Oocyte Deformability Measurement by Micropipette

Oocytes, placed in individual drops of modified human tubal fluid media, were measured, and individually tracked for outcomes. A micropipette was placed on the zona pellucida directly opposite to the location of the polar body (see Fig 3) to standardize the location of measurement in an area, a procedure performed similarly to the previous study [15 (link)]. Given the larger size of a human oocyte (~110 μm) as compared to that of a mouse embryo (~80 μm), 50-μm inner diameter of micropipettes (custom-made by Origio) and an applied pressure (-0.1 p.s.i.), which was modified to be slightly larger than the 40-μm inner diameter of micropipettes in Yanez et. al [15 (link)] and the applied pressure of ~0.5 kPa (~0.073 p.s.i.) in Young’s modulus for mouse embryo [17 (link)], were used and applied. The pressure was applied through a micropipette for 2 seconds and the movement of the zona pellucida inside the micropipette was recorded at 70 frames per second with a CMOS camera (Thorlabs DCC1545M). The pressure was regulated back to the balance pressure after each measurement to release the oocyte from the micropipette tip. The operator could easily navigate through the measurement steps displayed on the computer screen or pressure log file. This included monitoring pressure values both before and during measurements, allowing them to assess the success of each measurement.