The Activity and Localization of 3β-hydroxysteroid Dehydrogenase/Δ5-Δ4 Isomerase and Release of Androstenedione and Progesterone by Uterine Tissues During Early Pregnancy and the Estrous Cycle in Pigs

Steroid hormones are produced by the porcine uterus. We hypothesized that the uterus in pigs possesses active 3β-hydroxysteroid dehydrogenase/Δ⁵-Δ⁴ isomerase (3β-HSD) responsible for progesterone and androstenedione production, that uterine steroids may supplement the amount of steroid hormones produced by embryos and corpus luteum and that these steroids are necessary for maintenance of pregnancy. In this study, we examined 1) endometrial and myometrial expression of 3β-HSD mRNA, 2) uterine 3β-HSD protein activity and 3) in vitro production of A₄ and P₄ by uterine slices harvested from pigs on days 10 to 11, 12 to 13 and 15 to 16 of pregnancy and the estrous cycle. The expression of 3β-HSD and the presence and activity of 3β-HSD protein were different in the endometrium and the myometrium during the examined periods of pregnancy and the estrous cycle. Production of A₄ by the endometrium and myometrium was highest on days 12 to 13 of pregnancy and the estrous cycle. Endometrial secretion of P₄ did not differ in the course of early pregnancy and on the respective days of the estrous cycle. The gravid myometrium was the highest source of P₄ in pregnant pigs on days 12 to 13. The release of P₄ by the cyclic myometrium rose during the examined days of the estrous cycle. The steroidogenic activity of the uterus, as described in this study, may support early pregnancy or the luteal phase of the estrous cycle in pigs.     

Distribution of androgen receptor in the porcine uterus throughout pregnancy.

The uterus is a well-known target of endocrine, paracrine and autocrine acting molecules among which steroid hormones (oestrogens, androgens and progesterone) are of special importance. The uterine tissues (endometrium and myometrium) undergo morphological and physiological changes which are associated with changes in expression of steroid hormone receptors. Androgen receptors (AR) that mediate the action of androgens have already been detected in porcine uteri during the oestrous cycle and early pregnancy. To evaluate the role of AR in uterine physiology, the presence of ARmRNA and AR protein localization in the porcine uterus from day 10 to day 90 of pregnancy and in the uterus from the foetus of day 90 postcoitum (p.c.) and from the neonatal 1-day-old piglet was studied. ARmRNA was detected in the porcine endometrium up to day 18 p.c., while AR protein was detectable in glandular epithelium and stromal cells as through day 90 of pregnancy. AR was also detected in the myometrium on all investigated days of pregnancy; however, on day 90, the immunostaining was present only in a limited number of cells. AR immunostaining was clearly demonstrated in the uterus of the female foetuses on day 90 as well as in the uterus of 1-day-old piglets. The physiological relevance of this finding needs further elucidation.     

The dynamic expression of extracellular matrix in the bovine endometrium at implantation

Remodeling of uterine endometrial extracellular matrix (ECM) is pivotal to successful implantation and placentation, and has been well described in the rodents and humans. However, bovine endometrial ECM remodeling is still vaguely defined, especially at the time of implantation. Therefore, this study investigated the distribution of four ECMs namely, types I and IV collagen, laminin and fibronectin, from days 0 to 30 of gestation in bovine endometrium by immunofluorescence microscopy. A change in the distribution pattern of ECMs was evident by day 14 of gestation as features at this stage were clearly different from those of day 14 of the estrous cycle. The immunoreactivity of type I collagen, fibronectin and laminin decreased from day 14 of gestation and was obscured by day 24 of gestation. The type I collagen fibers formed were of thinner consistency than those of the estrous cycle and showed a coarser meshwork within the epithelium sites during the implantation period. In addition, the type IV collagen and laminin immunoreactivities of epithelial basement membrane also remarkably declined at exactly the same time. By day 30 of gestation, the four ECMs had regenerated with the formation of the placentome. In conclusion, this study reveals that remodeling of ECM is essential for the successful establishment of pregnancy in the bovine.     

