Therapeutic Potential of Pluripotent Stem Cells for Cardiac Repair after Myocardial Infarction

Astragaloside IV induces the protective effect of bone marrow mesenchymal stem cells derived exosomes in acute myocardial infarction by inducing angiogenesis and inhibiting apoptosis

Bone marrow mesenchymal stem cells (BMECs)-derived exosomes (MSC-Exo) can improve acute myocardial infarction (AMI). Astragaloside IV (AS-IV) has also been reported to have cardioprotective pharmacological effects. However, it is not entirely clear whether AS-IV can improve AMI by inducing MSC-Exo. BMSCs and MSC-Exo were isolated and identified, and we also established the AMI rat model and the OGD/R model with H9c2 cells. After MSC-Exo or AS-IV-mediated MSC-Exo treatment, cell angiogenesis, migration, and apoptosis were evaluated by tube formation, wound healing, and TUNEL staining. The cardiac function of the rats was measured by echocardiography. The pathological changes and collagen deposition in rats were also assessed with Masson and Sirius red staining. The levels of α-SMA, CD31 and inflammatory factors were determined by immunohistochemistry and enzyme-linked immunosorbent assay (ELISA). In vitro, AS-IV-mediated MSC-Exo can significantly enhance the angiogenesis and migration of H9c2 cells induced by OGD/R, and significantly reduce their apoptosis. In vivo, AS-IV-mediated MSC-Exo can improve the cardiac function of rats, and attenuate pathological damage and collagen deposition in AMI model rats. In addition, AS-IV-mediated MSC-Exo can also promote angiogenesis and reduce inflammatory factors in rats with AMI. AS-IV-stimulated MSC-Exo can improve myocardial contractile function, myocardial fibrosis and angiogenesis, reduce inflammatory factors and induce apoptosis in rats after AMI.

Role of Wnt/β-catenin pathway in cardiac lineage commitment of human umbilical cord mesenchymal stem cells by zebularine and 2'-deoxycytidine

Wnt/β-catenin, a highly conserved signaling pathway, is involved in determining cell fate. During heart development, Wnt signaling controls specification, proliferation and differentiation of cardiac cells. This study is aimed to investigate the role of Wnt/β-catenin signaling in cardiac lineage commitment of human umbilical cord mesenchymal stem cells (hUCMSCs) after treatment with demethylating agents, zebularine and 2'-deoxycytidine (2-DC). hUCMSCs were treated with 20 µM zebularine or 2-DC for 24 h and cultured for 14 days. Control and treated MSCs were analyzed for cardiac lineage commitment at gene and protein levels. Significant upregulation of early and late cardiac markers, GATA4, Nkx2.5, cardiac myosin heavy chain (cMHC), α-actinin, cardiac troponin T (cTnT) and cardiac troponin I (cTnI) was observed in treated MSCs as compared to the untreated control. We also analyzed gene expression of key Wnt/β-catenin signaling molecules in cultures of treated and untreated hUCMSCs at 24 h, and days 3, 7 and 14. The pattern of mRNA gene expression showed that Wnt/β-catenin signaling is regulated during cardiac lineage commitment of hUCMSCs in a time-dependent manner, with the pathway being activated early but inhibited later in cardiac development. Findings of this study can lead us to identify more specific and effective strategies for cardiac lineage commitment.

Microvascular fragments in microcirculation research and regenerative medicine

Adipose tissue-derived microvascular fragments (MVF) are functional vessel segments, which rapidly reassemble into new microvasculatures under experimental in vitro and in vivo conditions. Accordingly, they have been used for many years in microcirculation research to study basic mechanisms of endothelial cell function, angiogenesis and microvascular network formation in two- and three-dimensional environments. Moreover, they serve as vascularization units for musculoskeletal regeneration and implanted biomaterials as well as for the treatment of myocardial infarction and the generation of prevascularized tissue organoids. Besides, multiple factors determining the vascularization capacity of MVF have been identified, including their tissue origin and cellular composition, the conditions for their short- and long-term storage as well as their implantation site and the general health status and medication of the recipient. The next challenging step is now the successful translation of all these promising experimental findings into clinical practice. If this succeeds, a multitude of future therapeutic applications may significantly benefit from the remarkable properties of MVF.

