Transplantation of mouse ovarian tissue: comparison of the transplantation sites

Many studies have shown that ischemic injuries during the transplantation process were more detrimental than cryoinjuries for follicle survival and death, and it has been reported that transplantation sites can affect the outcomes of grafted ovarian tissue (OT). The purpose of this study was to assess the impact of different OT transplantation sites on follicular integrity and function of OT grafts. B6D2F1 mice were randomly assigned to control (sham) and four experimental groups according to transplantation sites (back muscle [BM], fat pad [FP], kidney capsule [KC], and subcutaneous [SC]). The ovaries from four groups were autotransplanted to each site. The OT recovery ratios on Days 2, 7, and 21 were significantly decreased in the FP group. The mean numbers of follicles were significantly lower in all the grafting groups compared with the sham group, except in the KC group on Days 7 and 21 and the BM group on Day 21. On Day 2, all the experimental groups showed low intact (G1) follicle ratio when compared with the sham group; however, the BM, KC, and FP groups recovered their morphologic integrity on Day 7, and only the SC group presented a significant decrease in G1 follicle ratios. On Day 21, the G1 follicle ratios of the FP and KC groups were greater than the sham control group. The proportion of apoptotic follicles of the four OT graft groups was higher than in the sham group on Day 2, followed by a significant decrease in the KC group and an increase in the SC group on Day 7. The serum follicle-stimulating hormone levels were significantly increased in all grafting groups on Day 2. On Day 7, only the SC group showed the high follicle-stimulating hormone level compared with the other groups. The mean numbers of oocytes from OT grafts were the highest in the KC group, except in the control group, and the lowest in the SC group. The ratios of mature oocytes were also significantly greater in the sham and KC groups. However, the ratios of normal spindle did not differ among the five groups. In conclusion, the KC was the optimal site for OT transplantation in this murine model, whereas the SC site was unfavorable for this procedure. In this study, we confirmed that the different grafting sites influenced the outcomes of transplantation.