小鼠子宫内膜凝集素结合特性的生殖周期改变

用４种酶标植物凝集素（ＣｏｎＡ,ＷＧＡ,ＳＢＡ,ＲＣＡ）作探针,研究了小鼠发情周期、妊娠期和产后子宫内膜上皮、固有膜细胞和腺上皮凝集素结合特性的变化。子宫内膜与这４种凝集素的结合,随发情周期而波动。与间情期相比,妊娠期子宫内膜上皮与ＣｏｎＡ的结合,由阴性转为阳性,并随妊娠的持续逐渐加强,产后又突然转为阴性。子宫内膜上皮与ＷＧＡ的结合,在间情期和妊娠１ｄ均为阳性,妊娠７ｄ减为弱阳性,继之又加强,产后达最强。无论妊娠期还是产后,子宫内膜上皮与ＲＣＡ的结合均为强阳性,与ＳＢＡ的结合均为阴性。结果提示,生殖周期子宫内膜与凝集素结合特性的规律性变化,可能与激素调节、胚泡的着床和分娩有关     

Expression and Hormonal Regulation of Hoxa10 in Canine Uterus During the Peri-implantation Period

Hoxa10, a homeobox gene, is necessary for endometrial receptivity to blastocyst implantation. The aim of this study was to investigate the differential expression of Hoxa10 in canine uterus during early pregnancy and its regulation under different conditions by in situ hybridization. Hoxa10 mRNA was mainly localized in glandular epithelium and myometrium in canine uterus. There was a low level of Hoxa10 expression in the glandular epithelium on days 6, 12 and 17 of pregnancy. On day 20 of pregnancy when embryo implanted, Hoxa10 mRNA was highly expressed in the glandular epithelium surrounding the embryo, but not in the luminal epithelium. The expression of Hoxa10 mRNA gradually declined from day 23 and reached a low level on day 28. In the myometrium, a low level of Hoxa10 mRNA signal was seen on days 6, 12 and 17 of pregnancy and reached a high level on day 20 of pregnancy. During the estrous cycle, a high level of Hoxa10 mRNA expression was seen in the estrous uterus. Either estrogen or progesterone significantly induced the expression of Hoxa10 mRNA in the ovariectomized canine uterus. These results suggest that Hoxa10 expression is closely related to canine embryo implantation and upregulated by estrogen and progesterone.     

Old,new and the newest concepts of inhibition of luteolysis during early pregnancy in pig

In 1977 Bazer and Thatcher proposed that maternal recognition of pregnancy in the pig involves the secretion of PGF(2alpha) towards the uterine lumen (exocrine) rather than towards the uterine venous drainage (endocrine) as occurs in the non-pregnant pig during the mid to late stages of the estrous cycle. The retrograde transfer of PGF(2alpha) from the venous blood and uterine lymph into the uterus and the ability of the uterine vein and artery wall to accumulate PGF(2alpha) could constitute a part of putative mechanism of corpus luteum protection during early pregnancy. A luteotropic/anti-luteolytic effect of PGE(2) in the pig also has been frequently demonstrated and it seems that the most effective agent in changing PGE(2):PGF(2alpha) secretion is estradiol. The role for oxytocin during luteolysis and early pregnancy is controversial. It appears, however, that the main function of this hormone is autocrine and/or paracrine stimulation of PGF(2alpha) secretion. Pig trophoblastic interferons, unlike those of ruminants, do not themselves exert an anti-luteolytic effect in pigs. It is likely, that cytokines and angiogenic growth factors are involved in the initiation of luteolysis and/or maintenance of corpora lutea (CL).A discovery of functional LH receptors in porcine endometrium opened a new possibility for this hormone in luteolysis and perhaps in recognition of pregnancy in pigs. The endogenous LH pulses can provoke prostaglandin secretion from endometrium in pigs. On the other hand prolongation of up-regulation of LH receptors in endometrium of early pregnant gilts can additionally increase angiogenic factor production before the process of implantation is completed. Finally new integrated concepts of luteolysis and inhibition of luteolysis in pigs based on selectively reviewed information are presented.     

FZD5在山羊妊娠早期的表达及激素调控

实验旨在研究雌性山羊早期妊娠和发情周期中 Frizzled-5(FZD5)蛋白在子宫中的表达,以及类固醇激素对 FZD5 的表达调控。选取发情周期、早期妊娠及雌激素(50 μg/mL)与孕酮(50 ng/mL)处理山羊的子宫组织,采用免疫组织化学染色、荧光定量 PCR和 Western blot检测 FZD5在山羊子宫中的表达规律。结果表明:FZD5 蛋白在山羊妊娠早期的子宫腔上皮和腺上皮中表达;FZD5 mRNA 和蛋白在胚胎与子宫的黏附前(D6)和黏附中(D16)表达较高,在黏附后(D19)和胎盘形成早期(D25)呈下降趋势;孕酮处理导致FZD5表达降低,表明山羊子宫中孕酮下调 FZD5的表达。研究提示FZD5可能在山羊胚胎着床过程中发挥作用。     

