Ovarian xenotransplantation is a promising alternative to preserve fertility of oncologic patients. However, several functional aspects of this procedure remained to be addressed. The aim of this study was evaluate the feasibility of xenotransplantation as a strategy to maintain bovine ovarian grafts and produce oocytes. Adult ovarian cortical pieces were xenotransplanted to the dorsal subcutaneous of female NOD-SCID mice (n = 62). Grafts were recovered ten days after xenotransplantation. Host and graft weights; folliculogenesis progression; blood perfusion, relative gene expression and number of macrophage and neutrophil of xenografts; in vitro developmental competence of graft-derived oocytes were evaluated. Folliculogenesis was supported in the grafts, as indicated by the presence of primordial, primary, secondary, antral, and atretic follicles. The xenografts showed a greater volumetric density of atretic follicles and higher hyperemia and number of host-derived macrophage and neutrophil (P<0.05), when compared to non-grafted fragments. There was a higher blood perfusion under the back skin in the transplantation sites of host animals than in control and non-grafted (P<0.01). BAX and PRDX1 genes were up-regulated, while BCL2, FSHR, IGF1R and IGF2R were down-regulated, when compared to the control (P<0.01). Twenty seven oocytes were successfully harvested from grafts, and some of these oocytes were able to give rise to blastocysts after in vitro fertilization. However, cleavage and blastocyst rates of xenograft derived oocytes were lower than in control (P<0.01). Despite showing some functional modifications, the ovarian xenografts were able to support folliculogenesis and produce functional oocytes.

Chemo- or radiotherapy negatively affects the fertility of female patients undergoing oncological treatments. Ovaries are sensitive to such treatments, resulting in an increasing number of premature ovarian failures. Graft techniques are a promising alternative to preserve the fertility of such patients. So far, 35 birthed from human ovarian cortex autografts were reported in the literature; however, in this approach there is a risk of neoplastic reincidence. The aim of the present study was to evaluate the feasibility of ectopic ovarian cortex xenograft (using the bovine model) under the back skin of immunodeficient mice. Female SCID mice (~60 days, n = 38) were anesthetized with ketamine/xilazine and were placed on ventral decubitus. Ovarian cortex fragments from 8 cows (1.5 mm3; n = 152) were grafted through incisions made in the dorsal region (4 grafts per mouse). Ten days after ovarian fragments xenograft, the recipients were killed and the xenografts were harvested. The mice and grafts were weighed before and after the transplant. From the xenografts recovered, 88 were either routinely processed for histology (n = 26), to evaluate the progression of folliculogenesis, or sliced (n = 62) to recover the cumulus‐oocyte complexes, which were morphologically classified and used for in vitro embryo production, using standard procedures (in vitro maturation, fertilization, and embryo culture). The remaining grafts recovered (64) were stored in liquid nitrogen for future studies. Differences between means were compared using Student’s t-test. There was no difference between the body weight of recipient mice before and after xenograft (20.5 ± 0.4 v. 21 ± 0.8 g, respectively; P > 0.05). On the other hand, the grafts increased weight (11.6 ± 3.4 v. 14.8 ± 5.2 mg before and after transplant; P < 0.01). Histological analysis of the slices showed primordial, primary, multilaminar, antral, and atretic follicles, indicating the progression of folliculogenesis and neo-angiogenesis in the grafts. Twenty-four viable cumulus‐oocyte complexes were recovered from ovarian xenografts, from which 2 blastocysts were produced in vitro 8 days later (8.3% blastocyst rate). In summary, this study showed that ovarian xenografts were (i) healthily maintained under the back skin of immunodeficient mice, (ii) responsive to murine gonadotrophins, and (iii) able to produce viable cumulus-oocyte complexes that, (iv) by in vitro fertilization, can originate blastocysts. In general, our findings show the feasibility of the ovary xenograft as an alternative technique to fertility preservation in oncogenic patients, avoiding the risk of neoplastic re-incidence. Study approved by Animal Experimentation Ethics Committee/FUSJ-009/15. Financial support was received from Fapemig and CNPq.