Abstract
Purpose: :
Dstncorn1 mice spontaneously develop epithelial defects and vascularization in the cornea and serve as a valuable model of corneal disorders. We have shown previously that epithelial stem cells may be distributed uniformly in the Dstncorn1 cornea, obliterating the importance of the limbus as the source of corneal epithelial stem cells. This study was initiated to determine whether epithelial cells in the Dstncorn1 limbus lost all features of normal limbal cells, by examining epithelial wound healing and limbal reactions to it.
Methods: :
Epithelial wound healing, both in the limbus and in the central cornea, was studied with Dstncorn1 mice and their age-matched normal control, AJ mice. A circular epithelial injury of about 1 mm was created by mechanical scraping, and the injury was allowed to heal naturally. The limbal injury included an equal size of the corneal and the conjunctival epithelium. Healing rates were determined with in vivo microscopy, measuring wound areas revealed by fluorescein staining. Mitotic rates were determined by labeling the animal with systemic 5-ethynyl-2'-deoxyuridine for 24 hours with an osmotic pump, followed by flat whole-mount histology.
Results: :
Wound healing of both the limbal and the central corneal injuries exhibited a lag of several hours followed by a biphasic kinetics - an initial fast healing phase and a following slow healing phase to a complete wound closure. Healing of central corneal injuries was faster in AJ than in Dstncorn1. In the limbal injury, the corneal half healed at a rate similar to that of a central corneal injury, which was much faster than the healing of the conjunctival half, in both Dstncorn1 and AJ. Rates of mitosis in an untouched Dstncorn1 cornea varied greatly depending on the location within the cornea - such as whether cells were in the hyperplastic zone or not, but they were generally higher than the rates in an AJ cornea. Mitotic rates in the limbal epithelium were also higher in Dstncorn1 than in AJ. Upon central corneal injury, limbal mitotic rates increased in both Dstncorn1 and AJ. Changes of mitotic rates in the vicinity of the injury was not substantial in both Dstncorn1 and AJ. There was no DNA synthesis inside the injury zone during a 24-hr period after a complete closure of a wound.
Keywords: cornea: epithelium • wound healing • immunohistochemistry