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The present study investigated the association between oocyte zona pellucida shear modulus (ZPSM) and implantation rate (IR). Ninety-three oocytes collected from 38 in-vitro fertilization patients who underwent intracytoplasmic sperm injection were included in this case-control study. The ZP was modeled as an isotropic compressible hyperelastic material with parameter [Formula: see text], which represents the ZPSM. Computational methodology was used to calculate the mechanical parameters that govern ZP deformation. Fifty-one developed embryos were transferred and divided into two groups-implanted and not implanted. Multivariate logistic regression analysis was performed to identify the association between ZPSM and IR while controlling for confounders. Maternal age and number of embryos per transfer were significantly associated with implantation. The IR of embryos characterized by [Formula: see text] values in the range of 0.20-0.40 kPa was 66.75%, while outside this range it was 6.70%. This range was significantly associated with implantation (p < 0.001). Geometric properties were not associated with implantation. Multivariate logistic regression analysis that controlled for relevant confounders indicated that this range was independently associated with implantation (adjusted OR 38.03, 95% confidence interval 4.67-309.36, p = 0.001). The present study suggests that ZPSM may improve the classic embryo selection process with the aim of increasing IR.

It has long been speculated that the mechanical properties of the human oocyte can be an indicator for oocyte viability. Recent studies have demonstrated that embryo implantation rates, following Intra-Cytoplasmic Sperm Injection (ICSI) procedures, may be increased if the shear modulus value of the oocyte Zona Pellucida (ZP) is taken into consideration during embryo transfer. The shear modulus was determined by an iterative oocyte specific finite element (FE) analysis based on the clinical ICSI data. Nevertheless, the results obtained from the computational analysis may depend on the choice of the constitutive model used for the ZP. In the current study, three different hyper-elastic strain energy density functions (SEDF's) are considered. The Neo-Hookean (NH), Mooney-Rivlin (MR) and Ogden models (OG) were used to determine the ZP shear modulus from ICSI clinical data. The sensitivity of each SEDF in extracting the oocyte specific shear modulus is examined, for the first time. It is demonstrated that the NH and MR models are more sensitive than the OG model for determining the ZP shear modulus from clinical ICSI data. It is also demonstrated that the accuracy of ZP shear modulus identification process greatly depends on the value of suction pressure applied during the ICSI procedure. [ABSTRACT FROM AUTHOR]