Keratinocyte growth factor-2 on the proliferation of corneal epithelial stem cells in rabbit alkali burned cornea.

PURPOSE

To determine whether the topical application of keratinocyte growth factor-2 (KGF-2) can enhance corneal epithelial healing in rabbit alkali burned cornea. In addition, the distribution and proliferation of corneal epithelial stem cells in KGF-2-treated and control corneas were investigated to explain their mechanisms of effects on the epithelium.

METHODS

Twenty-four New Zealand eyes were divided into four groups, treated with KGF-2 solution (1, 50, 100 microg/ml) and PBS solution. Eighth millimeter filter paper discs, produced by standard paper punch, were soaked for 15 sec in 0.5N NaOH solution. The alkali-soaked discs were applied to the central cornea, centered on the pupil and held gently in position with forceps for 1 min. The cornea was finally irrigated over 1 mm with 100 ml balanced salt solution (BSS). Keratinocyte growth factor-2 was then applied topically three times a day. The phosphate-buffered saline (PBS) group was served as a control. Each corneal epithelial defect was subsequently photographed every 24 hours with a slit lamp and was measured by computer-assisted digitizer. In each group, two rabbits were sacrificed for light microscopic examination after the interval of 7, 14 and 21 days. Meanwhile, the cornea epithelium was examined hy immunohistochemistry for P63, AE5, EGFR.

RESULTS

Topical application of 10 microg/ml to 100 microg/ml KGF-2 significantly accelerated corneal epithelial wound healing when compared with controls. After 24 hours, epithelial healing rate of the 100 microg/ml KGF-2 group and the PBS treated group was (74 +/- 6)% and (40 +/- 8)% (P < 0.05). After 48 hours, the rate of the C group was (94 +/- 6)%, whereas in the control group it was (73 +/- 12)% (P < 0.05). Epithelial defects were often recurrent, which happened only two times in the 100 microg/ml KGF-2-treated group, but many times in the control group. In the corneal epithelial stem cell analysis, the number of the P63 positive cells was higher in the KGF-2-treated