Transcriptional regulators TRIM28, SETDB1, and TP53 are aberrantly expressed in porcine embryos produced by in vitro fertilization in comparison to in vivo- and somatic-cell nuclear transfer-derived embryos

Association between the length of in vitro embryo culture, mode of ART, and the initial endogenous hCG rise in ongoing singleton pregnancies

STUDY QUESTION

Is there an association between the length of in vitro culture, mode of ART and the initial endogenous hCG rise, in cycles with a foetal heartbeat after single embryo transfer (ET) and implantation?

SUMMARY ANSWER

Both the length of in vitro culture and the mode of ART have an impact on the initial endogenous rise in hCG in singleton pregnancies.

WHAT IS KNOWN ALREADY

Different factors have been identified to alter the kinetics of hCG in pregnancies. Current studies show conflicting results regarding the kinetics of hCG after different types of ART (fresh vs frozen ET (FET)), the inclusion or not of preimplantation genetic testing (PGT), and the length of time in in vitro culture.

STUDY DESIGN, SIZE, DURATION

This was a multicentre cohort study, using prospectively collected data derived from 4938 women (5524 treatment cycles) undergoing IUI (cycles, n = 608) or ART (cycles, n = 4916) treatments, resulting a in singleton ongoing pregnancy verified by first-trimester ultrasound scan. Data were collected from the Danish Medical Data Centre, used by the three participating Danish public fertility clinics at Copenhagen University hospitals: Herlev Hospital, Hvidovre Hospital, and Rigshospitalet, from January 2014 to December 2021.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The fresh ET cycles included cleavage-stage (2 or 3 days in vitro) and blastocyst (5 days in vitro) transfers. FET cycles included cleavage-stage (3 days in vitro before cryopreservation) or blastocyst (5 or 6 days in vitro before cryopreservation) transfers. The IUI cycles represented no time in vitro. To attain a comparable interval for serum-hCG (s-hCG), the ovulation induction time was identical: 35-37 h before oocyte retrieval or IUI. The conception day was considered as: the insemination day for pregnancies conceived after IUI, the oocyte retrieval day for fresh ET, or the transfer day minus 3 or 5 as appropriate for FET of Day 3 or 5 embryos. Multiple linear regression analysis was used, including days post-conception for the hCG measurement as a covariate, and was adjusted for the women's age, the cause of infertility, and the centre. For FET, a sensitivity analysis was used to adjust for endometrial preparation.

MAIN RESULTS AND THE ROLE OF CHANCE

The study totally includes 5524 cycles: 2395 FET cycles, 2521 fresh ET cycles, and 608 IUI cycles. Regarding the length of in vitro culture, with IUI as reference (for no time in in vitro culture), we found a significantly lower s-hCG in pregnancies achieved after fresh ET (cleavage-stage ET or blastocyst transfer). S-hCG was 18% (95% CI: 13-23%, P < 0.001) lower after fresh cleavage-stage ET, and 23% (95% CI: 18-28%, P < 0.001) lower after fresh blastocyst transfer compared to IUI. In FET cycles, s-hCG was significantly higher after blastocyst transfers compared to cleavage-stage FET, respectively, 26% (95% CI: 13-40%, P < 0.001) higher when cryopreserved on in vitro Day 5, and 14% (95% CI: 2-26%, P = 0.02) higher when cryopreserved on in vitro Day 6 as compared to Day 3. Regarding the ART treatment type, s-hCG after FET blastocyst transfer (Day 5 blastocysts) cycles was significantly higher, 33% (95% CI: 27-45%, P < 0.001), compared to fresh ET (Day 5 blastocyst), while there was no difference between cleavage-stage FET (Days 2 + 3) and fresh ET (Days 2 + 3). S-hCG was 12% (95% CI: 4-19%, 0.005) lower in PGT FET (Day 5 blastocysts) cycles as compared to FET cycles without PGT (Day 5 blastocysts).

