Glycerol Permeation Through the Human Sperm Membrane During Cryopreservation

Cryopreservation of biological material is an important issue in many fields of biology and medicine, especially for assisted reproductive technologies. Cryoprotective media, including cell-permeating and non-permeating components, are used for effective cryopreservation of cells. Glycerol at various concentrations is often used as a permeating component. However, elucidating the mechanisms of the cryoprotective effect of these compounds, as well as increasing the proportion of surviving cells after cryopreservation, remain urgent tasks of cryobiology. In this study, the mechanism of glycerol transfer through sperm membranes with the participation of aquaporins was investigated by mathematical modeling. The presented model describes the dynamics of changes in sperm volume depending on the concentration of glycerol and sucrose in a cryoprotective medium. As a result of the analysis, the characteristic time for establishing equilibrium between the cryoprotective medium under study and the cells was calculated, which was t = 80 s in the presence of 12 vol. % of glycerol. The sucrose concentration (0.16 M) was determined at which the cell returns to its original volume after incubation in the cryoprotective medium. It has been shown that the human sperm can contain 6750 aquaporins of the 7th type with a permeability P_AQP7= 0.00366 µm³/s. The experiments performed showed an increase in the sperm motility index after adjusting the sucrose concentration in the solution in accordance with the simulation results.