Distribution of Corneal TRPV1 and Its Association With Immune Cells During Homeostasis and Injury.

Abstract

PurposeGiven the role of corneal sensory nerves during epithelial wound repair, we sought to examine the relationship between immune cells and polymodal nociceptors following corneal injury.MethodsYoung C57BL/6J mice received a 2 mm corneal epithelial injury. One week later, corneal wholemounts were immunostained using β-tubulin-488, TRPV1 (transient receptor potential ion channel subfamily V member-1, a nonselective cation channel) and immune cell (MHC-II, CD45 and CD68) antibodies. The sum length of TRPV1+ and TRPV1– nerve fibers, and their spatial association with immune cells, was quantified in intact and injured corneas.ResultsTRPV1+ nerves account for ∼40% of the nerve fiber length in the intact corneal epithelium and ∼80% in the stroma. In the superficial epithelial layers, TRPV1+ nerve terminal length was similar in injured and intact corneas. In intact corneas, the density (sum length) of basal epithelial TRPV1+ and TRPV1− nerve fibers was similar, however, in injured corneas, TRPV1+ nerve density was higher compared to TRPV1− nerves. The degree of physical association between TRPV1+ nerves and intraepithelial CD45+ MHC-II+ CD11c+ cells was similar in intact and injured corneas. Stromal leukocytes co-expressed TRPV1, which was partially localized to CD68+ lysosomes, and this expression pattern was lower in injured corneas.ConclusionsTRPV1+ nerves accounted for a higher proportion of corneal nerves after injury, which may provide insights into the pathophysiology of neuropathic pain following corneal trauma. The close interactions of TRPV1+ nerves with intraepithelial immune cells and expression of TRPV1 by stromal macrophages provide evidence of neuroimmune interactions in the cornea.