Inflammatory Proteases and Cardiac Repair after Myocardial Infarction

描述（由申请人提供）：心肌梗死（MI）后重构是一个复杂的生物学过程，可导致进行性左心室扩张和临床心力衰竭。限制或逆转心肌重构的不同治疗方法已被测试，但成功率有限。最近，以细胞为基础的治疗已被证明有望修复受伤的心脏。然而，细胞疗法的成功应用仍然受到持续细胞植入率低的阻碍，这是由于最初保留在目标组织中的细胞随后大量死亡造成的。因此，限制心肌细胞损失和增强心脏常驻祖细胞（CPC）存活和增殖的干预措施可能为设计治疗心力衰竭的新治疗策略提供重要见解。该建议通过抑制中性粒细胞衍生丝氨酸蛋白酶（NSPs）来对抗心肌梗死后引起的不良心脏重构，NSPs是炎症细胞在损伤部位激活后释放的蛋白酶。我们已经证明，NSPs通过降解参与细胞粘附和肌细胞收缩功能的关键蛋白，通过anoikis诱导肌细胞脱离和凋亡。初步研究表明，使用二肽基肽酶I （DPPI）的KO小鼠体内NSP缺失，缺乏主要NSP的小鼠减少心肌梗死后的心肌细胞死亡，导致梗死面积缩小并保留心功能。有趣的是，我们发现DPPI缺失也增加了心脏再生和损伤心肌修复的能力，这表明NSPs在心脏缺血损伤时对祖细胞的存活和增殖产生负面影响。使用培养的c-kit阳性cpc，我们发现NSPs通过泛素化和c-kit受体的蛋白酶体降解改变c-kit受体的稳定性和周转。这些数据支持了NSPs是c-kit受体稳定性和转换的关键调节剂的假设，限制了心脏驻留祖细胞在炎症区域的存活和增殖，并降低了它们在心肌梗死后替代心肌组织的能力。在这里，我们将阐明NSPs下游的信号通路，这些信号通路对介导c-kit信号改变和CPC死亡至关重要。此外，我们建议研究DPPI阻断治疗影响心肌梗死后修复的机制。本研究的意义在于确定DPPI阻滞剂是否可以安全有效地减少心肌细胞损失，增强心脏再生，并在心肌梗死后替代心肌组织。

DESCRIPTION (provided by applicant): Remodeling after myocardial infarction (MI) is a complex biological process that leads to progressive left ventricular dilation and clinical heart failure. Different therapies to limit or reverse post myocardial remodeling have been tested with limited success. Recently, cell-based therapies have been shown to hold promise of repairing an injured heart. However, the successful application of cell-based therapy remains hampered by a low rate of sustained cell engraftment which results from subsequent massive death of cells that have been initially retained in the target tissue. Thus, interventions to limit myocyte loss and enhance cardiac resident progenitor cell (CPC) survival and proliferation may provide important insights for designing new therapeutic strategies to treat heart failure. This proposal antagonizes the adverse cardiac remodeling induced after MI through inhibition of neutrophil-derived serine proteases (NSPs), proteases that are released by inflammatory cells upon their activation at site of injury. We have shown that NSPs induce myocyte detachment and apoptosis by anoikis through degradation of key proteins involved in cell adhesion and myocyte contractile function. Pilot study shows that NSP deletion in-vivo using DiPeptidyl Peptidase I (DPPI) KO mice, mice that lack major NSPs, attenuated myocyte death following MI and resulted in smaller infarct size and preserved cardiac function. Interestingly, we found that DPPI deletion also increased the capability of cardiac regeneration and repair of the injured myocardium, suggesting that NSPs negatively affect progenitor cell survival and proliferation in response to cardiac ischemic insult. Using cultured c-kit positive CPCs, we found that NSPs alter c-kit receptor stability and turnover through ubiquitylation and proteasomal degradation of c-kit receptors. These data support the hypothesis that NSPs are key modulators of c-kit receptor stability and turnover, limit cardiac resident progenitor cell survival and proliferation n area of inflammation and reduce their capability to replace myocardial tissue after MI. Here we will elucidate the signaling pathways downstream from NSPs that are critical for mediating c- kit signaling alterations and CPC death. Furthermore, we propose to investigate the mechanisms by which DPPI blockade therapy affects repair after myocardial infarction. The significance of the proposed work is to determine if effective administration of DPPI blocker could be performed safely to reduce myocyte loss, to enhance cardiac regeneration and to replace myocardial tissue after MI.