[Follicle freezing and autografting. A new method of medically assisted procreation?]

Although frozen human follicles were shown to be viable after thawing, more than forty years, the low yield of primordial follicles after cryopreservation has greatly limited research in this area. The aim of freezing follicles is to stock a patient's ovocytes before potentially destructive therapy for cancer then to reimplant the follicular tissue after successful treatment. The patient's ovulatory capacity would then theoretically be restored, allowing natural or possibly in vitro fertilization. As have other teams, we recently renewed work in cryopreservation of follicles in experimental models in search for a better cryopreservation agent and have had encouraging results suggesting that primordial human follicles or ovarian fragments can be grafted successfully after cryopreservation. Questions still under study include the optimal site for implantation, the survival time for grafts and the quantity of follicles needed to achieve pregnancy. Work on large animal models or xenografts of human tissues on immunotolerant animals may provide further insight. The possibilities of grafting primordial follicles, either alone or within ovarian tissue, may raise hope for many women, although new questions such as an age limit for reimplantation and use of allografts requiring preparation with major immunosuppressive therapy require further debate.