Growth and Function of Cultured Gastrointestinal Muscle

描述(申请人提供)：这项工作的总体假设是，IGF-I系统、？V？3整合素和？V？3整合素结合配体、玻璃体连接蛋白和纤维连接蛋白调节肠道中的平滑肌增生、过度的胶原生成和纤维化，这些是克罗恩病狭窄形成的中心，选择性的IGF-I和？V？3抑制剂可用于减少肌肉增生、纤维化和狭窄形成。我们在当前资助期间的研究已经确定了内源性IGF-I、IGFBP-5、IGFBP-3和？V？3整合素共同作用于调节正常肠道肌肉的平滑肌生长和II型胶原的产生，以及克罗恩病和TNBS诱导的结肠炎小鼠的肌肉过度生长、II型胶原的产生和纤维化的机制。V？3整合素被其配体玻璃体连接蛋白和纤维连接蛋白占据，调节IGF-I刺激的强度和持续时间，IGF-I受体的激活和作用。我们最近的工作和初步结果表明，与狭窄克罗恩病的平滑肌一样，TNBS诱导的结肠炎小鼠的平滑肌也增加了内源性V？3整合素配体。V？3整合素的激活以及内源性IGF-I和IGF结合蛋白的上调是平滑肌细胞增殖、II型胶原生成增加和由此导致的纤维化的中心介质。药物阻断V3整合素的激活或IGF-I受体的激活可以减少肌肉的增生、II型胶原的产生、V3整合素的依赖效应和纤维化。第一个特定目的是确定调节IGF-I和IGFBP-5表达增加的机制，以及它们在狭窄克罗恩病和慢性TNBS诱导的结肠炎中肌肉增生、胶原产生和纤维化发展中的作用。第二个特异点是研究V3整合素结合玻璃体连接蛋白和纤维连接蛋白表达的调控机制及其在V3整合素活化和肌肉增生、胶原生成及纤维化形成中的作用。第三个特异性目的是研究整合素βV和β3亚基表达的调节机制，以及整合素βV和β3在肌肉增生、胶原生成和纤维化中的作用。他们的完成将促进我们对炎症性肠炎中肠平滑肌增生、胶原产生、纤维化和狭窄形成的独特病理生理学的理解，并确定潜在的治疗策略，通过抑制V？3整合素和IGF-I受体来减少狭窄克罗恩病患者的狭窄形成。 公共卫生相关性：这项建议的目的是描述导致克罗恩病狭窄形成的内源性因素和相互依赖的信号通路，这些信号通路介导了导致克罗恩病狭窄形成的平滑肌增生、胶原生成和纤维化。该项目包括分析？V？3整合素及其配体在炎症过程中调节IGF-I依赖和IGF结合蛋白依赖的肌肉增生、胶原产生和纤维化的分子机制，并确定？V？3和IGF-I抑制剂在减少克罗恩病纤维化和狭窄形成中的适用性。

DESCRIPTION (provided by applicant): The overall hypotheses underlying this work are that IGF-I system, ?V?3 integrin and the ?V?3 integrin-binding ligands, vitronectin and fibronectin, regulate the smooth muscle hyperplasia, excess collagen production and fibrosis in the intestine that is central to stricture formation in Crohn's disease, and that selective IGF-I and ?V?3 inhibitors can be used to diminish muscle hyperplasia, fibrosis and stricture formation. Our studies during the current funding period have identified the mechanisms by which endogenous IGF-I, IGFBP-5, IGFBP-3 and ?V?3 integrin act jointly to regulate smooth muscle growth and collagen II production in normal intestinal muscle and excess muscle growth, collagen II production and fibrosis in Crohn's disease and in TNBS-induced colitis in mice. Occupancy of ?V?3 integrin by its ligands, vitronectin and fibronectin, regulates the intensity and duration of IGF-I-stimulated, IGF-I receptor activation and effects. Our recent work and preliminary results show that, like smooth muscle in stricturing Crohn's disease, smooth muscle of mice with TNBS-induced colitis have increased endogenous ?V?3 integrin ligands. The resulting activation of ?V?3 integrin jointly with upregulated endogenous IGF-I and IGF binding proteins are central mediators of smooth muscle cell hyperplasia, increased collagen II production and resulting fibrosis. Muscle hyperplasia, collagen II production, ?V?3 integrin-dependent effects and fibrosis can be decreased by pharmacologic blockade of ?V?3 integrin activation or of IGF-I receptor activation. The first specific aim is to identify the mechanisms regulating increased IGF-I and IGFBP-5 expression and their roles in the development of muscle hyperplasia, collagen production and fibrosis in stricturing Crohn's disease and chronic TNBS-induced colitis. The second specific aim is to characterize the mechanisms regulating ?V?3 integrin binding vitronectin and fibronectin expression and their function in ?V?3 integrin activation and development of muscle hyperplasia, collagen production and fibrosis in stricturing Crohn's disease and chronic TNBS- induced colitis. The third specific aim is to characterize the mechanisms regulating ?V and ?3 integrin subunit expression and the role of ?V?3 integrin activation in muscle hyperplasia, collagen production and fibrosis in stricturing Crohn's disease and chronic TNBS-induced colitis. Their completion will advance our understanding of the unique pathophysiology of intestinal smooth muscle hyperplasia, collagen production, fibrosis and stricture formation in the inflamed intestine and identify potential therapeutic strategies, via ?V?3 integrin and IGF-I receptor inhibition, to decrease stricture formation in patients with stricturing Crohn's disease. PUBLIC HEALTH RELEVANCE: The objective of this proposal is to characterize the endogenous factors and the interdependent signaling pathways that mediate smooth muscle hyperplasia, collagen production and fibrosis leading to stricture formation in Crohn's disease. The project involves analysis of the molecular mechanisms by which the ?V?3 integrin, and its ligands regulate IGF-I-dependent and IGF binding protein-dependent muscle hyperplasia, collagen production and fibrosis in the initiation and progression of stricture formation during inflammation and to determine the suitability of ?V?3 and IGF-I inhibitors to diminish fibrosis and stricture formation in Crohn's disease.