153. Exploring NGF Mechanisms in Innervation-dependent Corneal Healing: Novel Therapies for Neurotrophic Keratopathy

PURPOSE: Understanding NGF-driven corneal healing and its therapeutic potential in Neurotrophic Keratopathy.Corneal clarity is vital for vision, maintained by limbal stem cells (LSCs) at the corneal-conjunctival interface. These cells interact with corneal sensory nerves which release trophic factors, including nerve growth factor (NGF), essential for epithelial renewal. Pathological denervation leads to neurotrophic keratopathy (NK), a major cause of corneal blindness without a definitive cure. NGF, the only FDA-approved treatment for NK, is expensive, requires frequent dosing, and is ineffective in 30% of cases. Prior studies show NGF stimulates LSC proliferation but haven’t linked NGF signaling with corneal sensory innervation-mediated epithelial renewal. We hypothesize that NGF, locally expressed in its mature and premature (proNGF) forms, regulates LSC activity-dependent homeostatic and wound-induced corneal epithelial renewal via differential activation of its receptors TrkA and p75NTR, a process dependent on corneal sensory innervation. METHODS: A) We conducted in vivo experiments in wild-type and mutant mice and rats to elucidate the NGF signaling mechanism in corneal innervation-dependent epithelial renewal. We examined the effect of combinations of TrkA and p75NTR agonists and antagonists on the healing of experimentally wounded corneas, both intact and surgically denervated.B) To understand the role and mechanism of NGF signaling in LSC activity and its relevance to humans, we assessed the clonogenicity of cultured human LSCs (hLSCs) by pharmacologically modulating NGF receptors. RESULTS: A) Activation of TrkA induces rapid healing in denervated corneas. Activation of p75NTR prevents complete recovery in denervated corneas. While inactivation of TrkA prevents healing of normally innervated cornea, inactivation of p75NTR combined with a single daily dose of NGF induces complete and rapid healing of denervated de-epithelialized corneas. B) NGF or specific p75NTR inhibitor THX-B supported colonies’ formation by hLSCs that were further augmented by a combination of the two compounds. CONCLUSION: Corneal sensory nerve-associated expression of NGF in its both forms (NGF and proNGF) regulates the proliferation and differentiation of LSCs by differentially stimulating the activity of the NGF receptors. Combined pharmacological activation and inhibition of TrkA and p75NTR, respectively, will be applied in developing a superior NGF-based treatment of NK.