Management of copy number variants associated with incomplete penetrance and variable expressivity-Results of a French survey.

Increasing interest regarding neurodevelopmental disorders and democratization of chromosomal microarray analysis have led to growing identification of neuro-susceptibility copy number variations (CNVs). These CNVs have incomplete penetrance and variable expressivity (PIEV), which makes phenotypic features hard to predict. The French Consortium "AchroPuce" has provided a list of 17 CNVs that should be considered as PIEV CNVs. This list led to consensual French practices of healthcare professionals in postnatal diagnosis. However, no consensus was established in prenatal diagnosis and fetal pathology. 121 French health professionals were surveyed their opinions and practices regarding reporting of PIEV CNVs to patients, in order to identify key points so as to establish French recommendations. The survey showed that professionals in favor of reporting PIEV CNVs to patients in prenatal diagnosis and fetal pathology (respectively, 76% and 84% of respondents) considered highlighted that multidisciplinary consultation is the main point-of-care management before family survey. This statement is close to recommendations published worldwide. As a consequence, multidisciplinary expertise should be the basis of French recommendations concerning the reporting of PIEV CNVs and genetic counseling in prenatal diagnosis and fetal pathology.

Ovarian tissue cryopreservation can be combined simultaneously with oocyte retrieval after controlled ovarian hyperstimulation.

STUDY QUESTION: Can ovarian tissue cryopreservation (OTC) be performed after controlled ovarian hyperstimulation (COH)? SUMMARY ANSWER: Unilateral oophorectomy after transvaginal oocyte retrieval is feasible on stimulated ovaries during one surgical step. WHAT IS KNOWN ALREADY: In the fertility preservation (FP) field, the timeframe between patient referral and start of curative treatment is limited. Combining oocyte pick-up with ovarian tissue (OT) extraction has been reported to improve FP but COH applied before OT extraction is not currently recommended. STUDY DESIGN, SIZE, DURATION: This retrospective cohort-controlled study involved 58 patients who underwent oocyte cryopreservation immediately followed by OTC between September 2009 and November 2021. The exclusion criteria were a delay between oocyte retrieval and OTC of >24 h (n = 5) and IVM of oocytes obtained ex vivo in the ovarian cortex (n = 2). This FP strategy was performed either after COH (stimulated group, n = 18) or after IVM (unstimulated group, n = 33). PARTICIPANTS/MATERIALS, SETTING, METHODS: Oocyte retrieval followed by OT extraction on the same day was performed either without previous stimulation or after COH. Adverse effects of surgery and ovarian stimulation, mature oocyte yield and pathology findings of fresh OT were retrospectively analysed. Thawed OTs were analysed prospectively, for vascularization and apoptosis using immunohistochemistry, when patient consent was obtained. MAIN RESULTS AND THE ROLE OF CHANCE: No surgical complication occurred after OTC surgery in either group. In particular, no severe bleeding was associated with COH. The number of mature oocytes obtained increased after COH (median = 8.5 (25% = 5.3-75% = 12.0)) compared to the unstimulated group (2.0 (1.0-5.3), P < 0.001). Neither ovarian follicle density nor cell integrity was affected by COH. Fresh OT analysis showed congestion in half of the stimulated OT which was higher than in the unstimulated OT (3.1%, P < 0.001). COH also increased haemorrhagic suffusion (COH + OTC: 66.7%; IVM + OTC: 18.8%, P = 0.002) and oedema (COH + OTC: 55.6%; IVM + OTC: 9.4%, P < 0.001). After thawing, the pathological findings were similar between both groups. No statistical difference in the number of blood vessels was observed between the groups. The oocyte apoptotic rate in thawed OT was not statistically different between the groups (ratio of positive cleaved caspase-3 staining oocytes/total number of oocytes equal to median 0.50 (0.33-0.85) and 0.45 (0.23-0.58) in unstimulated and stimulated groups respectively, P = 0.720). LIMITATIONS, REASONS FOR CAUTION: The study reports FP from a small number of women following OTC. Follicle density and other pathology findings are an estimate only. WIDER IMPLICATIONS OF THE FINDINGS: Unilateral oophorectomy can be successfully performed after COH with limited bleeding risk and an absence of impact on thawed OT. This approach could be proposed to post pubertal patients when the number of mature oocytes expected is low or when the risk of residual pathology is high. The reduction of surgical steps for cancer patients also has positive implications for introducing this approach into clinical practice. STUDY FUNDING/COMPETING INTEREST(S): This work was made possible through the support of the reproductive department of Antoine-Béclère Hospital and of the pathological department of Bicêtre Hospital (Assistance Publique Hôpitaux de Paris, France). The authors have no conflict of interest to disclose in this study. TRIAL REGISTRATION NUMBER: N/A.

