Enhancement of maternal recognition of pregnancy with parthenogenetic embryos in bovine embryo transfer

Early transcriptomic changes in peripheral blood 7 days after embryo transfer in dairy cattle

A common goal of the dairy industry is to shorten the calving interval to reap several benefits associated with improved fertility. Early pregnancy detection is crucial to shorten this interval, allowing for prompt re-insemination of cows that failed to conceive after the first service. Currently, the industry lacks a method to accurately predict pregnancy within the first 3 wk. The polypeptide cytokine IFN-tau (IFNT) is the primary signal for maternal recognition of pregnancy in ruminants. As IFNT is released from the early conceptus, it initiates a cascade of effects, including upregulation of IFN-stimulated genes (ISG). Expression of ISG can be detected in the peripheral blood. The present study aimed to characterize peripheral transcriptomic changes, including the ISG, as early as d 7 after embryo transfer. A total of 170 Holstein heifers received in vitro-produced embryos. Whole blood was collected from these heifers within 24 h of the embryo transfer (d 0), d 7, and d 14 after embryo transfer. The heifers were divided into 2 groups, pregnant and nonpregnant, based on pregnancy diagnosis on d 28 via ultrasound. Total RNA was extracted from the peripheral blood of pregnant and nonpregnant heifers, pooled and sequenced. Expression analysis on d 7 heifers resulted in 13 significantly differentially expressed genes mostly related to innate immunity. Differential expression analysis comparing pregnant heifers on d 0 to the same heifers on d 14 showed 51 significantly differentially expressed genes. Eight genes were further quantified through reverse-transcription quantitative real-time PCR for biological validation. On d 7 after embryo transfer, mRNA transcriptions of EDN1, CXCL3, CCL4, and IL1A were significantly upregulated in pregnant heifers (n = 14) compared with nonpregnant heifers (n = 14), with respective fold changes of 8.10, 18.12, 29.60, and 29.97. Although on d 14 after embryo transfer, mRNA transcriptions of ISG15, MX2, OASY1, and IFI6 were significantly upregulated in the blood of pregnant heifers (n = 14) compared with the same heifers on d 0, with respective fold changes of 5.09, 2.59, 3.89, and 3.08. These findings demonstrate that several immune-related genes and ISG are activated during the first 2 wk after embryo transfer, which may explain how the maternal immune system accommodates the allogenic conceptus. To further investigate the diagnostic potentials of these genes, future studies are warranted to analyze the specificity and sensitivity of these biomarkers to predict early pregnancy.

Interferon-Stimulated Gene Expression in Peripheral Blood Leucocytes as a Convenient Prediction Marker for Embryo Status in Embryo-Transferred Japanese Black Cows during the Peri-Implantation Period

Pregnancy diagnosis during early gestation is important for cattle reproduction. The expression of interferon-stimulated genes (ISGs) in peripheral blood leukocytes (PBLs) was studied in embryo-transferred (ET) Japanese Black cattle. ISGs in PBLs-ISG15, MX1, MX2, and OAS1-were detected in multiple ovulation ET cattle using a real-time quantitative polymerase chain reaction, and receiver operating characteristic (ROC) curve analysis was performed. Gestational status was predicted using the average ISG levels during the normal estrous cycle (AVE) and the Youden index from the ROC curve analysis as cutoff values. The ISG15, MX1, and MX2 levels were significantly higher in pregnant cattle (n = 10) than in non-pregnant cattle (n = 23) on gestation day 21, whereas the levels of all ISGs were similar between non-pregnant and non-pregnant cattle with late embryonic death (n = 7). ISG15, MX1, and MX2 appropriately predicted the gestational status of ET cows. The statistical evaluation of the diagnostic accuracy in ET cows on day 21 of gestation presented higher values of sensitivity, specificity, accuracy, and positive predictive values of ISG15, MX1, and MX2 using the Youden index than using the AVE. Therefore, ISG15, MX1, and MX2 are excellent biomarkers of gestational status during the peri-implantation period in ET cattle.

