• Asian-Australasian Journal of Animal Sciences
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• v.13 no.6
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• pp.845-855
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• 2000

As high as 50% of pregnancies are known to fail and the majority of such losses occur during the peri-implantation period. For the establishment of pregnancy in mammalian species, therefore, implantation of the conceptus to the maternal endometrium must be completed successfully. Physiological events associated with implantation differ among mammals. In ruminant ungulates, an elongation of the trophohlast in early conceptus development is required before the attachment of the conceptus to the uterine endometrium. Moreover, implantation sites are restricted to each uterine caruncula where tissue remodeling, feto-maternal cell fusion and placentation take place in a coordinated manner. These unique events occur under strict conditions and are regulated by numerous factors from the uterine endometrium and trophoblast in a spatial manner. Interferon-tau (IFN-${\tau}$), a conceptus-derived anti-Iuteolytic factor, which rescues corpus luteum from its regression in ruminants, is particularly apt to play an important role as a local regulator in coordination with other factors, such as TGF-${\beta}$, Cox-2 and MMPs at the attachment and placentation sites.

• Journal of Animal Reproduction and Biotechnology
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• v.37 no.4
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• pp.255-265
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• 2022

The cellular communication network factor (CCN) family proteins regulate many biological events such as angiogenesis, tumor growth, placentation, implantation, and embryogenesis. The expression and function of CCN1, CCN2, and CCN3 at the maternal-conceptus interface are established in humans and rodents, but little is known about the role of CCN4 to CCN6 in the reproductive organs in any other species. Several studies in transcriptome analysis in pigs have shown that the expression of CCN4 and CCN6 increases in the endometrium during early pregnancy. However, their expression, regulation, and function in the endometrium throughout the estrous cycle and pregnancy have not been fully understood in pigs. Thus, we determined the expression, localization, and regulation of CCN4 and CCN6 during the estrous cycle and at the maternal-conceptus interface in pigs. We found that the levels of CCN4, but not CCN6, changed during the estrous cycle. The levels of CCN4 were greater during mid- to late pregnancy than in the early stage, and the levels of CCN6 were greatest on Day 15 of pregnancy. CCN4 and CCN6 were detected in conceptus tissues during early pregnancy and in chorioallantoic tissues during the later stage of pregnancy. CCN4 mRNA was mainly localized to epithelial cells, CCN6 mRNAs to epithelial and stromal cells in the endometrium. In endometrial explant cultures, CCN4 expression was increased by progesterone, and CCN6 expression by interferon-𝛾. These results suggest that CCN4 and CCN6 may play roles in the establishment and maintenance of pregnancy by regulating the endometrial epithelial cell functions in pigs.

• Animal Bioscience
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• v.36 no.8
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• pp.1167-1179
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• 2023

Objective: Matrix metalloproteinases (MMPs) are a family of endoproteases produced by various tissues and cells and play important roles in angiogenesis, tissue repair, immune response, and endometrial remodeling. However, the expression and function of MMPs in the pig endometrium during the estrous cycle and pregnancy have not been fully elucidated. Thus, we determined the expression, localization, and regulation of MMP2, MMP8, MMP9, MMP12, and MMP13 in the endometrium throughout the estrous cycle and at the maternal-conceptus interface during pregnancy in pigs. Methods: Endometrial tissues during the estrous cycle and pregnancy and conceptus and chorioallantoic tissues during pregnancy were obtained and the expression of MMPs was analyzed. The effects of steroid hormones and cytokines on the expression of MMPs were determined in endometrial explant cultures. Results: Expression levels of MMP12 and MMP13 changed during the estrous cycle, while expression of MMP2, MMP9, MMP12, and MMP13 changed during pregnancy. Expression of MMP2, MMP8, and MMP13 mRNAs was cell type-specific at the maternal-conceptus interface. Gelatin zymography showed that enzymatically active MMP2 was present in endometrial tissues. In endometrial explant cultures, estradiol-17β induced the expression of MMP8 and MMP12, progesterone decreased the expression of MMP12, interleukin-1β increased the expression of MMP2, MMP8, MMP9, and MMP13, and interferon-γ increased the expression of MMP2. Conclusion: These results suggest that MMPs expressed in response to steroids and cytokines play an important role in the establishment and maintenance of pregnancy by regulating endometrial remodeling and processing bioactive molecules in pigs.

