Immunosuppressive activity of a porcine high-molecular weight uterine macromolecule is associated with transforming growth factor-beta

Chemerin Effect on the Endometrial Proteome of the Domestic Pig during Implantation Obtained by LC-MS/MS Analysis

Chemerin (CHEM) is a hormone mainly expressed in adipocytes involved in the regulation of energy homeostasis and inflammatory response. CHEM expression has been demonstrated in the structures of the porcine hypothalamic-pituitary-gonadal axis, as well as in the uterus, trophoblasts and conceptuses of pigs. In this study, we performed high-throughput proteomic analyses (liquid chromatography with tandem mass spectrometry, LC-MS/MS) to examine the influence of CHEM (400 ng/mL) on differentially regulated proteins (DRPs) in the porcine endometrial tissue explants during implantation (15 to 16 days of gestation). Among all 352 DRPs, 164 were up-regulated and 188 were down-regulated in CHEM-treated group. DRPs were assigned to 47 gene ontology (GO) terms (p-adjusted < 0.05). Validation of four DRPs (IFIT5, TGFβ1, ACO1 and PGRMC1) by Western blot analysis confirmed the veracity and accuracy of the LC-MS/MS method used in the present study. We suggest that CHEM, by modulating various protein expressions, takes part in the endometrial cell proliferation, migration and invasion at the time of implantation. It also regulates the endometrial immune response, sensitivity to P4 and the formation of new blood vessels. Additionally, CHEM appears to be an important factor involved in endothelial cell dysfunction during the pathogenesis of preeclampsia. The identification of a large number of DRPs under the influence of CHEM provides a valuable resource for understanding the molecular mechanisms of this hormone action during implantation, which is a prerequisite for better control of pig reproduction.

Suppressor cell activity of ovine caruncular and intercaruncular tissues during the placentation period

We assessed the suppression of lymphocyte proliferation ovine endometrial cells recovered during each trimester (Days 45, 90, and 135) of pregnancy. We evaluated fractionated and unfractionated caruncular (C) and intercaruncular (IC) cells for suppression of cocultured peripheral blood lymphocytes (PBL) in phytohemagglutinin (PHA)-treated cultures. We also evaluated cells for the release of the suppressor factor into the culture medium and tested the factor for transforming growth factor-beta (TGF-beta) activity. Suppression of PHA-induced proliferation of PBL was evident for C and IC cells recovered from each day of pregnancy, and the activity was predominantly attributed to the population(s) of low-density (1.006-1.054 g/ml) cells. The activity was greater for unfractionated C than for IC cells on Day 45, whereas the pattern was reversed by Day 135 of pregnancy. For the C cells, the activity was greatest on Day 45 and least by Day 135. Although suppressor factor was released into the medium from cultured C and IC cells, its activity was not apparently mediated by TGF-beta. In conclusion, we observed a temporal pattern in suppressor activity for unfractionated endometrial cells during pregnancy. Suppression was predominately mediated by a population(s) of low-density cells. In addition, the cells released a soluble suppressor factor that seems to be unrelated to TGF-beta. The suppressor cells may provide immunological protection to the fetoplacental unit by suppressing specific lymphocyte responses directed toward conceptus tissues.

Temporal and spatial expression of connective tissue growth factor (CCN2; CTGF) and transforming growth factor beta type 1 (TGF-beta1) at the utero-placental interface during early pregnancy in the pig

AIMS

To determine the localisation and distribution of connective tissue growth factor (CCN2; CTGF) and transforming growth factor beta type 1 (TGF-beta1) in uterine tissues from cycling and early pregnant pigs.

METHODS

In situ hybridisation and immunohistochemistry were used to localise CCN2 (CTGF) or TGF-beta1 in uteri obtained from gilts on days 0, 5, 10, 12, 15, and 18 of the oestrous cycle or days 10, 12, 14, 16, 17, and 21 of gestation.

RESULTS

In cycling animals, CCN2 (CTGF) mRNA and protein were abundant in luminal epithelial cells (LECs) and glandular epithelial cells (GECs), with lesser amounts in stromal fibroblasts and little or none in endothelial cells. A similar pattern of staining was seen up to day 10 of pregnancy, except that overall staining intensities for CCN2 (CTGF) mRNA or protein were higher and that stromal and endothelial cells were CCN2 (CTGF) positive. However, on days 12-17 there was a striking decrease in the amount of CCN2 (CTGF) in LECs at the utero-conceptus interface, which was associated with maternal stromal matrix reorganisation and the onset of subepithelial neovascularisation. This differential distribution of CCN2 (CTGF) was localised to those LECs that were in close proximity to or in apposition with trophoblast cells. This decrease in CCN2 (CTGF) staining was transient in nature and high amounts of CCN2 (CTGF) were again apparent in LECs on days 17-21, when endometrial neovascularisation and matrix remodelling were complete. The expression of uterine TGF-beta1 was comparable to that of CCN2 (CTGF) at most stages of the oestrous cycle or early pregnancy. Pre-elongation blastocysts recovered on day 10 were positive for both CCN2 (CTGF) and TGF-beta1 in the extra-embryonic trophectoderm, endoderm, and inner cell mass. On day 12, trophectoderm expressed low amounts of TGF-beta1 mRNA and non-detectable amounts of TGF-beta1 protein or CCN2 (CTGF) mRNA or protein. By days 17-21, the expression of both growth factors in the extra-embyronic/placental membranes increased and frequently exceeded that seen in LECs.