A shared pattern of altered gene expression in human embryos affected by mitochondrial diseases.

STUDY QUESTION: Does mitochondrial deficiency affect human embryonic preimplantation development? SUMMARY ANSWER: The presence of a pathogenic mitochondrial variant triggers changes in the gene expression of preimplantation human embryos, compromising their development, cell differentiation, and survival. WHAT IS KNOWN ALREADY: Quantitative and qualitative anomalies of mitochondrial DNA (mtDNA) are reportedly associated with impaired human embryonic development, but the underlying mechanisms remain unexplained. STUDY DESIGN, SIZE, DURATION: Taking advantage of the preimplantation genetic testing for mitochondrial disorders in at-risk couples, we have compared gene expression of 9 human embryos carrying pathogenic variants in either mtDNA genes or nuclear genes encoding mitochondrial protein to 33 age-matched control embryos. PARTICIPANTS/MATERIALS, SETTING, METHODS: Single-embryo transcriptomic analysis was performed on whole human blastocyst embryos donated to research. MAIN RESULTS AND THE ROLE OF CHANCE: Specific pathogenic mitochondrial variants downregulate gene expression in preimplantation human embryos [566 genes in oxidative phosphorylation (OXPHOS)-deficient embryos], impacting transcriptional regulators, differentiation factors, and nuclear genes encoding mitochondrial proteins. These changes in gene expression primarily alter OXPHOS and cell survival pathways. LIMITATIONS, REASONS FOR CAUTION: The number of OXPHOS-deficient embryos available for the study was limited owing to the rarity of this material. However, the molecular signature shared by all these embryos supports the relevance of the findings. WIDER IMPLICATIONS OF THE FINDINGS: While identification of reliable markers of normal embryonic development is urgently needed in ART, our study prompts us to consider under-expression of the targeted genes reported here, as predictive biomarkers of mitochondrial dysfunction during preimplantation development. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the 'Association Française contre les Myopathies (AFM-Téléthon)' and the 'La Fondation Maladies Rares'. No competing interests to declare. TRIAL REGISTRATION NUMBER: N/A.

Preimplantation genetic testing for mitochondrial DNA mutation: ovarian response to stimulation, outcomes and follow-up.

RESEARCH QUESTION: How do carriers of pathogenic mitochondrial DNA (mtDNA) respond to ovarian stimulation? DESIGN: A single-centre, retrospective study conducted between January 2006 and July 2021 in France. Ovarian reserve markers and ovarian stimulation cycle outcomes were compared for couples undergoing preimplantation genetic testing (PGT) for maternally inherited mtDNA disease (n = 18) (mtDNA-PGT group) with a matched-control group of patients undergoing PGT for male indications (n = 96). The PGT outcomes for the mtDNA-PGT group and the follow-up of these patients in case of unsuccessful PGT was also reported. RESULTS: For carriers of pathogenic mtDNA, parameters of ovarian response to FSH and ovarian stimulation cycle outcomes were not different from those of matched-control ovarian stimulation cycles. The carriers of pathogenic mtDNA needed a longer ovarian stimulation and higher dose of gonadotrophins. Three patients (16.7%) obtained a live birth after the PGT process, and eight patients (44.4%) achieved parenthood through alternative methods: oocyte donation (n = 4), natural conception with prenatal diagnosis (n = 2) and adoption (n = 2). CONCLUSION: To the best of our knowledge, this is the first study of women carrying a mtDNA variant who have undergone a PGT for monogenic (single gene defects) procedure. It is one of the possible options to obtain a healthy baby without observing an impairment in ovarian response to stimulation.

