Of mice and men: long-term safety of assisted reproduction treatments

Impact of the polycarbonate strippers used in assisted reproduction techniques on embryonic development

STUDY QUESTION

Do daily manipulations of preimplantation embryos with polycarbonate (PC)-made bisphenol A (BPA)-releasing strippers influence embryo development?

SUMMARY ANSWER

Compared to glass strippers, PC strippers enhance the blastocyst development rate but this does not seem to be BPA-related.

WHAT IS KNOWN ALREADY

PC strippers have been shown to release tiny amounts (around 0.5 ng/ml BPA) of BPA in routine human IVF procedures. A chronic exposure to BPA either in vivo or in vitro during the preimplantation period can impact post-implantation and post-natal development. BPA can act rapidly by binding to membrane receptors and inducing rapid non-genomic effects.

STUDY DESIGN, SIZE, DURATION

This experimental study using mouse embryos had a balanced design and blinded evaluations of the endpoints.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In vivo fertilized zygotes were obtained from outbred Swiss CD1 mice crossings after an ovarian stimulation. The zygotes were allocated to three daily handling conditions (HCs) and cultured until Day 4 in a single human commercial medium. Each day, the embryos were handled for 20 s either in a PC stripper (HC1) or in a glass stripper (HC2). In HC3, the embryos were pre-exposed to 0.5 ng/ml BPA before being handled for 20 s in a glass stripper. Handling operations were repeated on Days 1, 2 and 3. Embryo development was assessed blindly on Day 4. Expanded blastocysts were selected for a transcriptomic analysis using Agilent Sureprint G3 Mouse GE v2 microarrays and the retrotransposon LINE1-Orf2 expression was analysed using qRT-PCR, as a proxy for a global evaluation of the epigenetic status.

MAIN RESULTS AND THE ROLE OF CHANCE

Compared to the embryos manipulated in HC2 (n = 243), those in HC1 (n = 228) developed significantly more often to the blastocyst stage (55 vs 46%; P < 0.05). It appears the effect of these PC strippers was not BPA-related because embryos pre-exposed to BPA (HC3, n = 230) showed no difference in the blastocyst rate when compared to HC2 (43 vs 46%). When analysing same-stage blastocysts, we noticed no difference in the embryo gene expression between the three HC groups.

LARGE SCALE DATA

https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE148868.

LIMITATIONS, REASONS FOR CAUTION

Our results using a mouse model designed to mimic human conditions (outbred strain, human commercial IVF dishes and a unique commercial human embryonic culture media) are reassuring since no gene was found to be differentially expressed, including LINE-1 genes, as a proxy for a global evaluation of the epigenetic status. However, no global epigenetic analysis of the genome has been performed. Furthermore, we did not evaluate post-implantation events, although BPA exposure during peri-conception could affect foeto-placental and post-natal development.

WIDER IMPLICATIONS OF THE FINDINGS

Based on the precautionary principle, several European countries banned the use of BPA in baby bottles and food packaging several years before European Agencies took an official position. The question of applying this principle to plastics in closed contact with human embryos is raised. Further studies are needed for a decision to be made.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by a grant from the Agence de Biomédecine (AOR 2016). The authors declare no competing interest.

Abnormal Glucose Metabolism in Male Mice Offspring Conceived by in vitro Fertilization and Frozen-Thawed Embryo Transfer

Frozen and thawed embryo transfer (FET) is currently widely applied in routine assisted reproductive technology (ART) procedure. It is of great necessity to assess the safety of FET and investigate the long-term effect including glucose metabolism on FET-conceived offspring. The mouse model is a highly efficient method to figure out the relationship between the process of FET and offspring health. In this study, we obtained mouse offspring of natural conception (NC), in vitro fertilization (IVF), and FET. Glucose and insulin tolerance test (GTT/ITT) were performed on both chow fed or high fat diet (HFD) fed offspring to examine the glucose metabolism status. We detected hepatic PI3K/AKT pathway by western blotting and transcriptome status by RNA-sequencing. Impaired glucose tolerance (IGT) and decreased insulin tolerance were occurred in FET conceived male offspring. After challenged with the HFD-fed, male offspring in FET group performed earlier and severer IGT than IVF group. Furthermore, higher HOMA-IR index and higher serum insulin level post glucose injected in FET-chow group suggested the insulin resistance status. The PI3K/AKT signaling pathway, the major pathway of insulin in the liver, were also disrupted in FET group. Transcriptomics of the liver reveals significantly downregulated in glucose metabolic process and insulin resistance in the FET-chow group. In our study, FET-conceived male mouse offspring presented glucose metabolism dysfunction mainly manifesting insulin resistance. The hepatic insulin signaling pathway were in concordance with reduced glycogen synthesis, increased glycolysis and enhanced gluconeogenesis status in FET-conceived male offspring.

