Histological aspects of rabbit ovarian tissue after cryopreservation

Purpose: to evaluate follicular preservation and histologic characteristics of the cryopreserved ovarian tissue and to compare with the fresh one, in rabbits. Methods: ten adult female white rabbits were submitted to right oophorectomy. The dried ovary was dissected and the cortex was maintained with approximately 1.5 millimeter thickness. The tissue was fractionated into small sections, some reserved for control histologic study and others destined for cryopreservation. Six weeks later the ovarian tissue was thawed and evaluated histologically. After histologic processing, the control and the experimental samples were stained with hematoxylin and eosin and treated immunohistochemically by the PCNA technique for evaluation of DNA preservation. Histologic alterations present in the fresh and in the cryopreserved tissues were identified, and cryopreserved tissue viability was evaluated. Results: in the cryopreserved tissue only primordial follicles persisted. Reversible alterations were identified: cytoplasmatic vacuolation (p= 0,039), stromal lysis (p= 0.648) and oocytes with irregular contours (p= 0.007). Irreversible alterations: (hyalin degeneration and pyknosis) were found, but not at significant levels (p= 0.210). The immunohistochemical analysis showed PCNA staining of follicles at different stages of development in the fresh tissue and primordial follicles in the cryopreserved tissue, indicating the presence of active DNA in both tissues. Conclusion: in the cryopreserved ovarian tissue the following were observed: survival of only primordial follicles; significant reversible histologic alterations (cytoplasmic vacuolation, stromal lysis and oocytes with irregular contours); irreversible alterations (hyalin degeneration and pyknosis), and PCNA staining of all follicles.