In vitro growth of human primordial follicles from frozen-banked ovarian tissue

The rarity of human oocytes frequently limits the success of assisted repro ductive technology and delays research progress. Development of technologie s to grow mature oocytes from the more abundant small follicles, perhaps af ter long-term storage at low temperatures, is a theoretically attractive so lution to both problems. The length of the follicular growth span from the primordial to Graafian stage and changes in the trophic requirements of the cells, cellular interactions, morphogenesis and the sheer increase in bulk as the antrum forms are major challenges for cell culture technology. Even so, much progress has been made with animal follicles, and has begun with human tissue. A multi-step procedure, which reflects these changes, is perh aps the most likely to succeed. At present, the best strategy appears to be to initiate follicle growth in situ and isolate the follicles or granulosa -oocyte complexes once they have progressed to preantral stages. The final step is to mature the oocytes within their cumulus cells. The prospects of succeeding at each stage, and producing a fertile gamete at the end, are li kely to be greater by preserving cellular interactions and the phenotype of follicle cells as these provide the physiological environment in which ooc ytes develop. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.