Passive slow freezing is an efficacious and cost-effective alternative to controlled slow freezing for ovarian tissue cryopreservation

We aimed to assess the feasibility of passive slow freezing (PSF using Mr. Frosty container, Nalgene) as an alternative to controlled slow rate freezing (CSF using (Freezal™, Air liquide)) for human ovarian tissue (OT) cryopreservation. Validation studies needed were determined after assessing the risk associated (EuroGTP-II ART tool) and were conducted in 66 OT samples from 10 transgender men aged 23.4 ± 5.1 y. Folliculogenesis was assessed in vitro (after 2 h and 2 days of culture) and in vivo (2, 4 and 6 weeks xenotransplantation in Balbc/nude mice) by haematoxilin-eosin staining. Fibrosis was assessed by Masson's trichrome staining. Immunohistochemistry was used to study cell proliferation (PCNA and Ki-67) and apoptosis (caspase-3 and TUNEL). Differences in percentages were estimated using a generalized estimated equations method. After 2 days of in vitro culture, higher odds of primordial follicles (PF) (OR 1.626; 95%CI (1.162-2.266); P = 0.004) and lower odds of growing follicles (GF) (OR 0.616; 95%CI (0.441-0.861); P = 0.004) were associated with the established CSF technique. No statistical differences were found in the mean estimated proportion of proliferating (Ki-67+ or PCNA+) or apoptotic (caspase-3+ or Tunel+) follicles. Two and 6 weeks after xenotransplantation, respectively lower odds of GF (OR 0.419; 95%CI (0.217-0.809); P = 0.010) and secondary follicles (OR 0.135; 95%CI (0.071-0.255); P < 0.001) were associated with CSF. Proportion of fibrosis was similar. This validation study shows a higher follicle activation after 2 days in vitro and after 2 weeks following xenotransplantation in mice using PSF. PSF may be an easy, cost-effective low-risk alternative to CSF for cryopreservation of human OT.

Effect of whey protein supplementation on sperm quality and fertility in male mice

Protein supplements are a billion-dollar industry and the intake of these supplements is increasing, especially among young men. However, little is known about whether consumption of these products affects the reproductive health. The aim of this study was to assess the effect of whey protein supplementation on the sperm quality and reproductive health of male mice. A total of 48 male NMRI mice were fed with either plain tap water or a high dose of whey protein (Whey100, BodyLab) supplemented in the drinking water for 3 months. Mice was individually housed with two female mice for five days and reproductive parameters were assessed. DNA fragmentation index (DFI) was assessed at 0 h and 4 h of in vitro incubation using a sperm DNA integrity test (SDI®-test). No significant differences were detected between the groups in the epididymal sperm count, sperm motility, DFI, oxidation-reduction potential (ORP), serum testosterone, body and seminal vesicles weights, relative testis and epididymal weights, testicular morphology, number of impregnated females, or litter size. No correlation was found between ORP and DFI. These results suggest that the highest recommended human dose of whey protein supplementation do not significantly impair the sperm quality and fertility in male mice.

Between innovation and precaution: how did offspring safety considerations play a role in strategies of introducing new reproductive techniques?

