Fertility preservation in gynecologic cancers

Successful cryoloop vitrification and subsequent in vitro maturation of mouse preantral follicles

The purpose of this study was to assess follicular viability and competence through in vitro maturation (IVM) of cryoloop vitrified mouse preantral follicles. Early mouse preantral follicles were isolated and vitrified using the cyroloop vitrification technique. After thawing, the preantral follicles and oocytes were cultured and in vitro matured for 10 d to the metaphase two stage (M2). Oocytes were assessed for viability at 2 and 10 d of IVM and compared to a control group of freshly isolated preantral follicles undergoing IVM. Of vitrified follicles, 94.0% (345/367) were recovered after thawing. The survival rate after the first two-days of IVM culture was 82.3% (284/345) for the cryoloop vitrified follicles and 100% for the control follicles (437/437). The percentage of oocytes in the cryoloop group that developed to M2 was 70.2% (174/248), comparable to that of the control group at 68.7% (241/351) (p value 0.12). Our results indicate that cyroloop vitrification is a viable and practical technique for cryopreservation of mouse preantral follicles. Human oocyte cryopreservation by means of cryoloop vitrification may prove to be useful as a possible treatment modality for human fertility preservation.

Parthenogenesis in human oocytes that were collected from resected ovarian tissue and matured in vitro

Currently, a major hurdle in the progress of human embryonic stem (hES) cell research is the lack of human oocytes with which to perform experiments. The collection process is a logistical and ethical challenge and usually involves the use of excess oocytes donated after assisted reproduction procedures. We collected resected human ovarian tissue after routine surgical procedures. Oocytes were isolated from the tissue and matured in vitro to the meiosis II (MII) stage, when the first polar body is extruded. With the large antral and smaller preantral follicles, the efficiencies of the maturation were nearly 50% and 25%, respectively. The quality of the matured oocytes was assessed by inducing parthenogenesis and >50% of the in vitro matured oocytes were competent enough to develop pronuclei and 33% developed at least to the two-cell stage 48 h after activation. Parthenotes continued to develop by 72 h but with significant blastomere fragmentation. These results provide evidence that resected ovarian tissue, which is normally discarded, may be a suitable alternative source for oocytes in hES cell research.