Cryopreservation of follicles in human ovarian cortical tissue. Comparison of serum and human serum albumin in the cryoprotectant solutions

Background: Cryopreservation of follicles in ovarian cortical tissue has been suggested as a method for preserving fertility for young women who need to undergo cytotoxic therapy. Varying compositions of cryoprotectant solutions have been used to prevent tissue damage during cryopreservation and thawing. We compared human serum [20% (v/v)] and human serum albumin (HSA) (25 mg/ml) in cryoprotectant solutions containing propanediol and sucrose to evaluate whether serum-free medium could be used for this purpose. Methods: Biopsies of ovarian cortical tissue were obtained from 23 subjects after informed consent. Fourteen underwent Caesarean section and nine underwent sterilization by laparoscopy. The cortical tissue was cut into pieces of 1-1.5 mm(3) and cryopreserved in cryoprotectant solutions containing serum or HSA. After thawing, a total of 1318 follicles were analysed using light microscopy, transmission electron microscopy (TEM) or live/dead assay. Results: Viability of the follicles was 99.3% in freshly dissected tissue. After thawing, 65% of the follicles and 75% of the oocytes were viable with serum, and 69 and 74%, respectively, with HSA. No significant differences were observed between results in solutions containing serum versus HSA. TEM showed similar results; however, poor survival of stromal tissue was evident in this analysis. The live/dead assay showed 82% viability after thawing for both groups. No benefits were seen from post-thawing culture for 4 h before histological preparation. Conclusions: A cryoprotectant solution containing HSA was equally effective as one containing serum. Good viability of follicles was confirmed when using propanediol and sucrose as cryoprotectants, with a large number of follicles.