Knowledge, acceptability and personal attitude toward pre-implantation 1 genetic testing (PGT) and pre-natal diagnosis (PND) for females carrying BRCA pathogenic variant according to fertility preservation experience.

PURPOSE: Preimplantation genetic testing (PGT-M) and prenatal diagnosis (PND) followed by medical termination of pregnancy when the fetus is affected are two procedures developed to avoid the transmission of a severe hereditary disease which can be proposed to females that carried BRCA pathogenic variants. These females can also be offered fertility preservation (FP) when diagnosed with cancer or even before a malignancy occurs. The aim of the study was to evaluate the acceptability and personal attitude of women carrying a BRCA mutation toward techniques that can prevent BRCA transmission to their progeny. METHODS: Female mutated for BRCA1 or BRCA2 were invited to complete an online survey of 49 queries anonymously between June and August 2022. RESULTS: A total of 87 participants responded to the online survey. Overall, 86.2% of women considered that PGT-M should be proposed to all BRCA mutation carriers regardless of the severity of the family history, and 47.1% considered or would consider PGT-M for themselves. For PND, these percentages were lower reaching 66.7% and 29.9%, respectively. Females with personal history of breast cancer or FP achievement were more prone to undergo PND for themselves despite the overall acceptability of this procedure. Among the subgroup who had undergone FP (n = 58), there was no significant difference in acceptance of principle and personal attitude toward PGT-M and PND compared to the group without FP. CONCLUSION: BRCA pathogenic variants female carriers do need information about reproductive issues, even if they are not prone to undergo PGT-M nor PND for themselves. TRIAL REGISTRATION NUMBER: N/A.

Mouse model of radiation-induced premature ovarian insufficiency reveals compromised oocyte quality: implications for fertility preservation.

RESEARCH QUESTION: What is the impact of radiation exposure on oocyte quality and female fertility? DESIGN: Prepubertal mice underwent whole-body irradiation with a single dose (0.02, 0.1, 0.5, 2, 8 Gy) of gamma- or X-rays. Oocytes were quantified in irradiated (n = 36) and sham-treated (n = 8) mice. After a single exposure to 2 Gy, formation of DNA double-strand breaks (n = 10), activation of checkpoint kinase (Chk2) (n = 10) and dynamics of follicular growth (n = 18) were analysed. Fertility assessment was performed in adult irradiated mice and controls from the number of pups per mouse (n = 28) and the fetal abortion rate (n = 24). Ploidy of mature oocytes (n = 20) was analysed after CREST immunostaining, and uterine sections were examined. RESULTS: Radiation exposure induced a massive loss of primordial follicles with LD50 below 50 mGy for both gamma and X-rays. Growing follicles survived doses up to 8 Gy. This difference in radiosensitivity was not due to a different amount of radio-induced DNA damage, and Chk2 was activated in all oocytes. Exposure to a 2 Gy dose abolished the long-term fertility of females due to depletion of the ovarian reserve. Detailed analysis indicates that surviving oocytes were able to complete folliculogenesis and could be fertilized. This transient fertility allowed irradiated females to produce a single litter albeit with a high rate of fetal abortion (23%, P = 0.0096), related to altered ploidy in the surviving oocytes (25.5%, P = 0.0035). CONCLUSIONS: The effects of radiation on surviving oocyte quality question natural conception as a first-line approach in cancer survivors. Together, the data emphasize the need for fertility preservation before radiation exposure and call for reassessment of the use of cryopreserved oocytes.

Live birth rate after use of cryopreserved oocytes or embryos at the time of cancer diagnosis in female survivors: a retrospective study of ten years of experience.

