Angiogenesis of the frozen-thawed human fetal ovarian tissue at the early stage after xenotransplantation and the positive effect of Salviae miltiorrhizae

Cryopreserving ovarian tissue followed by transplantation has been suggested to preserve fertility for young cancer survivors. However, ischemia in the early stage after transplantation causes massive follicle loss. The aim was to investigate the histological and ultrastructural characteristics of the frozen-thawed human fetal ovarian tissue after xenotransplantation and the effects of Salviae miltiorrhizae (SM) on the angiogenesis. The human fetal ovarian tissues were frozen-thawed, xenografted into the immunodeficient nu/nu mice, and then collected 2, 7, and 28 days after transplantation. SM was administered. Compared with that of the frozen-thawed ovarian tissue, the total follicle number of the grafts was greatly reduced. Nearly half of the primordial follicles were damaged at different levels on day 2. Moreover, edema was prevalent in the stroma during the first week after the graft, especially on day 2. The microvessel density of the grafts was increased on day 2, reached a peak on day 7, and then declined on day 28. Both healthy primordial follicle proportion and the total healthy primordial follicles pool in the SM group were significantly higher than those of the control group (P = 0.003 and P = 0.001). We found a statistically significant difference of microvessel density between the two groups on day 2 (P < 0.001). In the frozen-thawed fetal ovarian grafts, angiogenesis has been begun on day 2, and the first week is the critical time for the grafts to regain their function, in which SM can facilitate graft vascularization and improve the preservation of primordial follicles.