生殖周期小鼠输卵管粘膜糖复合物结合特性

为了解输卵管粘膜糖复合物的特点和变化规律,用４种酶标植物凝集素（ＣｏｎＡ、ＳＢＡ、ＲＣＡ１２０、ＷＧＡ）作探针,研究了小鼠发情周期、妊娠早期（７ｄ）、产后（１ｄ）的输卵管粘膜凝集素结合糖复合物染色特性的变化。结果发现,输卵管粘膜与ＣｏｎＡ、ＳＢＡ、ＲＣＡ１２０的结合,无论在发情周期还是妊娠早期（７ｄ）及产后（１ｄ）,均有波动,而与ＷＧＡ的结合始终保持最强阳性。提示输卵管粘膜凝集素结合特性的变化,可能与生殖周期激素的波动和胚泡的调节有关。     

Kontaktaufnahme zwischen Trophoblast und Uterusepithel während der frühen Implantation beim Rind

Development of contact between trophoblast and uterine epithelium during the early stages of implantation in the cow Implantation in the cow may be divided into precontact, apposition, and adhesion phases. These can be recognized grossly at the site of nidation (18 or 19 days post inseminationem) by changes in the endometrium and in the embryonic chorion, which differs from the extraembryonic chorion. Also light and electronmicroscopical examinations of the trophoblast and uterine epithelium during the course of nidation show typical phase-correlated differences. The surfaces of trophoblastic and uterine epithelia increase and unite by interdigitiation of their microvilli. The functional relationship between blastocyst and uterus at the time of contact, as determined from their structure, is discussed.     

Expression profiles of perforin,granzyme B and granulysin genes during the estrous cycle and gestation in the bovine endometrium

The conceptus is susceptible to destruction by maternal cytotoxic lymphocytes, which have cytotoxic potential. Therefore, it is expected that mechanisms for regulating cytotoxic lymphocytes exist, but little is known about the expression of cytotoxic genes in the endometrium. In the present study, we examined the spatial and temporal expression patterns of the cytotoxic genes perforin, granzyme B, and granulysin during the estrous cycle and gestation in the bovine endometrium. Endometrial tissues were collected from cows during the estrous cycle and gestation. The gene expression patterns of the three cytotoxic genes were examined using quantitative polymerase chain reaction and in situ hybridization, and cytotoxic lymphocyte subsets were characterized using immunohistochemistry. During mid‐ to late gestation in the intercaruncular (ICAR), granulysin expression was significantly increased, and a large number of granulysin‐expressing cells were localized in the luminal epithelium. Perforin and granzyme B displayed similar expression profiles and were highly expressed in the peri‐implantation endometrium, but few cells expressing these genes were found in the endometrial stroma. In conclusion, these findings suggest that in the ICAR epithelium granulysin may play important roles in the establishment and maintenance of gestation during normal pregnancy.     

The potential function of endometrial‐secreted factors for endometrium remodeling during the estrous cycle

Uterine has a pivotal role in implantation and conceptus development. To prepare a conducive uterine condition for possibly new gestation during the estrous cycle, uterine endometrium undergoes dramatic remodeling. In addition, angiogenesis is an indispensable biological process of endometrium remodeling. Furthermore, essential protein expressions related to important biological processes of endometrium remodeling, which are vascular endothelial growth factor (VEGF), myoglobin (MYG), collagen type IV (COL4), fucosyltransferase IV (FUT4), and cysteine‐rich protein 2 (CRP2), were detected in the endometrial tissue reported in many previous studies and recently discovered in histotroph substrates during the estrous cycle. Those proteins, which are liable for provoking new vessel development, cell proliferation, cell adhesion, and cell migration, were expressed higher in the histotroph during the luteal phase than follicular phase. Histotroph proteins considerably contribute to endometrium remodeling during the estrous cycle. To that end, the following review will discuss and highlight the relevant information and evidence of the uterine fluid proteins as endometrial‐secreted factors that adequately indicate the potential role of the uterine secretions to be involved in the endometrial remodeling process.     

