CELL-KINETICS OF CONJUNCTIVAL AND CORNEAL EPITHELIUM DURING REGENERATION OF DIFFERENT-SIZED CORNEAL EPITHELIAL DEFECTS

Rats with small (diam. 1.7 mm), medium sized (diam. 3.5 mm) or large ( diam. 5.5 mm) corneal epithelial erosions in one eye were killed 1, 2 or 4 days after the injury. The proliferative response was evaluated b y measuring the labelling index and the mitotic rate in the corneal ep ithelium and in the adjacent conjunctiva. The small erosions triggered a proliferative response in the cornea only with the maximum response occurring midperipherally. The medium sized erosions induced a higher and more extensive response in the cornea and also a slight increase of the labelling index in the limbal area. The large erosions induced an even more pronounced response in the peripheral cornea and an incre ase both of the labelling index and the mitotic rate well beyond the l imbal part of the conjunctiva. It is concluded that the magnitude and the extent both of the conjunctival and the corneal regenerative respo nse to a corneal abrasion is correlated to the size of the corneal def ect. Temporary reduction in the conjunctival epithelial cell number sh ows that both cells in the limbal and the extralimbal conjunctiva migr ate centripetally during healing of large corneal wounds. It is sugges ted that the stem cell theory should be modified. The limbal area is p robably an area in which conjunctival epithelial cells or conjunctiva- derivated cells transform or differentiate to corneal epithelial cells .