Growth and Function of Cultured Gastrointestinal Muscle

描述(由申请人提供)：这项工作的总体假设是，AV？3整合素及其配体纤维连接蛋白和玻璃体连接蛋白调节IGF-I在正常组织中刺激的生长，它们与炎症中IGF-I和Igfbp5的增加一起在启动平滑肌增生中起关键作用。人类肠道平滑肌的生长在一定程度上是通过内源性生长肽的相互作用来调节的。我们在前一个资助时期的研究已经确定了两种生长因子，IGF-I和IGFBP-5，它们共同作用于调节人类肠道平滑肌的生长。内源性IGF-I通过IGF-I受体刺激细胞增殖和抑制细胞凋亡。IGFBP-5促进IGF-I受体的激活。IGFBP-5还通过激活其自身的IGFBP-5受体来刺激肠平滑肌的生长。IGF-I和IGFBP-5之间刺激生长和彼此分泌的独特相互作用加强了它们对生长的单独影响，并可能导致肠道炎症引起的肌肉增生。初步结果表明，IGF-I刺激的IGF-I受体激活、肌肉生长和IGFBP-5的分泌受Av？3整合素调节，并可被Av？3整合素配体FN增强。我们发现纤维连接蛋白和玻璃体连接蛋白在发炎的肠肌中表达上调。因此，本研究的目的是确定整合素A3及其配体纤维连接蛋白和玻璃体连接蛋白调节IGF-I受体活性的机制，以及这些AV3配体以及IGF-I和IGF结合蛋白-5(IGFBP-5)表达增加在炎症过程中启动肌肉增生的意义。 第一个特异性目的是研究Av？3整合素信号通路对IGF-I刺激的IGF-I受体磷酸化的调节作用。第二个目的是研究IGF-I刺激的肌肉细胞增殖的调节，IGFBP-5的上调，以及内源性AV？3整合素配体对细胞凋亡的抑制。第三个特定的目的是确定上调的整合素配体在启动IGF-I刺激的炎症性肠平滑肌生长中的作用。每个具体目标都得到大量初步研究的支持。它们的完成应该会促进我们对正常肌肉中平滑肌生长的调节以及在炎症背景下启动平滑肌增生的关键机制的理解。

DESCRIPTION (provided by applicant): The overall hypotheses underlying this work are that aV¿3 integrin and its ligands, fibronectin and vitronectin, regulate IGF-I stimulated growth in normal tissue, and that their increased production together with IGF-I and IGFBP5 in inflammation are crucial in initiating smooth muscle hyperplasia. Growth of human intestinal smooth muscle is regulated in part through the interplay of endogenous growth peptides. Our studies during the previous funding period have identified two growth factors, IGF-I and IGFBP-5, which act in concert to regulate human intestinal smooth muscle growth. Endogenous IGF-I stimulates proliferation and inhibits apoptosis via the IGF-I receptor. IGFBP-5 facilitates activation of the IGF-I receptor by IGF-I. IGFBP-5 also stimulates growth of intestinal smooth muscle by activating its own IGFBP- 5 receptor. A unique interaction between IGF-I and IGFBP-5 to stimulate growth and each others' secretion reinforces their individual effects on growth and may contribute to the muscle hyperplasia resulting from intestinal inflammation. Preliminary results showed that IGF-I receptor activation, muscle growth and IGFBP-5 secretion stimulated by IGF-I were regulated by the aV¿3 integrin and could be augmented by the aV¿3 integrin ligand, fibronectin. We showed that fibronectin and vitronectin are upregulated in inflamed intestinal muscle. The objective of this proposal therefore is to determine the mechanisms by which the aV¿3 integrin and its ligands, fibronectin and vitronectin, regulate IGF-I receptor activity and the significance of increased expression of these aV¿3 ligands as well as IGF-I and IGF binding protein-5 (IGFBP-5) in initiating muscle hyperplasia during inflammation. The first specific aim is to characterize the regulation of IGF-I-stimulated IGF-I receptor phosphorylation by aV¿3 integrin signaling pathways in intestinal smooth muscle cells. The second aim is to examine the regulation of IGF-I-stimulated muscle cell proliferation, upregulation of IGFBP-5; and inhibition of apoptosis by endogenous aV¿3 integrin ligands. The third specific aim is to identify the role of upregulated aV¿3 integrin ligands in initiating altered IGF-I-stimulated growth in inflamed intestinal smooth muscle. Each specific aim is supported by substantial preliminary studies. Their completion should advance our understanding of the regulation of smooth muscle growth in normal muscle and mechanisms crucial to initiating smooth muscle hyperplasia in the setting of inflammation.