Lysophosphatidic acid as a regulator of endometrial connective tissue growth factor and prostaglandin secretion during estrous cycle and endometrosis in the mare

Equine endometrosis is a chronic degenerative condition, described as endometrial fibrosis that forms in the stroma, under the basement membrane and around the endometrial glands. The role of lysophosphatidic acid (LPA) in the development of tissue fibrosis varies depending on the organ, and its profibrotic role in mare endometrosis remains unclear. The study aimed to establish the endometrial presence of LPA and its receptors (LPAR1-4), together with its effects on connective tissue growth factor (CTGF) and prostaglandins (PG) secretion from equine endometrium under physiological (estrous cycle), or pathological conditions (endometrosis). Mare endometria in the mid-luteal phase (n = 5 for each category I, IIA, IIB, III of Kenney and Doig) and in the follicular phase (n = 5 for each category I, IIA, III and n = 4 for IIB) were used. In experiment 1, the levels of LPA, LPAR1-4 mRNA level and protein abundance were investigated in endometria at different stages of endometrosis. In experiment 2, the in vitro effect of LPA (10 M) on the secretion of CTGF and PGs from endometrial tissue explants at different stages of endometrosis were determined. Endometrial LPA concentration was higher in the mid-luteal phase compared to the follicular phase in category I endometrium (P