticles (MPs) loaded with NRG1 and FGF1 using the NOGA MYOSTAR injection catheter in a porcine model of ischemia-reperfusion. NRG1- and FGF1-loaded MPs were prepared using a multiple emulsion solvent-evaporation technique. Infarcted pigs were treated one week after ischemia-reperfusion with MPs containing NRG1, FGF1 or non-loaded MPs delivered via clinically-translatable percutaneous transendocardial-injection. Three months post-treatment, echocardiography indicated a significant improvement in systolic and diastolic cardiac function. Moreover, improvement in bipolar voltage and decrease in transmural infarct progression was demonstrated by electromechanical NOGA-mapping. Functional benefit was associated with an increase in myocardial vascularization and remodeling. These findings in a large animal model of ischemia-reperfusion demonstrate the feasibility and efficacy of using MPs as a delivery system for growth factors and provide strong evidence to move forward with clinical studies using therapeutic proteins combined with catheter-compatible biomaterials.

Adipose-Derived Stem Cells Induce Angiogenesis via Microvesicle Transport of miRNA-31

Cell secretion is an important mechanism for stem cell-based therapeutic angiogenesis, along with cell differentiation to vascular endothelial cells or smooth muscle cells. Cell-released microvesicles (MVs) have been recently implicated to play an essential role in intercellular communication. The purpose of this study was to explore the potential effects of stem cell-released MVs in proangiogenic therapy. We observed for the first time that MVs were released from adipose-derived stem cells (ASCs) and were able to increase the migration and tube formation of human umbilical vein endothelial cells (HUVECs). Endothelial differentiation medium (EDM) preconditioning of ASCs upregulated the release of MVs and enhanced the angiogenic effect of the released MVs in vitro. RNA analysis revealed that microRNA was enriched in ASC-released MVs and that the level of microRNA-31 (miR-31) in MVs was notably elevated upon EDM-preconditioning of MV-donor ASCs. Further studies exhibited that miR-31 in MVs contributed to the migration and tube formation of HUVECs, microvessel outgrowth of mouse aortic rings, and vascular formation of mouse Matrigel plugs. Moreover, factor-inhibiting HIF-1, an antiangiogenic gene, was identified as the target of miR-31 in HUVECs. Our findings provide the first evidence that MVs from ASCs, particularly from EDM-preconditioned ASCs, promote angiogenesis and the delivery of miR-31 may contribute the proangiogenic effect.

SIGNIFICANCE

This study provides the evidence that microvesicles (MVs) from adipose-derived stem cells (ASCs), particularly from endothelial differentiation medium (EDM)-preconditioned ASCs, promote angiogenesis. An underlying mechanism of the proangiogenesis may be the delivery of microRNA-31 via MVs from ASCs to vascular endothelial cells in which factor-inhibiting HIF-1 is targeted and suppressed. The study findings reveal the role of MVs in mediating ASC-induced angiogenesis and suggest a potential MV-based angiogenic therapy for ischemic diseases.

Harnessing the secretome of cardiac stem cells as therapy for ischemic heart disease

Adult stem cells continue to promise opportunities to repair damaged cardiac tissue. However, precisely how adult stem cells accomplish cardiac repair, especially after ischemic damage, remains controversial. It has been postulated that the clinical benefit of adult stem cells for cardiovascular disease results from the release of cytokines and growth factors by the transplanted cells. Studies in animal models of myocardial infarction have reported that such paracrine factors released from transplanted adult stem cells contribute to improved cardiac function by several processes. These include promoting neovascularization of damaged tissue, reducing inflammation, reducing fibrosis and scar formation, as well as protecting cardiomyocytes from apoptosis. In addition, these factors might also stimulate endogenous repair by activating cardiac stem cells. Interestingly, stem cells discovered to be resident in the heart appear to be functionally superior to extra-cardiac adult stem cells when transplanted for cardiac repair and regeneration. In this review, we discuss the therapeutic potential of cardiac stem cells and how the proteins secreted from these cells might be harnessed to promote repair and regeneration of damaged cardiac tissue. We also highlight how recent controversies about the efficacy of adult stem cells in clinical trials of ischemic heart disease have not dampened enthusiasm for the application of cardiac stem cells and their paracrine factors for cardiac repair: the latter have proved superior to the mesenchymal stem cells used in most clinical trials in the past, some of which appear to have been conducted with sub-optimal rigor.

