A Possible Function of ß– and –Crystallins in Vascular Remodeling

Abstract

Abstract: : Purpose: To demonstrate a possible role of ß– and γ–crystallins in vascular remodeling in the Nuc1 spontaneous mutant rat, in which the embryonic vasculature of the eye fails to regress normally, and which is accompanied by abnormal remodeling of the retinal vasculature during development, and to compare this anomaly in Nuc1 with human PFV (persistent fetal vasculature) disease. Methods: Sections through the optic nerve head were stained with standard H&E or PAS. VEGF, GFAP, and ß– and γ–crystallins were detected and localized by immunofluorescence. Real–time RT–PCR and metabolic labeling were used to determine crystallin expression. Whole isolated retinas of Nuc1 homozygous and wild–type rats at different stages of post–natal development were flat–mounted and observed under immunofluorescence microscopy after cardiac injection of FITC–conjugated dextran. 3–Nitropropionic acid (3–NP) was used to investigate the effects of hypoxia on crystallin and VEGF expression in a human astrocyte cell line. Results: Normal regression of the hyaloid vascular system was inhibited in the Nuc1 mutant rat. Real–time RT–PCR analysis and metabolic labeling confirmed our microarray data, indicating increased ß–and γ–crystallin expression in the retina of Nuc1 homozygous rats. Immunofluorescence with specific antibodies localized the increased expression of crystallins and VEGF predominantly to the GFAP–positive astrocytes associated with the intraocular vessels. A similar pattern was also observed in the retained hyaloid vasculature of human PFV patients. Cultured human astrocytes exposed to 3–NP, an established model of neuronal hypoxia, increased VEGF expression, as expected, but also increased expression of ß– and γ–crystallins. Conclusions: These data for the first time suggest that crystallins are involved in mediating vascular maturation and that they may function together with VEGF during vascular remodeling. Interestingly, in human PFV disease, astrocytes express both VEGF and crystallins, as in the Nuc1 mutant rat.

Keywords: crystallins • vascular cells • astrocytes: optic nerve head