The chicken cornea as a model of wound healing and neuronal re-innervation

The cornea is the major refractive component of the eye and serves as a barrier to the external environment. Understanding how the cornea responds to injury is important to developing therapies to treat vision disorders that affect the integrity and refractive properties of the cornea. Thus, investigation of the wound healing responses of the cornea to injury in a cost-effective animal model is a valuable tool for research. This study characterizes the wound healing responses in the corneas of White Leghorn chicken. Linear corneal wounds were induced in post-natal day 7 (P7) chicks and cellular proliferation, apoptosis and regulation of structural proteins were assessed using immunohistochemical techniques. We describe the time course of increased expression of different scar-related markers, including vimentin, vinculin, perlecan and smooth muscle actin. We find evidence for acute necrotic cell death in the corneal region immediately surrounding cite of incision, whereas we failed to find evidence of delayed cell death or apoptosis. We find that the neuronal re-innervation of SV2-positive axon terminals within the corneal stroma and epithelium occurs very quickly after the initial scarring insult. We describe an accumulation of cells within the stroma immediately underlying the scar, which results, at least in part, from the local proliferation of keratocytes. Further, we provide evidence for scar-induced accumulations of CD45-positive monocytes in injured corneas. We conclude that the chick cornea is an excellent model system in which to study wound healing, formation of scar tissue, and neuronal re-innervation of sensory endings.