Role of mast cells in pressure overload induced right ventricular remodeling and failure

几种类型的先天性心脏病、肺血管疾病和伴有肺静脉压升高的左心疾病导致右心室后负荷增加和右心肥大。虽然许多研究集中在左心室肥大的机制，只有有限的信息是关于右心室（RV）的重塑过程。最重要的是，RV性能决定了先天性心脏病、肺动脉高压、晚期左心衰竭患者，甚至稳定心血管疾病患者的预后。尽管为所有疾病制定了减少后负荷的策略，但肺血管阻力仍然高度升高。因此，保留RV功能是一个治疗目标，可能会影响患者的生存。因此，我们开发了一种RV肥大的动物模型，该模型不依赖于通过结扎肺动脉的后负荷变化。利用这种肺动脉带（PAB）模型，可以密切监测RV重构的参数（例如，心肌细胞肥大、间质和血管周围重构、毛细血管化），并且可以对RV功能测试新的治疗策略。基于我们的初步数据，我们现在假设肥大细胞和它们的蛋白酶可能参与了对血流动力学负荷增加的反应。为了解决肥大细胞的作用，我们将首先调查这些细胞在重塑RV肥大细胞数量的系统形态分析，以及通过采用嵌合小鼠（骨髓移植小鼠从增强型绿色荧光蛋白（EGFP）转基因小鼠）的起源。第二，为了获得肥大细胞在RV肥大中的作用的功能性洞察，将对肥大细胞缺陷型WBB 6 F1-KitW/KitW-v小鼠进行PAB。将通过高分辨率超声心动图、右心导管插入术和组织形态测量技术监测RV重塑。第三，我们将调查糜酶，丝氨酸蛋白酶表达的肥大细胞，通过采用糜酶缺陷的动物（mMCP-4和mMCP-5缺陷小鼠）的作用。在体外实验中，我们将心肌细胞和心脏成纤维细胞与来自野生型和糜酶缺陷动物的骨髓来源的培养肥大细胞共培养。在体内，将在mMCP-4和mMCP-5缺陷小鼠中研究PAB后的RV重塑。第四，我们将尝试通过使用临床上可用的肥大细胞稳定剂克罗诺平来逆转有害的RV重塑。第五，将在PAB模型中研究糜酶抑制剂如BCEAB的功效。更好地了解肥大细胞糜酶在RV重塑过程中的作用可能会提供有关潜在病理生理机制和可能的候选靶点的重要线索，这将有助于我们开发新的治疗策略，专门针对RV，从而提高患者的生存率。

Several types of congenital heart defects, pulmonary vascular diseases and left heart disease with increased pulmonary venous pressure lead to an increase in right ventricular afterload and right heart hypertrophy. While many investigations focused on the mechanisms of left heart hypertrophy, only limited information is available about the remodeling process of the right ventricle (RV). Most importantly, the RV performance defines prognosis in patients with congenital heart disease, pulmonary arterial hypertension, advanced left heart failure, and even in patients with stable cardiovascular diseases. Despite afterload-reducing strategies developed for all diseases, the pulmonary vascular resistance remains highly elevated. Thus preservation of RV function is a therapeutic goal which might have impact on patient survival. We therefore developed an animal model of RV hypertrophy that is independent of changes in afterload by ligation of the pulmonary artery. With this pulmonary arterial banding (PAB) model, parameters of RV remodeling (e.g. cardiomyocyte hypertrophy, interstitial and perivascular remodeling, capillarisation) can be closely monitored and new therapeutic strategies can be tested on RV function. Based on our preliminary data, we now hypothesize that mast cells and their proteases might be involved in RV remodeling in response to an increased hemodynamic load. In order to address the role of mast cells, we will first investigate the origin of these cells in the remodeled RV by systematic morphometric analysis of mast cell number as well as by employing chimeric mice (bone marrow-transplanted mice from enhanced green fluorescence protein (EGFP)-transgenic mice). Second, to gain functional insight in the role of mast cells in RV hypertrophy, mast cell-deficient WBB6F1-KitW/KitW-v mice will be subjected to PAB. RV remodeling will be monitored by high resolution echocardiography, right heart catheterization and histomorphometric techniques. Third, we will investigate the role of chymase, a serine protease expressed exclusively by mast cells, by employing chymase deficient animals (mMCP-4- and mMCP-5-deficient mice). In in vitro experiments, we will co-culture cardiomyocytes and cardiofibroblasts with bone marrow derived cultured mast cells from wild type and chymase deficient animals. In vivo, RV remodeling after PAB will be investigated in mMCP-4- and mMCP-5-deficient mice. Fourth, we will try to reverse deleterious RV remodeling by employing a clinically available mast cell stabilizing agent cromolyn. Fifth, the efficacy of chymase inhibitors like BCEAB will be studied in the PAB model. A better understanding of the role of mast cell chymase in the process of RV remodeling may provide important clues about underlying pathophysiological mechanisms and possible candidate targets which will help us develop novel therapeutic strategies directed specifically to the RV and thus improve survival in patients.