Cryopreservation of bovine ovarian tissue: Structural normality of follicles after thawing and culture in vitro

The recovery of viable follicles from cryopreserved ovarian tissue would be of benefit in many areas of assisted reproduction. Structural integrity ne eds to be maintained following cryopreservation of ovarian tissue in order to retrieve healthy follicles which can then be cultured in vitro to produc e viable oocytes. We have assessed the effect of ill vitro culture of bovin e tissue for 0, 1, 4, 24, or 48 h after exposure to, or cryopreservation in , dimethylsulphoxide. Immediately after freezing, normality of primary and preantral follicles within the tissue was significantly lower than for tiss ue exposed to the cryoprotectant without freezing or for control tissue. Af ter 3 h in culture, cryopreserved tissue appeared to have recovered from da mage caused by freezing, although the percentage of tissue with normal morp hology declined after 24 and 48 h of culture. There was no significant diff erence between percentage normality in control tissue and tissue exposed to the cryoprotectant without freezing for any of the culture rimes studied. These data indicate that it is possible to freeze/thaw bovine ovarian tissu e while retaining a reasonable yield of morphologically intact follicles an d that a short period of post-thaw culture may enhance follicle recovery. ( C) 1999 Academic Press.