LIMITATIONS, REASONS FOR CAUTION

The retrospective design is a limitation which introduces the risk of possible bias and confounders such as embryo score, parity, and ovarian stimulation.

WIDER IMPLICATIONS OF THE FINDINGS

This study elucidates how practices in medically assisted reproduction treatment are associated with the hCG kinetics, underlining a potential impact of in vitro culture length and mode of ART on the very early embryo development and implantation. The study provides clinicians knowledge that the type of ART used may be relevant to take into account when evaluating s-hCG for the prognosis of the pregnancy.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was received for this study. AP has received consulting fees, research grants, or honoraria from the following companies: Preglem, Novo Nordisk, Ferring Pharmaceuticals, Gedeon Richter, Cryos, Merck A/S, and Organon. AZ has received grants and honoraria from Gedeon Richter. NLF has received grants from Gedeon Richter, Merck A/S, and Cryos. MLG has received honoraria fees or research grants from Gedeon Richter, Merck A/S, and Cooper Surgical. CB has received honoraria from Merck A/S. MB has received research grants and honoraria from IBSA. MPR, KM, and PVS all report no conflicts of interest.

TRIAL REGISTRATION NUMBER

The study was registered and approved by the Danish Protection Agency, Capital Region, Denmark (Journal-nr.: 21019857). No approval was required from the regional ethics committee according to Danish law.

Comparing mRNA and sncRNA profiles during the maternal-to-embryonic transition in bovine IVF and scNT embryos

Production of embryos with high developmental competence by somatic cell nuclear transfer (scNT) is far less efficient than for in vitro fertilized (IVF) embryos, likely due to an accumulation of errors in genome reprogramming that results in aberrant expression of RNA transcripts, including messenger RNAs (mRNA) and, possibly, microRNAs (miRNA). Thus, our objectives were to use RNAseq to determine the dynamics of mRNA expression in early developing scNT and IVF embryos in the context of the maternal-to-embryonic transition (MET) and to correlate apparent transcriptional dysregulation in cloned embryos with miRNA expression profiles. Comparisons between scNT and IVF embryos indicated large scale transcriptome differences, which were most evident at the 8-cell and morula stages for genes associated with biological functions critical for the MET. For two miRNAs previously identified as differentially expressed in scNT morulae, miR-34a and miR-345, negative correlations with some predicted mRNA targets were apparent, though not widespread among the majority of predicted targets. Moreover, although large-scale aberrations in expression of mRNAs were evident during the MET in cattle scNT embryos, these changes were not consistently correlated with aberrations in miRNA expression at the same developmental stage, suggesting that other mechanisms controlling gene expression may be involved.

Characterization of transcriptional activity during ZGA in mammalian SCNT embryo

Developmental arrest of somatic cell nuclear transfer (SCNT) embryos first occurs at zygotic/embryonic genome activation (ZGA/EGA), which is critical for preimplantation development. However, study on transcriptome of SCNT embryos during ZGA/EGA is limited. In the present study, we performed RNA-seq of the 8-cell SCNT embryos in goat and provide cross-species analysis of transcriptional activity of SCNT embryos during ZGA/EGA in mice, human, bovine, and goat. RNA-seq data revealed 3966 differentially expressed genes (DEGs) failed to be reprogrammed or activated during EGA of SCNT embryos in goat. Series test of cluster analysis showed four clusters of DEGs and similar changes of the clusters in the four species. Specifically, genes in cluster 3 were somehow upregulated compared with the donor cells and the IVF embryo. Moreover, the histone methylation key players and N6-methyladenosine modifiers (SUV39H1, SETDB1, SETD2, KDM5B, IGF2BP1, and YTHDF2) were differentially expressed in SCNT embryos of all species. Finally, we identified three modules correlated with the development of SCNT embryos in mice and screened 288 genes (such as BTG4, WEE1, KLF3, and USP21) that are likely critical for SCNT reprogramming using weighted gene correlation network analysis. Our data will broaden the current understanding of transcriptome activity during stochastic reprogramming events and provide an excellent source for future studies.