CONCLUSIONS

The pattern of CCN2 (CTGF) production during the initial attachment phase supports a role for this factor in stromal remodelling and neovascularisation, although alternative functions at later stages such as epithelial-epithelial interactions are also possible. In most major cell types in the uterus or utero-placental unit, CCN2 (CTGF) expression was highly correlated with that of TGF-beta(1), indicating that CCN2 (CTGF) may mediate some of the functions of TGF-beta in the reproductive tract during the oestrous cycle and pregnancy. The data further highlight epithelium as an important source of CCN2 (CTGF) in the regulation of uterine function.

Immunosuppressive macromolecules of endometrial and conceptus origins in livestock species

Since the mid- to late-1970s, intrauterine immunosuppressive macromolecules recovered from endometrial and conceptus secretions have been reported for livestock species. Using primarily in vitro assays, in conjunction with a limited number of techniques conducted in vivo, these macromolecules were shown to suppress various T-cell responses. Some macromolecules were also shown to suppress cytolytic activities of non T-cells. It remains unknown as to whether these macromolecules actually afford protection to the conceptus by suppressing cell-mediated immune responses directed toward conceptus tissues. Endometrial effector cells in the ewe respond to antigenic stimulation and preattachment trophoblastic cells of pigs and sheep can be lysed by effector cells. Consequently, these observations suggest a need for immunosuppression, either locally at placentation sites or within the entire uterus. This review describes the intrauterine macromolecules that have been shown to suppress lymphocyte responses. Additional information, although limited at this time, refers to their origin and possible mechanisms of action. As more reagents become available to complete the identification of the intrauterine immune cells in livestock animals, experiments (e.g. antibody-mediated depletion of cells) can be conducted to determine the precise functions of all these cells. Knowing their functions will help delineate whether or not immunosuppressive macromolecules have a role in the regulation and maintenance of conceptus tissues during pregnancy.

Beta transforming growth factors (TGFbeta) at the porcine conceptus-maternal interface. Part II: uterine TGFbeta bioactivity and expression of immunoreactive TGFbetas (TGFbeta1, TGFbeta2, and TGFbeta3) and their receptors (type I and type II)

Porcine uterine tissues were collected from Days 10 to 14 of gestation (peri-implantation period) or corresponding days of the estrous cycle. Results indicated a marked increase in beta transforming growth factors (TGFbeta1, TGFbeta2, and TGFbeta3) and TGFbeta receptor (type I and type II) immunostaining in uterine luminal epithelium (ULE) between Days 10 and 14 of gestation, but there was no increase in ULE immunostaining on the corresponding days of the estrous cycle. Uterine glands and stroma were intensely immunopositive in pregnant gilts for TGFbeta isoforms and their receptors, but immunostaining was weak to undetectable in cycling gilts. No differences were detected in myometrium, in which immunostaining was moderate in both cycling and pregnant gilts. Additionally, TGFbeta2 and TGFbeta receptor (type I and type II) immunostaining was detected in uterine monocyte/macrophage-like cells. Western blotting detected the presence of all three TGFbeta isoforms in uterine luminal flushings. The CCL64 cell TGFbeta bioassay detected bioactive TGFbetas++ in uterine luminal flushings on Days 12, 13, an 14 of gestation. These results strongly indicate that uterine expression of TGFbetas and their receptors is pregnancy specific and that bioactive TGFbetas are present at the conceptus-maternal interface in the peri-implantation period in pigs. Thus TGFbetas are likely to be involved in autocrine-paracrine interactions between the maternal uterus and the conceptus.

Regulation of uterine immune function by progesterone--lessons from the sheep

Survival of the fetal allograft results from orchestrated adjustments in activity of maternal lymphoid cells as well as in trophoblast gene expression. One molecule that regulates uterine immune responsiveness is progesterone. In fact, uterine skin graft survival and susceptibility to bacterial infections are increased by progesterone. This review focuses on the role of progesterone in regulation of uterine immune function in the sheep. While the importance of progesterone as a regulator of immune function likely varies between species, concepts derived from the sheep model may prove pertinent to other species also. The actions of progesterone on uterine immune function in the ewe change during pregnancy. Before day 50 of gestation, i.e. when the uterus is still dependent upon the corpus luteum as a source of progesterone, concentrations of progesterone are probably not high enough at the maternal fetal interface to inhibit lymphocyte activation. During this early period of pregnancy, progesterone inhibits uterine immune function by inducing endometrial secretion of a protein called uterine milk protein (UTMP) that itself is inhibitory to lymphocyte function. After day 50 of pregnancy, it is likely that the placenta produces sufficient amounts of progesterone to directly inhibit lymphocyte proliferation. Additional inhibition is achieved because of sustained synthesis of UTMP. Accordingly, progesterone acts to regulate uterine immune function in ways that allows for inhibition of immune responses at the utero-placental interface without systemic immunosuppression.