Inflammatory Proteases and Cardiac Repair after Myocardial Infarction

描述（由申请人提供）：心肌梗死（MI）后的重塑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。限制或逆转后心肌重塑的不同疗法已经过测试，但成功率有限。最近，基于细胞的疗法已被证明有望修复受伤的心脏。然而，基于细胞的治疗的成功应用仍然受到低的持续细胞植入率的阻碍，这是由于最初保留在靶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驻留祖细胞（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。该提议通过抑制嗜中性粒细胞衍生的丝氨酸蛋白酶（NSP）拮抗MI后诱导的不利的心脏重塑，所述丝氨酸蛋白酶是在损伤部位激活时由炎性细胞释放的蛋白酶。我们已经发现，NSP通过降解参与细胞粘附和肌细胞收缩功能的关键蛋白，通过失巢凋亡诱导肌细胞脱离和凋亡。初步研究显示，使用二肽基肽酶I（DPPI）KO小鼠（缺乏主要NSP的小鼠）体内NSP缺失减轻了MI后的肌细胞死亡，并导致较小的梗死面积和保留的心脏功能。有趣的是，我们发现DPPI缺失也增加了心脏再生和修复受损心肌的能力，表明NSP对心脏缺血损伤后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NSP通过c-kit受体的泛素化和蛋白酶体降解来改变c-kit受体的稳定性和周转率。这些数据支持以下假设：NSP是c-kit受体稳定性和转换的关键调节剂，限制心脏驻留祖细胞在炎症区域的存活和增殖，并降低它们在MI后替代心肌组织的能力。在这里，我们将阐明从NSP下游的信号传导途径，这是至关重要的介导c-kit信号改变和CPC死亡。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。拟议工作的意义是确定是否可以安全地进行DPPI阻滞剂的有效给药，以减少心肌细胞损失，增强心脏再生，并取代心肌梗死后的心肌组织。

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.