Apoptosis of the hyaloid artery in the rat eye.

The hyaloid artery is a vestigial vessel situated on the optic nerve extending to the posterior surface of the lens in the vitreous cavity of the eye. We studied the nature and pattern of cell death during regression of the hyaloid artery. The cells comprising the hyaloid artery appear to be alive for 20 days after birth in the rat, and cell death during regression of the hyaloid artery has the characteristics of apoptosis. We observed apoptotic bodies containing condensed chromatin and identified the hyaloid vessels as targets of macrophage-mediated remodelling. Using the "TUNEL method" for labeling fragmented DNA in vascular cells, we assessed the pattern of apoptotic cell death during hyaloid artery regression. Our study demonstrated the appearance of apoptosis in pericytes as well as endothelial cells during regression in the vasculature. In pericytes, apoptosis appeared to begin or to occur more frequently than in endothelial cells. Both morphological and TUNEL analyses indicated that capillary apoptosis occurs mainly from day 10 to day 20 after birth rather than from the 1st day. Macrophages were present near the hyaloid artery and these may influence apoptosis.