Cell kinetics of normal and healing rat corneal epithelium during organ culture.

Local epithelial proliferation in corneal, limbal, and conjunctival rat epithelium was investigated during organ culture of corneo-scleral shells, by relating the number of tritium labelled cells to the total number of cells (labelling index). The changes in labelling index after a mechanically induced central corneal abrasion were also studied. Local labelling indices were measured 2 h, 1, 2, 4 and 7 days after incubation. The average labelling index increased in un-abraded specimens 4-fold after 4 days of incubation, while the total number of cells only decreased 30-50%. In eyes with a central corneal abrasion the labelling index increased 10-fold in the surrounding epithelial cells after 1 day. The labelling index of the limbal and conjunctival epithelial cells increased to the same extent after 2 days of incubation. The finding of a reduced total number of cells and an increased cell proliferation in un-abraded eyes may be explained by increased loss of mature cells normally producing growth-inhibitory substances (chalones). Alternatively, the culture medium may contain an excess of growth-stimulatory substances. The results also suggest that the proliferative response spreads in a centrifugal direction during in vitro healing of a central corneal abrasion.