l-Proline Enhanced Whole Ovary Cryopreservation by Inhibiting Ice Crystal Growth and Reducing Oxidative Stress

Cryopreservation and transplantation of ovaries are considered to be effective methods for preserving the fertility of female cancer patients. However, ice crystal and oxidative damage occur during the freeze-thaw cycle, significantly reducing the effectiveness of cryopreservation and limiting its clinical application. Thus, new technologies or agents must be explored to enhance ovarian cryopreservation. Recently, l-proline, a natural amino acid, has been proven to have good biocompatibility and can clear reactive oxygen species produced during cryopreservation. Whether l-proline can play a positive role in ovarian cryopreservation has not yet been explored. Here, the effect of l-proline on ovarian cryopreservation was investigated. The oxidative antioxidant system, mitochondrial function, and cell apoptosis and proliferation after thawing were systematically evaluated. Moreover, the ice crystal inhibition of l-proline was examined. Furthermore, the morphology and function of oocytes in ovaries, as well as the state of the ovaries after heterotopic renal capsule transplantation, were evaluated to validate the feasibility and reliability of this study. The above results confirm that l-proline can effectively inhibit ice crystal growth, reduce reactive oxygen species production, and enhance cryopreservation effects at the optimal concentration of 20 mM. Altogether, l-proline can significantly improve the cryopreservation effect of ovaries, which is expected to provide a new perspective for the cryopreservation of female fertility.