Selim Aslan

Canine placenta: a source of prepartal prostaglandins during normal and antiprogestin-induced parturition

Expression of cyclooxygenase 2 (COX2, now known as PTGS2), prostaglandin E2 synthase (PTGES, PGES), and prostaglandin F2alpha synthase (PGFS), of the respective receptors PTGFR (FP), PTGER2 (EP2), and PTGER4 (EP4) and of the progesterone receptor (PGR, PR) was assessed by real-time PCR, immunohistochemistry (IHC), or in situ hybridization (ISH) in utero/placental tissue samples collected from three to five bitches on days 8-12 (pre-implantation), 18-25 (post-implantation), and 35-40 (mid-gestation) of pregnancy and during the prepartal luteolysis. Additionally, ten mid-pregnant bitches were treated with the antiprogestin aglepristone (10 mg/kg bw (2x/24 h)); ovariohysterectomy was 24 and 72 h after the second treatment. Plasma progesterone and 15-ketodihydro-PGF2alpha (PGFM) concentrations were determined by RIA. Expression of the PGR was highest before implantation and primarily located to the endometrium; expression in the placenta was restricted to the decidual cells. PTGS2 was constantly low expressed until mid-gestation; a strong upregulation occurred at prepartal luteolysis concomitant with an increase in PGFM. PGFS was upregulated after implantation and significantly elevated through early and mid-gestation. PTGES showed a gradual increase and a strong prepartal upregulation. PTGFR, PTGER2, and PTGER4 were downregulated after implantation; a gradual upregulation of PTGFR and PTGER2 occurred towards parturition. ISH and IHC co-localized PGFS, PTGFR, PTGES, and PTGS2 in the trophoblast and endometrium. The changes following application of aglepristone were in the same direction as those observed from mid-gestation to prepartal luteolysis. These data suggest that the prepartal increase of PGF2alpha results from a strong upregulation of PTGS2 in the fetal trophoblast with the withdrawal of progesterone having a signalling function and the decidual cells playing a key role in the underlying cell-to-cell crosstalk.

Time related changes in luteal prostaglandin synthesis and steroidogenic capacity during pregnancy, normal and antiprogestin induced luteolysis in the bitch

In nonpregnant and pregnant dogs the corpora lutea (CL) are the only source of progesterone (P4) which shows an almost identical secretion pattern until the rapid decrease of P4 prior to parturition. For the nonpregnant dog clear evidence has been obtained that physiological luteal regression is devoid of a functional role of the PGF2alpha-system and seems to depend on the provision of StAR. Yet in pregnant dogs the rapid prepartal luteal regression, coinciding with an increase of PGF2alpha, may be indicative for different regulatory mechanisms. To assess this situation and by applying semi-quantitative Real Time (Taq Man) RT-PCR, expression patterns were determined for the following factors in CL of pregnant and prepartal dogs and of mid-pregnant dogs treated with the antiprogestin Aglepristone: cyclooxygenase 2 (Cox2), prostaglandin E2 synthase (PGES), prostaglandin F2alpha synthase (PGFS), its receptors (EP2, EP4 an FP), the steroidogenic acute regulatory protein (StAR), 3beta-hydroxysteroid-dehydrogenase (3betaHSD) and the progesterone receptor (PR). Peripheral plasma P4 concentrations were determined by RIA. CL were collected via ovariohysterectomy from pregnant bitches (n=3-5) on days 8-12 (Group 1, pre-implantation period), days 18-25 (Group 2, post-implantation period), days 35-40 (Group 3, mid-gestation period) and during the prepartal progesterone decline (Group 4). Additionally, CL were obtained from groups of 5 mid-pregnant dogs (days 40-45) 24h, respectively 72h after the second treatment with Aglepristone. Expression of Cox2 and PGES was highest during the pre-implantation period, that of PGFS and FP during the post-implantation period. EP4 and EP2 revealed a constant expression pattern throughout pregnancy with a prepartal upregulation of EP2. 3betaHSD and StAR decreased significantly from the pre-implatation period to prepartal luteolysis, it was matched by the course of P4 concentrations. Expression of the PR was higher during mid-gestation and prepartal luteolysis than in the two preceding periods. After application of Aglepristone the overall mRNA-expression resembled the situation during prepartal luteolysis except for EP2, which remained unchanged. These data suggest that - as in the nonpregnant bitch - also in the pregnant bitch luteal production of prostaglandins is associated with luteal support rather than luteolysis. On the other hand induction of luteolysis by the PR blocker Aglepristone points to a role of luteal P4 as an autocrine factor in a positive loop feedback system controlling the availability of P4, StAR and 3betaHSD.

