Targeted inhibition of fibrosis for the prevention of heart failure

 描述（由申请方提供）：心肌细胞在病理刺激下发生重塑，导致细胞形态改变、蛋白质合成增加和胎儿基因上调。虽然最初是代偿性的，但最终这些变化证明是适应不良的，诱导纤维化和不利的心室重塑。在响应心脏应激和/或损伤时，Ras相关的小G蛋白RhoA的激活先前显示介导有害的体内病理反应。然而，最近，RhoA也被证明可以促进细胞存活，并在心肌梗死（MI）损伤后具有心脏保护作用。为了确定RhoA在心肌中这些相反作用的分子机制，我们产生了心肌细胞特异性缺失RhoA的小鼠（RhoAfl/fl-aMHC-Cre）。在对慢性损伤（横向主动脉缩窄，TAC）的响应中，我们发现来自RhoAfl/fl-aMHC-Cre小鼠的心脏发展了加速扩张，具有显著的收缩功能丧失。尽管如此，并且平行地，来自这些小鼠的心脏也显示出显著降低的心脏纤维化，其中证实了参与纤维化反应的基因的转录激活降低，包括血清反应因子（SRF）和心肌蛋白相关转录因子（MRTF）。两者合计，我们的数据表明，RhoA作为一个关键的双节点，在响应心脏损伤，从而下游信号的一个组成部分是必需的，以保持收缩性，而其他介导激活适应不良反应，由于激活促纤维化基因。因此，我们假设靶向抑制下游RhoA介导的促纤维化基因（SRF和MRTF）不仅可以预防纤维化的发生和随后与MI损伤相关的适应不良反应，而且还可以保留RhoA平行信号传导途径产生的收缩性上游心脏保护作用。 纳米材料在疾病治疗中具有广泛的适用性，因为它们具有调节药物性质的能力，包括循环时间和定位到感兴趣的组织。重要的是，在靶向纳米颗粒内掺入治疗部分允许其位点特异性递送，从而使产生治疗效果所需的剂量最小化，同时降低全身反应。利用这项技术，我们将研究新的靶向配体的细胞特异性输送心肌损伤后的心脏纤维化抑制剂。使用体内、离体和体外分析，我们将1）产生并充分表征掺入抑制剂的靶向纳米剂，所述抑制剂被选择用于防止MI后胶原蛋白的沉积; 2）检查合成的纳米剂的体外和体内结合和抑制功效;以及3）纵向评估抑制剂在MI的鼠模型中的靶向递送的治疗功效。重要的是，我们预计这项技术的疗效将超越MI，并适用于更慢性的疾病，如心脏肥大和/或瓣膜疾病引起的纤维化。

 DESCRIPTION (provided by applicant): Cardiomyocytes undergo remodeling in response to pathological stimuli, causing altered cell morphology, increased protein synthesis and upregulation of fetal genes. While initially compensatory, ultimately, these changes prove maladaptive, inducing fibrosis and adverse ventricular remodeling. In response to cardiac stress and/or injury, activation of the Ras-related small G protein RhoA was previously shown to mediate deleterious in vivo pathological responses. However, more recently, RhoA has also been shown to promote cell survival and be cardio-protective after myocardial infarct (MI) injury. To determine the molecular mechanisms that underlie these opposing roles for RhoA in the myocardium, we generated mice with a cardiomyocyte-specific deletion of RhoA (RhoAfl/fl-aMHC-Cre). In response to chronic injury (transverse aortic constriction, TAC), we found that hearts from RhoAfl/fl-aMHC-Cre mice developed an accelerated dilation, with significant loss of contractile function. Despite this, and in parallel, hearts from these mice also showed significantly decreased cardiac fibrosis, with a demonstrated decrease in transcriptional activation of genes involved in the fibrotic response, including the serum response factor (SRF) and the myocardin related transcription factor (MRTF). Taken together, our data suggest that RhoA serves as a critical bi-nodal point in response to cardiac injury, whereby a component of the downstream signaling is required to preserve contractility, while the other mediates activation of maladaptive responses due to activation of profibrotic genes. Therefore, we hypothesize that targeted inhibition of downstream RhoA-mediated pro-fibrotic genes (SRF and MRTF) will not only prevent onset of fibrosis and subsequent maladaptive responses associated with MI injury, but will also allow for the preservation of the upstream cardio-protective effects n contractility exerted by RhoA parallel signaling pathways. Nanomaterials have found wide applicability in the treatment of disease, as they possess the ability to modulate the properties o drugs, including circulation times and localization to tissues of interest. Importantly, the incorporation of therapeutic moieties within targeted nanoparticles allows for their site-specific delivery, minimizing the dose required to bring about a therapeutic effect, while concomitantly decreasing systemic repercussions. Using this technology, we will investigate novel targeting ligands for the cell specific delivery of inhibitors of cardiac fibrosis following myocardial injur. Using in-vivo, ex-vivo and in-vitro analyses, we will 1) generate and fully characterize targeted nanoagents incorporating inhibitors chosen to prevent the deposition of collagen after MI; 2) examine the in vitro and in vivo binding and inhibitory efficacy of the synthesized nanoagents; and 3) longitudinally assess the therapeutic efficacy of the targeted delivery of inhibitors in murine models of MI. Importantly, we expect that the efficacy of this technology to extend beyond MI, and be applicable to more chronic conditions, such as fibrosis caused by cardiac hypertrophy and/or valvular disease.