Interferon-Tau regulates a plethora of functions in the corpus luteum

The corpus luteum (CL) plays a vital role in regulating the reproductive cycle, fertility, and in maintaining pregnancy. Interferon-tau (IFNT) is the maternal recognition of a pregnancy signal in domestic ruminants; its uterine, paracrine actions, which extend the CL lifespan, are widely established. However, considerable evidence also suggests a direct, endocrine role for IFNT. The purpose of this review is to highlight the importance of IFNT in CL maintenance, acting directly and in a cell-specific manner. A transcriptomic study revealed a distinct molecular profile of IFNT-exposed day 18, pregnant bovine CL, compared to the non-pregnant gland. A substantial fraction of the differentially expressed genes was downregulated, many of which are known to be elevated by prostaglandin F2A (PGF2A). In vitro, IFNT was found to mimic changes observed in the luteal transcriptome of early pregnancy. Key luteolytic genes such as endothelin-1 (EDN1), transforming growth factor-B1 (TGFB1), thrombospondins (THBSs) 1&2 and serpine-1 (SERPINE1) were downregulated in luteal endothelial cells. Luteal steroidogenic large cells (LGCs) were also found to be a target for the antilutelotytic actions of IFNT. IFNT-treated LGCs showed a significant reduction in the expression of the proapoptotic, antiangiogenic THBS1&2, as well as TGFBR1 and 2. Furthermore, IFNT was shown to be a potent survival factor for luteal cells in vivo and in vitro, activating diverse pathways to promote cell survival while suppressing cell death signals. Pentraxin 3 (PTX3), robustly upregulated by IFNT in various luteal cell types, mediated many of the prosurvival effects of IFNT in LGCs. A novel reciprocal inhibitory crosstalk between PTX3 and THBS1 lends further support to their respective survival and apoptotic actions in the CL. Even though IFNT did not directly regulate progesterone synthesis, it could maintain its concentrations, by increasing luteal cell survival and by supporting vascular stabilization. The direct effects of IFNT in the CL, enhancing cell survival and vasculature stabilization while curbing luteolytic activities, may constitute an important complementary branch leading to the extension of the luteal lifespan during early pregnancy.

Impaired placentomal interferon signaling as the possible cause of retained fetal membrane in parturition-induced cows

Although hormonal induction of parturition in cattle results in the successful delivery of healthy calves, the risk of retained fetal membrane is significantly increased. In a previous study, a combination of the long-acting glucocorticoid, triamcinolone acetonide, with a high dose of betamethasone partially normalized the placentomal gene expression during parturition; however, the incidence of retained fetal membrane remained high. This study further explored placentomal dysfunction and aimed to elucidate the mechanism of retained fetal membrane in parturition-induced cows. In this study, transcriptome analysis revealed that enhanced glucocorticoid exposure normalized the expression of a substantial fraction of genes in the cotyledons. In contrast, a significant reduction in the multiple signaling pathway activities, including interferon signaling, was found in the caruncles during induced parturition. Real-time PCR showed that the expression of interferon-tau in the caruncles, but not interferon-alpha or interferon-gamma, was significantly lower in induced parturition than spontaneous parturition. Interferon-stimulated gene expression was also significantly decreased in the caruncles during induced parturition. These results indicate that interferon signaling could be important for immunological control in placentomes during parturition. Additionally, this suggests that interferon-tau might be a pivotal ligand for interferon receptors in the caruncles. This study revealed that peripheral blood leukocytes in prepartum cows transcribed interferon-tau. Macrophage infiltration in the placentome is known to participate in the detachment of the fetal membrane from the caruncle. Thus, this study raised the possibility that immune cells migrating into the caruncles at parturition may act as a source of ligands that activate interferon signaling.

