Trophoblast Major Histocompatibility Complex Class I Expression Is Associated with Immune-Mediated Rejection of Bovine Fetuses Produced by Cloning

Extensive rewiring of the gene regulatory interactions between in vitro-produced conceptuses and endometrium during attachment

Pregnancy loss is a significant problem when embryos produced in vitro are transferred to a synchronized uterus. Currently, mechanisms that underlie losses of in vitro-produced embryos during implantation are largely unknown. We investigated this problem using cattle as a model of conceptus attachment by analyzing transcriptome data of paired extraembryonic membrane and endometrial samples collected on gestation days 18 and 25, which spans the attachment window in cattle. We identified that the transfer of an in vitro-produced embryo caused a significant alteration in transcript abundance of hundreds of genes in extraembryonic and endometrial tissues on gestation days 18 and 25, when compared to pregnancies initiated by artificial insemination. Many of the genes with altered transcript abundance are associated with biological processes that are relevant to the establishment of pregnancy. An integrative analysis of transcriptome data from the conceptus and endometrium identified hundreds of putative ligand-receptor pairs. There was a limited variation of ligand-receptor pairs in pregnancies initiated by in vitro-produced embryos on gestation day 18, and no alteration was observed on gestation day 25. In parallel, we identified that in vitro production of embryos caused an extensive alteration in the coexpression of genes expressed in the extraembryonic membranes and the corresponding endometrium on both gestation days. Both the transcriptional dysregulation that exists in the conceptus or endometrium independently and the rewiring of gene transcription between the conceptus and endometrium are a potential component of the mechanisms that contribute to pregnancy losses caused by in vitro production of embryos.

Seahorse Male Pregnancy as a Model System to Study Pregnancy, Immune Adaptations, and Environmental Effects

Seahorses, together with sea dragons and pipefishes, belong to the Syngnathidae family of teleost fishes. Seahorses and other Syngnathidae species have a very peculiar feature: male pregnancy. Among different species, there is a gradation of paternal involvement in carrying for the offspring, from a simple attachment of the eggs to the skin surface, through various degrees of egg coverage by skin flaps, to the internal pregnancy within a brood pouch, which resembles mammalian uterus with the placenta. Because of the gradation of parental involvement and similarities to mammalian pregnancy, seahorses are a great model to study the evolution of pregnancy and the immunologic, metabolic, cellular, and molecular processes of pregnancy and embryo development. Seahorses are also very useful for studying the effects of pollutants and environmental changes on pregnancy, embryo development, and offspring fitness. We describe here the characteristics of seahorse male pregnancy, its regulatory mechanisms, the development of immune tolerance of the parent toward the allogeneic embryos, and the effects of environmental pollutants on pregnancy and embryo development.

The Role of Interferon (IFN)-γ in Extravillous Trophoblast Cell (EVT) Invasion and Preeclampsia Progression

The involvement of the immune system in pregnancy is a controversial subject. The functions of T helper (Th) 1 and Th2 cells have been proposed, that Th1 cytokines promoting allograft rejection may impair pregnancy, whereas Th2-type cytokines suppressing Th1 responses improve allograft tolerance and hence embryonic survival. Maternal-fetal tolerance begins in the uterus; therefore, optimal adaptation to the fetus is the result of a complex interference. The invasion of extravillous trophoblast cells (EVTs) into the decidua and the inner third of the myometrium is essential for a healthy pregnancy. The mechanisms that influence trophoblast invasion are unknown; however, cytokines from uterine natural killer (uNK) cells, NKT cells, macrophages, and T cells appear to be involved. All these cells are major sources of interferon gamma (IFN-γ). Recent studies have shown that IFN-γ can inhibit EVT invasion via a mechanism dependent on an increase in EVT apoptosis and a decrease in matrix metalloproteinases (MMPs). Regarding controversies in this context, this study aimed to comprehensively review the role of IFN-γ and IFN-γ-producing cells in EVT invasion, successful pregnancy, and preeclampsia.

