Ischemia and vasculogenesis after transplantation of frozen and vitrified human ovarian tissue onto Chick Embryo Chorioallantoic Membrane (CAM).

The first days of post-ovarian transplantation are critical periods, as the ischemic injury can diminish the success rate. In this study, the first day's events of ovarian transplantation in two dimensions of structure and ultrastructure following slow freezing and vitrification were assessed. Ovarian tissues (OTs) from 10 cancerous patients were frozen in two methods of slow freezing and vitrification. Tissues were transplanted onto the CAM and then retrieved at 5 and 10 days of culture. Nine groups were assigned as follows; I-III; fresh, 5 and 10 days culture, IV-VI; vitrification, 5 and 10 days culture, and VII-IX; slow freezing, 5 and 10 days culture. Structural and ultra-structural studies were done to assess the tissue viability and integrity following CAM transplantation. Image J software was used to measure the amounts of fibrosis and necrosis. The first sign of successful transplantation was found on day 3 post-transplantation. Vitrified tissues showed higher viability and transplantation rate compared to the slow frozen group (65% vs 57.5%) (p = 0.7). Tissue fibrosis and areas didn't increase significantly after cryopreservation using two methods (p > 0.05). The areas of fibrosis and necrosis and avian vessels increased significantly after 5 and 10 days of culture (p < 0.05). Large ultra-structural follicular deformities were noticed after 10 days of CAM transplantation. Better stromal ultrastructure features can be found after vitrified tissue culture. Also, the CAM transplantation technique had negative effects on the integrity of follicles, independent of the freezing procedure. Evaluation of early events of the ovarian post-transplantation is of amount importance, since the hypoxia during this period may accelerate follicular pool depletion, before the tissue stability. Vitrification can be considered a reliable alternative for slow freezing. CAM transplantation is a good technique for confirmation of tissue viability after warming but damaged the follicle ultrastructure in a short period.

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Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.