First PGT-A using human in vivo blastocysts recovered by uterine lavage: comparison with matched IVF embryo controls†

STUDY QUESTION

After controlled ovarian stimulation (COS) and IUI, is it clinically feasible to recover in vivo conceived and matured human blastocysts by uterine lavage from fertile women for preimplantation genetic testing for aneuploidy (PGT-A) and compare their PGT-A and Gardner scale morphology scores with paired blastocysts from IVF control cycles?

SUMMARY ANSWER

In a consecutive series of 134 COS cycles using gonadotrophin stimulation followed by IUI, uterine lavage recovered 136 embryos in 42% (56/134) of study cycles, with comparable in vivo and in vitro euploidy rates but better morphology in in vivo embryos.

WHAT IS KNOWN ALREADY

In vivo developed embryos studied in animal models possess different characteristics compared to in vitro developed embryos of similar species. Such comparative studies between in vivo and in vitro human embryos have not been reported owing to lack of a reliable method to recover human embryos.

STUDY DESIGN, SIZE, DURATION

We performed a single-site, prospective controlled trial in women (n = 81) to evaluate the safety, efficacy and feasibility of a novel uterine lavage catheter and fluid recovery device. All lavages were performed in a private facility with a specialized fertility unit, from August 2017 to June 2018. Subjects were followed for 30 days post-lavage to monitor for clinical outcomes and delayed complications. In 20 lavage subjects, a single IVF cycle (control group) with the same ovarian stimulation protocol was performed for a comparison of in vivo to in vitro blastocysts.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

Women were stimulated with gonadotrophins for COS. The ovulation trigger was given when there were at least two dominant follicles ≥18 mm, followed by IUI of sperm. Uterine lavage occurred 4–6 days after the IUI. A subset of 20 women had a lavage cycle procedure followed by an IVF cycle (control IVF group). Recovered embryos were characterized morphologically, underwent trophectoderm (TE) biopsy, vitrified and stored in liquid nitrogen. Biopsies were analyzed using the next-generation sequencing technique. After lavage, GnRH antagonist injections were administered to induce menstruation.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 134 lavage cycles were performed in 81 women. Uterine lavage recovered 136 embryos in 56 (42%) cycles. At the time of cryopreservation, there were 40 (30%) multi-cell embryos and 96 (70%) blastocysts. Blastocysts were of good quality, with 74% (70/95) being Gardener grade 3BB or higher grade. Lavage blastocysts had significantly higher morphology scores than the control IVF embryos as determined by chi-square analysis (P < 0.05). This is the first study to recover in vivo derived human blastocysts following ovarian stimulation for embryo genetic characterization. Recovered blastocysts showed rates of chromosome euploidy similar to the rates found in the control IVF embryos. In 11 cycles (8.2%), detectable levels of hCG were present 13 days after IUI, which regressed spontaneously in two cases and declined after an endometrial curettage in two cases. Persistent hCG levels were resolved after methotrexate in three cases and four cases received both curettage and methotrexate.

LIMITATIONS, REASON FOR CAUTION

The first objective was to evaluate the feasibility of uterine lavage following ovarian stimulation to recover blastocysts for analysis, and that goal was achieved. However, the uterine lavage system was not completely optimized in our earlier experience to levels that were achieved late in the clinical study and will be expected in clinical service. The frequency of chromosome abnormalities of in vivo and IVF control embryos was similar, but this was a small-size study. However, compared to larger historical datasets of in vitro embryos, the in vivo genetic results are within the range of high-quality in vitro embryos.

WIDER IMPLICATIONS OF THE FINDINGS

Uterine lavage offers a nonsurgical, minimally invasive strategy for recovery of embryos from fertile women who do not want or need IVF and who desire PGT, fertility preservation of embryos or reciprocal IVF for lesbian couples. From a research and potential clinical perspective, this technique provides a novel platform for the use of in vivo conceived human embryos as the ultimate benchmark standard for future and current ART methods.

