Histologic and ultrastructural evaluation of fresh and frozen-thawed human ovarian xenografts in nude mice☆

Abstract 

Objective: To compare histologic and ultrastructural characteristics of fresh 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-thawed 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] vascularization of the grafted tissue, and [4] ultrastructural evaluation.

Result(s): A greater fibrosis relative surface area was noted in frozen-thawed transplanted tissue than in fresh transplants. Regardless of this fibrosis, a similar follicular density was observed in fresh and frozen-thawed ovarian tissue 24 days after transplantation. Active angiogenesis was proved by both immunohistochemical study of the vascular endothelial growth factor and morphometric study of the vascular network. Normal ultrastructural characteristics 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. The greater fibrosis observed in grafts after cryopreservation and implantation does not seem to affect the primordial and primary ovocyte population and their ultrastructural characteristics, but further studies must be conducted to prove that after cryopreservation and transplantation, ovocytes may achieve full maturation and fertilization.

Keywords:  Cryopreservation, ovarian xenograft, primordial follicle, angiogenesis, electron microscopy