• Journal of Animal Reproduction and Biotechnology
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• v.38 no.3
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• pp.89-98
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• 2023

Background: The regulation of maternal immunity is critical for the establishment and maintenance of successful pregnancy. Among many cell types regulating the immune system, innate lymphoid cells (ILCs) are known to play an important role in innate immunity. Although some reports show that ILCs are present at the maternalconceptus interface in humans and mice, the expression and function of ILCs in the endometrium have not been studied in pigs. Methods: Thus, we determined the expression, localization, and regulation of ILC markers, CD127 (a common marker for ILCs), BCL11B (a ILC2 marker), and RORC (a ILC3 marker) at the maternal-conceptus interface in pigs. Results: The expression of BCL11B and RORC, but not CD127, in the endometrium changed during pregnancy in a stage-specific manner and the expression of CD127, BCL11B, and RORC was greatest on Day 15 during pregnancy. CD127, BCL11B, and RORC were also expressed in conceptus tissues during early pregnancy and in chorioallantoic tissues during the later stage of pregnancy. BCL11B and RORC proteins were localized to specific cells in endometrial stroma. The expression of CD127 and BCL11B, but not RORC, was increased by the increasing doses of interferon-γ (IFNG) in endometrial explants. Conclusions: These results suggest that ILCs present at the maternal-conceptus interface may play a role in the establishment and maintenance of pregnancy by regulating the innate immunity in pigs.

• Journal of Animal Science and Technology
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• v.51 no.6
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• pp.471-484
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• 2009

The peri-implantation period in mammals is critical with respect to survival of the conceptus (embryo/fetus and associated extraembryonic membranes) and establishment of pregnancy. During this period of pregnancy, reciprocal communication between ovary, conceptus, and endometrium is required for successful implantation and placentation. At this time, interferon tau (IFNT) is synthesized and secreted by the mononuclear trophectodermal cells of the conceptus between days 10 and 21~25. The actions of IFNT to signal pregnancy recognition and induce or increase expression of IFNT-stimulated genes (ISGs), such as ISG15 and OAS, are mediated by the Type I IFN signal transduction pathway. This article reviews the history, signaling pathways of IFNT and the uterine expression of several IFNT-stimulated genes during the peri-implantation period. Collectively, these newly identified genes are believed to be critical to unraveling the mechanism(s) of reciprocal fetal-maternal interactions required for successful implantation and pregnancy.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.1
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• pp.44-51
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• 2012

Calcium ions play an important role in the establishment and maintenance of pregnancy, but molecular and cellular regulatory mechanisms of calcium ion action in the uterine endometrium are not fully understood in pigs. Previously, we have shown that calcium regulatory molecules, transient receptor potential vanilloid type 5 (TRPV6) and calbindin-D9k (S100G), are expressed in the uterine endometrium during the estrous cycle and pregnancy in a pregnancy status- and stage-specific manner, and that estrogen of conceptus origin increases endometrial TRPV6 expression. However, regulation of S100G expression in the uterine endometrium and conceptus expression of S100G has been not determined during early pregnancy. Thus, we investigated regulation of S100G expression by estrogen and interleukin-$1{\beta}$ (IL1B) in the uterine endometrium and conceptus expression of S100G during early pregnancy in pigs. We obtained uterine endometrial tissues from day (D) 12 of the estrous cycle and treated with combinations of steroid hormones, estradiol-$17{\beta}$ ($E_2$) and progesterone ($P_4$), and increasing doses of IL1B. Real-time RT-PCR analysis showed that $E_2$ and IL1B increased S100G mRNA levels in the uterine endometrium, and conceptuses expressed S100G mRNA during early pregnancy, as determined by RT-PCR analysis. To determine if endometrial expression of S100G mRNA during the implantation period was affected by the somatic cell nuclear transfer (SCNT) procedure, we compared S100G mRNA levels in the uterine endometrium from gilts with SCNT-derived conceptuses with those from gilts with conceptuses derived from natural mating on D12 of pregnancy. Real-time RT-PCR analysis showed that levels of S100G mRNA in the uterine endometrium from gilts carrying SCNT-derived conceptuses was significantly lower than those from gilts carrying conceptuses derived from natural mating. These results showed that S100G expression in the uterine endometrium was regulated by estrogen and IL1B of conceptus origin, and affected by the SCNT procedure during early pregnancy. These suggest that conceptus signals regulate S100G, an intracellular calcium transport protein, for the establishment of pregnancy in pigs.

