Transport of Glycerol Through the Human Sperm Membrane during Cryopreservation

Cryopreservation of biological material is an important task in many areas of biology and medicine especially for assisted reproductive technologies. Cryoprotective media including cell-penetrating and non-penetrating components are used for effective cryopreservation of cells. Usually glycerin in various concentrations acts as a penetrating component. However, elucidating the mechanisms of the cryoprotective action of these compounds as well as increasing the proportion of surviving cells after cryopreservation remain urgent objective of cryobiology. The work examines the mechanism of glycerol transfer through sperm membranes with the participation of aquaporins using the method of mathematical modeling. The presented model describes dynamics of changes in sperm volume depending on the concentration of glycerol and sucrose in the cryoprotective medium. As a result of the analysis the characteristic time for establishing equilibrium between the studied cryoprotective medium and cells was calculated and amounts to t = 80 s in the presence of glycerol 12% vol. The concentration of sucrose (0.16 M) at which the cell returns to its original volume after incubation in a cryoprotective medium was determined. It has been shown that human sperm can contain 6750 AQP7 with a permeability PAQP7 = 0.00366 µm3/s. The experiments performed showed an increase in the sperm motility index when correcting the concentration of sucrose in the solution according to the modeling results.