Atomic force spectroscopy‐based essay to evaluate oocyte postovulatory aging

Abstract

Postovulatory aging is a process occurring in the mature (MII) oocyte leading the unfertilized ones to apoptosis. The optimal time window of fertility for different mammalian species after oocytes maturation depends on its timeliness: the higher the time elapsed from the accomplishment of the MII stage, the lower are the chances of fertilization and of development of a viable embryo. In the in vitro fertilization, the selection of competent oocytes for intracytoplasmic sperm injection (ICSI) is mostly made by the visual inspection of the MII oocyte morphology, which does not allow to determine the oocyte postovulatory age. On the other hand, more specific tests usually involve some kind of staining, thus compromising the viability of the oocyte for reproductive purposes.Hence, the need of a noninvasive analysis of oocyte aging to improve the success rate of in vitro fertilization procedures. Here, we exploit atomic force microscopy to examine the evolution of the mechanical properties of mouse oocytes during in vitro postovulatory aging. Three hours before the occurrence of any visual morphological feature related to degradation, we observe a sudden change of the mechanical parameters: the elastic modulus doubles its initial value, while the viscosity decreases significantly. These mechanical variations are temporally correlated with the release of the cortical granules, investigated by fluorescence microscopy. Interestingly, the oocyte mechanics correlates as well with the yield of embryo formation, evaluated up to the blastocyst formation stage. These results demonstrate that minimally invasive mechanical measurements are very sensitive to the aging of the oocyte and can be used as a label-free method to detect the age of the postovulatory oocytes.

Filopodia-like protrusions of adjacent somatic cells shape the developmental potential of oocytes

“…If so, this could change its mechanical properties. We thus assessed the mechanical properties of the zona pellucida of control and Myo10 full knockouts using atomic force microscopy (AFM) as in Reference 22 . Our experiments show decreased zona pellucida elasticity in Myo10 full knockouts compared with controls ( Fig S4H ).…”

How great thou ART: biomechanical properties of oocytes and embryos as indicators of quality in assisted reproductive technologies

“…The amount of deflection is used to calculate the force exerted on the tip by the sample’s surface ( Viljoen et al, 2021 ). In its noninvasive form, in a similar manner to CT measurements, atomic force spectroscopy is limited to the studies of the zona pellucida ( Boccaccio et al, 2012 ; Andolfi et al, 2016 ; Battistella et al, 2022 ).…”

Simple bioelectrical microsensor: oocyte quality prediction via membrane electrophysiological characterization

“…2 The mechanical properties of the zona pellucida and cells, as well as the deformation of egg cells due to mechanical pressure, were studied to assess their hardness. Various methods like indentation, tension, constriction, or vibration 11,[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] were employed to apply mechanical pressure. In some instances, magnetic 29,30 or electrical forces 31,32 were also used to apply or measure mechanical pressure.…”