Biomedical subjects

Martin Wilding

Publications and source records attributed to Martin Wilding.

9 recordsLinked to original sources

PubMed2026

Base editing reveals an essential role for NANOG in human embryogenesis.

Understanding how the first cell lineages in human development are specified and maintained has fundamental importance and clinical implications for regenerative medicine, infertility and pregnancy loss. Although mouse models have provided valuable insights into transcription factors regulating early development, translating these findings to human embryos has been limited by ethical, technical and biological constraints. Functional studies of transcription factors in human embryos have been hindered by nuclease-based genome editing approaches that induce genotoxicity1-3. Here, to overcome this, we applied ABE8e adenine base editing4,5 to precisely target an exon splice donor site, resulting in a splicing defect and functional knockout of the developmental regulator NANOG in human embryos. This approach did not trigger genotoxicity and showed limited off-target editing. Loss of NANOG disrupts pluripotent epiblast specification and instead cells differentiate towards a primitive endoderm (yolk sac) or trophectoderm (placental) transcriptional programme. Retention of primitive endoderm differentiation in NANOG-edited human embryos reveals a functional compensation that is distinct from mouse, underscoring the importance of directly investigating human development. Our findings demonstrate an essential role for NANOG in human pluripotency and epiblast specification and highlight the utility of base editing for functional interrogation of human development.

Journal Article↗

PubMed2006

The effect of extended culture of cumulus-oocyte complexes in follicular fluid during in vitro fertilisation cycles.

PURPOSE: To assess the clinical and biological effect of the preincubation of oocytes in follicular fluid prior to IVF and ICSI cycles. METHODS: A series of patients were treated by the preincubation of oocytes in the patients' follicular fluid for 3 h after oocyte retrieval followed by processing with standard protocols. Control oocytes were preincubated in normal IVF culture medium. Fluorescence techniques were used to examine oocyte mitochondrial membrane potential. RESULTS: Fertilisation, pregnancy, and implantation rates were all significantly improved after the preincubation of oocytes in follicular fluid. Further tests suggested that differences in pH between follicular fluid and artificial culture medium may be critical to these differences. CONCLUSIONS: Preincubation of human oocytes in follicular fluid improves the results after IVF. This may be partly due to the use of a non-"physiological" pH in artificial culture media during in vitro fertilisation procedures.

Adult↗

PubMed2005

The maternal age effect: a hypothesis based on oxidative phosphorylation.

The 'maternal age effect' in human reproduction, characterized by a negative relationship between maternal age and reproductive efficiency, remains a poorly understood phenomenon. Current data suggest that oocyte physiology determines this relationship. In this review, we present a hypothesis of a mitochondrial role in the physiology of ageing in human oocytes. We suggest that the efficiency of oxidative phosphorylation in the ageing human oocyte is degraded by free radical attack on the primordial oocytes residing in the ovary. Although deficiencies in oxidative phosphorylation can be accounted for in the short term by anaerobic respiration, we suggest that, in the long term, the level of oxidative phosphorylation strongly influences oocyte quality.

Female↗

PubMed2004

Secondary male factor infertility after Roux-en-Y gastric bypass for morbid obesity: case report.

Surgical treatments such as the Roux-en-Y gastric bypass operation result in the successful treatment of morbid obesity; however, this type of operation may cause long-term side effects due to the reduced absorption of nutrients. Here, we present data suggesting that this operation can result in secondary infertility in males. Six healthy, previously fertile male subjects presented in our centre for secondary infertility after a Roux-en-Y gastric bypass operation for morbid obesity. Reproductive function was assessed with a series of spermiograms, and by testicular biopsy. Secondary azoospermy with complete spermatogenic arrest was diagnosed. The results suggest that weight reduction surgery may cause reproductive dysfunction.

Adult↗

PubMed2004

Preimplantation genetic diagnosis for the treatment of failed in vitro fertilization-embryo transfer and habitual abortion.

OBJECTIVE: To apply preimplantation genetic diagnosis (PGD) for the treatment of patients with a history of failed IVF-ET or habitual aborters. DESIGN: Prospective clinical study. SETTING: Tertiary center for assisted reproduction. PATIENT(S): Ninety-four couples with failed IVF-ET after >2 IVF cycles and 64 couples with >2 spontaneous abortions. INTERVENTION(S): Patients were prepared for oocyte retrieval using standard controlled ovarian hyperstimulation protocols after standard laboratory techniques. Blastomeres from 6- to 8-cell embryos were analysed using fluorescence in situ hybridization with commercial chromosomal probes, and normoploid embryos were transferred on day 3 after fertilization. MAIN OUTCOME MEASURE(S): Pregnancy and implantation rates and live births. RESULT(S): Both 3- and 5-probe PGD resulted in a significantly higher outcome than controls for failed IVF-ET. Five-probe PGD appeared to be more suitable for habitual aborters. CONCLUSION(S): This pilot study suggests that 3-probe PGD is a valid option for failed IVF-ET patients. The use of five or more probes is indicated for habitual aborters.