• BMB Reports
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• v.42 no.2
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• pp.72-80
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• 2009

In mammals, major progress has recently been made with the dissection of early embryonic cell specification, the isolation of stem cells from early embryos, and the production of embryonic-like stem cells from adult cells. These studies have overcome long-standing species barriers for stem cell isolation, have revealed a deeper than expected similarity of embryo cell types across species, and have led to a better understanding of the lineage identities of embryo-derived stem cells, most notably of mouse and human embryonic stem (ES) cells. Thus, it has now become possible to propose a species-overarching classification of embryo stem cells, which are defined here as pre- to early post-implantation conceptus-derived stem cell types that maintain embryonic lineage identities in vitro. The present article gives an overview of these cells and discusses their relationships with each other and the conceptus. Consequently, it is debated whether further embryo stem cell types await isolation, and the study of the earliest extraembryonically committed stem cells is identified as a promising new research field.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.12
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• pp.1708-1714
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• 2005

Keratinocyte growth factor (KGF) functions in epithelial growth and differentiation in many tissues and organs. KGF is expressed in the uterine endometrial epithelial cells during the estrous cycle and pregnancy in pigs, and receptors for KGF (KGFR) are expressed by conceptus trophectoderm and endometrial epithelia. KGF has been shown to stimulate the proliferation and differentiation of conceptus trophectoderm. However, the role of KGF on the endometrial epithelial cells has not been determined. Therefore, this study determined the effect of KGF on proliferation and differentiation of endometrial epithelial cells in vitro and in vivo using an immortalized porcine luminal epithelial (pLE) cell line and KGF infusion into the uterine lumen of pigs between Days 9 and 12 of estrous cycle. Results showed that KGF did not stimulate proliferation of uterine endometrial epithelial cells in vitro and in vivo determined by the $^3$H]thymidine incorporation assay and the proliferating cell nuclear antigen staining, respectively. Effects of KGF on expression of several markers for epithelial cell differentiation, including integrin receptor subunits $\alpha$4, $\alpha$5 and $\beta$1, plasmin/trypsin inhibitor, uteroferrin and retinol-binding protein were determined by RT-PCR, Northern and slot blot analyses, and immunohistochemisty, and KGF did not affect epithelial cell differentiation in vitro and in vivo. These results show that KGF does not induce epithelial cell proliferation and differentiation, suggesting that KGF produced by endometrial epithelial cells acts on conceptus trophectoderm in a paracrine manner rather than on endometrial epithelial cells in an autocrine manner.

• Journal of Animal Science and Technology
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• v.53 no.3
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• pp.203-209
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• 2011

Lysophosphatidic acid (LPA) is a small lipid molecule that plays an important role through LPA receptors (LPARs) in reproductive processes. Our previous study has shown maximal expression of LPAR3 in the uterine endometrium on day (D) 12 of pregnancy in pigs, the period when conceptus secretes various molecules such as estrogen and interleukin-$1{\beta}$ (IL1B) and initiates implantation. We determined that endometrial expression of LPAR3 was increased by conceptus estrogen in the previous study, but the effect of IL1B on LPAR3 expression has not been determined. Thus, in this study we examined whether LPAR3 expression was also affected by IL1B. Endometrial explant cultures from D12 of the estrous cycle showed that levels of endometrial LPAR3 expression did not changed in response to IL1B. We also investigated LPAR3 expression in the uterine endometrium on D12 and D30 of pregnancy from gilts with conceptuses derived from somatic cell nuclear transfer (SCNT). The expression of LPAR3 mRNA was lower in endometria from gilts with conceptuses resulting from SCNT compared with those from gilts with embryos resulting from natural mating on D12 of pregnancy, but it was not different between them on D30 of pregnancy. Our results indicate that estrogen of conceptus origin is responsible for induction of LPAR3 expression during the peri-implantation period and appropriate LPA signaling is impaired in the uterine endometrium with SCNT-derived conceptuses during the implantation period in pigs.

