Molecular Cloning and Spatiotemporal Expression of Prostaglandin F Synthase and Microsomal Prostaglandin E Synthase-1 in Porcine Endometrium

Abstract

Endometrial prostaglandins (PGs) and the PGE2/PGF2alpha ratio play an important role in regulating the estrous cycle and establishment of pregnancy. The enzymes downstream of cyclooxygenase-2 may determine the PGE2/PGF2alpha ratio in the porcine uterus. Thus, we have cloned porcine PGF synthase (PGFS) and microsomal PGE synthase-1 (mPGES-1) and characterized their expression in porcine endometrium during the estrous cycle and early pregnancy. PGFS and mPGES-1 amino acid sequences possessed a high degree (>67% and >77%, respectively) of identity with the other mammalian homologs. There was little modulation of mPGES-1 throughout the estrous cycle; however, PGFS expression was highly up-regulated in endometrium around the time of luteolysis. During early pregnancy, PGFS at the protein level showed a time-dependent increase (low on d 10-13, intermediate on d 14-23, and high on d 24-25). In pregnancy, expression of mPGES-1 was intermediate on d 10-11 and low on d 14-17 and then increased after d 22, reaching the maximum on d 24-25. Immunohistochemistry showed localization of PGFS and mPGES-1 proteins mainly in luminal and glandular epithelium. Concluding, the spatiotemporal expression of PGFS throughout the estrous cycle indicates an involvement of PGFS in regulating luteolysis in the pig. The comparison of endometrial PGFS and mPGES-1 expression on d 10-13 of the estrous cycle and pregnancy suggest a supportive role of these enzymes in determining the increase of uterine PGE2/PGF2alpha ratio during maternal recognition of pregnancy. Moreover, high expression of both PG synthases after initiation of implantation may indicate their significant role in placentation.

Novel insights into the mechanisms of pregnancy establishment: regulation of prostaglandin synthesis and signaling in the pig

“…However, another group reported that this difference in PGF 2a concentration in the ovarian-uterine vein is much less between cyclic and pregnant animals (Hunter & Poyser 1982). Our results indicate that the content of PGF synthase (PGFS) mRNA and/or protein in the conceptus and endometrium is decreased in the first day of maternal recognition of pregnancy, between days 10 and 13 compared with later stages of pregnancy (Waclawik et al 2006). However, after day 14 of pregnancy, content of PGFS mRNA and protein increases in both the endometrium and conceptus (Waclawik et al 2006, Waclawik & Ziecik 2007.…”

“…Endometrial mPGES-1 expression exhibits a biphasic profile, corresponding with the profile of conceptus estrogen secretion (Waclawik et al 2006). Our recent results indicate that estrogen elevates PGE 2 synthesis and the PGE 2 :PGF 2a ratio by an increase of expression enzymes involved in PGE 2 synthesis (PTGS2 and mPGES-1) and a decrease in the content of enzymes involved in PGF 2a production (PGFS and CBR1) in the endometrium on days 11-12 after estrus (Waclawik et al 2009a).…”

“…Our results indicate that the content of PGF synthase (PGFS) mRNA and/or protein in the conceptus and endometrium is decreased in the first day of maternal recognition of pregnancy, between days 10 and 13 compared with later stages of pregnancy (Waclawik et al 2006). However, after day 14 of pregnancy, content of PGFS mRNA and protein increases in both the endometrium and conceptus (Waclawik et al 2006, Waclawik & Ziecik 2007. Moreover, uterine flushings of pregnant pigs contain higher amounts of PGF 2a than those from cyclic animals (Zavy et al 1980).…”

“…The conceptus and endometrium synthesize increased amounts of PGE 2 before implantation (Waclawik et al 2006, Waclawik & Ziecik 2007. A greater PGE 2 :PGF 2a ratio stimulates progesterone and E 2 secretion by luteal cells collected on days 10-12 of the estrous cycle (Gregoraszczuk & Michas 1999).…”

“…Moreover, PGE 2 can be converted into PGF 2a by PG 9-ketoreductase/carbonyl reductase (CBR1). It was demonstrated that highly inducible forms of PTGS and PGE synthase in the porcine endometrium are PTGS2 (also known as PGHS-2 or COX-2; Ashworth et al 2006) and microsomal PGE synthase-1 (mPGES-1), respectively (Waclawik et al 2006).…”