Expression and functional implications of peroxisome proliferator-activated receptor gamma (PPARγ) in canine reproductive tissues during normal pregnancy and parturition and at antiprogestin induced abortion.

PPARγ is a nuclear hormone receptor of the PPAR family of transcription factors closely related to the steroid hormone receptors serving multiple roles in regulating reproductive function. Endogenous factors from the arachidonic acid metabolites group serve as ligands for PPARs. PPARγ modifies the steroidogenic capacity of reproductive tissues and has been defined as a key mediator of biological actions of progesterone receptor in granulosa cells; it modulates biochemical and morphological placental trophoblast differentiation during implantation and placentation. However, no such information is available for the dog. Hence, the expression and possible functions of PPARγ were assessed in corpora lutea (CL) and utero/placental (Ut/Pl) compartment collected from bitches (n = 3 to 5) on days 8 to 12 (pre-implantation), 18 to 25 (post-implantation), 35 to 40 (mid-gestation) of pregnancy and at prepartal luteolysis. Additionally, 10 mid-pregnant bitches were treated with the antiprogestin Aglepristone [10mg/Kg bw (2x/24h)]; ovariohysterectomy was 24h and 72 h after the 2nd treatment. Of the two PPARγ isoforms, PPARγ1 was the only isoform clearly detectable in all canine CL and utero/placental samples. The luteal PPARγ was upregulated throughout pregnancy, a prepartal downregulation was observed. Placental expression of PPARγ was elevated after implantation and at mid-gestation, followed by a prepartal downregulation. All changes were more pronounced at the protein-level suggesting that the PPARγ expression may be regulated at the post-transcriptional level. Within the CL PPARγ was localized to the luteal cells. Placental expression was targeted solely to the fetal trophoblast cells; a regulatory role of PPARγ in canine placental development possibly through influencing the invasion of fetal trophoblast cells is suggested. Treatment with Aglepristone led to downregulation of PPARγ in either compartment, implying the functional interrelationship with progesterone receptor.

Evaluation of genes involved in prostaglandin action in equine endometrium during estrous cycle and early pregnancy

The aim was to evaluate expression of genes involved in the biosynthesis of prostaglandins (PTG), Prostaglandin H Synthase-1 (PTGS1) and PTGS2, PGF synthase (PTGFS), and PGE synthase (PTGES), PGF receptor (PTGFR), PGE receptors (PTGER2 and PTGER4), prostaglandin transporter (SLCO2A1) and hydroxyprostaglandin dehydrogenase-15 (HPGD). Endometrial biopsies were obtained from mares on day of ovulation (d0, n=4), late diestrus (LD, n=4), early luteolysis (EL, n=4) and after luteolysis (AL, n=4) during the cycle. Stages of the cycle were confirmed by plasma progesterone concentrations measured daily and ultrasound examinations. Biopsies were also taken on days 14 (P14; n=4), 15 (P15, n=4), 18 (P18, n=4) and 22 (P22; n=4) of pregnancy. Relative mRNA expressions were quantified using real-time RT-PCR. A mixed model was fitted on the normalized data and least significant difference test (α=0.05) was employed. Expression of PTGS1 mRNA was low throughout the estrous cycle and early days of pregnancy, but upregulated on P18 and P22. PTGS2 expression was increased on EL, but it was suppressed by pregnancy on P15, P18, and P22. PTGFS expression was upregulated in both cyclic and pregnant mares compared to d0 and its level was the highest on LD. PTGFR expression was transiently increased on LD and EL and was suppressed during early pregnancy. Both PTGES and PTGER2 expressions were increased on LD, EL, and early pregnancy, but were decreased after the luteolysis in cyclic mares as they remained high on P18 and P22. PTGER4 expression did not change throughout the cycle and early pregnancy. Levels of HPGD and SLCO2A1 were significantly increased only on P22. In conclusion, PTGS2 expression increases around the time of luteolysis and concurrent upregulation of PTGFS and PTGES indicates that equine endometrium has increased capability of PTG production around the time of luteolysis. However, pregnancy reduces PTGS2 expression, but maintains the high levels of PTGES during early pregnancy along with PTGER2 while PTGFR expression was suppressed. These findings suggest that possible luteotrophic action of PGE₂ is required in early equine pregnancy. PTGS1 is only upregulated later in the early pregnancy suggesting that it is not involved in luteolysis, but could be the main PTGS enzyme at this time during early pregnancy. An increase in HPGD and SLCO2A1 levels on P22 indicates a tight regulation of PTG action by pregnancy.

