Establishment of an In Vitro Model of "Blood Brain Barrier" and an Attempt with it to Develop a Brain-Specific Transport Vector

(1)在本研究中，我们建立了体外“血脑屏障”模型。在血管内皮细胞、周细胞和星形胶质细胞共培养系统中，重建了选择性的屏障和转运活动，通过了多阳离子白蛋白，但在生理极性上排除了天然白蛋白或菊粉。这个模型似乎在筛选可能对中枢神经系统起作用的物质和评估它们进入大脑的输送方面很有用。本研究还证实星形胶质细胞具有将非脑型内皮细胞“转分化”为脑型内皮细胞的能力：与星形胶质细胞共培养的人脐静脉内皮细胞表达了脑内皮特异性基因，包括γ -转谷氨酰转肽酶基因、转铁蛋白受体基因和p -糖蛋白基因，并具有抗菊粉屏障特性。尽管我们未能开发出脑特异性运输载体，但新的发现(2)晚期糖基化终产物通过与细胞表面受体的相互作用选择性地损伤周细胞，(3)内皮细胞和血管平滑肌细胞具有合成和响应醛固酮的装置，醛固酮是一种涉及血压调节的类固醇，(4)在本研究过程中，我们发现了缺氧诱导血管细胞在自分泌血管内皮生长因子介导下的增殖，从而提出了糖尿病微血管病、高血压和血管生成等多种人类血管疾病发生发展的新机制。

(1) In the present study, we have established an in vitro model of "blood brain barrier". With vascular endothelial cell, pericyte and astroglial cell co-culture systems, the barrier as well as transport activities selective to brain vessels were reconstituted, which passed polycationic albumin but excluded native albumin or inulin in the physiological polarity. This model would seem to be useful in screeeing substances that could act on the central nervous system and in evaluating their delivery into the brain. The present study has also demonstrated that astroglial cells are capable of "transdifferentiating "non-brain-type endothelial cells into brain-type ones : human umbilical vein endothelial cells co-cultured with astroglial cells did express the brain endothelium-specific genes, including those for gamma-transglutamyl transpeptidase, transferrin receptor and P-glycoprotein, and aquired the anti-inulin barrier propert. Although we failed to develop brain-specific transport vectors, new discoveries (2) that advanced glycation endproducts selectively injure pericytes through interactions with their cell-surface receptors, (3) that endothelial cells and vascular smooth muscle cells possess the devices both for synthesizing and for responding to aldosterone, a steroid implicated in the regulation of blood pressure, and (4) that hypoxia-induced proliferation of vascular cells in mediated by autocrine vascular endothelial growth factor, were made during the course of this study, and we have thus proposed novel mechanisms underlying the development and progression of various human vascular disorders including diabetic microangiopathy, hypertension and angiogenesis.