Interleukin 22 receptor alpha1 is expressed by both the luminal and glandular epithelia of the day 34 pregnant mare uterus (P6319)

Abstract

Abstract Invasive trophoblast cells of the equine chorionic girdle (CG) migrate through maternal endometrium to form endometrial cups, dense accumulations of cells that produce equine chorionic gonadotropin from days 40 to 120 of pregnancy. At day 37 CG cells attach to the luminal epithelium, passing through and phagocytosing the epithelial cells. The CG cells then migrate into the stroma to form the mature endometrial cups and the luminal surface of the endometrium re-epithelializes. Penetration of the stroma occurs in association with endometrial glands, but the glandular epithelium is undisturbed. Interleukin 22 (IL22) is involved in the preservation of epithelia. Previously we identified high expression of IL22 in CG cells using a gene expression array on placental tissues from day 34 of gestation. qRT-PCR analysis showed a striking increase in IL22 mRNA in CG cells from days 32 to 35, and absence of IL22 in other conceptus tissues. Our discovery of IL22 in the CG was novel, as this cytokine had been reported only in immune cells. qRT-PCR also detected IL22 receptor mRNA in pregnant endometrium at levels similar to other equine epithelia. Using in situ hybridization we have now visualized IL22RA1 mRNA in both the luminal and glandular epithelia of the pregnant mare uterus. We hypothesize that IL22 produced by the CG binds IL22RA1 on luminal endometrium and glands, serving as a mechanism of fetal-maternal communication and ensuring the integrity of epithelial surfaces.