Pericytes in Pathogenesis of Germinal-Matrix Hemorrhage

描述(申请人提供)：生发基质出血(GMH)是早产儿的主要问题，因为大量早产儿会发展为脑瘫、脑积水和智力低下。血脑屏障的组成部分可能有助于脑血管的稳定，包括内皮紧密连接、星形胶质细胞末端足部和毛细血管周细胞。由于周细胞为血管提供了结构完整性，并且我们的初步数据表明，在易患GMH的早产儿中，会发育紧密连接分子和星形胶质细胞终足，因此我们假设：1)与大脑皮层和白质相比，生发基质血管中的周细胞减少；2)在血管生成过程中，招募周细胞的生长因子包括血管生成素、血小板衍生生长因子-B和转化生长因子-β(TGF-β)及其受体在生发基质中的表达较脑其他区域减少。由于产前糖皮质激素可降低GMH的发生率，并调节这些生长因子在脑以外器官血管中的表达，我们还认为糖皮质激素治疗通过调节生长因子血管生成素、PDGF-B和转化生长因子-β及其受体的表达来增加周细胞在生发基质中的募集。我们将用免疫组织化学和原位杂交的方法检测血管生成素、PDGF-B、转化生长因子-β及其受体Tie-1、-2、PDGFR-β、ALK-1和-5在人胎儿和早产儿(16-40周)额叶皮质和白质生发基质中的表达。此外，我们还将使用电子显微镜对周细胞进行量化。我们将评估糖皮质激素对周细胞的影响，以及招募周细胞及其各自受体的生长因子在产前暴露和未暴露于糖皮质激素的早产儿中的作用。我们还将检查糖皮质激素在新生兔模型中的作用，以消除早产儿存在的混杂变量。我们的数据可能有助于理解GMH的病因，并可能解释产前糖皮质激素治疗的基础。它还可能确定预防和治疗GMH的新战略。

DESCRIPTION (provided by applicant): Germinal matrix hemorrhage (GMH) is a major problem of premature infants because a large number of these babies develop cerebral palsy, hydrocephalus and mental retardation. Components of the blood brain barrier, which potentially contribute to the stabilization of cerebral vessels, include endothelial tight junctions, astrocyte end-feet and capillary pericytes. Since pericytes provide structural integrity to blood vessels and since our preliminary data suggest that tight junction molecules and coverage of astrocyte end-feet are developed in premature infants vulnerable to GMH, we hypothesize that 1) pericytes are decreased in germinal matrix vasculature compared to cerebral cortex and white matter and that 2) the expression of growth factors recruiting pericytes during angiogenesis including angiopoetins, platelet derived growth factor-B (PDGF-B) and transforming growth factor-beta (TGF-beta) and their receptors are decreased in germinal matrix compared to the other areas of the brain. Since prenatal glucocorticoids decrease the incidence of GMH as well as modulate the expression of these growth factors in blood vessels of organs other than the brain, we also propose that glucocorticoid treatment increases the recruitment of pericytes in germinal matrix by modulating the expression of growth factors angiopoietin, PDGF-B and TGF-beta and their receptors. We will determine the expression of angiopoietin, PDGF-B, TGF-beta and their respective receptors Tie-1, -2, PDGFR-beta, ALK-1 and -5 in the germinal matrix compared to cortex and white matter of the frontal lobe in human fetuses and premature infants (16-40 weeks) using immunohistochemistry and in-situ hybridization. In addition we will quantify pericytes using electron microscopy. We will assess the effect of glucocorticoids on pericytes and the growth factors recruiting pericytes as well as their respective receptors in preterm infants exposed and not exposed to prenatal glucocorticoids. We will also examine the effect of glucocorticoids in a neonatal rabbit model to eliminate confounding variables present in premature infants. Our data may help in understanding the etiology of GMH and may explain the basis of prenatal glucocorticoid therapy. It may also identify new strategies in the prevention and treatment of GMH.