Tumour necrosis factor in the canine endometrium: an immunohistochemical study

Tumour necrosis factor (TNF), a pleiotropic cytokine that regulates cell growth and differentiation as well as the synthesis of other cytokines, has been identified in the uterus of several species describing a cyclic pattern, eventually under ovarian steroid regulation. Information is yet limited on the presence of TNF protein in the canine endometrium during the oestrous cycle and early pregnancy. This study depicts the temporal immunolocalization of TNF in the bitch endometrium along the oestrous cycle and changes associated with the early steps of embryo invasion. TNF immunolabelling was found in both the stromal fibroblasts and epithelial components of the canine endometrium in all stages studied. Stromal immunostaining was more intense than that of the epithelia, in all the stages of the oestrous cycle. In addition, a tendency for a decrease in the surface epithelium intensity score was found in early dioestrus. A positive glandular content was only observed in anoestrus and proestrus stages. In early pregnancy (days 13-16), TNF immunolabelling was detected at the embryo-maternal surface, in the syncytium cords and the trophoblast, as well in the endometrial stroma and the basal endometrial glands, but not in the lacunar epithelium. The overall TNF immunoreactivity was higher in early pregnancy samples in comparison with those of the early dioestrus and dioestrus stages, suggesting it plays a role during implantation.     

Expression and Hormonal Regulation of IL-11Rα in Canine Uterus During Early Pregnancy

Embryo implantation is critical for the successful establishment of pregnancy. Interleukin-11 (IL-11) is essential for adequate decidualization in the mouse and human via binding to the specific IL-11 receptor α (IL-11Rα). But the expression and regulation of IL-11 and IL-11Rα in the canine endometrium remain unknown. The aim of this study was to investigate the differential expression of IL-11Rα in canine uterus during early pregnancy and its regulation under different conditions by in situ hybridization. Interleukin-11Rα mRNA was mainly localized in glandular epithelium in canine uterus. There was a low level of IL-11Rα expression in the glandular epithelium on days 6, 12 and 17 of pregnancy. On day 20 of pregnancy when embryo implanted, IL-11Rα mRNA was highly expressed in the glandular epithelium surrounding the embryo, but not in the luminal epithelium and stroma. On day 23 of pregnancy, the expression of IL-11Rα mRNA maintained a constant level compared with the expression of day 20 and increased on day 28 of pregnancy. During the oestrous cycle, a high level of IL-11Rα mRNA expression was seen in the oestrous uterus. Progesterone slightly induced the expression of IL-11Rα mRNA in the ovariectomized canine uterus. These results suggest that IL-11Rα expression is closely related to canine implantation and up-regulated by progesterone.     

Pre‐ and Post‐Partum Mild Underfeeding Influences Gene Expression in the Reproductive Tract of Cyclic Dairy Cows

Undernutrition before and after calving has a detrimental effect on the fertility of dairy cows. The effect of nutritional stress was previously reported to influence gene expression in key tissues for metabolic health and reproduction such as the liver and the genital tract early after calving, but not at breeding, that is, between 70 and 90 days post‐partum. This study investigated the effects of pre‐ and post‐partum mild underfeeding on global gene expression in the oviduct, endometrium and corpus luteum of eight multiparous Holstein cows during the early and middle phases of an induced cycle 80 days post‐partum. Four control cows received 100% of energy and protein requirements during the dry period and after calving, while four underfed received 80% of control diet. Oestrous synchronization treatment was used to induce ovulation on D80 post‐partum. Oviducts, ovaries and the anterior part of each uterine horn were recovered surgically 4, 8, 12 and 15 days after ovulation. Corpora lutea were dissected from the ovaries, and the endometrium was separated from the stroma and myometrium in each uterine horn. The oviduct segments were comprised of ampulla and isthmus. RNAs from ipsi‐ and contralateral samples were pooled on an equal weight basis. In each tissue, gene expression was assessed on a custom bovine 10K array. No differentially expressed gene (DEG) in the corpus luteum was identified between underfed and control, conversely to 293 DEGs in the oviduct vs 1 in the endometrium under a false discovery rate (FDR) < 0.10 and 1370 DEGs vs 3, respectively, under FDR < 0.15. Additionally, we used dedicated statistics (regularized canonical correlation analysis) to correlate the post‐partum patterns of six plasma metabolites and hormones related to energy metabolism measured weekly between calving and D80 with gene expression. High correlations were observed between post‐partum patterns of IGF‐1, insulin, β‐hydroxybutyrate and the expression in the oviduct of genes related to reproductive system disease, connective tissue disorders and metabolic disease. Moreover, we found special interest in the literature to retinoic acid‐related genes (e.g. FABP5/CRABP2) that might indicate abnormalities in post‐partum tissue repair mechanisms. In conclusion, this experiment highlights relationships between underfeeding and gene expression in the oviduct and endometrium after ovulation in cyclic Holstein cows. This might help to explain the effect of mild undernutrition on fertilization failure and early embryonic mortality in post‐partum dairy cows.