Profound Actions of an Agonist of Growth Hormone–Releasing Hormone on Angiogenic Therapy by Mesenchymal Stem Cells

OBJECTIVE: The efficiency of cell therapy is limited by poor cell survival and engraftment. Here we studied the effect of the growth hormone-releasing hormone agonist, JI-34, on mesenchymal stem cells (MSCs) survival and angiogenic therapy in a mouse model of critical limb ischemia. APPROACH AND RESULTS: Mouse bone marrow-derived MSCs were incubated with or without 10(−8) mol/L JI-34 for 24 hours. MSCs were then exposed to hypoxia and serum deprivation to detect the effect of preconditioning on cell apoptosis, migration and tube formation. For in vivo, critical limb ischemia was induced by femoral artery ligation. After surgery, mice were received 50μl phosphate buffer saline or with 1×10(6) MSCs or with 1×10(6) JI-34 preconditioned MSCs. Treatment of MSCs with JI-34 improved MSCs viability and mobility and markedly enhanced their capability to promote endothelial tube formation in vitro. These effects were paralleled by increased phosphorylation and nuclear translocation of STAT3. In vivo, JI-34 pre-treatment enhanced the engraftment of MSCs into ischemic hindlimb muscles and augmented reperfusion and limb salvage compared with untreated MSCs. Significantly more vasculature and proliferating CD31(+) and CD34(+) cells were detected in ischemic muscles that received MSCs treated with JI-34. CONCLUSIONS: Our studies demonstrate a novel role for JI-34 to markedly improve therapeutic angiogenesis in hindlimb ischemia by increasing the viability and mobility of MSCs. These findings support additional studies to explore the full potential of Growth hormone-releasing hormone agonists to augment cell therapy in the management of ischemia

The effects of stabilizing and directional selection on phenotypic and genotypic variation in a population of RNA enzymes

The distribution of variation in a quantitative trait and its underlying distribution of genotypic diversity can both be shaped by stabilizing and directional selection. Understanding either distribution is important, because it determines a population’s response to natural selection. Unfortunately, existing theory makes conflicting predictions about how selection shapes these distributions, and very little pertinent experimental evidence exists. Here we study a simple genetic system, an evolving RNA enzyme (ribozyme) in which a combination of high throughput genotyping and measurement of a biochemical phenotype allow us to address this question. We show that directional selection, compared to stabilizing selection, increases the genotypic diversity of an evolving ribozyme population. In contrast, it leaves the variance in the phenotypic trait unchanged

Current status of cell-based therapy for heart failure

In the last two decades, morbidity and mortality of patients with chronic heart failure could be further reduced by improved pharmacological and cardiac device therapies. However, despite these advances, there is a substantial unmet need for novel therapies, ideally specifically addressing repair and regeneration of the damaged or lost myocardium and its vasculature, given the limited endogenous potential for renewal of cardiomyocytes in adults. In this respect, cardiac cell-based therapies have gained substantial attention and have entered clinical feasibility and safety studies a decade ago. Different cell-types have been used, including bone marrow-derived mononuclear cells, bone marrow-derived mesenchymal stem cells, mobilized CD34+ cells, and more recently cardiac-derived c-kit+ stem cells and cardiosphere-derived cells. Some of these studies have suggested a potential of cell-based therapies to reduce cardiac scar size and to improve cardiac function in patients with ischemic cardiomyopathy. While first clinical trials examining the impact of cardiac cell-based therapy on clinical outcome have now been initiated, improved understanding of underlying mechanisms of action of cell-based therapies may lead to strategies for optimization of the cardiac repair potential of the applied cells. In experimental studies, direct in vivo reprogramming of cardiac fibroblasts towards cardiomyocytes, and microRNA-based promotion of cardiomyocyte proliferation and cardiac repair have recently been reported that may represent novel therapeutic approaches for cardiac regeneration that would not need cell-administration but rather directly stimulate endogenous cardiac regeneration. This review will focus mainly on recently completed clinical trials (within the last 2 years) investigating cardiac cell-based therapies and the current status of experimental studies for cardiac cell-based repair and regeneration with a potential for later translation into clinical studies in the future