mRNA transcription of prostaglandin synthases and their products in the equine endometrium in the course of fibrosis

Abstract

Accurate regulation of the reproductive cycle and successful implantation depend on proper functioning of the endometrium. The aim of this study was to determine whether mRNA transcription of specific enzymes responsible for prostaglandin (PG) synthesis (prostaglandin-endoperoxide synthase, PTGS-2; prostaglandin F(2α) synthase, PGFS; and prostaglandin E(2) synthases, PGES) and PG concentrations in endometrial extracts would change in moderate (Kenney's Category II) and severe phases of fibrosis (Kenney's Category III; endometrosis), compared with healthy endometrium (Kenney's Category I), during the estrous cycle. Endometrial tissues samples were obtained from mares at the early (n = 12), mid (n = 12) and late (n = 12) luteal phases and the follicular phase (n = 12) of the estrous cycle. Additionally, all endometria were classified microscopically as belonging to Categories I and II or III according to the Kenney classification, resulting in allocation of 4 samples for each subcategory, e.g., mid luteal I, II and III. Relative mRNA transcription was quantified using Real-time PCR. Concentrations of PGE(2) and PGF(2α) in the endometrial extracts were determined using enzyme-linked immunosorbent assay (EIA). In Category I, PTGS-2 mRNA transcription was upregulated at the mid (P < 0.05) and late luteal phases (P < 0.001) and at the follicular phase (P < 0.05) compared to the early luteal phase. PGFS mRNA transcription as well as PGF(2α) concentrations increased at the mid (P < 0.01) and late (P < 0.05) luteal phases compared to the early luteal phase in Category I. PGES mRNA transcription was higher at the mid (P < 0.01) and late luteal phases (P < 0.05) compared to the early luteal and follicular phases in Category I. Prostaglandin E(2) concentration in Category I was higher at the mid luteal phase (P < 0.01) compared to all other phases of the estrous cycle. During incipient endometrosis (Category II) and under full endometrosis (Category III), PTGS-2, PGFS and PGES mRNA transcription and PG concentration were altered compared to the respective estrous phases in healthy endometria (P < 0.05). It may be concluded that serious changes in mRNA transcription of PG synthases and PG production that occur in the equine endometrium during the course of fibrosis in the estrous cycle could be responsible for disturbances leading to disorders of the estrous cycle and early embryo losses.