PURPOSE: The aim of this study was to evaluate the outcomes of frozen oocytes or embryos cryopreserved after controlled ovarian stimulation (COS) or in vitro maturation (IVM) for female cancer patients who underwent a fertility preservation (FP) prior to gonadotoxic therapy. METHODS: A retrospective cohort study from 2009 to December 2017 was conducted. Among the 667 female cancer patients who underwent oocytes or embryos cryopreservation for FP, 40 (6%) have returned to the fertility clinic between 2011 and 2019 to use their frozen material after being cured. We compared these thaw cycles outcomes according to the techniques used at the time of cryopreservation. RESULTS: Among the 40 women cancer survivors who used their cryopreserved material, thirty patients have benefited from at least one embryo transfer. Ten patients did not have an embryo transfer since the oocytes did not survive after the thawing process or because no embryo was obtained after fertilization. We related three live births following FP using IVM (two from frozen oocytes and one after embryo cryopreservation). Five live births were obtained when COS was performed at the time of FP (one from frozen oocytes and four after embryo cryopreservation). CONCLUSIONS: Our preliminary results, although they are obtained in a small sample, are encouraging and show that different FP techniques can be used in female cancer patients and lead to live births. IVM is one of the options available that does not delay the start of chemotherapy or if ovarian stimulation using gonadotropins is contraindicated.

Estradiol Regulates mRNA Levels of Estrogen Receptor Beta 4 and Beta 5 Isoforms and Modulates Human Granulosa Cell Apoptosis.

Estrogen receptor beta (ERß) plays a critical role in granulosa cell (GC) functions. The existence of four human ERß splice isoforms in the ovary suggests their differential implication in 17ß-estradiol (E2) actions on GC apoptosis causing follicular atresia. In this study, we investigated whether E2 can regulate ERß isoforms expression to fine tune its apoptotic activities in human GC. For this purpose, we measured by RT-qPCR the expression of ERß isoforms in primary culture of human granulosa cells (hGCs) collected from patients undergoing in vitro fertilization, before and after E2 exposure. Besides, we assessed the potential role of ERß isoforms on cell growth and apoptosis after their overexpression in a human GC line (HGrC1 cells). We confirmed that ERß1, ERß2, ERß4, and ERß5 isoform mRNAs were predominant over that of ERα in hGCs, and found that E2 selectively regulates mRNA levels of ERß4 and ERß5 isoforms in these cells. In addition, we demonstrated that overexpression of ERß1 and ERß4 in HGrC1 cells increased cell apoptosis by 225% while ERß5 or ERß2 had no effect. Altogether, our study revealed that E2 may influence GC fate by specifically regulating the relative abundance of ERß isoforms mRNA to modulate the balance between pro-apoptotic and non-apoptotic ERß isoforms.

Does the prognosis after PGT for structural rearrangement differ between female and male translocation carriers?

RESEARCH QUESTION: Chromosomal translocations are known genetic causes of premature ovarian insufficiency syndrome. Are certain translocations associated with decreased capacity of small antral follicles to respond to exogenous FSH? Does the prognosis after preimplantation genetic testing for structural rearrangements differ in couples with female or male translocation carriers and according to the type of translocation? DESIGN: A single-centre, retrospective, observational study covering a 10-year period. One hundred and thirty-nine females carrying a translocation were compared with 192 partners of male translocation carriers. To evaluate ovarian response to FSH, the follicular output rate was used, defined by ratio between the pre-ovulatory follicle count on day of HCG x 100/antral follicle count (AFC). To determine a cut-off of metaphase II oocytes and biopsied embryos as predictor of obtaining a balanced embryo transfer, receiver operator characteristic curves were plotted. RESULT: A decreased capacity of small antral follicles to respond to exogenous FSH in female translocation carriers was found. The number of metaphase II oocytes in both groups was weakly informative as a predictor of obtaining an embryo transfer. The number of biopsied embryos had some clinical value, however, and allowed a cut-off of 6.5 to be determined for female translocation carriers versus 5.5 for the partners of male translocation carriers. Live birth rates, however, were not different between female and male translocations carriers. CONCLUSIONS: Female translocation carriers may respond poorly to ovarian stimulation, and present a higher rate of unbalanced embryos, which means that higher gonadotrophin doses may be required to increase the number of biopsied embryos.

Chromosomal translocations and semen quality: A study on 144 male translocation carriers.

