RESUMO
OBJECTIVE: To compare conventional slow equilibrium cooling and directional freezing for cryopreservation of whole ovaries. DESIGN: Experimental animal study. SETTING: Academic research environment. ANIMAL(S): Adult ewes. INTERVENTION(S): Eighty-one ovaries were randomly assigned to fresh control, conventional freezing (CF), and directional freezing (DF) group. Ovaries of CF and DF groups were perfused via the ovarian artery with Leibovitz L-15 medium, 10% fetal bovine serum, and 1.5 M dimethyl sulfoxide for 5 minutes. Each ovary was inserted into a glass test tube containing 10 mL of the same solution and cooled to -100°C or -70°C, respectively. Ovaries were stored in liquid nitrogen for a minimum of 2 weeks. MAIN OUTCOME MEASURE(S): Structural integrity of cortical and medulla regions, vascular integrity, follicle in vitro development, cell proliferation, and DNA damage and repair. RESULT(S): All examined parameters indicate that the structure of DF ovaries remains largely intact and comparable to fresh controls, whereas significant damages were observed in CF ovaries. CONCLUSION(S): Directional freezing allows good preservation of whole ovaries, with most of the parameters taken into consideration almost identical to those recorded in fresh control samples. This encourages a reconsideration of the possible use of whole-ovary cryopreservation as a viable alternative to cortical fragments.