Development and characterization of type I interferon receptor knockout sheep: A model for viral immunology and reproductive signaling

Type I interferons (IFNs) initiate immune responses to viral infections. Their effects are mediated by the type I IFN receptor, IFNAR, comprised of two subunits: IFNAR1 and IFNAR2. One or both chains of the sheep IFNAR were disrupted in fetal fibroblast lines using CRISPR/Cas9 and 12 lambs were produced by somatic cell nuclear transfer (SCNT). Quantitative reverse transcription-polymerase chain reaction for IFN-stimulated gene expression showed that IFNAR deficient sheep fail to respond to IFN-alpha. Furthermore, fibroblast cells from an IFNAR2^−/− fetus supported significantly higher levels of Zika virus (ZIKV) replication than wild-type fetal fibroblast cells. Although many lambs have died from SCNT related problems or infections, one fertile IFNAR2^−/− ram lived to over 4 years of age, remained healthy, and produced more than 80 offspring. Interestingly, ZIKV infection studies failed to demonstrate a high level of susceptibility. Presumably, these sheep compensated for a lack of type I IFN signaling using the type II, IFN-gamma and type III, IFN-lambda pathways. These sheep constitute a unique model for studying the pathogenesis of viral infection. Historical data supports the concept that ruminants utilize a novel type I IFN, IFN-tau, for pregnancy recognition. Consequently, IFNAR deficient ewes are likely to be infertile, making IFNAR knockout sheep a valuable model for studying pregnancy recognition. A breeding herd of 32 IFNAR2^+/− ewes, which are fertile, has been developed for production of IFNAR2^−/− sheep for both infection and reproduction studies.

Changes in mononuclear immune cells during bovine pregnancy

This study aimed to determine the differences in gene expression between mononuclear cells derived from peripheral blood and endometrium during pregnancy in cattle and to determine the proportion of mononuclear cells in the endometrium of pregnant and diestrous cows. Endometrial tissue and peripheral blood were collected from Day 34±2 pregnant cows, and mononuclear cell populations were quantified and sorted (n =5). The relative mRNA levels of inflammatory mediators was assessed by quantitative real time polymerase chain reaction. During pregnancy, the proportion of CD8+ , CD4+ , CD4+ CD25- and CD4+ CD25dim cells among mononuclear cells was greater in blood than endometrium, and cells positive for CD14 and CD68 expressed greater mRNA amounts of interleukin (IL ) 6 , CXCL8 and IL10 in endometrium compared with blood. Cells positive for γ/δ-T cell receptor expressed greater amounts of IL1A transcript in the endometrium than in blood of diestrous cows, CD4+ CD25bright cells expressed more CTLA4 mRNA in the endometrium compared with blood of diestrous cows, and endometrial natural killer cells expressed greater CXCL8 mRNA compared with blood of pregnant and diestrous cows. The percentages of CD21+ , NCR1+ , CD8+ , FoxP3+ , CD3+ and CD68+ cells were greater in the endometrium of Day 35 pregnant cows compared with diestrous cows.

Increased expression of pro-inflammatory cytokines at the fetal-maternal interface in bovine pregnancies produced by cloning

PROBLEM

A significant rate of spontaneous abortion is observed in cattle pregnancies produced by somatic cell nuclear transfer (SCNT). Major histocompatibility complex class I (MHC-I) proteins are abnormally expressed on the surface of trophoblast cells from SCNT conceptuses.

METHOD OF STUDY

MHC-I homozygous compatible (n = 9), homozygous incompatible (n = 8), and heterozygous incompatible (n = 5) pregnancies were established by SCNT. Eight control pregnancies were established by artificial insemination. Uterine and trophoblast samples were collected on day 35 ±1 of pregnancy, the expression of immune-related genes was examined by qPCR, and the expression of trophoblast microRNAs was assessed by sequencing.

RESULTS

Compared to the control group, trophoblast from MHC-I heterozygous incompatible pregnancies expressed increased levels of CD28, CTLA4, CXCL8, IFNG, IL1A, IL2, IL10, IL12B, TBX21, and TNF, while GNLY expression was downregulated. The MHC-I homozygous incompatible treatment group expressed increased levels of IFNG, IL1A, and IL2 while the MHC-I homozygous compatible group did not differentially express any genes compared to the control group. In the endometrium, relative to the control group, MHC-I heterozygous incompatible pregnancies expressed increased levels of CD28, CTLA4, CXCL8, IFNG, IL10, IL12B, and TNF, while GATA3 expression was downregulated. The MHC-I homozygous incompatible group expressed decreased amounts of CSF2 transcripts compared with the control group but did not have abnormal expression of any other immune-related genes. MHC-I incompatible pregnancies had 40 deregulated miRNAs compared to control pregnancies and 62 deregulated microRNAs compared to MHC-I compatible pregnancies.

