Astrocytes modulate retinal vasculogenesis : effects on fibronectin expression

• Published in: Journal of cell science Vol. 107; no. 9; pp. 2499 - 2508
• Main Authors: JIANG, B, LIOU, G. I, BEHZADIAN, M. A, CALDWELL, R. B
• Format: Journal Article
• Language: English
• Published: Cambridge Company of Biologists 01.09.1994
• Subjects: Animals; Animals, Newborn; Astrocytes - physiology; Biological and medical sciences; Cell Differentiation; Cell Movement; Cells, Cultured; Endothelium, Vascular - cytology; Endothelium, Vascular - metabolism; Extracellular Matrix - metabolism; Fibronectins - biosynthesis; Fibronectins - genetics; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Developmental; Isolated neuron and nerve. Neuroglia; Laminin - biosynthesis; Rats; Rats, Wistar; Retina - cytology; Retinal Vessels - cytology; Retinal Vessels - growth & development; Retinal Vessels - metabolism; RNA, Messenger - biosynthesis; RNA, Messenger - genetics; Stem Cells - cytology; Vertebrates: nervous system and sense organs; Endothelial cell; Rat; Rodentia; Retina; Neuroglía; Astrocyte; Gene expression; Fibronectin; Eye; Visual system; Vertebrata; Mammalia; Laminin
• ISSN: 0021-9533; 1477-9137
• 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.