Heat stress modulates polymorphonuclear cell response in early pregnancy cows: I. interferon pathway and oxidative stress

One of the major causes of early pregnancy loss is heat stress. In ruminants, interferon tau (IFNT) is the embryo signal to the mother. Once the interferon signaling pathway is activated, it drives gene expression for interferon-stimulated genes (ISGs) and alters neutrophils responses. The aim of the present study was to evaluate interferon (IFN) pathway, ISGs and gene expression in polymorphonuclear leukocytes (PMN) and oxidative stress in dairy cows under heat stress. Pregnant cows had their estrous cycle synchronized and randomly assigned to a comfort or heat stress group. Blood samples were collected at artificial insemination (AI) and on Days 10, 14 and 18 following AI. Pregnant cows were pregnancy checked by ultrasound on Day 30 and confirmed on Day 60 post-AI. Results are presented as mean ± SEM. The corpus luteum (CL) diameter was not different between groups of pregnant cows; concentration of progesterone of pregnant cows on Day 18 following AI was greater in comfort group compared to heat stressed group. Comfort pregnant cows had higher expression of all analyzed genes from interferon pathway, except for IFNAR1, on both Days 14 and 18. Conversely, heat stressed cows did not show altered expression of IFNT pathway genes and ISGs between Days 10, 14, and 18 after AI. The oxidative stress, determined as malondialdehyde (MDA) levels, was greater in heat stress group on Days 10, 14 and 18, independent of pregnancy status. Heat stress negatively influences expression of ISGs, IFN pathway gene expression in neutrophils, and oxidative stress. Our data suggest that lower conception rates in cows under heat stress are multifactorial, with the association of interferon pathway activation and the unbalanced oxidative stress being main contributing factors.

Downregulated luteolytic pathways in the transcriptome of early pregnancy bovine corpus luteum are mimicked by interferon-tau in vitro

Background

Maintenance of the corpus luteum (CL) beyond the time of luteolysis is essential for establishing pregnancy. Identifying the distinct features of early pregnancy CL remains unresolved, hence we analyzed here the transcriptome of CL on day 18 pregnant (P) and non-pregnant (NP) cows using RNA-Seq. CL of P cows expressed ISGs, verifying exposure to the pregnancy recognition signal, interferon-tau (IFNT), whereas the CL of NP cows had elevated luteal progesterone levels, implying that luteolysis had not yet commenced.

Results

The DEGs, IPA, and metascape canonical pathways, along with GSEA analysis, differed markedly in the CL of P cows from those of NP cows, at the same day of the cycle. Both metascape and IPA identified similar significantly enriched pathways such as interferon alpha/beta, sonic hedgehog pathway, TNFA, EDN1, TGFB1, and PDGF. However, type-1 interferon and sonic hedgehog pathways were positively enriched whereas most of the enriched pathways were downregulated in the P compared to NP samples. Thirty-four % of these pathways are known to be elevated by PGF2A during luteolysis. Notably, selective DEGs in luteinized granulosa cells were modulated by IFNT in vitro in a similar manner to their regulation in the CL of P cows.

Conclusion

This study unraveled the unique transcriptomic signature of the IFNT-exposed, early pregnancy CL, highlighting the abundance of downregulated pathways known to be otherwise induced during luteolysis. These and IFNT-regulated in vitro pregnancy-specific DEGs suggest that IFNT contributes to the characteristics and maintenance of early pregnancy CL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07747-3.

Interferon-Tau Exerts Direct Prosurvival and Antiapoptotic Actions in Luteinized Bovine Granulosa Cells

Interferon-tau (IFNT), serves as a signal to maintain the corpus luteum (CL) during early pregnancy in domestic ruminants. We investigated here whether IFNT directly affects the function of luteinized bovine granulosa cells (LGCs), a model for large-luteal cells. Recombinant ovine IFNT (roIFNT) induced the IFN-stimulated genes (ISGs; MX2, ISG15, and OAS1Y). IFNT induced a rapid and transient (15–45 min) phosphorylation of STAT1, while total STAT1 protein was higher only after 24 h. IFNT treatment elevated viable LGCs numbers and decreased dead/apoptotic cell counts. Consistent with these effects on cell viability, IFNT upregulated cell survival proteins (MCL1, BCL-xL, and XIAP) and reduced the levels of gamma-H2AX, cleaved caspase-3, and thrombospondin-2 (THBS2) implicated in apoptosis. Notably, IFNT reversed the actions of THBS1 on cell viability, XIAP, and cleaved caspase-3. Furthermore, roIFNT stimulated proangiogenic genes, including FGF2, PDGFB, and PDGFAR. Corroborating the in vitro observations, CL collected from day 18 pregnant cows comprised higher ISGs together with elevated FGF2, PDGFB, and XIAP, compared with CL derived from day 18 cyclic cows. This study reveals that IFNT activates diverse pathways in LGCs, promoting survival and blood vessel stabilization while suppressing cell death signals. These mechanisms might contribute to CL maintenance during early pregnancy.