CONCLUSIONS

MHC-I compatibility between the dam and fetus prevented an exacerbated maternal immune response from being mounted against fetal antigens.

Lymphocyte soluble factors from pregnant cows modulate mRNA transcript abundances encoding for proteins associated with trophoblast growth and development

This study was conducted to determine whether T cell populations are responsible for modulating placental development during gestation in cattle. It was hypothesized that CD4+CD25+ and γ/δ+ T cells modulate gene expression, based on mRNA transcript abundances, and promote proliferation and survival of trophoblast cells. Peripheral blood was collected from cows at 160 to 180 days of gestation and non-pregnant cows, T cell populations CD8+, CD4+, CD4+CD25+, CD24+CD25-, and γ/δ+ T cells were isolated, cultured for 48 h, and supernatant was collected. Placental samples were digested, and trophoblast cells were cultured for 24 h. Trophoblast cells were cultured with 50 μL of T cell-conditioned media and 50 μL of fresh culture media for an additional 48 h. Samples in control wells were treated with unconditioned media. Trophoblast cell proliferation, apoptosis, and mRNA transcript assays were conducted. There was no effect of T cell population on trophoblast apoptosis rate, proliferation, and relative mRNA transcript abundances. The T cell supernatant from pregnant and non-pregnant cows induced greater apoptosis rates in trophoblast cells than unconditioned media. Trophoblast cells proliferated less when treated with T cell supernatant from pregnant compared to unconditioned medium and non-pregnant cows. Treatment with the T cell supernatant from pregnant cows resulted in larger abundances of BMP5, IGF1R, PAG10, FGF2, RSPO3 and TMED2 and also a lesser abundance of FGF2 mRNA transcript than non-pregnant group and unconditioned media treatments. Supernatant from T cell derived from pregnant cows modulates trophoblast mRNA transcript abundances differently from T cell supernatant of non-pregnant cows.

Assessment of microchimerism following somatic cell nuclear transfer and natural pregnancies in goats

Microchimerism is defined as the presence of a small population of cells or DNA in 1 organism originated from a genetically different organism. It is well established that this phenomenon occurs in humans and mice as cells are exchanged between mother and fetus during gestation. Currently, no information is available about the presence of maternal microchimerism in goats, and the only published study is limited to an evaluation of fetal and fetal-fetal microchimerism in blood samples following natural breeding. In order to determine whether bidirectional fetal-maternal cell or DNA trafficking occurs in goats, we assessed: 1) fetal microchimerism in surrogates that gave birth to somatic cell nuclear transfer (SCNT)-derived transgenic offspring (n = 4), 2) maternal microchimerism following natural breeding of SCNT-derived transgenic does with a nontransgenic buck (n = 4), and 3) fetal-fetal microchimerism in nontransgenic twins of transgenic offspring (n = 3). Neomycin-resistance gene (NEO) gene was selected as the marker to detect the presence of the αMHC-TGF-β1-Neo transgene in kidney, liver, lung, lymph node, and spleen. We found no detectable maternal or fetal-fetal microchimerism in the investigated tissues of nontransgenic offspring. However, fetal microchimerism was detected in lymph node tissue of one of the surrogate dams carrying a SCNT pregnancy. These results indicate occurrence of cell trafficking from fetus to mother during SCNT pregnancies. The findings of this study have direct implications on the use and disposal of nontransgenic surrogates and nontransgenic offspring.

Spontaneous Atrial Fibrillation in Transgenic Goats With TGF (Transforming Growth Factor)-β1 Induced Atrial Myopathy With Endurance Exercise

BACKGROUND

There is increasing evidence that endurance exercise is associated with increased risk of atrial fibrillation (AF). However, it is unknown if the relationship between endurance exercise and AF is dependent on an atrial myopathy.

METHODS

Six cardiac-specific TGF (transforming growth factor)-β1 transgenic and 6 wild-type (WT) goats were utilized for these studies. Pacemakers were implanted in all animals for continuous arrhythmia monitoring and AF inducibility. AF inducibility was evaluated using 5 separate 10 s bursts of atrial pacing (160-200 ms). Three months of progressive endurance exercise (up to 90 minutes at 4.5 mph) was performed. Quantitative assessment of circulating microRNAs and inflammatory biomarkers was performed.

