Vitrification: Which prospects for ovarian cryopreservation ? Physical basis of cryobiology, advantages and limits

Ovarian cryopreservation is presently indicated in patients who undergo a gonadotoxic treatment, most commonly for anticancer procedures. These procedures can strongly alter fertility by damaging the follicular ovarian reserve. Although six human live births have been described in the world after ovarian tissue cryopreservation and autografting, the techniques of cryopreservation techniques are not consensual. Vitrification is a physical process that allows cryopreservation without formation of ice crystals, by transformation of a highly concentrated solution in a glassy or amorphous state. Vitrification is at present rapidly expanding in the biology of reproduction. With the classic methods of freezing, formation of ice crystals within the ovarian tissue is systematic and can entail cellular lesions. Which is why more and more teams question the theoretical advantage of the vitrification for ovarian cryopreservation. Our objective was to summarize the fundamental physical basis of cryobiology, necessary for an understanding of vitrification. From our experience, we also wanted to point out the practical difficulties of this technique, and we are proposing a model of evaluation and validation that uses differential scanning calorimetry, applicable to any protocol of vitrification. (C) 2009 Elsevier Masson SAS. All rights reserved.