ROCK Inhibitor Enhances Neurite Outgrowth In Vitro and Corneal Sensory Nerve Reinnervation In Vivo

PURPOSE . The intraepithelial corneal nerves are essential to corneal health. Rho kinase or ROCK inhibitors (RIs) have been reported to play a role in neuron survival after injury. Here we assess integrin and extracellular matrix expression in primary mouse neurons and determine whether treating cells with RI impacts neurite outgrowth in vitro and reinnervation after trephine and debridement injury in mice in vivo. METHODS . Cocultures of human corneal limbal epithelial cells and E11.5 mouse trigeminal neurons and neurons alone were grown on glass coverslips. High-resolution imaging was performed to localize integrins and laminin on neurons and to determine whether RI impacts neurite outgrowth in vitro and in vivo after both 1.5-mm trephine and 1.5-mm debridement injuries. R ESULTS . Several integrin alpha (alpha 3, alpha 6, alpha v) chains as well as 9 4 integrin are expressed on neuron axons and growth cones in cocultures. RI treatment of isolated neurons, cocultures, and in conditioned media increases neurite outgrowth. In vivo, RI positively impacts sensory nerve reinnervation after trephine and debridement injury. C ONCLUSIONS . These studies are the first to demonstrate expression of 9 4 integrin on trigeminal sensory neurons and preferential adhesion of neurons to the laminin-enriched matrices found in footprints deposited by human corneal limbal epithelial cells. In addition, we also document for the first time the positive impact of RI on neurite outgrowth in vitro and reinnervation in vivo.