Effect of conceptus on expression of prostaglandin F2α receptor in the porcine endometriumby Piotr Kaczynski, Agnieszka Waclawik

Theriogenology

About

Year
2013
DOI
10.1016/j.theriogenology.2012.12.003
Subject
Equine / Food Animals / Small Animals / Animal Science and Zoology

Text

ex porcine endometrium

Piotr Kaczynski, Agnieszka Wac

Institute of Animal Reproduction and Food Research o a r t i c l e i n f o

Article history:

Received 8 August 2012

Received in revised form 10 December 2012

Accepted 15 December 2012

Keywords:

Endometrium

Conceptus

Pregnancy 1. Introduction

Prostaglandin F2a (PGF2a) as a tissue specific hormone is involved in many physiologic processes. In most mammals,

PGF2a is claimed to be the main luteolytic factor which controls progesterone secretionbyactingon luteal cells [1–4].

PGF2a exerts its function through PGF2a receptor (PTGFR) which belongs to the G–protein-coupled receptor family. Activated PTGFR binds to Gq protein, that leads to protein kinase C-mediated elevation of intracellular Ca2þ concentration [5]. PTGFR can also activate other signal * Corresponding author. Tel.: þ48 89 5357422; fax: þ48 89 5357421.

E-mail address: waclawik@pan.olsztyn.pl (A. Waclawik).

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Theriogenology 79 (2013) 784–790abolished by incubation of LE cells in the presence of the estrogen receptor antagonist (ICI182,780; P < 0.01). Summarizing, the conceptus upregulated expression of PTGFR in the endometrium during the implantation period. Moreover, this study indicates that expression of PTGFR genewas elevated in LE cells of endometrium by embryonic signal of estradiol.

Our results suggest para- and autocrine effects of PGF2a through its receptor PTGFR in the porcine endometrium, especially in luminal epithelium which is in direct contact with the conceptus during the implantation period.  2013 Elsevier Inc. All rights reserved.Prostaglandin F2a receptor

Pig

Prostaglandin F2a0093-691X/$ – see front matter  2013 Elsevier Inc http://dx.doi.org/10.1016/j.theriogenology.2012.12.00lawik* f Polish Academy of Sciences, Olsztyn, Poland a b s t r a c t

Increased synthesis of prostaglandin F2a (PGF2a) in the endometrium and conceptus during the implantation period results in elevated concentration of PGF2a in the uterine lumen in pregnant gilts. PGF2a exerts its effects through PGF2a receptor (PTGFR), a G–protein-coupled receptor. However, besides studies concerning the function of PTGFR in endometrial abnormalities, the role of PTGFR in the endometrium during early pregnancy has not been elucidated. Therefore, the aim of this study was: (1) to evaluate the profile of PTGFR gene and protein expression in the porcine endometrium during early pregnancy and the estrous cycle; (2) to determine if the effect of conceptus on PTGFR expression is dependent on type of endometrial cellsdluminal epithelial (LE) or stromal (ST) cells; and (3) to elucidate if the putative effect of conceptus on endometrial PTGFR expression is mediated by estrogen receptor. We evaluated the expression pattern of PTGFR gene and protein in the endometrium during day 9,11,12,15, and 18 of the estrous cycle and pregnancy (N¼ 4–6 per group).

The expression of PTGFRmRNAwas greater on day 18 of pregnancy and the estrous cycle (vs. days 9–15 of the estrous cycle and pregnancy, P < 0.05). Expression of PTGFR protein was approximately 10-fold upregulated in the endometrium on day 15 of pregnancy when compared with day 15 of the estrous cycle (P < 0.01). Endometrial expression of PTGFR protein increased from day 12 to 18 of pregnancy (P < 0.05). PTGFRmRNAwas expressed in

LE and ST cells. In a subsequent experiment, we used a coculture model in which LE cells were cultured on collagen-coated inserts placed in wells plated with ST cells. Day 11 or 15 conceptus-exposed medium (CEM) elevated expression of PTGFR mRNA (2- and 1.5-fold, respectively, P < 0.05) in LE cells cocultured with ST cells. CEM did not have an effect on

PTGFR mRNA expression in ST cells. The 11-day CEM-induced increase of PTGFR mRNA wasEffect of conceptus on pression of prostaglandin F2a receptor in thejournal homepage:. All rights reserved. 3ology . ther io journal .com

P. Kaczynski, A. Waclawik / Theriogenology 79 (2013) 784–790 785transduction pathways such as Rho, focal adhesion kinase signaling, and mitogen-activated protein kinase [6,7].

PTGFR is approximately a 40 kDa protein with a seven transmembrane domain that is highly conserved among prostanoid receptors. PTGFR gene consists of three exons and two introns [8].

In the porcine corpus luteum (CL) the expression of

PTGFR is lower on days 7 and 8 of the estrous cycle, which is believed to protect luteal cells from the lytic effects of PGF2a.

The upregulation of PTGFR expression in the porcine CL on days 13 and 15 of the estrous cycle coincides with onset of luteolysis [9]. However, during early pregnancy in the pig, estradiol (E2) produced by the conceptus in a biphasic manner on days 11 to 12 and 15 to 30 of pregnancy prolongs luteal progesterone production [10].

Interestingly, average concentration, amplitude, and the frequency of PGF2a pulses are lower in the porcine uteroovarian vein on day 13 to 17 of pregnancy than in pigs on day 13 to 17 of the estrous cycle [11]. To avoid luteolytic influence of PGF2a on the CL in ovary, PGF2a is sequestered in the uterus probably by redirection of its secretion from the uterine venous drainage (endocrine) into the uterine lumen (exocrine) by conceptus signaldE2 [12]. The antiluteolytic mechanism could also involve the retrograde transfer of PGF2a from the venous blood and uterine lymph into the uterine lumen and ability of uterine veins and arterial walls to accumulate PGF2a [13]. Another potential mechanism by which the conceptus can contribute to prevention of luteolysis is by changing prostaglandin (PG) synthesis in favor of PGE2 during the maternal recognition of pregnancy, on days 10 to 13 in the pig [14–16]. PGE2 plays an important role as a luteoprotective factor and a local mediator of embryo signal on uterus [15,17–20]. Our previous study indicated the existence of a putative PGE2 autoamplification loop in the endometrium that can be involved in an increase of the PGE2/PGF2a ratio on days 10 to 13 of pregnancy [16]. In this period, synthesis of PGF2a seems to be undesired because of its luteolytic effect on the