Purpose: While transformation of epithelial cells to a motile form is the first step in wound healing of the corneal epithelium, the migratory mechanism in these cells is not fully understood. We studied the expression of proto-oncogene mRNAs: c-fos; c-jun; fos B; jun B; jun D in injured corneal epithelium using in situ hybridization. Moreover, we examined immunolocalization of c-Fos and c-Jun protein products to elucidate the transcriptional activation prior to the onset of migration in corneal epithelium.
Methods: An epithelial defect was made on one cornea of 60 Wistar rats. The affected eye was enucleated immediately (within 5 min) or was allowed to heal for 15, 30, 60, 90, 120 and 180 min. Frozen sections were processed for in situ hybridization with c-fos, c-jun, fos B, jun B and jun D mRNAs or were stained with anti-c-fos and anti-c-jun antibodies.
Results: Fifteen min after the epithelial ablation, weak signals for c-fos and c-jun mRNAs were detected in the corneal epithelium surrounding the wound. These signals reached a peak 30 to 60 min after ablation, but were no longer evident at 120 min. Immunoreactivities for these proteins were also detected in the same area at 60 to 120 min after the epithelial ablation. Fos B mRNA was detected in the same region at 30 min after the ablation, and reached its peak after 30 to 60 min, but was no longer evident at 120 min. Jun B mRNA was detected in the epithelium around the defect 60 min after the ablation, later than the other proto-oncogenes, and reached its peak after 90 min. The message for jun D was detected in normal epithelium, and was not affected by wounding.
Conclusions: These findings indicate that transcriptional activation of epithelial cells is initiated in the early phase after epithelial ablation, before the cells start to migrate, and that these proto-oncogene products may play important roles in wound healing in corneal epithelium. The time lag of the peak of expression of these proto-oncogenes in this process.