Steroid inhibition of limbal blood and lymphatic vascular cell growth.

Steroids are widely used in the prevention of corneal neovascularization in a wide range of natural and experimental situations. However, no information is available on their effect on the growth of the individual limbal blood vascular cells or of lymphatic cells involved in corneal neovascularization. In addition, tritiated thymidine labelling index is commonly used as an indicator of cell population but doubt exists as to whether it truly represents cell growth. Remote thermal cautery of the rat cornea was used to elicit corneal neovascularization. New cell growth was measured by tritiated thymidine uptake and by the number of cell nuclei per section. Cells investigated were the arteriolar, venular, capillary and lymphatic endothelial cells as well as the arteriolar and venular perivascular cells. A total of 89,320 blood vascular endothelial and perivascular cell nuclei and 12,075 lymphatic nuclei were counted. Thermal cautery elicited a significant increase in labelling index and cell population of all limbal vascular cell types. Steroid application elicited a significant short term inhibition or delay for all six cell types although this was not apparent for venular endothelial cells using labelling index as a growth indicator. At six days only the lymphatic endothelial cell population showed a significant (p < 0.001) increase associated with steroid use.