STUDY FUNDING/COMPETING INTEREST(S)

Previvo Genetics, Inc., is the sole sponsor for the Punta Mita, Mexico, clinical study. S.M. performs consulting for CooperGenomics. J.E.B. and S.A.C. are co-inventors on issued patents and patents owned by Previvo and ownshares of Previvo. S.N. is a co-author on a non-provisional patent application owned by Previvo and holds stock options in Previvo. S.T.N. and M.J.A. report consulting fees from Previvo. S.T.N., S.M., M.V.S., M.J.A., C.N. and J.E.B. are members of the Previvo Scientific Advisory Board (SAB) and hold stock options in Previvo. J.E.B and S. M are members of the Previvo Board of Directors. A.N. and K.C. are employees of Previvo Genetics. L.V.M, T.M.M, J.L.R and S. S have no conflicts to disclose.

TRIAL REGISTRATION NUMBER

Protocol Registration and Results System (PRS) Trial Registration Number and Name: Punta Mita Study TD-2104: Clinical Trials NCT03426007.

TRIM28 down-regulation on methylation imprints in bovine preimplantation embryos

TRIM28/KAP1/TIF1β was identified as a universal transcriptional co-repressor and is critical for regulating post-fertilization methylation reprogramming in preimplantation embryos. In this study, three siRNAs (si647, si742, and si1153) were designed to target the TRIM28 mRNA sequence. After transfection of the mixture of the three siRNA (siMix) into bovine fibroblast cells, the most effective one for TRIM28 knockdown was selected. By injecting RNAi directed against TRIM28 mRNA, we found that TRIM28 knockdown in oocytes had the most effect on the H19 gene, in which differentially methylated region (DMR) methylation was almost completely absent at the 2-cell stage (1.4%), while control embryos showed 74% methylation. In addition, global H3K9me3 levels at the 2-cell stage were significantly higher in the in vitro fertilization (IVF) group than in the TRIM28 knockdown group (P<0.05). We further show that TRIM28 is highly expressed during oocyte maturation and reaches peak levels at the 2-cell stage. In contrast, at this stage, TRIM28 expression in somatic cell nuclear transfer (SCNT) embryos decreased significantly (P<0.05), suggesting that Trim28 transcripts are lost during SCNT. TRIM28 is required for the maintenance of methylation imprints in bovine preimplantation embryos, and the loss of TRIM28 during SCNT may contribute to the unfaithful maintenance of imprints in cloned embryos.

Iloprost supports early development of in vitro-produced porcine embryos through activation of the phosphatidylinositol 3-kinase/AKT signalling pathway

Despite evidence of the presence of prostaglandin (PG) I₂ in mammalian oviducts, its role in early development of in vitro-produced (IVP) embryos is largely unknown. Thus, in the present study we examined the effects of iloprost, a PGI₂ analogue, on the in vitro developmental competence of early porcine embryos and the underlying mechanism(s). To examine the effects of iloprost on the development rate of IVF embryos, iloprost was added to the in vitro culture (IVC) medium and cultured for 6 days. Supplementation of the IVC medium with iloprost significantly improved developmental parameters, such as blastocyst formation rate, the trophectoderm:inner cell mass ratio and cell survival in IVF and parthenogenetically activated (PA) embryos. In addition, post-blastulation development into the expanded blastocyst stage was improved in iloprost-treated groups compared with controls. Interestingly, the phosphatidylinositol 3-kinase (PI3K)/AKT signalling pathway was significantly activated by iloprost supplementation in a concentration-dependent manner (10-1000nM), and the beneficial effects of iloprost on the early development of porcine IVF and PA embryos was completely ablated by treatment with 2.5μM wortmannin, a PI3K/AKT signalling inhibitor. Importantly, expression of the PI3K/AKT signalling pathway was significantly reduced in somatic cell nuclear transfer (SCNT) compared with IVF embryos, and iloprost supported the early development of SCNT embryos, as was the case for IVF and PA embryos, suggesting a consistent effect of iloprost on the IVC of IVP porcine embryos. Together, these results indicate that iloprost can be a useful IVC supplement for production of IVP early porcine embryos with high developmental competence.