Construction of extracellular matrix-based 3D hydrogel and its effects on cardiomyocytes

Some discoveries resulted from 2-dimensional (2D) cultured cardiac cells have been disqualified in animal testing and later clinical trials. Extracellular matrix (ECM) plays a vital role in cardiac homeostasis, cardiac ECM (cECM)-based 3D cell cultures can mimics the physiological and pathological conditions in vivo closely, it is hopeful of addressing this challenge. Construction of cECM-based 3-dimensional (3D) hydrogel (cECM3DH) and its effects on cell behaviors were studied here. The results indicated that cellular compartments could be efficiently removed from heart tissue via sodium dodecyl sulfonate (SDS)- and Triton X-100-mediated decellularization, remaining the natural fibrous network structure and major proteins. 3D hydrogel consisted of 1 × 107 cells/mL cells and 75% cECM could promote the proliferation and anti-apoptosis ability of human embryonic kidney (HEK)-293T cells. 0.25% trypsin or 0.20% collagenase was suitable to retrieve these cells from 3D hydrogel for further researches. Compared with 2D culture system, cECM3DH could significantly increase the proportion of GATA 4+ cardiomyocytes (CMs) derived from heart tissue of neonatal mouse or induced differentiation of embryonic stem cells (ESCs) (P < 0.05) The expression levels of mature genes including cTnT, JCN, CaV1.2, MYL2, CASQ2, NCX1, and Cx43 of these CMs in adult pig cECM-based 3D hydrogel (APcECM3DH) were significantly higher than that in 2D culture system and in newborn piglet cECM-based 3D hydrogel (NPcECM3DH), respectively (P < 0.05). Therefore, cECM3DH supports the generation of primary CMs and ESC-derived CMs, APcECM3DH was more conducive to promoting CM maturation, which contributes to building 3D model for pathogenesis exploration, drug screening, and regenerative medicine of heart diseases.

Cell sheet formation enhances the therapeutic effects of human umbilical cord mesenchymal stem cells on myocardial infarction as a bioactive material

Stem cell-based therapy has been used to treat ischaemic heart diseases for two decades. However, optimal cell types and transplantation methods remain unclear. This study evaluated the therapeutic effects of human umbilical cord mesenchymal stem cell (hUCMSC) sheet on myocardial infarction (MI).

Methods

hUCMSCs expressing luciferase were generated by lentiviral transduction for in vivo bio-luminescent imaging tracking of cells. We applied a temperature-responsive cell culture surface-based method to form the hUCMSC sheet. Cell retention was evaluated using an in vivo bio-luminescent imaging tracking system. Unbiased transcriptional profiling of infarcted hearts and further immunohistochemical assessment of monocyte and macrophage subtypes were used to determine the mechanisms underlying the therapeutic effects of the hUCMSC sheet. Echocardiography and pathological analyses of heart sections were performed to evaluate cardiac function, angiogenesis and left ventricular remodelling.

Results

When transplanted to the infarcted mouse hearts, hUCMSC sheet significantly improved the retention and survival compared with cell suspension. At the early stage of MI, hUCMSC sheet modulated inflammation by decreasing Mcp1-positive monocytes and CD68-positive macrophages and increasing Cx3cr1-positive non-classical macrophages, preserving the cardiomyocytes from acute injury. Moreover, the extracellular matrix produced by hUCMSC sheet then served as bioactive scaffold for the host cells to graft and generate new epicardial tissue, providing mechanical support and routes for revascularsation. These effects of hUCMSC sheet treatment significantly improved the cardiac function at days 7 and 28 post-MI.

Conclusions

hUCMSC sheet formation dramatically improved the biological functions of hUCMSCs, mitigating adverse post-MI remodelling by modulating the inflammatory response and providing bioactive scaffold upon transplantation into the heart.

Translational perspective

Due to its excellent availability as well as superior local cellular retention and survival, allogenic transplantation of hUCMSC sheets can more effectively acquire the biological functions of hUCMSCs, such as modulating inflammation and enhancing angiogenesis. Moreover, the hUCMSC sheet method allows the transfer of an intact extracellular matrix without introducing exogenous or synthetic biomaterial, further improving its clinical applicability.

