Intestinal adaptation and epidermal growth factor

描述(由申请人提供)：在大量小肠切除(SBR)后，剩余的肠道通过一个称为适应的关键过程进行补偿。适应在很大程度上是促进肠细胞增殖的有丝分裂信号，从而产生更高的绒毛，以及更大的肠道口径和长度。虽然目前还不清楚切除诱导肠上皮细胞增殖的机制，但我们已经确定表皮生长因子受体(EGFR)信号转导是至关重要的。使用p21waf1/cip1缺失的小鼠，我们确定在没有这种细胞周期蛋白依赖的激酶抑制剂的情况下，SBR后增殖被矛盾地消除。作为这些观察的延伸，我们提出了全球假说，即EGFR信号调节p21的表达，以启动SBR后肠细胞的增殖。为了验证这一假说，我们的目的是：1)描述SBR和EGFR操作对肠道p21表达的影响。激光捕获显微解剖(LCM)显微镜将被用来建立SBR后隐窝绒毛轴上p21mRNA和蛋白的时间、区域和肠道细胞特异性表达。体内和体外的适应模型都将在EGFR刺激和抑制的条件下进行研究。2)确定EGFR对p21的调控机制。为了验证EGFR通过STAT调控p21表达的假设，我们将在体内和体外阐明SBR后STAT的表达和激活。然后，我们将描绘在STAT抑制后的体外适应过程中和在STATL缺失小鼠体内的p21表达。3)确定p21基因缺失小鼠切除后增殖受阻的机制。这一目标将检验这样一种假设，即p21基因缺失的小鼠由于p27kip1表达的代偿性增加而阻止了切除后的增殖。在p21基因缺失的小鼠中，将确定p27表达的时间和细胞间隔分布。然后将阐明p27缺失和p21/p27双缺失小鼠的适应程度。这些研究将大大有助于加强对参与适应调节的关键早期信号通路的理解。这些信息对安全有效的临床治疗的未来发展是基本的，旨在扩大这一重要过程。

DESCRIPTION (provided by applicant): After massive small bowel resection (SBR), the remaining intestine compensates by a critical process termed adaptation. Adaptation is largely a mitogenic signal for increased enterocyte proliferation, thus generating taller villi, and greater bowel caliber and length. While the mechanism for resection-induced enterocyte proliferation is presently unknown, we have established that epidermal growth factor receptor (EGFR) signaling is critical. Using p21waf1/cip1-null mice, we determined that proliferation was paradoxically abolished after SBR in the absence of this cyclin dependent kinase inhibitor. As an extension of these observations, we propose the global hypothesis that EGFR signaling regulates the expression of p21 to initiate enterocyte proliferation after SBR. To test this hypothesis, our aims are: 1) Delineate the effects of SBR and EGFR manipulations on intestinal p21 expression. Laser capture microdissection (LCM) microscopy wilt be employed to establish a temporal, regional, and enterocyte-specific expression of p21 mRNA and protein along the crypt-villus axis after SBR. Both in vivo and in vitro models of adaptation will be studied under conditions of EGFR stimulation and inhibition. 2) Determine the mechanism for EGFR regulation of p21. To test the hypothesis that EGFR governs p21 expression via STAT, we will elucidate STAT expression and activation after SBR in vivo and in vitro. We will then delineate p21 expression during adaptation in vitro after inhibition of STAT and in vivo in STATl-null mice. 3) Determine the mechanism for blocked postresection proliferation in p21-null mice. This aim will test the hypothesis that postresection proliferation is prevented in p21-null mice because of compensatory increased expression of p27kip1. A temporal and cell compartment profile of P27 expression will be determined in p21-null mice. The magnitude of adaptation will then be elucidated in p27-null and p21/p27 double-null mice. These studies will contribute substantially toward an enhanced understanding of critical early signaling pathways involved in the regulation of adaptation. This information is fundamental toward the future development of safe and effective clinical therapy designed to amplify this important process.