• Clinical and Experimental Reproductive Medicine
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• v.23 no.3
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• pp.247-268
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• 1996

It has been known for a long time that gonadotropins and steroid hormones play a pivotal role in a series of reproductive biological phenomena including the maturation of ovarian follicles and oocytes, ovulation and implantation, maintenance of pregnancy and fetal growth & development, parturition and mammary development and lactation. Recent investigations, however, have elucidated that in addition to these classic hormones, multiple growth factors also are involved in these phenomena. Most growth factors in reproductive organs mediate the actions of gonadotropins and steroid hormones or synergize with them in an autocrine/paracrine manner. The insulin-like growth factor(IGF) system, which is one of the most actively investigated areas lately in the reproductive organs, has been found to have important roles in a wide gamut of reproductive phenomena. In the present communication, published literature pertaining to the intrauterine IGF system will be reviewed preceded by general information of the IGF system. The IGF family comprises of IGF-I & IGF-II ligands, two types of IGF receptors and six classes of IGF-binding proteins(IGFBPs) that are known to date. IGF-I and IGF-II peptides, which are structurally homologous to proinsulin, possess the insulin-like activity including the stimulatory effect of glucose and amino acid transport. Besides, IGFs as mitogens stimulate cell division, and also play a role in cellular differentiation and functions in a variety of cell lines. IGFs are expressed mainly in the liver and messenchymal cells, and act on almost all types of tissues in an autocrine/paracrine as well as endocrine mode. There are two types of IGF receptors. Type I IGF receptors, which are tyrosine kinase receptors having high-affinity for IGF-I and IGF-II, mediate almost all the IGF actions that are described above. Type II IGF receptors or IGF-II/mannose-6-phosphate receptors have two distinct binding sites; the IGF-II binding site exhibits a high affinity only for IGF-II. The principal role of the type II IGF receptor is to destroy IGF-II by targeting the ligand to the lysosome. IGFs in biological fluids are mostly bound to IGFBP. IGFBPs, in general, are IGF storage/carrier proteins or modulators of IGF actions; however, as for distinct roles for individual IGFBPs, only limited information is available. IGFBPs inhibit IGF actions under most in vitro situations, seemingly because affinities of IGFBPs for IGFs are greater than those of IGF receptors. How IGF is released from IGFBP to reach IGF receptors is not known; however, various IGFBP protease activities that are present in blood and interstitial fluids are believed to play an important role in the process of IGF release from the IGFBP. According to latest reports, there is evidence that under certain in vitro circumstances, IGFBP-1, -3, -5 have their own biological activities independent of the IGF. This may add another dimension of complexity of the already complicated IGF system. Messenger ribonucleic acids and proteins of the IGF family members are expressed in the uterine tissue and conceptus of the primates, rodents and farm animals to play important roles in growth and development of the uterus and fetus. Expression of the uterine IGF system is regulated by gonadal hormones and local regulatory substances with temporal and spatial specificities. Locally expressed IGFs and IGFBPs act on the uterine tissue in an autocrine/paracrine manner, or are secreted into the uterine lumen to participate in conceptus growth and development. Conceptus also expresses the IGF system beginning from the peri-implantation period. When an IGF family member is expressed in the conceptus, however, is determined by the presence or absence of maternally inherited mRNAs, genetic programming of the conceptus itself and an interaction with the maternal tissue. The site of IGF action also follows temporal (physiological status) and spatial specificities. These facts that expression of the IGF system is temporally and spatially regulated support indirectly a hypothesis that IGFs play a role in conceptus growth and development. Uterine and conceptus-derived IGFs stimulate cell division and differentiation, glucose and amino acid transport, general protein synthesis and the biosynthesis of mammotropic hormones including placental lactogen and prolactin, and also play a role in steroidogenesis. The suggested role for IGFs in conceptus growth and development has been proven by the result of IGF-I, IGF-II or IGF receptor gene disruption(targeting) of murine embryos by the homologous recombination technique. Mice carrying a null mutation for IGF-I and/or IGF-II or type I IGF receptor undergo delayed prenatal and postnatal growth and development with 30-60% normal weights at birth. Moreover, mice lacking the type I IGF receptor or IGF-I plus IGF-II die soon after birth. Intrauterine IGFBPs generally are believed to sequester IGF ligands within the uterus or to play a role of negative regulators of IGF actions by inhibiting IGF binding to cognate receptors. However, when it is taken into account that IGFBP-1 is expressed and secreted in primate uteri in amounts assessedly far exceeding those of local IGFs and that IGFBP-1 is one of the major secretory proteins of the primate decidua, the possibility that this IGFBP may have its own biological activity independent of IGF cannot be excluded. Evidently, elucidating the exact role of each IGFBP is an essential step into understanding the whole IGF system. As such, further research in this area is awaited with a lot of anticipation and attention.