Technical Aspects of Laparoscopic Ovarian Autograft in Ewes After Cryopreservation by Slow-Cooling Protocol

Cryostorage and retransplantation of ovarian tissue as an infertility treatment

While still considered an experimental procedure in most countries, ovarian tissue cryopreservation and transplantation has been increasingly applied worldwide to restore fertility in patients with malignant and non-malignant pathologies with risk of premature ovarian insufficiency. It has yielded more than 130 live births up to now and almost all transplanted patients recovered their ovarian function. This study summarizes ovarian tissue cryopreservation and transplantation indications, procedures, their efficacy and main results and proposes different strategies to improve this strategy. Although the main focus of this study is on ovarian tissue cryopreservation and transplantation as a strategy to restore fertility, we believe that it is also important to discuss other applications for this approach.

Heterotopic ovarian transplantation results in less apoptosis than orthotopic transplantation in a minipig model

Background

Ovarian autotransplantation has shown increasing promise as a clinical method for the preservation of fertility and hormonal function. However, information regarding the success rate of this type of transplantation is limited. We hypothesized that results vary according to the site of the ovarian transplantation. To test this hypothesis, fresh or cryopreserved ovarian strips were autotransplanted to orthotopic or heterotopic sites. The strips were later collected, and the morphology and expression of selected markers of apoptosis were evaluated. We compared the Bax, Bcl-2 and cleaved caspase-3 staining levels and the morphometric aspects of autotransplanted fresh and cryopreserved ovarian strips placed at orthotopic and heterotopic sites in minipigs.

Methods

Forty female minipigs were allocated to the following five groups: group 1 (control), ovarian tissue removed during oophorectomy; group 2, transplantation of fresh ovarian strips to a heterotopic site; group 3, transplantation of fresh ovarian strips to an orthotopic site; group 4, transplantation of cryopreserved ovarian strips to a heterotopic site; and group 5, transplantation of ovarian trips to an orthotopic site. On day 7 after transplantation, ovarian strips were collected, and the morphology and expression of apoptosis markers were evaluated.

Results

In all groups, follicles across all stages of development were detected. The numbers of primordial, primary and secondary follicles were similar in all groups, but the numbers of antral follicles were lower in the cryopreserved groups in comparison with freshly derived ovarian tissue, with no significant differences observed between fresh and cryopreserved transplants. In all transplanted groups, Bcl-2 expression was lower and Bax expression was higher than in the control group. Furthermore, increased expression of apoptosis markers was detected in fresh intraperitoneal transplants. Lastly, the expression of cleaved caspase-3 was higher in the cryopreserved orthotopic group compared with the heterotopic group.

Conclusions

Orthotopic and heterotopic ovarian strip transplantations are feasible options using these techniques. Importantly, we found that heterotopic transplantation preserves ovarian follicle integrity to a greater degree (i.e., lower expression of apoptosis markers) than orthotopic transplantation, and cryopreservation does not exacerbate expression of apoptosis’s markers. These findings have major clinical applications and enhance the discussion regarding the heterotopic transplantation of ovarian tissue.