RESEARCH QUESTION: Chromosomal translocations are known genetic causes of male infertility. Are certain translocations or chromosomal regions more directly associated with sperm defects? Is there a threshold of sperm impairment that can be relevant for detection of translocations? DESIGN: This is a monocentric retrospective observational study covering a 10-year period. Eighty-one patients carrying a reciprocal translocation (RCT) and 63 carrying a Robertsonian translocation (ROBT) were compared with 105 fertile patients. Semen quality before and after sperm migration was compared. The aims were to define whether a threshold based on sperm analysis could be proposed for detection of translocations and to identify whether some redundant chromosomal regions might be associated with sperm quality defects. RESULTS: The number of progressive spermatozoa retrieved after sperm preparation (NPS-ASP) was altered in both RCT and ROBT carriers compared with controls, with a stronger alteration in ROBT. Based on the NPS-ASP results in this large group of translocation carriers, a relatively robust threshold, fixed at less than 5 million, may be proposed for detection of translocations. The alteration of NPS-ASP was independent of the chromosome involved in ROBT, while in RCT, four redundant chromosomal regions (1q21, 6p21, 16q21, 17q11.2) were associated with poor or very poor NPS-ASP. CONCLUSIONS: The NPS-ASP appears to be a good parameter to assess sperm function and would be a useful tool to detect chromosomal translocations. Four redundant regions have been identified on four chromosomes, suggesting that they may contain genes of interest to study sperm functions.

Human foetal ovary shares meiotic preventing factors with the developing testis.

STUDY QUESTION: How can pre-meiotic germ cells persist in the human foetal ovary? SUMMARY ANSWER: Numerous oogonia escaping meiotic entry were retrieved throughout human ovarian development simultaneously with the expression of signalling pathways preventing meiosis, typically described in the rodent embryonic testis. WHAT IS KNOWN ALREADY: The transition from mitosis to meiosis is a key event in female germ cells that remains poorly documented in research on the human ovary. Previous reports described a strikingly asynchronous differentiation in the human female germ line during development, with the persistence of oogonia among oocytes and follicles during the second and third trimesters. The possible mechanisms allowing some cells to escape meiosis remain elusive. STUDY DESIGN SIZE, DURATION: In order to document the extent of this phenomenon, we detailed the expression profile of germ cell differentiation markers using 73 ovaries ranging from 6.4 to 35 weeks post-fertilization. PARTICIPANTS/MATERIALS SETTING, METHODS: Pre-meiotic markers were detected by immunohistochemistry or qRT-PCR. The expression of the main meiosis-preventing factors identified in mice was analysed, and their functionality assessed using organ cultures. MAIN RESULTS AND THE ROLE OF CHANCE: Oogonia stained for AP2γ could be traced from the first trimester until the end of the third trimester. Female germ cell differentiation is organized both in time and space in a centripetal manner in the foetal human ovary. Unexpectedly, some features usually ascribed to rodent pre-spermatogonia could be observed in human foetal ovaries, such as NANOS2 expression and quiescence in some germ cells. The two main somatic signals known to inhibit meiosis in the mouse embryonic testis, CYP26B1 and FGF9, were detected in the human ovary and act simultaneously to repress STRA8 and meiosis in human foetal female germ cells. LARGE SCALE DATA: N/A. LIMITATIONS REASON FOR CAUTION: Our conclusions relied partly on in vitro experiments. Germ cells were not systematically identified with immunostaining and some may have thus escaped analysis. WIDER IMPLICATIONS OF THE FINDINGS: We found evidence that a robust repression of meiotic entry is taking place in the human foetal ovary, possibly explaining the exceptional long-lasting presence of pre-meiotic germ cells until late gestational age. This result calls for a redefinition of the markers known as classical male markers, which may in fact characterize mammalian developing gonads irrespectively of their sex. STUDY FUNDING/COMPETING INTEREST(S): This research was supported by the Université Paris Diderot-Paris 7 and Université Paris-Sud, CEA, INSERM, and Agence de la Biomédecine. The authors declare no conflict of interest.

Mutation dependance of the mitochondrial DNA copy number in the first stages of human embryogenesis.