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Cell sheet formation of hUCMSCs dramatically improves post transplantation cell survival in the infarcted heart.

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hUCMSC sheet protects cardiomyocytes from infarction by alleviating acute inflammation.

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The ECM of cell sheet serves as bioactive scaffold to allow the host cells to integrate and form new epicardial tissue.

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The new epicardial tissue can provide mechanical support and new routes for revascularization.

AMPK/SIRT1 Pathway is Involved in Arctigenin-Mediated Protective Effects Against Myocardial Ischemia-Reperfusion Injury

Arctigenin, one of the active ingredients extracted from Great Burdock (Arctium lappa) Achene, has been found to relieve myocardial infarction injury. However, the specific mechanism of Arctigenin against myocardial infarction remains largely unknown. Here, both acute myocardial ischemia-reperfusion injury (AMI/R) rat model and oxygen glucose deprivation (OGD)-induced myocardial cell injury model were constructed to explore the underlying role of AMPK/SIRT1 pathway in Arctigenin-mediated effects. The experimental data in our study demonstrated that Arctigenin ameliorated OGD-mediated cardiomyocytes apoptosis, inflammation and oxidative stress in a dose-dependent manner. Besides, Arctigenin activated AMPK/SIRT1 pathway and downregulated NF-κB phosphorylation in OGD-treated cardiomyocytes, while inhibiting AMPK or SIRT1 by the Compound C (an AMPK inhibitor) or SIRT1-IN-1 (a SIRT1 inhibitor) significantly attenuated Arctigenin-exerted protective effects on cardiomyocytes. In the animal experiments, Arctigenin improved the heart functions and decreased infarct size of the AMI/R-rats, accompanied with downregulated oxidative stress, inflammation and apoptotic levels in the heart tissues. What's more, Arctigenin enhanced the AMPK/SIRT1 pathway and repressed NF-κB pathway activation. Taken together, our data indicated that Arctigenin reduced cardiomyocytes apoptosis against AMI/R-induced oxidative stress and inflammation at least via AMPK/SIRT1 pathway.

Cell Therapy With Human ESC-Derived Cardiac Cells: Clinical Perspectives

In the ongoing quest for the “ideal” cell type for heart repair, pluripotent stem cells (PSC) derived from either embryonic or reprogrammed somatic cells have emerged as attractive candidates because of their unique ability to give rise to lineage-specific cells and to transplant them at the desired stage of differentiation. The technical obstacles which have initially hindered their clinical use have now been largely overcome and several trials are under way which encompass several different diseases, including heart failure. So far, there have been no safety warning but it is still too early to draw definite conclusions regarding efficacy. In parallel, mechanistic studies suggest that the primary objective of “remuscularizing” the heart with PSC-derived cardiac cells can be challenged by their alternate use as ex vivo sources of a biologically active extracellular vesicle-enriched secretome equally able to improve heart function through harnessing endogenous repair pathways. The exclusive use of this secretome would combine the advantages of a large-scale production more akin to that of a biological medication, the likely avoidance of cell-associated immune and tumorigenicity risks and the possibility of intravenous infusions compatible with repeated dosing.

The Emergence of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes (hiPSC-CMs) as a Platform to Model Arrhythmogenic Diseases

There is a need for improved in vitro models of inherited cardiac diseases to better understand basic cellular and molecular mechanisms and advance drug development. Most of these diseases are associated with arrhythmias, as a result of mutations in ion channel or ion channel-modulatory proteins. Thus far, the electrophysiological phenotype of these mutations has been typically studied using transgenic animal models and heterologous expression systems. Although they have played a major role in advancing the understanding of the pathophysiology of arrhythmogenesis, more physiological and predictive preclinical models are necessary to optimize the treatment strategy for individual patients. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have generated much interest as an alternative tool to model arrhythmogenic diseases. They provide a unique opportunity to recapitulate the native-like environment required for mutated proteins to reproduce the human cellular disease phenotype. However, it is also important to recognize the limitations of this technology, specifically their fetal electrophysiological phenotype, which differentiates them from adult human myocytes. In this review, we provide an overview of the major inherited arrhythmogenic cardiac diseases modeled using hiPSC-CMs and for which the cellular disease phenotype has been somewhat characterized.