C-Kit Positive Cardiac Stem Cells and Bone Marrow-Derived Mesenchymal Stem Cells Synergistically Enhance Angiogenesis and Improve Cardiac Function After Myocardial Infarction in a Paracrine Manner.

BACKGROUND: Stem cell transplantation offers a promising treatment for heart failure. Recent studies show that both c-kit positive cardiac stem cells (CSCs) and bone marrow-derived mesenchymal stem cells (BM-MSCs) are good candidates for stem cell therapy to treat heart failure; however, the exact mechanism of stem cell therapy in improving cardiac function of ischemic cardiomyopathy is not fully known. Our objective was to test our hypothesis that CSCs and/or BM-MSCs repair the damaged heart by boosting post-myocardial infarction (MI) angiogenesis in a paracrine manner. METHODS AND RESULTS: We isolated and purified CSCs and BM-MSCs from rats. Intramyocardial injections of CSCs and/or BM-MSCs were performed at 28 days after MI. We applied cardiac ultrasound and histological analysis to evaluate the effect of cell therapy on cardiac function and cardiac remodeling. In vivo donor cell transplantation experiments showed that CSCs and/or BM-MSCs improved cardiac function after MI and reduced infarct size. However, in vivo cell tracking experiments showed that minimal donor cells remained in the myocardium after cell transplantation. Our further in vitro and in vivo experiments showed that transplantation of CSCs enhanced the expression of pro-angiogenic factors and boosted post-MI angiogenesis in the myocardium in a paracrine manner, which in part contributed to the effect of CSCs on cardiac recovery after MI. CSCs and BM-MSCs synergistically inhibited CSC/BM-MSC apoptosis and enhanced their proliferation in a paracrine manner. This resulted in a larger number of transplanted cells remaining in the post-MI myocardium after coinjection of CSCs and BM-MSCs, and therefore the accumulation of more pro-angiogenic factors in the heart tissue compared to transplantation of CSCs or MSCs alone. Consequently, transplantation of both CSCs and BM-MSCs was superior to transplantation of either CSCs or BM-MSCs alone to boost post-MI angiogenesis and improve cardiac function after MI. CONCLUSION: C-kit+ CSC and/or BM-MSC transplantation can improve cardiac function after MI in a paracrine manner. Coinjection of both CSCs and BM-MSCs improves cardiac function more significantly than CSC or BM-MSC transplantation alone in a paracrine manner by improving the engraftment of donor cells and boosting the expression of multiple pro-angiogenic factors.

Neonatal Heart-Enriched miR-708 Promotes Differentiation of Cardiac Progenitor Cells in Rats.

Cardiovascular disease is becoming the leading cause of death throughout the world. However, adult hearts have limited potential for regeneration after pathological injury, partly due to the quiescent status of stem/progenitor cells. Reactivation of cardiac stem/progenitor cells to create more myocyte progeny is one of the key steps in the regeneration of a damaged heart. In this study, miR-708 was identified to be enriched in the neonatal cardiomyocytes of rats, but this has not yet been proven in adult humans. A lower level of miR-708 in c-kit(+) stem/progenitor cells was detected compared to non-progenitors. Overexpression of miR-708 induced cardiomyocyte differentiation of cardiac stem/progenitor cells. This finding strengthened the potential of applying miRNAs in the regeneration of injured hearts, and this indicates that miR-708 could be a novel candidate for treatment of heart diseases.

IL-17 contributes to the pathogenesis of obliterative bronchiolitis via regulation of M1 macrophages polarization in murine heterotopic trachea transplantation models.

Acute allograft rejection is a principal conundrum in lung obliterative bronchiolitis (OB). Monocytes/macrophages infiltration has been proved to be the main reason for acute rejection. IL-17 contributes to the recruitment and function of macrophages. However, the mechanism of IL-17 underlying OB progression remains elusive. In the present study, we showed that the deficiency of IL-17 attenuated the pathology of murine heterotopic trachea allografts. Compared to WT recipients, IL-17-/- mice displayed higher frequency of CD206+ cells and lower ratio of CD86+ cells among F4/80+ macrophages in allografts and spleens on day 7 post heterotopic trachea transplantation. Moreover, mRNA levels of pro-inflammatory cytokines including IL-6, TNF-α, and IL-1ß decreased in allografts of IL-17-/- recipients, but these of MRC1 and Arg-1 increased in comparison with WT. IL-17 deficiency can inhibit LPS induced M1 while promote IL-4 induced M2 polarization of bone marrow-derived macrophages. Further data demonstrated that the deficiency of IL-17 suppressed the lipopolysaccharide-induced M1 polarization and function through prevention of phosphorylation of both STAT3 and STAT5. Therefore, IL-17 contributes to OB pathogenesis through regulating macrophages function, thereby it may unravel part of the complexity of IL-17 in OB and enhance future therapeutic development.

Neonatal Heart-Enriched miR-708 Promotes Proliferation and Stress Resistance of Cardiomyocytes in Rodents.

Adult heart has limited potential for regeneration after pathological injury due to the limited cell proliferation of cardiomyocytes and the quiescent status of progenitor cells. As such, induction of cell-cycle reentry of cardiomyocytes is one of the key strategies for regeneration of damaged heart. In this study, a subset of miRNAs including miR-708 were identified to be much more abundant in the embryonic and neonatal cardiomyocytes than that in adult rodents. Overexpression of miR-708 promoted cellular proliferation of H9C2 cells or primary cardiomyocytes from neonatal rats or mice in vitro. Lipid nanoparticle delivery of miR-708 promoted myocardial regeneration and heart function recovery in vivo. In addition, miR-708 protected cardiomyocytes against stress-induced apoptosis under hypoxia or isoproterenol treatments. miR-708 inhibited the expression of MAPK14, which has been demonstrated arresting the cell cycle in cardiomyocytes. The cell proliferation-promoting function of miR-708 was dependent at least partly on the expression of MAPK14. These findings strengthen the potential of applying miRNAs to reconstitute lost cardiomyocytes in injured hearts, and may provide a novel miRNA candidate for promoting heart regeneration.

Chebulagic acid inhibits the LPS-induced expression of TNF-α and IL-1ß in endothelial cells by suppressing MAPK activation.

Inflammatory response in the vasculature, including the overexpression of tumor necrosis factor (TNF)-α and interleukin (IL)-1ß, has been demonstrated to increase the risk of thrombosis development. Chebulagic acid (CA) is a key chemical component in the traditional Mongolian anti-thrombotic drug Garidi-13, and has been suggested to exert anti-inflammatory and anti-infective effects. The present study aimed to evaluate the regulatory impact of CA on a number of biological processes, including lipopolysaccharide (LPS)-induced inflammation, LPS-promoted mitogen-activated protein kinase (MAPK) activation and the expression of toll-like receptor (TLR)4 in EA.hy926 human endothelial cells. The results indicated that CA significantly inhibited the LPS-induced upregulation of TNF-α and IL-1ß in a dose- and time-dependent manner. Furthermore, LPS-activated MAPK signaling was inhibited by CA treatment in the EA.hy926 cells. However, TLR4, which serves a key function in LPS-induced inflammation as the receptor of LPS, was not regulated by the CA treatment. In summary, the results of the present study indicate that CA inhibits the LPS-induced promotion of TNF-α and IL-1ß in endothelial cells by suppressing MAPK activation, which may contribute to the anti-thrombotic effect of Garidi-13.