Enhanced cell transplantation: preventing apoptosis increases cell survival and ventricular function

Abstract

Cell transplantation prevents cardiac dysfunction after myocardial infarction. However, because most implanted cells are lost to ischemia and apoptosis, the benefits of cell transplantation on heart function could be improved by increasing cell survival. To examine this possibility, male Lewis rat aortic smooth muscle cells (SMCs; 4 ϫ 10 6 ) were pretreated with antiapoptotic Bcl-2 gene transfection or heat shock and then implanted into the infarcted myocardium of anesthetized, syngenic female rats (n ϭ 23 per group). On the first day after transplantation, apoptotic SMCs were quantified by using transferase-mediated dUTP nick-end labeling staining. On days 7 and 28, grafted cell survival was quantified by using real-time PCR, and heart function was assessed with the use of echocardiographyandtheLangendorffapparatus.SMCsgivenantiapoptotic pretreatments exhibited improvements in each measure relative to controls. Apoptosis was reduced in Bcl-2-treated cells relative to all other groups (P Ͻ 0.05), whereas survival (P Ͻ 0.01) was increased. Heat shock also significantly decreased apoptosis and increased survival relative to control groups (P Ͻ 0.05 for group effect), although these effects were less pronounced than in the Bcl-2-treated group. Further, scar areas were reduced in both Bcl-2-and heat shock-treated groups relative to controls (P Ͻ 0.05), and fractional area change and cardiac function were greater (P Ͻ 0.05 for both measures). These results indicate that antiapoptosis pretreatments reduced grafted SMC loss after transplantation and enhanced grafted cell survival and ventricular function, which was directly related (r ϭ 0.72; P ϭ 0.002) to the number of surviving engrafted cells. cell therapy; Bcl-2; heat shock; ventricular modulation; angiogenesis SKELETAL MYOBLAST TRANSPLANTATION prevents scar thinning and ventricular dilatation after a myocardial infarction and has been associated with improved regional and global function in both animal experimentation (5,17,26) and the initial clinical trials of this intervention (6, 15). The mechanism responsible for this beneficial effect has not been elucidated but may include angiogenesis, altering the elasticity of the ventricular wall, and/or modifying matrix remodeling. These mechanisms were suggested because none of the myriad of implanted cells have been demonstrated to differentiate into functioning cardiomyocytes, nor have they been demonstrated to beat synchronously with the remaining recipient cardiomyocytes. Therefore, the goal of cell transplantation is to establish a graft of viable cells within the infarct region to modify ventricular remodeling and prevent congestive heart failure. If the grafted cells could contribute to the contractility of the infarct scar, the beneficial effect would be enhanced. In the present study, our first aim was to evaluate the efficacy of smooth muscle cell (SMC) transplantation to augment cardiac function, because these cells routinely induce angiogenesis and matrix remodeling and might be ideally suited to efficient...

<b>Adipose stem cell sheets improved cardiac function in the rat myocardial infarction, but did not alter cardiac contractile responses to β-adrenergic stim</b><b>ulation </b>

“…ASC sheets also improved systolic and diastolic functions of the MI hearts without their differentiation to cardiac myocytes. These results indicated that paracrine effects, especially, these of VEGF secreted from ASC sheets could be responsible for improvement of the cardiac contraction, since VEGF-dependent angiogenesis has been reported to contribute to cardiac contractile reserve after MI (13). Unfortunately, ASC as well as myoblast cell sheets failed to restore cardiac contractile responses to β-adrenergic stimulation.…”

“…Each data of three groups were obtained from 6 independent experiments. cell survival and ventricular function (13), ASC sheets were expected to have a higher tolerance for ischemia and hypoxia than myoblast cell sheets, when they were transplanted into MI hearts. However, in in vivo study, there were not any significant differences in restoration of cardiac function and cardiac remodeling between ASC and myoblast cell sheets, suggesting that secretion of higher concentration of angiogenic factors from ASC sheets might not overcome the benefit of myoblast cell sheets (20).…”

Anoikis: an emerging hallmark in health and diseases

“…In addition, the survival rate of transplanted human mesenchymal stem cells in a mouse heart reaches <0.5% at 4 days after transplantation [165]. These discouraging results were also reported using different cell types, such as skeletal myoblasts, smooth muscle cells and unfractionated bone marrow cells, which can survive only few days after transplantation [166][167][168]. In vivo, bone marrow-derived circulating mesenchymal stem cells are able to repopulate damaged tissues, leading to reconstruction of their function, due to the secretion of soluble factors exerting proliferative and anti-apoptotic actions [169].…”

Systems approaches to preventing transplanted cell death in cardiac repair

“…Bcl-2 inhibits cell death by blocking cytochrome C release from the mitochondria [67], that otherwise leads to caspase activation and cell death. Bcl-2 is up-regulated in surviving ventricular myocytes in the context of MI [68], and transgenic over-expression of Bcl-2 in the engrafted cells limits myocardial infarct size after ischemia/reperfusion [69]. Li and colleagues have demonstrated the pro-survival effects of transduced Bcl-2 in two cell types: smooth muscle cells [69] and mesenchymal stem cells [70].…”

“…Bcl-2 is up-regulated in surviving ventricular myocytes in the context of MI [68], and transgenic over-expression of Bcl-2 in the engrafted cells limits myocardial infarct size after ischemia/reperfusion [69]. Li and colleagues have demonstrated the pro-survival effects of transduced Bcl-2 in two cell types: smooth muscle cells [69] and mesenchymal stem cells [70]. In each case, engraftment was improved as measured by cell graft size and ventricular function.…”