Expression of Genes in the Canine Pre‐implantation Uterus and Embryo: Implications for an Active Role of the Embryo Before and During Invasion

Abstract

The aim of the present study was to assess genes expressed in maternal uterine tissue and pre-implantation embryos which are presumably involved in maternal recognition and establishment of canine pregnancy. For this purpose, 10 pregnant bitches were ovariohysterectomized between days 10 and 12 after mating. Four non-pregnant bitches served as controls. Early pregnancy was verified by flushing the uterine horns with PBS solution. The collected embryos (n = 60) were stored deep-frozen (-80 degrees C). Uterine tissue was excised, snaps frozen in liquid nitrogen and homogenized using TRI Reagent. All embryos from one litter were thawed together and also homogenized in TRI Reagent. RT-PCR was performed to prove mRNA expression of progesterone receptor, key enzymes of the prostaglandin synthesis pathway, selected growth factors, cytokines, immune cell receptors, major histocompatibility complex (MHC) and matrix-metalloproteinases (MMP). Only pregnant uteri revealed the presence of mRNA for interferon (IFN)-gamma, IL-4 and CD-8, which resembles the milieu in humans and other mammalians. Similarly, in day 10 embryos, mRNA for transforming growth factor-beta, insulin-like growth factor-1,-2, hepatocyte growth factor, leukaemia inhibitor factor, tumour necrosis factor-alpha, interleukin-1beta,-6,-8, cyclooxygenase-2, CD4(+) cells, and MMP-2 and -9 were detected, but not MHC-I or -II. We therefore suppose that the canine embryo, like its human counterpart, actively initiates measures to prevent attacks from the maternal immune system to prepare its own adhesion, nidation, growth and further development.

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

“…Recently, CD8, IL4 and IFNg mRNA were found as being abundantly expressed in the early-pregnant uterus, while the expression of CD4, TNF and IL6 mRNA seemed to be targeted to the nonpregnant uterus (Schafer-Somi et al 2008. In contrast to insulin-like growth factor 1 (IGF1), the expression of IGF2 mRNA was found both during early pregnancy and in the nonpregnant uterus (Schafer-Somi et al 2008).…”

“…Recently, CD8, IL4 and IFNg mRNA were found as being abundantly expressed in the early-pregnant uterus, while the expression of CD4, TNF and IL6 mRNA seemed to be targeted to the nonpregnant uterus (Schafer-Somi et al 2008. In contrast to insulin-like growth factor 1 (IGF1), the expression of IGF2 mRNA was found both during early pregnancy and in the nonpregnant uterus (Schafer-Somi et al 2008). Even though these data, which are mostly based on qualitative transcriptional analysis studies, still need further confirmation, they indicate the differential regulation of the uterine function in the pregnant vs nonpregnant dogs and suggest a possible role of the pre-implantation embryo in this process.…”

The Dog: Nonconformist, Not Only in Maternal Recognition Signaling

“…Among the most interesting fi ndings was the expression of CD8, IL4, and IFNγ mRNA, which seemed to be targeted to the preimplantation uterus, whereas the expression of CD4, TNFα, and IL6 was found abundantly in the nonpregnant uterus (Schafer-Somi et al 2008 ). Additionally, in the same study, transcripts encoding for TGFβ, IL2, IL10, and LIF were only detected in the early pregnant uterus.…”

“…It needs to be emphasized that all of the aforementioned studies (Schafer-Somi et al 2008Bukowska et al 2011 ;Gram et al 2013 ;Gram et al 2014a , b ;Kautz et al 2014 ) describe changes in the uterine response to free-fl oating canine embryos between days 10 and 12 of gestation. This corresponds to pregnancy stages in other species, i.e., ruminants and pigs, when the embryonic antiluteolytic signals are initiated.…”

Interdisciplinary Collaborative Team for Blastocyst Implantation Research: inception and perspectives

“…An intriguing pro-inflammatory cytokine expressed in a number of mammalian species during the period of implantation is IL1B (Simon et al 1994a, 1997a; Takacs and Kauma 1996; Kruessel et al 1997; Schäfer-Somi et al 2008). The presence of IL1B might play a role in immunotolerance at the maternal-placental interface and has been proposed as one of the mediators in placental viviparity (Paulesu et al 2008).…”