Mitochondrial DNA (mtDNA) content is thought to remain stable over the preimplantation period of human embryogenesis that is, therefore, suggested to be entirely dependent on ooplasm mtDNA capital. We have explored the impact of two disease-causing mutations [m.3243A>G myopathy, encephalopathy, lactic acidosis and stroke-like syndrome (MELAS) and m.8344A>G myoclonic epilepsy associated with ragged-red fibers (MERRF)] on mtDNA amounts in human oocytes and day 4-5 preimplantation embryos. The mtDNA amount was stable in MERRF and control materials, whereas gradually increasing from the germinal vesicle of oogenesis to the blastocyst stage of embryogenesis in MELAS cells, MELAS embryos carrying ∼3-fold higher mtDNA amount than control embryos (P = 0.0003). A correlation between mtDNA copy numbers and mutant loads was observed in MELAS embryos (R(2) = 0.42, P < 0.0013), suggestive of a compensation for the respiratory chain defect resulting from high mutation levels. These results suggest that mtDNA can replicate in early embryos and emphasize the need for sufficient amount of wild-type mtDNA to sustain embryonic development in humans.

Poor correlations in the levels of pathogenic mitochondrial DNA mutations in polar bodies versus oocytes and blastomeres in humans.

Because the mtDNA amount remains stable in the early embryo until uterine implantation, early human development is completely dependent on the mtDNA pool of the mature oocyte. Both quantitative and qualitative mtDNA defects therefore may negatively impact oocyte competence or early embryonic development. However, nothing is known about segregation of mutant and wild-type mtDNA molecules during human meiosis. To investigate this point, we compared the mutant levels in 51 first polar bodies (PBs) and their counterpart (oocytes, blastomeres, or whole embryos), at risk of having (1) the "MELAS" m.3243A>G mutation in MT-TL1 (n = 30), (2) the "MERRF" m.8344A>G mutation in MT-TK (n = 15), and (3) the m.9185T>G mutation located in MT-ATP6 (n = 6). Seven out of 51 of the PBs were mutation free and had homoplasmic wild-type counterparts. In the heteroplasmic PBs, measurement of the mutant load was a rough estimate of the counterpart mutation level (R(2) = 0.52), and high mutant-load differentials between the two populations were occasionally observed (ranging from -34% to +34%). The mutant-load differentials between the PB and its counterpart were higher in highly mutated PBs, suggestive of a selection process acting against highly mutated cells during gametogenesis or early embryonic development. Finally, individual discrepancies in mutant loads between PBs and their counterparts make PB-based preconception diagnosis unreliable for the prevention of mtDNA disorder transmission. Such differences were not observed in animal models, and they emphasize the need to conduct thorough studies on mtDNA segregation in humans.

Msx1 and Msx2 promote meiosis initiation.

The mechanisms regulating germ line sex determination and meiosis initiation are poorly understood. Here, we provide evidence for the involvement of homeobox Msx transcription factors in foetal meiosis initiation in mammalian germ cells. Upon meiosis initiation, Msx1 and Msx2 genes are strongly expressed in the foetal ovary, possibly stimulated by soluble factors found there: bone morphogenetic proteins Bmp2 and Bmp4, and retinoic acid. Analysis of Msx1/Msx2 double mutant embryos revealed a majority of undifferentiated germ cells remaining in the ovary and, importantly, a decrease in the number of meiotic cells. In vivo, the Msx1/Msx2 double-null mutation prevented full activation of Stra8, a gene required for meiosis. In F9 cells, Msx1 can bind to Stra8 regulatory sequences and Msx1 overexpression stimulates Stra8 transcription. Collectively, our data demonstrate for the first time that some homeobox genes are required for meiosis initiation in the female germ line.

Involvement of doublesex and mab-3-related transcription factors in human female germ cell development demonstrated by xenograft and interference RNA strategies.