The transfer of parthenogenetic embryos following artificial insemination in cows can enhance pregnancy recognition via the secretion of interferon tau

Repeat breeding is a reproductive disorder in cattle. Embryo transfer following artificial insemination (AI) improves pregnancy rate by replenishing interferon tau (IFNT), but it results in a notably higher rate of twin occurrence. This study hypothesized that parthenogenetic (PA) embryo transfer following AI (AI + PA) could improve the conception rate because that PA embryo become as a supplemental source of IFNT without twins. PA embryos showed higher IFNT mRNA expression than in vitro fertilization (IVF) embryos. An examination of the effect of the cultured conditioned media (CM) of PA or IVF embryos on Madin-Darby bovine kidney cells with stably introduced promoter-reporter constructs of interferon-stimulated gene 15 (ISG15, marker of IFN response) showed higher stimulation levels of ISG15 promoter activity with PA than with IVF embryo. We investigated in vivo the effect of AI + PA on healthy Japanese Black cattle. Cattle transferred with PA embryo alone were non-fertile, but those that underwent AI + PA showed a pregnancy rate of 53.3%, the similar as that with AI alone (60%). In pregnant cattle in AI + PA group, adding the PA embryo upregulated the expression of ISGs and plasma progesterone concentration. No twin were generated in AI only and AI + PA groups. Using repeat breeding Holstein cows that did not become pregnant with 4-9 times of AI, transfer of PA embryo following AI resulted in a higher pregnancy rate than that of control (AI only). We suggest that AI + PA may be beneficial for improving maternal pregnancy recognition in repeat breeder cattle while avoiding twin generation.

Effects of culture media conditions on production of eggs fertilized in vitro of embryos derived from ovary of high grade Hanwoo

Background

This study was investigated the effects of culture media conditions on production of eggs fertilized in vitro of embryos from ovaries of high grade Korean native cow, Hanwoo.

Methods

The IVMD 101 and IVF 100 were used for in vitro maturation of selected Hanwoo oocytes and In vitro embryo culture after in vitro fertilization, respectively. The IVMD 101 and IVD 101 were used for in vitro culture and completely free of serum.

Results

The cleavage rates of 2-cell embryos in reference to Hanwoo oocytes were 86.7, 92.9 , and 90.1 % in the control group, IVDM101 medium and IVD101 medium, respectively which indicates that the IVDM101 medium and IVD101 medium may result favorable outcomes. The in vitro development rates of blastocysts were 12.4, 38.4 and 32.4 % in the control group, serum free IVMD101 medium and IVD101 medium, respectively. For hatched blastocysts, it was 5.3, 33.9, and 28.6 % in the control group, serum free IVMD101 medium and IVD101 medium, respectively. Hence, more favorable results were expected for the hatched blastocysts in which the IVMD101 medium and IVD101 medium were used than the control group. Average cell numbers of blastocysts were 128.3, 165.7, and 163.6 in the groups of TCM-199 + 10 % FBS medium, IVMD 101 medium, and IVD 101 medium, respectively which clearly show that the IVMD 101 and IVD 101 medium consequence significantly higher cell numbers compared to the control group (i.e., TCM-199 + 10 % FBS medium). Pregnancy rate after embryo transfer was 39.6 % when the serum free medium was used which is higher than that of the medium supplemented with serum (32.8 %). In addition, stillbirth rates were 4.9 % in the group of serum free medium whereas it was 13.6 % in the serum supplemented medium (13.6 %).

Conclusions

Taken altogether, serum free media, the IVMD 101 and IVD 101 represented more favorable results in the embryo development rate of embryos, cell numbers of blastocyst, and pregnancy rate. Of note, the IVMD 101 medium showed better outcomes hence, it might be a better option for future applications for in vitro culture of bovine embryos.