Poro-viscoelastic behaviour of the zona pellucida: Impact of three-dimensional modelling on material characterisation.

The development of objective biomarkers for the qualitative assessment of oocytes prior to in-vitro fertilisation procedures is crucial, and in this respect the mechanical response of cells has already emerged as a promising and valid measure. The test setups derived from this conceptual approach usually induce complex, partly asymmetric deformation states, so that the process of material parameter identification can only be realised via three-dimensional, mathematical models. In the present study, a three-dimensional model for oocytes is proposed and implemented in the form of the finite element method. In particular, the contribution of each cellular component to the overall mechanical response is considered by including an anisotropic poro-, viscoelastic approach for the zona pellucida and an incompressible neo-Hookean material for the ooplasm. The model is calibrated and validated using experiments on porcine oocytes under plate-plate compression and indentation during quasi-static cyclic and relaxation tests. In addition to investigating the influence of glycoprotein orientation on the shape and extent of deformation, the applicability of the model to identify mechanical properties is demonstrated and discussed in relation to real, complex testing devices.

Pregnancy Outcomes After Frozen-Thawed Embryo Transfer in the Absence of a Corpus Luteum.

Background: Nowadays, frozen-thawed embryo transfer (FET) cycles represent a high proportion of fertility treatments worldwide. Recent studies suggest differences in pregnancy outcomes depending on the FET treatment protocol used. The reason for this is still unclear, but the number of corpora lutea (CL) at conception is discussed as a possible factor. This study aims to investigate whether maternal and neonatal outcomes for pregnancies following FET lacking a CL differ from FET with one or more CL in order to explore a potential link between CL absence and adverse pregnancy outcomes. Methods: The study was designed as a retrospective, multi-center observational study with two cohorts after singleton live birth [0 CL cohort (FET in a programmed cycle, n = 114) and ≥ 1 CL cohort (FET in a natural or stimulated cycle, n = 68)]. Participants completed a questionnaire on the outcome of pregnancy and birth records were analyzed in a descriptive way. Multivariable logistic and linear regressions were performed in order to explore associations between CL absence and pregnancy outcomes. The strength of the agreement between the information in the survey and the diagnoses extracted from the files was assessed by Cohen's Kappa. Results: The risk of hypertensive disorders of pregnancy was higher after FET in the absence of a CL compared to FET with CL presence (aOR 5.56, 95% CI 1.12 - 27.72). Birthweights and birthweight percentiles were significantly higher in the 0 CL group. CL absence was a predictor of higher birthweight (adjusted coefficient B 179.74, 95% CI 13.03 - 346.44) and higher birthweight percentiles (adjusted coefficient B 10.23, 95%, 95% CI 2.28 - 18.40) particularly in female newborns of the 0 CL cohort. While the strength of the agreement between the reported information in the survey and the actual diagnoses extracted from the files was good for the majority of outcomes of interest it was fair in terms of hypertension (κ = 0.38). Conclusion: This study supports observations suggesting a potential link between a lack of CL at conception and adverse maternal and neonatal outcomes. Further investigations on causes and pathophysiological relationships are yet to be conducted.

Spontaneous antral follicle formation and metaphase II oocyte from a non-stimulated prepubertal ovarian tissue xenotransplant.

BACKGROUND: Current strategies in cancer treatment have markedly increased the rates of remission and survival for cancer patients, but are often associated with subsequent sterility. While there are various options available to an adult female depending on the patient's particular situation, the only realistic option for preserving fertility in prepubertal females is to cryopreserve ovarian tissue. This is the first report of a morphologically mature oocyte collected from non-stimulated prepubertal ovarian tissue xenotransplants. METHODS: Ovarian tissue from a 6 year old patient suffering from nephroblastoma was removed and cryopreserved for fertility preservation. The frozen-thawed ovarian tissue fragments were xenotransplanted to bilaterally oophorectomized severe combined immunodeficiency (SCID) mice to assess follicle development. RESULTS: Antral follicle formation occurred post-xenotransplantation in a single ovarian fragment without exogenous hormone stimulation. A morphologically maturing oocyte was harvested from these follicles. CONCLUSIONS: Prepubertal human ovarian follicles and oocytes can be matured after xenotransplantation even without exogenous hormone stimulation. These results indicate that tissue collected from prepubertal patients can support fertility in cancer survivors.