Histologic and ultrastructural evaluation of fresh and frozen-thawed humanovarian xenografts in nude mice

Objective: To compare histologic and ultrastructural characteristics of fre sh and frozen-thawed human ovarian cortical tissue grafted into nude mice. Design: Experimental prospective study. Setting: An academic research environment. Patient(s): Ovarian biopsy specimens were obtained from 13 women undergoing laparoscopy for tubal ligation or infertility. Animal(s): Forty nude mice. Intervention(s): A minilaparotomy was performed to place fresh and frozen-t hawed ovarian grafts subcutaneously (sc) or intraperitoneally (ip). Removal of the ovarian grafts was performed at 24 days. Main Outcome Measure(s): [1] the follicular population, [2] fibrosis, [3] v ascularization of the grafted tissue, and [4] ultrastructural evaluation. Result(s): A greater fibrosis relative surface area was noted in frozen-tha wed transplanted tissue than in fresh transplants. Regardless of this fibro sis, a similar follicular density was observed in fresh and frozen-thawed o varian tissue 24 days after transplantation. Active angiogenesis was proved by both immunohistochemical study of the vascular endothelial growth facto r and morphometric study of the vascular network. Normal ultrastructural ch aracteristics were noted in frozen-thawed ovarian biopsies. Conclusion(s): Angiogenesis allows implantation of the graft even if it has been cryopreserved and thawed similarly to implantation of fresh tissue. T he greater fibrosis observed in grafts after cryopreservation and implantat ion does not seem to affect the primordial and primary ovocyte population a nd their ultrastructural characteristics, but further studies must be condu cted to prove that after cryopreservation and transplantation, ovocytes may achieve full maturation and fertilization. (Fertil Steril(R) 2000;74:122-9 . (C) 2000 by American Society for Reproductive Medicine.)