INTESTINAL ADAPTATION--ROLE OF HORMONES & GROWTH FACTORS

描述：这份修订后的申请侧重于角色和机制 胰岛素样生长因子(IGF-I)及其结合蛋白(IGFBPs)的表达 肠道适应。系统生长激素(GH)和IGF-I促进 以内分泌的方式进行肠道适应。IGF-I介导了许多 生长激素在肠道中的作用。生长激素和胰岛素样生长因子-I治疗慢性粒细胞白血病的临床研究 短肠综合征和其他肠道疾病正在进展中。然而，在那里 几乎没有关于细胞内机制的直接信息 IGF-I在肠道中的作用。小肠粘膜生长的适应性变化 与局部表达的IGF-I水平相关，表明旁分泌或 IGF-I在肠道中的自分泌作用。生长激素增加局部IGF-I的表达 在小肠内。局部表达的胰岛素样生长因子-I在适应性生长中的作用 对小肠粘膜的定义不明确。此信息对以下方面至关重要 了解与系统性IGF-I比较的治疗的相对益处 肠道疾病患者合并生长激素。以及IGF-I，粘膜 间充质细胞表达三种IGFBPs：IGFBP3、IGFBP4和Igfbp5。本地 在肠粘膜的适应性生长过程中，IGFBPs的表达发生变化。这个 局部表达的IGF-I对粘膜生长的作用可能依赖于 IGF-I是否分泌到细胞外液中，是否分泌 IGF-I与分泌的IGFBPs相关，以及IGF-I是否被隔离在 细胞表面或细胞外基质通过与IGFBPs的相互作用。 特定目标1将使用SMP-IGF-I转基因小鼠来验证这一假设 间充质细胞来源的IGF-I改变大鼠肠道的生长和功能 活着。SMP-IGF-I和WT小鼠的小肠粘膜将进行比较 肿块、隐窝细胞增殖、细胞凋亡和刷状缘酶活性 确定局部表达的间充质细胞来源的IGF-I在 调节粘膜生长和功能。特定目标2将使用IRS-1 NULL 小鼠和IRS-1 Null/SMP-IGF-I杂交以检验以下假设 IRS-1介导IGF-I对肠道的细胞特异性营养作用。特定的 目标3将检验IGFS/IGFBPs表达差异的假设 调节两种肠道成纤维细胞亚型和/或表型的差异 它们对肠道生长和分化的不同影响 上皮组织。对于这些研究，共培养系统具有两个表型 不同的肠道成纤维细胞亚型优先介导 肠道的增殖(A1：F1细胞)或分化(F1：G9细胞) 内胚层。特定目标4将获得带有α-SM-肌动蛋白的转基因小鼠 启动子(SMP)介导的胰岛素样生长因子类似物DES-IGF-I的过表达 对IGFBPs的亲和力较低，以检验IGFBPs调节的假设 IGF-I在活体肠道的细胞特异性自分泌/旁分泌作用。

DESCRIPTION: This revised application focuses on the roles and mechanisms of Insulin-like growth factor (IGF-I) and IGF binding proteins (IGFBPs) in intestinal adaptation. Systemic growth hormone (GH) and IGF-I promote intestinal adaptation in an endocrine manner. IGF-I mediates many of the actions of GH in bowel. Clinical trials of GH and IGF-I as therapy for short bowel syndrome and other bowel diseases are in progress. Yet, there is virtually no direct information about the intracellular mechanisms of IGF-I action in bowel. Adaptive changes in growth of small bowel mucosa correlate with levels of locally expressed IGF-I indicating paracrine or autocrine effects of IGF-I in bowel. GH increases local expression of IGF-I within small bowel. The role of locally expressed IGF-I in adaptive growth of the small bowel mucosa is not defined. This information is critical for understanding the relative benefits of therapy with systemic IGF-I compared with GH in patients with bowel disease. As well as IGF-I, mucosal mesenchymal cells express three IGFBPs, IGFBP3, IGFBP4 and IGFBP5. Local expression of IGFBPs is altered during adaptive growth of bowel mucosa. The actions of locally expressed IGF-I on mucosal growth likely depend on whether IGF-I is secreted into the extracellular fluid, whether secreted IGF-I associates with secreted IGFBPs and whether IGF-I is sequestered onto the cell surface or extracellular matrix via interactions with IGFBPs. Specific aim 1 will use SMP- IGF-I transgenic mice to test the hypothesis that mesenchymal cell derived IGF-I alters growth and function of bowel in vivo. Small bowel of SMP- IGF-I and WT mice will be compared for mucosal mass, crypt cell proliferation, apoptosis and brush border enzyme activities to define the role of locally expressed, mesenchymal cell derived IGF-I in regulating mucosal growth and function. Specific aim 2 will use IRS-1 null mice and IRS-1 null/SMP- IGF-I crossbreeds tot test the hypothesis that IRS-1 mediates cell specific, trophic actions of IGF-I on bowel. Specific aim 3 will test the hypothesis that differences in expression of IGFs/IGFBPs mediate phenotypic differences in two intestinal fibroblast subtypes and/or their distinct effects on growth and differentiation of intestinal epithelium. For these studies the co-culture system with two phenotypically distinct intestinal fibroblast subtypes that preferentially mediate proliferation (A1:F1 cells) or differentiation (F1:G9 cells) of intestinal endoderm. Specific aim 4 will derive transgenic mice with alpha-SM-actin promoter (SMP) mediated over-expression of des-IGF-I, an analog of IGF-I with low affinity for IGFBPs, to test the hypothesis that IGFBPs modulate the cell specific autocrine/paracrine actions of IGF-I in bowel in vivo.