Cardiac Nerve Growth Factor Overexpression Induces Bone Marrow-derived Progenitor Cells Mobilization and Homing to the Infarcted Heart

Reparative response by bone marrow (BM)-derived progenitor cells (PCs) to ischemia is a multistep process that comprises the detachment from the BM endosteal niche through activation of osteoclasts and proteolytic enzymes (such as matrix metalloproteinases (MMPs)), mobilization to the circulation, and homing to the injured tissue. We previously showed that intramyocardial nerve growth factor gene transfer (NGF-GT) promotes cardiac repair following myocardial infarction (MI) in mice. Here, we investigate the impact of cardiac NGF-GT on postinfarction BM-derived PCs mobilization and homing at different time points after adenovirus-mediated NGF-GT in mice. Immunohistochemistry and flow cytometry newly illustrate the temporal profile of osteoclast and activation of MMP9, PCs expansion in the BM, and liberation/homing to the injured myocardium. NGF-GT amplified these responses and increased the BM levels of active osteoclasts and MMP9, which were not observed in MMP9-deficient mice. Taken together, our results suggest a novel role for NGF in BM-derived PCs mobilization/homing following MI.

Zirconium oxide ceramic foam: a promising supporting biomaterial for massive production of glial cell line-derived neurotrophic factor

This study investigated the potential application of a zirconium oxide (ZrO2) ceramic foam culturing system to the production of glial cell line-derived neurotrophic factor (GDNF). Three sets of ZrO2 ceramic foams with different pore densities of 10, 20, and 30 pores per linear inch (PPI) were prepared to support a 3D culturing system. After primary astrocytes were cultured in these systems, production yields of GDNF were evaluated. The biomaterial biocompatibility, cell proliferation and activation of cellular signaling pathways in GDNF synthesis and secretion in the culturing systems were also assessed and compared with a conventional culturing system. In this study, we found that the ZrO2 ceramic foam culturing system was biocompatible, using which the GDNF yields were elevated and sustained by stimulated cell proliferation and activation of signaling pathways in astrocytes cultured in the system. In conclusion, the ZrO2 ceramic foam is promising for the development of a GDNF mass production device for Parkinson's disease treatment.

De-novo collateral formation following acute myocardial infarction: Dependence on CCR2⁺ bone marrow cells

Wide variation exists in the extent (number and diameter) of native pre-existing collaterals in tissues of different strains of mice, with supportive indirect evidence recently appearing for humans. This variation is a major determinant of the wide variation in severity of tissue injury in occlusive vascular disease. Whether such genetic-dependent variation also exists in the heart is unknown because no model exists for study of mouse coronary collaterals. Also owing to methodological limitations, it is not known if ischemia can induce new coronary collaterals to form ("neo-collaterals") versus remodeling of pre-existing ones. The present study sought to develop a model to study coronary collaterals in mice, determine whether neo-collateral formation occurs, and investigate the responsible mechanisms. Four strains with known rank-ordered differences in collateral extent in brain and skeletal muscle were studied: C57BLKS>C57BL/6>A/J>BALB/c. Unexpectedly, these and 5 additional strains lacked native coronary collaterals. However after ligation, neo-collaterals formed rapidly within 1-to-2 days, reaching their maximum extent in ≤7 days. Rank-order for neo-collateral formation differed from the above: C57BL/6>BALB/c>C57BLKS>A/J. Collateral network conductance, infarct volume(-1), and contractile function followed this same rank-order. Neo-collateral formation and collateral conductance were reduced and infarct volume increased in MCP1(-/-) and CCR2(-/-) mice. Bone-marrow transplant rescued collateral formation in CCR2(-/-) mice. Involvement of fractalkine➔CX3CR1 signaling and endothelial cell proliferation were also identified. This study introduces a model for investigating the coronary collateral circulation in mice, demonstrates that neo-collaterals form rapidly after coronary occlusion, and finds that MCP➔CCR2-mediated recruitment of myeloid cells is required for this process.

