Detailed Morphological Analysis of Cryoinjury in Human Ovarian Tissue Following Vitrification or Slow Freezing

Cryopreservation of human ovarian tissue represents a key procedure for fertility preservation. The two most widely used cryopreservation methods for human ovarian cortex samples are slow freezing\thawing (SF\T) and vitrification\warming (V\W). The aim of the present study was to analyze the effects of SF\T and V\W using a metal chamber, on specific follicle and oocyte structures and on the stromal organization post-cryopreservation. We did histology analysis of SF\T and V\W ovarian fragments from nine healthy subjects. Overall results showed that cryopreserved tissues presented significant rates of damage in primordial and primary follicles. Altered nuclear structure of primordial follicles and cell detachment from primordial and primary follicles were the main injuries observed after V/W and SF/T. The stromal components were similarly well preserved after cryopreservation. We conclude that both cryopreservation methods may be used for fertility preservation purposes with similar outcomes in terms of follicular and stromal integrity. Detachment of follicle cells from basal membrane represents an important cryoinjury that deserves further investigation.