Myofibroblasts and fibrosis after cardiac transplant

移植心脏中的慢性排斥反应与冠状动脉床中的间质纤维化和进行性新生内膜病变形成相关，其损害组织灌注至功能破坏的程度。我们在项目3中的目的是研究移植心脏中特别涉及激活的基质肌成纤维细胞的伤口修复过程。我们认为，在术后早期的同种异体抗原非依赖性缺血/再灌注损伤以及长期接受的移植物中TGF β 1的慢性、同种异体抗原依赖性释放通过基于活性氧（ROS）的共同信号通路促进肌成纤维细胞活化和组织发生性重塑。肌成纤维细胞在心脏移植物的冠状动脉外膜和心脏内膜中积累，在那里它们表达由MSYI（冷休克结构域（CSD）转录调节蛋白）调节的几种损伤应答基因。MSY 1及其相关蛋白是组织应激和氧化还原失衡的转录应答的重要介质。这项研究的目的是检测控制VSM α-肌动蛋白启动子活性的MSY 1蛋白复合物中TGF β 1和ROS依赖的变化。慢性排斥反应期间VSM α-肌动蛋白表达的错误调节与肌成纤维细胞、纤维收缩性瘢痕组织、新生内膜平滑肌细胞和低分化心肌细胞的积累相关。VSM α-肌动蛋白由一个原型损伤反应基因编码，该基因与伤口修复所需的其他基因共享MSY 1控制元件。分析MSY 1和其他TRP之间的相互作用所需的损伤反应基因表达在人基质肌成纤维细胞应提供新的信息，在慢性排斥反应的分子控制点。在人类病理学和心肌内活检样本中，MSY 1：TRP结构和功能的评估可能为移植患者在移植物破坏性纤维化发展之前评估和分期慢性排斥反应提供新的预后指标。从移植血管硬化的角度来看，基质肌成纤维细胞的研究特别相关，因为外膜成纤维细胞在新生内膜形成中的重要性以及建立新的微血管灌注回路对心脏移植物的长期存活至关重要。最后，TGF β 1和/或ROS可以调节其它MSY 1依赖性慢性排斥相关基因的表达，例如编码MHC II类分子的那些基因，其补充了项目1和2的目标，该项目1和2的目标涉及同种抗体产生、单核细胞/巨噬细胞FcR接合以及TGF β 1在移植物接受相对于纤维化中的作用。

Chronic rejection in the transplanted heart is associated with interstitial fibrosis and progressive neointimal lesion formation in the coronary arterial bed that impairs tissue perfusion to the point of functional disruption. Our intention in Project 3 is to examine wound repair processes in the transplanted heart that specifically involve activated stromal myofibroblasts. We propose that alloantigen-independent ischemia/reperfusion injury during the early post-operative period as well as chronic, alloantigen-dependent release of TGFbeta1 in long-term accepted grafts promote myofibroblasts activation and histogenic remodeling via a common signaling pathways based on reactive oxygen species (ROS). Myofibroblasts accumulate in the coronary adventitia and cardiac interstitium of heart grafts where they express several injury- response genes that are regulated by MSYI, a cold-shock domain (CSD) transcriptional regulatory protein. MSY1 and related proteins are important mediators of the transcriptional response to tissue stress and redox imbalance. The goal of the proposed research is to examine TGFbeta1- and ROS-dependent changes in MSY1 protein complexes that govern VSM alpha-actin promoter activity. Mis-regulation of VSM alpha-actin expression during chronic rejection is associated with accumulation of myofibroblasts, fibrocontractile scar tissue, neointimal smooth muscle cells, and poorly differentiated cardiomyocytes. VSM alpha-actin is encoded by a prototypical injury response gene that shares MSY1 control elements with other genes required for wound repair. Analysis of interactions between MSY1 and other TRPs required for injury-response gene expression in human stromal myofibroblasts should provide new information about molecular control points in chronic rejection. In human pathology and intramyocardial biopsy samples, assessment of MSY1:TRP structure and function may provide new prognostic indicators for evaluating and staging chronic rejection in transplant patients before the development of graft-destructive fibrosis. From the standpoint of transplant vascular sclerosis, studiers of stromal myofibroblasts are especially relevant given the demonstrated importance of adventitial fibroblasts in neointima formation as well as the establishment of new microvascular perfusion circuits that are critical for long-term heart graft survival. Finally, TGFbeta1 and/or ROS may modulate expression of other MSY1-dependent, chronic rejection- associated genes such as those encoding MHC class II molecules which compliments Project 1 and 2 aims pertaining to alloantibody production, monocyte/macrophage FcR engagement, and the role of TGFbeta1 in graft acceptance vs. fibrosis.