Abortion, Habitual↗

PubMed2003

Chaotic mosaicism in human preimplantation embryos is correlated with a low mitochondrial membrane potential.

OBJECTIVE: To determine the relationship between the intrinsic mitochondrial deltapsi of human embryos and the embryo karyotype. DESIGN: Analysis of mitochondrial deltapsi of living embryos followed by chromosomal enumeration with fluorescence in situ hybridization. A tertiary center for assisted reproduction technology. PATIENT(S): Fifty-two patients attending the fertility center for assisted reproduction. INTERVENTION(S): Donated embryos were loaded with a mitochondrial deltapsi-sensitive fluorescence dye. MAIN OUTCOME MEASURE(S): Mitochondrial deltapsi was measured by confocal microscopy. Subsequently, embryos were fixed and fluorescence in situ hybridization analysis was used to denote embryo karyotype. MAIN OUTCOME MEASURE(S): Mitochondrial deltapsi and embryo karyotype. RESULT(S): An association was observed between low mitochondrial deltapsi and the detection of chaotic mosaicism. Analysis of oocytes suggested that this was due to the effect of low mitochondrial deltapsi on the morphology of the meiotic apparatus. CONCLUSION(S): The data suggest that the intrinsic mitochondrial deltapsi of human oocytes programs the developmental fate of embryos through an effect on the ability of oocytes to form a normal meiotic apparatus and not through nondisjunction.

Blastocyst↗

PubMed2002

Absence of sperm sex chromosome aneuploidies in an X0/XYY man.

OBJECTIVE: To determine appropriate genetic counseling of patients with a mosaic karyotype who wished to undergo assisted reproduction technology. DESIGN: Case report. SETTING: A tertiary center for assisted reproduction technology. PATIENT(S): A male with a mosaic karyotype X0/XYY. INTERVENTION(S): Analysis of ejaculated spermatozoa by using fluorescence in situ hybridisation with probes directed against chromosomes X, Y, and 18. MAIN OUTCOME MEASURE(S): Degree of sex chromosome aneuploidies in spermatozoa. RESULT(S): Levels of sex chromosome aneuploidies in spermatozoa were normal. On the basis of these findings, the couple proceeded to assisted reproduction technology without preimplantation genetic diagnosis and conceived a healthy male baby. CONCLUSION(S): Sex chromosome mosaicism in men does not necessarily lead to high levels of abnormal spermatozoa. Sex chromosome aneuploidies may be eliminated in the testes through the selective degeneration of abnormal spermatogenic cells.

Adult↗

PubMed2002

Zygote versus embryo transfer: a prospective randomized multicenter trial.

PURPOSE: To determine the efficiency of transferring human zygotes as opposed to human day 2 or 3 embryos. METHODS: A prospective, randomized, Multicenter trial. Patients were randomized into zygote or embryo transfer. Patients were prepared for oocyte retrieval using standardized protocols. Oocyte retrieval was performed under general anesthesia. Oocytes and spermatozoa were treated using standard laboratory techniques. All protocols were coordinated by the coordinating center. RESULTS: A total of 386 patients were included in the trial. Pregnancy rates were 36.5% after zygote transfer and 42% after embryo transfer. Implantation rates were equivalent (17%) in both groups. CONCLUSIONS: No general difference was observed for zygote or embryo transfer. The results suggest that zygote transfer is a valid alternative to embryo transfer.

Adult↗

PubMed2002

High outcome predictability after IVF using a combined score for zygote and embryo morphology and growth rate.

BACKGROUND: A scoring system has been developed to determine preimplantation embryo quality, and used to select embryos for transfer into the uterus of patients. METHODS AND RESULTS: The system was used to study early embryo development and to test whether these scores alone can accurately predict IVF outcome. Following zygote and embryo scores through early development, the data showed that a top quality zygote does not necessarily indicate that the resulting embryo will be top quality after in-vitro culture. The embryo quality score can change dramatically when embryos are cultured to day 2 or 3 post-fertilization. Pregnancy rates and implantation rates were compared with the cumulative and separated zygote and embryo scores. Analysis of the predictability of scoring systems suggested that morphological scores alone are relatively unpredictive of IVF outcome. When weighted for in-vitro growth rate, scores were highly predictive, more so than the rate of development alone. CONCLUSIONS: These data suggested that a combination of in-vitro growth rate and morphological analysis both of zygotes and embryos was highly indicative of outcome after IVF. The results can be adopted to the single embryo transfer approach to IVF.

Blastocyst↗