Differential expression of key subunits of SWI/SNF chromatin remodeling complexes in porcine embryos derived in vitro or in vivo

In vitro embryo production is an established method for both humans and animals, but is fraught with inferior development and health issues in offspring born after in vitro fertilization procedures. Analysis of epigenetic changes caused by exposure to in vitro conditions should shed light on potential sources of these phenotypes. Using immunocytochemistry, we investigated the localization and relative abundance of components associated with the SWI/SNF (Switch/Sucrose non‐fermentable) chromatin‐remodeling complex—including BAF155, BAF170, BAF180, BAF53A, BAF57, BAF60A, BAF45D, ARID1A, ARID1B, ARID2, SNF5, and BRD7—in oocytes and in in vitro‐produced and in vivo‐derived porcine embryos. Differences in the localization of BAF155, BAF170, BAF60A, and ARID1B among these sources indicate that improper timing of chromatin remodeling and cellular differentiation might occur in early preimplantation embryos produced and cultured in vitro.

Methods of RNA preparation affect mRNA abundance quantification of reference genes in pig maturing oocytes

To ensure accurate normalization and quantification of target RNA transcripts using reverse transcription quantitative polymerase chain reaction (RT-qPCR), most studies focus on the identification of stably expressed gene(s) as internal reference. However, RNA preparation methods could also be an important factor, especially for test samples of limited quantity (e.g. oocytes). In this study, we aimed to select appropriate reference gene(s), and evaluate the effect of RNA preparation methods on gene expression quantification in porcine oocytes and cumulus cells during in vitro maturation. Expression profiles of seven genes (GAPDH, 18S, YWHAG, BACT, RPL4, HPRT1 and PPIA) were examined, on RNA samples extracted from cumulus cells (RNeasy Kit) and oocytes (RNeasy Kit and Lysis Kit) during in vitro maturation, respectively. Interestingly, different RNA preparation methods were found to potentially affect the quantification of reference gene expression in pig oocytes cultured in vitro. After geNorm analyses, the most suitable genes for normalization were identified, GAPDH/18S for cumulus cells and YWHAG/BACT for oocytes, respectively. Thus, our results provide useful data and information on the selection of better reference genes and RNA preparation method for related functional studies.

Transcriptome Analysis of Pig In Vivo, In Vitro-Fertilized, and Nuclear Transfer Blastocyst-Stage Embryos Treated with Histone Deacetylase Inhibitors Postfusion and Activation Reveals Changes in the Lysosomal Pathway

Genetically modified pigs are commonly created via somatic cell nuclear transfer (SCNT). Treatment of reconstructed embryos with histone deacetylase inhibitors (HDACi) immediately after activation improves cloning efficiency. The objective of this experiment was to evaluate the transcriptome of SCNT embryos treated with suberoylanilide hydroxamic acid (SAHA), 4-iodo-SAHA (ISAHA), or Scriptaid as compared to untreated SCNT, in vitro-fertilized (IVF), and in vivo (IVV) blastocyst-stage embryos. SAHA (10 μM) had the highest level of blastocyst development at 43.9%, and all treatments except 10 μM ISAHA had the same percentage of blastocyst development as Scriptaid (p<0.05). Two treatments, 1.0 μM ISAHA and 1.0 μM SAHA, had higher mean cell number than No HDACi treatment (p<0.021). Embryo transfers performed with 10 μM SAHA- and 1 μM ISAHA-treated embryos resulted in the birth of healthy piglets. GenBank accession numbers from up- and downregulated transcripts were loaded into the Database for Annotation, Visualization and Integrated Discovery to identify enriched biological themes. HDACi treatment yielded the highest enrichment for transcripts within the Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway, lysosome. The mean intensity of LysoTracker was lower in IVV embryos compared to IVF and SCNT embryos (p<0.0001). SAHA and ISAHA can successfully be used to create healthy piglets from SCNT.