The effect of corneal epithelial cells on the collagen gel contraction by keratocytes

To understand the mechanism of the contraction of cicatricial tissues after corneal stromal wounding, we investigated the effect of corneal epithelial cells on the collagen gel contraction by keratocytes. Subcultured rabbit keratocytes were embedded in type I collagen gel and cultured. Rabbit corneal epithelial cells were cultured separately and the culture medium was collected and used as an epithelial cell-conditioned medium (ECCM). The collagen gel contraction by keratocytes was determined by measuring the diameters of the collagen disks once a day for 5 days. In the presence of fetal calf serum, the diameter of the collagen gel decreased in linear proportion to the number of keratocytes, but in inverse proportion to the concentration of collagen. The addition of the ECCM enhanced the collagen gel contraction by keratocytes in a dose-dependent manner. This stimulatory activity was found in the ECCM obtained from 3- to 7-day cultures of epithelial cells. These findings suggest that corneal epithelial cells secrete factor(s) that stimulate the collagen gel contraction by keratocytes.