Mechanical Characterization of Murine Oocytes by Atomic Force Microscopy

The quality of murine and human oocytes correlates to their mechanical properties, which are tightly regulated to reach the blastocyst stage after fertilization. Oocytes are nonadherent spherical cells with a diameter over 80 μm. Their mechanical properties have been studied in our lab and others using the micropipette aspiration technique, particularly to obtain the oocyte cortical tension. Micropipette aspiration is affordable but has a low throughput and induces cell-scale deformation. Here we present a step-by-step protocol to characterize the mechanical properties of oocytes using atomic force microscopy (AFM), which is minimally invasive and has a much higher throughput. We used electron microscopy grids to immobilize oocytes. This allowed us to obtain local and reproducible measurements of the cortical tension of murine oocytes during their meiotic divisions. Cortical tension values obtained by AFM are in agreement with the ones previously obtained by micropipette aspiration. Our protocol could help characterize the biophysical properties of oocytes or other types of large nonadherent samples in fundamental and medical research.