Expression of genes in the canine pre-implantation uterus and embryo: implications for an active role of the embryo before and during invasion.

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.

Luteal and placental function in the bitch: spatio-temporal changes in prolactin receptor (PRLr) expression at dioestrus, pregnancy and normal and induced parturition

BackgroundEndocrine mechanisms governing canine reproductive function remain still obscure. Progesterone (P4) of luteal origin is required for maintenance of pregnancy. Corpora lutea (CL) are gonadotrop-independent during the first third of dioestrus; afterwards prolactin (PRL) is the primary luteotropic factor. Interestingly, the increasing PRL levels are accompanied by decreasing P4 concentrations, thus luteal regression/luteolysis occurs in spite of an increased availability of gonadotropic support. PRL acts through its receptor (PRLr), the expression of which has not yet been thoroughly investigated at the molecular and cellular level in the dog.MethodsThe expression of PRLr was assessed in CL of non-pregnant dogs during the course of dioestrus (days 5, 15, 25, 35, 45, 65 post ovulation; p.o.) as well as in CL, the utero/placental compartments (Ut/Pl) and interplacental free polar zones (interplacental sites) from pregnant dogs during the pre-implantation, post-implantation and mid-gestation period of pregnancy and during the normal and antigestagen-induced luteolysis. Expression of PRLr was tested by Real Time PCR, immunohistochemistry and in situ hybridization.ResultsIn non-pregnant CL the PRLr expression was significantly upregulated at day 15 p.o. and decreased significantly afterwards, towards the end of dioestrus. CL of pregnancy showed elevated PRLr expression until mid gestation while prepartal downregulation was observed. Interestingly, placental but not interplacental expression of PRLr was strongly time-related; a significant upregulation was observed towards mid-gestation. Within the CL PRLr was localized to the luteal cells; in the Ut/Pl it was localized to the fetal trophoblast and epithelial cells of glandular chambers. Moreover, in mid-pregnant animals treated with an antigestagen, both the luteal and placental, but not the uterine PRLr were significantly downregulated.ConclusionsThe data presented suggest that the luteal provision of P4 in both pregnant and non-pregnant dogs may be regulated at the PRLr level. Furthermore, a role of PRL not only in maintaining the canine CL function but also in regulating the placental function is strongly suggested. A possible functional interrelationship between luteal P4 and placental and luteal PRLr expression also with respect to the prepartal luteolysis is implied.

Rating of putative housekeeping genes for quantitative gene expression analysis in cyclic and early pregnant equine endometrium

