The effect of thawing protocols on follicle conservation in human ovarian tissue cryopreservation.

Ovarian tissue cryopreservation has the potential to improve fertility preservation for a growing number of patients undergoing sterilising therapy, particularly where oocyte or embryo cryopreservation is not suitable. However, its success is limited by significant follicular apoptosis upon thawing, and there is wide variation in thawing protocols used with little evidence of efficacy.To determine the best warming rates to maintain tissue viability.Ovarian tissue biopsies from 11 patients were taken with informed consent and divided into four pieces, which were allocated to either fresh assessment or to one of several freeze-thaw protocols. Cryopreservation was undertaken using a Stirling cycle cryo-cooler and cryopreserved samples were exposed to different warming protocols. Tissue conservation was then assessed using a marker, neutral red, to identify viable follicles.The results showed greatest follicle conservation rates in fresh samples, followed by those thawed using a rapid thawing protocol (Protocol 1). Tissue thawed using an ultra fast protocol (Protocol 2) and slow warming (Protocol 3) resulted in greater follicle loss.These preliminary results indicate thawing conditions significantly affect follicle conservation in cryopreserved human ovarian tissue.