Abstract
Purpose :
Oxytocin (OXTR) and secretin receptors (SCTR) have demonstrated anti-inflammatory and anti-nociceptive roles in various tissues. The purpose of this study is to determine the presence of OXTR and SCTR within ocular tissues, to establish a basis for anti-inflammatory and anti-nociceptive roles on the ocular surface.
Methods :
Immunofluorescence imaging: Human cornea from discarded transplant (DMEK, DSAEK) materials were divided into central (no endothelial layer) and peripheral (cornea, conjunctiva/sclera) regions. Mouse ocular tissues were obtained from wild type C57BL/6J mice. Tissue sections were stained with anti-OXTR or anti-SCTR primary antibody and Alexa Fluor 488 secondary antibody. Images were taken on a Zeiss LSM900 Airyscan confocal microscope.
Gene expression analysis: Human cornea (4 peripheral, 3 central), tarsus (3), and caruncle (1) were obtained from discarded surgical tissues. Mouse cornea, conjunctiva, tarsus, retina, and control (skin, muscle) tissues were extracted from 2 male and 2 female wild type C57BL/6J mice. RNA was extracted and converted to cDNA for qPCR with primers for human and mouse Oxtr, Sctr, and control genes (Hprt, Tbp). Relative RNA expression for Oxtr and Sctr in experimental tissues compared to control tissues (known to have low amounts of Oxtr / Sctr expression) was determined using Livak analysis.
Results :
Immunofluorescence imaging shows OXTR and SCTR expression on the epithelial surface of central and peripheral human cornea and OXTR expression in mouse meibomian glands. In humans, there was higher Oxtr RNA expression in peripheral cornea (62.1x), tarsus (12.1x), caruncle (5.7x), and central cornea (4.9x) and higher Sctr RNA expression in tarsus (12.2x), peripheral cornea (8.9x), caruncle (3.3x), and central cornea (1.5x), compared to muscle control tissue. In female mice, Oxtr RNA showed highest expression in conjunctiva (18.6x) followed by retina (14.6x), cornea (7.5x), and tarsus (4.6x) compared to muscle control tissue. In male mice, Oxtr RNA showed highest expression in retina (14.6x), cornea (11.6x), tarsus (6.7x), and conjunctiva (5.50x) compared to muscle tissue. There was low expression of Sctr RNA in male and female mice ocular tissues.
Conclusions :
OXTR and SCTR are expressed on both the human and mouse ocular surface, with high levels of OXTR in conjunctiva. This warrants further investigation of the role that OXTR and SCTR may have in ocular inflammatory and pain pathways.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.