The aim was an evaluation of a set of housekeeping genes (HKGs) to be used in the normalization of gene expression in the equine endometrium. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), hypoxanthine ribosyl transferase 1 (HPRT1), ubiquitin B (UBB), tubulin alpha 1 (TUBA1), ribosomal protein L32 (RPL32), beta-2-microglobulin (B2M), 18S rRNA (18S), and 28S rRNA (28S) HKGs were evaluated using real-time PCR and were compared in different physiological stages of the endometrium. Endometrial biopsies were obtained from mares on day of ovulation (d0, n=4), at late diestrus (LD, n=4), after luteolyis (AL, n=4) of the cycle and on days 14 (P14; n=3), 18 (P18, n=3) and 22 (P22; n=3) of pregnancy. A model based on REML with support of descriptive statistics was proposed in accordance with experimental design and was further confirmed with principal component analysis (PCA). Results were compared with widely used software including geNorm, BestKeeper, and NormFinder. Results indicated that GAPDH was the most stable HKG and RPL32 was ranked as the second best. 18S and 28S were found to be the least stable. The proposed model, PCA, geNorm, and BestKeeper were in agreement in detecting the most stable and the least stable HKGs in the equine endometrium during the estrous cycle and early pregnancy.

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

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 β (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.

Cytokines, growth factors and prostaglandin synthesis in the uterus of pregnant and non-pregnant bitches: the features of placental sites.

Uterine tissue from pregnant bitches was investigated by qualitative RT-PCR for the gene expression of local factors potentially important for the implantation of canine embryos. For this purpose, 10 bitches identified as being at the time of implantation or early placentation by means of ultrasonography before ovariohysterectomy (days 20-35, n = 10) provided tissues for comparison to tissue collected in a previous study and identified as early pregnant (n = 10) or non-pregnant (n = 4) by embryo flushing after ovariohysterectomy (days 10-12 after mating; Schäfer-Somi et al. 2008). Uterine tissue was excised from the middle of the left horn from early pregnant and non-pregnant animals, including from interplacental and placentation sites. The following genes were investigated: CD-4, -8; cyclooxygenase (COX)-1, -2; granulocyte macrophage-colony stimulating factor (GM-CSF); hepatocyte growth factor (HGF); insulin-like growth factor (IGF)-1, -2; transforming growth factor (TGF) and tumour necrosis factor (TNF)-alpha; interferon (IFN)-gamma; interleukin (IL)-1beta, -2, -4, -6, -8, -10, -12; leukaemia inhibitory factor (LIF) and leptin. Gene expression for CD-8, COX-1, TGF-beta, HGF, IGF-1, IL-2, -4,-10, IFN-gamma and LIF were detected in the pre-implantation uterus, and all except IL-2 and -10 were still detectable during the implantation and placentation stage. During implantation, mRNA for IGF-2 and GM-CSF were additionally detected. The dioestrous uterus differed from the pregnant uterus because of the absence of CD-8, IL-4 and IFN-gamma and the expression of CD-4, TNF-alpha and IL-6. The results suggest that IL-4, IFN-gamma, CD-8, GM-CSF and IGF-2 are regulated in a pregnancy-specific manner and that GM-CSF and IGF-2 probably have growth supporting and immune modulating functions during implantation of the canine embryo.

Vascular endothelial (VEGF) and epithelial growth factor (EGF) as well as platelet-activating factor (PAF) and receptors are expressed in the early pregnant canine uterus.

The aim of this study was to investigate the course of expression of platelet-activating factor (PAF), PAF-receptor (PAF-R), epidermal growth factor (EGF), EGF-R, vascular endothelial growth factor (VEGF), VEGF-R1 and VEGF-R2 in uterine tissue during canine pregnancy. For this purpose, 20 bitches were ovariohysterectomized at days 10-12 (n = 10), 18-25 (n = 5) and 28-45 (n = 5) days after mating, respectively. The pre-implantation group was proven pregnant by embryo flushing of the uterus after the operation, the others by sonography. Five embryo negative, that is, non-pregnant, bitches in diestrus (day 10-12) served as controls. Tissue samples from the uterus (placentation sites and horn width, respectively) were excised and snap-frozen in liquid nitrogen after embedding in Tissue Tec(®). Extraction of mRNA for RT-PCR was performed with Tri-Reagent. In the embryos, mRNA from all factors except VEGF was detected. In the course of pregnancy, significantly higher expression of PAF and PAFR as well as VEGF and VEGFR2 during the pre-implantation stage than in all other stages and a strong upregulation of EGF during implantation were characteristic. The course of EGF was in diametrical opposition to the course of the receptor. These results point towards an increased demand for VEGF, EGF and PAF during the earliest stages of canine pregnancy.