Heat-shock protein 70 expression in the equine cornea

Objective: Expression of the 70-kDa heat-shock protein (HSP70) has been demonstrated in normal canine corneal epithelium, and inducible expression has been suggested to facilitate wound resolution through organized migration, proliferation, and adhesion of the corneal epithelial cells. Diminished expression of HSP70 may therefore contribute to prolonged healing in the pathologic cornea of other companion animal species, including the horse. Animal studied: Normal and pathologic equine cornea was evaluated to determine whether the expression of HSP70 is correlated with appropriate corneal epithelial wound healing. Procedures: Paraffin-embedded tissue from normal equine cornea and therapeutic keratectomies of sterile keratopathies was subject to routine immunohistochemistry for HSP70. Results: Normal equine corneas exhibited the baseline expression of HSP70 in the nuclei of all epithelial cells as well as the cytoplasm of the basal epithelium. Expression of HSP70 in suspected immune-mediated keratitis was localized to the cytoplasm of basal epithelial cells and nuclei of all epithelial cells, similar to the normal equine cornea. Expression in indolent ulcers was diminished; weak, diffuse staining was noted in the cytoplasm of all epithelial cells. Conclusions: These findings suggest the expression of HSP70 is induced in the normal equine cornea during re-epithelialization and may be altered in sterile keratopathies.