The field of reproductive medicine has been criticized for introducing ARTs without systematic research on possible safety risks and for failing to meet the standards of evidence-based innovation held elsewhere in medicine. In this paper, firstly, we ask whether ‘responsible innovation’ has been a concern for the field, and if so, how it has understood the practical implications of this idea for the development and introduction of potentially risky new ARTs. Secondly, we consider whether the field has indeed fallen short of its responsibilities in this respect, and if so, how things can be improved. To answer these questions, we present three case studies involving the introduction of a new reproductive technology: ICSI, preimplantation genetic testing and mitochondrial replacement therapy. As a framework for analyzing these cases, we used Per Sandin’s account of the four dimensions of dealing with risks (threat, uncertainty, action, command) that are central to debates about the possible role of the so-called precautionary principle. We conclude that, although offspring safety concerns have been on the agenda of the debate about bringing the relevant technologies to the clinic, systematic safety and effectiveness studies were not always conducted. As professionals in assisted reproduction have a responsibility to take account of the welfare of the children they are creating, we suggest a policy of proceeding with systematic caution. Legal measures may be needed to ensure that professional guidance is followed in practice. Finally, an open question concerns the threshold for acceptable risk in the context of introducing new ARTs. Multiple stakeholders, including professional societies and patient organizations, should have a role in the urgent debate about this.

'Serious' factor-a relevant starting point for further debate: a response

In this reply, we wish to defend our original position and address several of the points raised by two excellent responses. The first response (De Miguel Beriain) questions the relevance of the notion of 'serious' within the context of human germline genome modification (HGGM). We argue that the 'serious' factor is relevant and that there is a need for medical and social lenses to delineate the limits of acceptability and initial permissible applications of HGGM. In this way, 'serious' acts as a starting point for further discussions and debates on the acceptability of the potential clinical translation of HGGM. Therefore, there is a pressing need to clarify its scope, from a regulatory perspective, so as to prevent individuals from using HGGM for non-therapeutic or enhancement purposes. The second response (Kalsi) criticizes the narrow interpretation of the objectivist approach and the apparent bias towards material innovations when discussing the right to benefit from scientific advancements. As an in-depth discussion of the objectivist and constructivist approaches was beyond the scope of our original paper, we chose to focus on one specific objectivist account, one which focuses on biological and scientific facts. We agree, however, with the critique that material innovations should not be the sole focus of the right to benefit from scientific advancements, which also incorporates freedom of scientific research and access to scientific knowledge scientific freedom and knowledge, including the influence of these on ethical thinking and cultures.

The placental transcriptome of the first-trimester placenta is affected by in vitro fertilization and embryo transfer

BACKGROUND

The placenta is a highly specialized temporary organ that is related to fetal development and pregnancy outcomes, and epidemiological data demonstrate an increased risk of placental abnormality after in vitro fertilization and embryo transfer (IVF-ET).

METHODS

This study examines alterations in the transcriptome profile of first-trimester placentas from IVF-ET pregnancies and analyzes the potential mechanisms that play a role in the adverse perinatal outcomes associated with IVF-ET procedures. Four human placental villi from first-trimester samples were obtained through fetal bud aspiration from patients subjected to IVF-ET due to oviductal factors. An additional four control human placental villi were derived from a group of subjects who spontaneously conceived a twin pregnancy. We analyzed their transcriptomes by microarray. Then, RT-qPCR and immunohistochemistry were utilized to analyze several dysregulated genes to validate the microarray results. Biological functions and pathways were analyzed with bioinformatics tools.

RESULTS

A total of 3405 differentially regulated genes were identified as significantly dysregulated (> 2-fold change; P < 0.05) in the IVF-ET placenta in the first trimester: 1910 upregulated and 1495 downregulated genes. Functional enrichment analysis of the differentially regulated genes demonstrated that the genes were involved in more than 50 biological processes and pathways that have been shown to play important roles in the first trimester in vivo. These pathways can be clustered into coagulation cascades, immune response, transmembrane signaling, metabolism, cell cycle, stress control, invasion and vascularization. Nearly the same number of up- and downregulated genes participate in the same biological processes related to placental development and maintenance. Procedures utilized in IVF-ET altered the expression of first-trimester placental genes that are critical to these biological processes and triggered a compensatory mechanism during early implantation in vivo.

CONCLUSION

These data provide a potential basis for further analysis of the higher frequency of adverse perinatal outcomes following IVF-ET, with the ultimate goal of developing safer IVF-ET protocols.