We identified three doublesex and mab-3-related transcription factors (DMRT) that were sexually differentially expressed in human fetal gonads and present in the ovaries at the time of meiotic initiation. These were also identified in murine embryonic female germ cells. Among these, we focused on DMRTA2 (DMRT5), whose function is unknown in the developing gonads, and clarified its role in human female fetal germ cells, using an original xenograft model. Early human fetal ovaries (8-11 weeks post-fertilization) were grafted into nude mice. Grafted ovaries developed normally, with no apparent overt changes, when compared with ungrafted ovaries at equivalent developmental stages. Appropriate germ cell density, mitotic/meiotic transition, markers of meiotic progression and follicle formation were evident. Four weeks after grafting, mice were treated with siRNA, specifically targeting human DMRTA2 mRNA. DMRTA2 inhibition triggered an increase in undifferentiated FUT4-positive germ cells and a decrease in the percentage of meiotic γH2AX-positive germ cells, when compared with mice that were injected with control siRNA. Interestingly, the expression of markers associated with pre-meiotic germ cell differentiation was also impaired, as was the expression of DMRTB1 (DMRT6) and DMRTC2 (DMRT7). This study reveals, for the first time, the requirement of DMRTA2 for normal human female embryonic germ cell development. DMRTA2 appears to be necessary for proper differentiation of oogonia, prior to entry into meiosis, in the human species. Additionally, we developed a new model of organ xenografting, coupled with RNA interference, which provides a useful tool for genetic investigations of human germline development.

Is it acceptable to destroy or include human embryos before day 5 in research programmes?

Day-3 poor-quality embryos (PQE) from IVF-embryo transfer cycles are usually destroyed or are included in research programmes. Knowing that these embryos have the ability to evolve to the blastocyst stage and yield embryonic stem cell lines, this study postulated that they could also give rise to live births. This is a prospective study including 186 IVF-embryo transfer candidates who had obtained at least one supernumerary PQE on day 3. PQE were kept for extended culture and high-quality blastocysts were frozen. A total of 620 PQE were eligible for the study, 217 (35.0%) reached the blastocyst stage and 73 (33.6%) were frozen. Blastulation rates were 7-fold higher (OR 7.29, 95% CI 5.01-10.61) in embryos compacted on day 4. Of the frozen blastocysts, 40 were thawed during 33 thawed blastocyst transfer cycles, which led to 10 clinical pregnancies. These pregnancies resulted in five miscarriages and five healthy live births at full term. PQE may achieve their development to the blastocyst stage, be frozen-thawed and harbour reasonable implantation potential. These results, thereby, raise an ethical issue regarding the fate reserved to PQE.

Live birth after frozen-thawed oocytes matured in vitro in a PCOS patient: a model for improving implantation rates in IVM cycles and objectively assessing the real potential of development of frozen oocytes matured in vitro.

Over the past 20 years, in vitro maturation (IVM) of oocytes has emerged in the strategy of infertility treatment, with the main indication being in patients suffering from polycystic ovarian syndrome (PCOS). More recently, IVM has been proposed as an option for fertility preservation in women having to undergo gonadotoxic treatments. However, despite the increasing application of IVM, the potential of development of in vitro matured oocytes after thawing remains ill-established and few pregnancies have been reported so far. We report herein a case of live birth after frozen-thawed oocytes matured in vitro and embryo transfer during an artificial cycle in a 29-year-old patient with primary infertility due to PCOS. The present case demonstrates that the transfer of frozen-thawed IVM oocytes during an artificial cycle in PCOS patients is feasible and leads to pregnancy and live birth. This strategy may also be an interesting option to objectively assess the developmental potential of these oocytes after freezing and thawing, which is a major concern for physicians who include the IVM approach in their fertility preservation program.

PGT and deferred embryo transfer: Is blastocyst biopsy more effective than cleaved embryo biopsy?

