Abstract
Purpose :
Angiogenesis in the normally avascular cornea underlies common corneal diseases. Corneal sensory nerves, derived from the trigeminal ganglion (TG), are master regulators of ocular surface homeostasis. Here we seek to determine whether corneal nerves directly modulate angiogenesis and investigate the role of neuropeptide alpha-Melanocyte-Stimulating Hormone (α-MSH).
Methods :
TG neurons were isolated from C57BL/6 mice and cultured in Neurobasal A medium. A co-culture system was set up by placing TG neurons in in the top chamber of a transwell and vascular endothelial cells (VEC, MILE SVEN1 cell line) in the bottom chamber. VEC proliferation, migration, and tube formation were determined with and without TG neurons. In vivo corneal angiogenesis was induced by placing intrastromal sutures in BALB/C mouse corneas.
Results :
Presence of TG neurons in co-culture decreased VEC proliferation by 35% (P=0.008) and migration by 20% (P=0.046). Similarly, conditioned media (CM) of TG neurons reduced VEC proliferation (P<0.0001), migration (p=0.017), and the number of junctions (P=0.004) and length of tubes (P=0.001) formed by VEC. Topical application of neuron CM led to a 76% reduction in suture induced-corneal angiogenesis in vivo (P=0.025). More than 80% of TG neurons and 90% of subbasal corneal nerves express α-MSH. α-MSH (100nM) reduced VEC proliferation, migration, and tube formation in vitro and subconjunctival injection of α-MSH reduced corneal angiogenesis by 56% (P=0.008) in vivo. Antagonizing α-MSH signaling with Agouti-signaling protein or siRNA knock-down in TG neurons reversed the inhibitory effects of neuron CM on VEC proliferation, migration, and tube formation.
Conclusions :
TG neurons and corneal nerves express anti-angiogenic neuropeptide α-MSH, which plays a critical role in the direct modulation of corneal angiogenesis by peripheral sensory nerves.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.