MicroRNAs in vascular tissue engineering and post-ischemic neovascularization

Increasing numbers of paediatric patients with congenital heart defects are surviving to adulthood, albeit with continuing clinical needs. Hence, there is still scope for revolutionary new strategies to correct vascular anatomical defects. Adult patients are also surviving longer with the adverse consequences of ischemic vascular disease, especially after acute coronary syndromes brought on by plaque erosion and rupture. Vascular tissue engineering and therapeutic angiogenesis provide new hope for these patients. Both approaches have shown promise in laboratory studies, but have not yet been able to deliver clear evidence of clinical success. More research into biomaterials, molecular medicine and cell and molecular therapies is necessary. This review article focuses on the new opportunities offered by targeting microRNAs for the improved production and greater empowerment of vascular cells for use in vascular tissue engineering or for increasing blood perfusion of ischemic tissues by amplifying the resident microvascular network.

Contemporary perspective on endogenous myocardial regeneration

Considering the complex nature of the adult heart, it is no wonder that innate regenerative processes, while maintaining adequate cardiac function, fall short in myocardial jeopardy. In spite of these enchaining limitations, cardiac rejuvenation occurs as well as restricted regeneration. In this review, the background as well as potential mechanisms of endogenous myocardial regeneration are summarized. We present and analyze the available evidence in three subsequent steps. First, we examine the experimental research data that provide insights into the mechanisms and origins of the replicating cardiac myocytes, including cell populations referred to as cardiac progenitor cells (i.e., c-kit+ cells). Second, we describe the role of clinical settings such as acute or chronic myocardial ischemia, as initiators of pathways of endogenous myocardial regeneration. Third, the hitherto conducted clinical studies that examined different approaches of initiating endogenous myocardial regeneration in failing human hearts are analyzed. In conclusion, we present the evidence in support of the notion that regaining cardiac function beyond cellular replacement of dysfunctional myocardium via initiation of innate regenerative pathways could create a new perspective and a paradigm change in heart failure therapeutics. Reinitiating cardiac morphogenesis by reintroducing developmental pathways in the adult failing heart might provide a feasible way of tissue regeneration. Based on our hypothesis “embryonic recall”, we present first supporting evidence on regenerative impulses in the myocardium, as induced by developmental processes.

Therapeutic angiogenesis promotes efficacy of human umbilical cord matrix stem cell transplantation in cardiac repair

OBJECTIVES

Although previous studies have confirmed the beneficial effects of human umbilical cord matrix stem cell (hUCM) transplantation post myocardial infarction (MI), but this stem cell resource has no potential to induce angiogenesis. In order to achieve the process of angiogenesis and cardiomyocyte regeneration, two required factors for cardiac repair agents were examined namely; hUCM and VEGF on an infarcted heart. The main objective of this research is to investigate the combinatory effect of dhUCM and VEGF transplantation on an infarcted heart.

MATERIALS AND METHODS

45 min of ligating the left anterior descending coronary artery, the MI-induced animals received 50 μl PBS, 5 μg VEGF, 5×10(6) hUCM cells alone, combined with 5 μg VEGF and 5×10(6) differentiated hUCM cells alone or combined with 5 μg VEGF through intramyocardial injection. MI group, without hUCM and VEGF served as the control group. Left ventricular function and angiogenesis were also evaluated.

RESULTS

After eight weeks post MI, there were significant rise in left ventricular ejection farction in dhUCM+VEGF group compared to the other treated and non-treated groups (P<0.05). Fibrosis tissue was markedly lower in the dhUCM+VEGF and hUCM+VEGF groups compared to the other treated and non-treated groups (P<0.05). Despite these benefits, vascular density in dhUCM+VEGF group was not markedly different compared to VEGF and hUCM+VEGF groups. The transplanted hUCM and dhUCM cells survived and migrated to the infarcted area.

CONCLUSION

Our findings demonstrated that the dhUCM cells transplantation combined with VEGF were more efficient on an infarcted heart.

The cell secretome, a mediator of cell-to-cell communication

We are witnessing the emergence of a novel type of biological regulation, namely, the communication between cells via their secreted substances, the secretome. This brief overview is based on the available published data and our own experience. We discuss three vignettes illustrating the importance of communication via the secretome: (1) the secretome of stem cells and its effects in sepsis and systemic inflammatory response; (2) the profibrotic secretomes partially responsible for development of fibrotic complications; and (3) the contribution of senescence-associated secretory products to the propagation of the senescence phenotype. Considering the richness of secretomes of different cells under diverse conditions, it becomes imperative to gain insights into their individual components in an attempt to harness cell secretomes for therapeutic purposes.