In-situ measurement and modeling of mechanical properties of porcine oocytes

The quality of porcine oocytes determines the developmental potential of early porcine embryos, while the quality of porcine oocytes can be qualitatively described by their mechanical properties. In previous studies, porcine oocytes were often considered as a homogeneous spheroid, which was clearly contrary to its physiological structure consisting of multiple layers of components from the inside out. In this study, we first measured the mechanical properties of different subcellular components of porcine oocytes in situ using atomic force microscopy (AFM). The whole porcine oocyte and cytoplasm were subjected to multiple single-point indentations in situ under ramp mode, and the Young’s modulus was obtained by fitting the force curve with the Sneddon model. In ramp mode, when the preset force was reached, the magnitude of the force was kept unchanged and the change of probe position was recorded to obtain the viscoelastic properties of each subcellular component. Then, a finite element model of porcine oocytes was established. Finally, we performed narrow-neck pipette pass-through experiments and suction penetration experiments of porcine oocytes to verify the accuracy of our model. The finite element model of porcine oocytes established by us is of great significance for further study of oocyte micromanipulation under different conditions.