Jiang B, Liou G I, Behzadian M A, Caldwell R B
Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta 30912-2000.
J Cell Sci. 1994 Sep;107 ( Pt 9):2499-508. doi: 10.1242/jcs.107.9.2499.
Vasculogenesis is the formation of blood-vessels by differentiation of vascular precursor cells. Experiments using retinal models were designed to test the hypothesis that astrocytes influence this process by effects on the composition of the extracellular matrix. Retinal vasculogenesis was studied in relation to the migration of astrocytes and expression of the extracellular matrix proteins laminin and fibronectin by in vivo experiments in neonatal rats. The results show that astrocytes spread into the retina just ahead of the newly formed vessels, where they probably initiate vasculogenesis. They also establish that fibronectin, but not laminin, is expressed in the zone of vasculogenesis immediately prior to vessel formation. Increased amounts of fibronectin mRNA indicate that fibronectin is synthesized by cells within this same region during this same time period. Later, as the new vessels form, differentiation of endothelial cells is correlated with the appearance of pericytes in the vessel wall and laminin in the vascular basement membrane. In vitro experiments using conditioned medium approaches showed that astrocytes stimulate endothelial cell fibronectin expression. Taken together with the in vivo observations these in vitro results suggest that fibronectin expression is an essential component in the initiation of retinal vasculogenesis. This study is the first indication that astrocytes influence the fibronectin component of the extracellular matrix during retinal vasculogenesis and that expression of fibronectin precedes that of laminin in this process.
血管生成是指血管前体细胞分化形成血管的过程。利用视网膜模型进行的实验旨在验证以下假说：星形胶质细胞通过影响细胞外基质的组成来影响这一过程。通过对新生大鼠进行体内实验，研究了视网膜血管生成与星形胶质细胞迁移以及细胞外基质蛋白层粘连蛋白和纤连蛋白表达之间的关系。结果表明，星形胶质细胞在新形成的血管前方扩散到视网膜中，它们可能在那里启动血管生成。研究还证实，在血管形成前的血管生成区域表达的是纤连蛋白，而非层粘连蛋白。纤连蛋白mRNA含量的增加表明，同一区域的细胞在同一时期合成了纤连蛋白。后来，随着新血管的形成，内皮细胞的分化与血管壁中周细胞的出现以及血管基底膜中层粘连蛋白的出现相关。使用条件培养基方法进行的体外实验表明，星形胶质细胞可刺激内皮细胞纤连蛋白的表达。结合体内观察结果，这些体外实验结果表明，纤连蛋白的表达是视网膜血管生成起始过程中的一个重要组成部分。这项研究首次表明，星形胶质细胞在视网膜血管生成过程中会影响细胞外基质的纤连蛋白成分，且在此过程中纤连蛋白的表达先于层粘连蛋白。
