Trigeminal ganglion neurons affect corneal epithelial phenotype. Influence on type VII collagen expression in vitro.

PURPOSE To examine whether trigeminal ganglion (TG) neurons in tissue culture influence expression of Type VII collagen (a major component of the anchoring fibrils involved in the attachment of the epithelium to the underlying stroma) by cultured corneal epithelial cells. METHODS A two-chambered coculture system was used. Fetal rabbit TG neurons were cultured into a central chamber on collagen- or laminin-coated tissue culture dishes. After good neurite outgrowth (average 7 days), rabbit corneal epithelial explants were placed into the outer chamber. Once neurite-epithelial cell interaction occurred, the cultures were immunostained for Type VII collagen. Direct coculture of TG neurons onto confluent passaged rabbit corneal epithelium also was studied. RESULTS Neurites in contact with the epithelial cells in the outer chamber formed branching complexes, but staining for Type VII collagen was negative. In cocultures of TG neurons onto confluent passaged rabbit corneal epithelium, there was extensive neurite branching on and around the epithelial cells within a week. Scattered epithelial cells, many in clusters, were found to express Type VII collagen, as determined by immunofluorescence staining. CONCLUSIONS Based on the finding from this study that TG neurons influence production of Type VII collagen by rabbit corneal epithelium in vitro, it is likely that TG neurons influence corneal epithelial phenotypic characteristics that are critical to the maintenance of healthy epithelium in vivo.