RESULTS

Sustained AF (≥30 s) was induced with 10 s of atrial pacing in 4 out of 6 transgenic goats compared with 0 out of 6 WT controls at baseline (P<0.05). No spontaneous AF was observed at baseline. Interestingly, between 2 and 3 months of exercise 3 out of 6 transgenic animals developed self-terminating spontaneous AF compared with 0 out of 6 WT animals (P<0.05). There was an increase in AF inducibility in both transgenic and WT animals during the first 2 months of exercise with partial normalization at 3 months (transgenic 67%; 100%; 83% versus WT 0%; 67%; 17%). These changes in AF susceptibility were associated with a decrease in circulating microRNA-21 and microRNA-29 during the first 2 months of exercise with partial normalization at 3 months in both transgenic and WT animals. Finally, MMP9 (matrix metallopeptidase 9) was increased during the second and third months of exercise training.

CONCLUSIONS

This study demonstrates a novel transgenic goat model of cardiac fibrosis (TGF-β1 overexpression) to demonstrate that endurance exercise in the setting of an underlying atrial myopathy increases the incidence of spontaneous AF. Furthermore, endurance exercise seems to increase inducible AF secondary to altered expression of key profibrotic biomarkers that is independent of the presence of an atrial myopathy.

Gene expression and lymphocyte population at the fetal-maternal interface in sheep pregnancies established by somatic cell nuclear transfer

The hypothesis of this study was that the leukocyte populations and expression levels of genes related to immune response, growth factors and apoptosis would be altered at the fetal-maternal interface in somatic cell nuclear transfer (SCNT)-generated sheep pregnancies. Placental and endometrial samples from sheep pregnancies established by SCNT and natural breeding (control) were collected at 45 days and at term. Expression of genes related to growth factors, apoptosis and immune response was examined using quantitative reverse transcription polymerase chain reaction. Endometrial leukocyte populations and major histocompatibility class I (MHC-I) protein expression were examined by immunohistochemistry. At term we observed altered expression of genes related to apoptosis, growth factors and immune response in placental and endometrial tissue of SCNT pregnancies. In Day-45 pregnancies there was less-pronounced abnormal expression and only genes related to apoptosis and growth factors were abnormal in the placenta. Endometrial gene expression profiles were similar to age-matched controls. Placental MHC-I protein expression was similar in SCNT and controls at 45 days but increased in the SCNT at term. The altered gene expression at the fetal-maternal interface likely contributes to the placental dysfunction and overgrowth observed in sheep SCNT pregnancies.

Genetic and epigenetic regulation of major histocompatibility complex class I gene expression in bovine trophoblast cells

Problem

The regulatory mechanisms governing differential expression of classical major histocompatibility complex (MHC) class I (MHC‐Ia) and non‐classical MHC class I (MHC‐Ib) genes are poorly understood.

Method of study

Quantitative reverse transcription‐ polymerase chain reaction (PCR) was used to compare the abundance of MHC‐I transcripts and related transcription factors in peripheral blood mononuclear cells (PBMC) and placental trophoblast cells (PTC). Methylation of MHC‐I CpG islands was detected by bisulfite treatment and next‐generation sequencing. Demethylation of PBMC and PTC with 5′‐aza‐deoxycytidine was used to assess the role of methylation in gene regulation.

Results

MHC‐I expression was higher in PBMC than PTC and was correlated with expression of IRF1, class II MHC transactivator (CIITA), and STAT1. The MHC‐Ia genes and BoLA‐NC1 were devoid of CpG methylation in PBMC and PTC. In contrast, CpG sites in the gene body of BoLA‐NC2, ‐NC3, and ‐NC4 were highly methylated in PBMC but largely unmethylated in normal PTC and moderately methylated in somatic cell nuclear transfer PTC. In PBMC, demethylation resulted in upregulation of MHC‐Ib by 2.8‐ to 6‐fold, whereas MHC‐Ia transcripts were elevated less than 2‐fold.

Conclusion

DNA methylation regulates bovine MHC‐Ib expression and is likely responsible for the different relative levels of MHC‐Ib to MHC‐Ia transcripts in PBMC and PTC.