OBJECTIVE: Blastocyst biopsy has recently been implemented in our laboratory for PGT with a "freeze all" indication. The aim of this study is to compare PGT results between embryos biopsied at the cleaved and embryos biopsied at the blastocyst stage. STUDY DESIGN: This is a retrospective cohort study conducted from January 2017 to December 2022 in France. All couples with a "freeze all" indication the day of hCG trigerring during the study period were included in the study. Patients were retrospectively assigned in one group of two groups based on the day of embryo biopsy: the cleavage group if a blastomere biopsy was performed on day 3/4 or the blastocyst group if a trophectoderm biopsy was performed on day 5/6. We evaluated and compared the results between the two groups for biological parameters and clinical outcomes. RESULTS: In total, 325 PGT cycles (291 patients) were included in our study. Frozen-thawed embryo transfer was performed for 285 cycles, 122 in the blastocyst group and 163 in the cleavage group. The number of biopsied embryos per cycle is significantly higher in the cleavage group with a mean of 7.2 ± 4.1 embryos biopsied per cycle vs. 2.9 ± 2.8 embryos in the blastocyst group (p < 0.001). The rate of the useful embryos was similar between the two groups with 14.6 % of frozen healthy embryos among the 1352 cleaved embryos obtained in blastocyst group, compared to 17.1 % in the cleavage group. No significant differences in clinical pregnancy rate per transfer and implantation rate were observed between the blastocyst and cleavage groups (36.4% vs. 40.4 % and 33.1% vs. 33.2 % respectively). CONCLUSIONS: For "freeze all" PGT cycles, the day of embryo biopsy (cleaved vs blastocyst biopsy) does not impact pregnancy outcomes. Knowing how to perform embryo biopsy at different stages helps to better organize daily laboratory activity and to rescue some undiagnosed embryos after day 3 biopsy.

[How to preserve female fertility before cancer treatments?]. / Comment préserver la fertilité féminine lors du traitement d'un cancer en vue de rendre possible une grossesse ultérieure?

Over the past decades, major advances in diagnosis and treatment have markedly improved the rates of cure for many young adults and children cancers. As a result, the field of fertility preservation (FP) has developed to overcome the adverse effects of cancer treatments on gonadal function. The strategy of FP will depend on patient's age, the puberty status, and the time frame before the initiation of gonadotoxic treatments. Embryo or oocyte cryopreservation after controlled ovarian hyperstimulation is currently the most established technique of FP, but ovarian tissue freezing may also be offered despite it is still considered experimental. More recently, in vitro maturation (IVM) of oocyte has been proposed in the strategy of FP since it does not require ovarian stimulation and can be performed at any time of the menstrual cycle. Therefore, IVM represents an attractive approach for urgent FP or/and in patients suffering from estrogen-sensitive cancers. In addition, GnRH agonists administration during chemotherapy has also been considered as a technique of FP, with controversial results.

Preimplantation genetic testing in patients with genetic susceptibility to cancer.

Data on preimplantation genetic testing (PGT-M) in patients with genetic susceptibility to cancer are scarce in the literature, while there is, in our experience, a growing familiarity with assisted reproduction techniques (ART) among pathogenic variant heterozygotes. We performed a retrospective multicenter study of PGT-M outcomes among French patients with genetic susceptibility to cancer. Our objectives were to collect data on this complex issue, and to help cancer geneticists counsel their patients of reproductive age. We also wanted to increase awareness regarding PGT-M among cancer genetics professionals. Patients from three university hospital cancer genetics clinics who had requested PGT-M between 2000 and 2019 were included retrospectively. Data were extracted from medical records. Patients were then contacted directly to collect missing and up-to-date information. Out of 41 eligible patients, 28 agreed explicitly to participate when contacted and were therefore included. They carried PV in VHL (n = 9), APC (n = 8), CDH1 (n = 5), STK11 (n = 2), AXIN2, BRCA1, MEN1, and FH (n = 1). Seven patients were denied PGT-M based on multidisciplinary team meetings or subsequently by the ART hospital teams, two changed their minds, and two were yet to start the process. PGT-M was successful in seven patients (25%), with a mean age at PGT-M request of 27. Most had von Hippel-Lindau. PGT-M failed in the remaining ten, with a mean age at PGT-M request of 32. The main reason for failure was non-implantation of the embryo. Of these, four patients were pursuing PGT-M at the time of last contact. PGT-M outcomes in patients with cancer susceptibility syndromes were satisfactory. These patients should be informed about PGT-M more systematically, which would imply greater awareness among cancer genetics professionals regarding ART. Our series was not representative of cancer susceptibility syndromes in general; the predominance of cases with syndromes characterized by early-onset, highly penetrant disease is explained by the restrictive French guidelines.