Abstract
Purpose :
Corneal sensory nerves protect the cornea from injury. They are also thought to stimulate limbal stem cells (LSCs) to produce transparent epithelial cells constantly, enabling vision. Neurotrophic Keratopathy (NK), caused by corneal denervation, is a major cause of corneal blindness. We identified the corneal nerve-associated Schwann cells (SCs) as essential regulators of the LSC niche. SC-secreted nerve growth factor (NGF) is the only clinically-used agent to treat NK. However, results from treatment of NK with NGF are not consistent, require extremely high dosing and duration, and the absolute amount of corneal ulcer healing is relatively low. The purpose of this study is to define the role and mechanism of NGF in LSCs activity to refine NGF-based therapeutics for NK.
Methods :
Previous studies demonstrate that NGF-induced proliferation and maintenance of cultured human LSCs, which express both NGF receptors TrkA and p75NTR. To confirm the expression of the NGF receptors by LSCs and correlate between their activation and innervation-dependent corneal epithelial healing, we applied biochemical and immunohistochemical analyses of healthy, deepithelialized or denervated rodent corneas. To define the involvement of the NGF receptors in regulation of corneal nerve dependent activity of LSCs, we examined the effect of different combinations of systemic or/and topical TrkA and p75NTR agonists or antagonists on healing of experimentally deepithelialized normally innervated, denervated, or genetically SC-ablated rodent corneas. Finally, to assess relevance to humans, we tested the effect of different sets of the NGF receptor modulators on clonogenicity and gene expression of cultured primary human LSCs.
Results :
1. NGF-activated TrkA induces epithelial renewal that is dependent on the presence of corneal nerve-associated SCs. 2. NGF-activated TrkA induces LSC proliferation, maintenance and differentiation. 3. Active p75NTR interferes with corneal epithelial renewal and LSC activity, while its inhibition intensifies the positive effect of TrkA.
Conclusions :
Antagonistic activity of NGF receptors is involved in regulation of LSCs maintenance and activity in innervation-dependent corneal wound healing and homeostatic epithelial renewal. This relationship is of high biological significance and enables advancement of novel therapeutics for NK.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.