Expression of genes involved in the embryo–maternal interaction in the early-pregnant canine uterus

Abstract

Although there is no acute luteolytic mechanism in the absence of pregnancy in the bitch, a precise and well-timed embryo-maternal interaction seems to be required for the initiation and maintenance of gestation. As only limited information is available about these processes in dogs, in this study, the uterine expression of possible decidualization markers was investigated during the pre-implantation stage (days 10-12) of pregnancy and in the corresponding nonpregnant controls. In addition, the expression of selected genes associated with blastocyst development and/or implantation was investigated in embryos flushed from the uteri of bitches used for this study (unhatched and hatched blastocysts). There was an upregulated expression of prolactin receptor (PRLR) and IGF2 observed pre-implantation. The expression of PRL and of IGF1 was unaffected, and neither was the expression of progesterone-or estrogen receptor b (ESR2). In contrast, (ESR1) levels were elevated during early pregnancy. Prostaglandin (PG)-system revealed upregulated expression of PGE2-synthase and its receptors, PTGER2 and PTGER4, and of the PG-transporter. Elevated levels of AKR1C3 mRNA, but not the protein itself, were noted. Expression of prostaglandin-endoperoxide synthase 2 (PTGS2) remained unaffected. Most of the transcripts were predominantly localized to the uterine epithelial cells, myometrium and, to a lesser extent, to the uterine stroma. PGES (PTGES) mRNA was abundantly expressed in both groups of embryos and appeared higher in the hatched ones. The expression level of IGF2 mRNA appeared higher than that of IGF1 mRNA in hatched embryos. In unhatched embryos IGF1, IGF2, and PTGS2 mRNA levels were below the detection limit.

The Dog: Nonconformist, Not Only in Maternal Recognition Signaling

“…Similarly, at the same time, IGF2 expression was higher than that of IGF1 in the hatched embryos, suggesting a possible predominant role of IGF2 during the establishment of early canine pregnancy. Both IGF1 and IGF2 were below the detection limits in the unhatched embryos (Kautz et al 2014 ). The presence of early preimplantation embryos was also associated with increased expression of receptors for two other important growth factors, i.e., platelet-activating factor (PAF) and epidermal growth factor (EGF) (Schafer-Somi et al 2013 ) (Fig.…”

“…As for the steroidogenic hormone receptors, ERα was signifi cantly upregulated in early pregnant canine uteri compared with nonpregnant diestrus controls, while ERβ and progesterone receptor (PGR) remained unaffected (Kautz et al 2014 ). Similarly to the situation with PRL, the increased expression of ERα could possibly counteract the low availability of estradiol of luteal origin during canine pregnancy (Fig.…”

“…In addition to these earlier studies, lately we have investigated the uterine expression of several target genes potentially involved in the process of early decidualization (the so-called "decidualization markers") (Kautz et al 2014 ). The uterine response to the presence of free-fl oating embryos during the preimplantation stage of pregnancy (days 10-12 of gestation, determined by uterine fl ushings) was investigated.…”

“…Thus, the uterus does not seem to contribute strongly to the overall circulating PRL in the dog. However, the highly upregulated PRLR expression (Kowalewski et al 2011b ;Kautz et al 2014 ) could serve to compensate for low PRL expression and thereby to locally increase its relative availability. The expression of LH receptor, which was recently suggested to be involved in implantation in mice (Gridelet et al 2013 ), was signifi cantly reduced in the early pregnant canine uterus (Kautz et al 2014 ).…”

Synthesis and reception of prostaglandins in corpora lutea of domestic cat and lynx

“…Afterwards, the slides were incubated in 10% goat serum (for PTGFR in 5% BSA in PBS) in order to block non-specific binding sites. Thereafter, the slides were overlaid overnight with canine-specific polyclonal antibodies: guinea pig anti-PTGES (1:2500 , Kautz et al 2014 …”