REGULATION OF FETAL HEPATIC DEVELOPMENT

对出生后生活的适应涉及肝脏的生长和功能 分化 这个子项目的基本假设是， 正常的和受干扰的肝细胞分化与 肝细胞增殖 该项目的前期工作表明， 胎鼠肝细胞具有增殖表型， 由旁分泌或自分泌的有丝分裂原发出信号。 而且这 “不依赖于促分裂原”的生长显示出在细胞间复杂的个体发生模式。 妊娠第17天和产后第一周结束时。 最 值得注意的是， 分娩前后24小时。 产后第四天以后， 肝细胞逐渐达到其静止、成熟状态。 本 该提案的重点是细胞周期机制，负责 这种模式。 诱导胎鼠肝细胞的培养系统 在体外静止超过96小时。 因此，我们建议 从细胞水平研究肝细胞增殖的调控 细胞周期依赖性蛋白激酶（CDKs），CDK阳性调节因子 （细胞周期蛋白）和CDK抑制剂（CKIs）。 这些成果将得到补充 通过对CDK、Cyclin和CKI在体内表达和调控的研究。 一 所提出的研究的主要目标是确定细胞间的 CKIs对细胞周期负调控与肝细胞的关系 分化 后者将使用 肝葡萄糖所需两种酶免疫细胞/组织化学 生产，葡萄糖-6-磷酸酶和PEPCK，以及其他肝细胞- 特定的标记。 我们的观察将扩展到一个动物模型， 胎儿生长受损，分娩前母体饥饿48小时， 在老鼠的术语。 特别是，胰岛素在调节这些 将研究来自IUGR胎儿的培养肝细胞中的过程 为了阐明宫内生长的肝脏病理生理学 迟钝

The adaptation to postnatal life involves liver growth and functional differentiation. The underlying hypothesis for this subproject is that normal and perturbed hepatocyte differentiation are co-regulated with hepatocyte proliferation. Previous work on this project has shown that fetal rat hepatocytes have a proliferative phenotype which is independent of signaling by paracrine or autocrine mitogens. Furthermore, this "mitogen-independent" growth shows a complex ontogenic pattern between the 17th day of gestation and the end of the first postnatal week. Most notably, there is a temporary cessation of proliferation for approximately 24 hr surrounding parturition. Beyond the fourth postnatal day, hepatocytes gradually attain their quiescent, adult state. The present proposal focuses on the cell cycle mechanisms which are responsible for this pattern. A culture system in which fetal rat hepatocytes are induced to quiesce in vitro over 96 hr has been developed. Thus, we propose to study regulation of hepatocyte proliferation in culture at the level of cell cycle-dependent protein kinases (CDKs), CDK positive regulators (Cyclins) and CDK inhibitors (CKIs). These results will be complemented by studies on CDK, Cyclin and CKI expression and regulation in vivo. A primary goal of the proposed studies is to determine the cell-to-cell relationship between negative cell cycle regulation by CKIs and hepatocyte differentiation. The latter will be assessed using immunocyto/histochemistry for two enzymes required for hepatic glucose production, glucose-6-phosphatase and PEPCK, as well as other hepatocyte- specific markers. Our observations will be extended to an animal model of impaired fetal growth, maternal starvation for 48 hr prior to delivery at term in the rat. In particular, the role of insulin in regulating these processes in cultured hepatocytes from IUGR fetuses will be investigated in order to elucidate the hepatic pathophysiology of intrauterine growth retardation.