Effects of mouse ovarian tissue cryopreservation on granulosa cell-oocyte interaction

Current ovarian tissue cryopreservation protocols have yet to be assessed in terms of somatic-germ cell interaction. Accordingly, post-thaw analysis of antral follicles can yield relevant data on the disruption of the granulosa-oocyte interface.

We compared fresh mouse ovarian tissue with tissues that had been either cryopreserved using dimethylsulphoxide (DMSO) or glycerol as cryoprotectants, or exposed to such cryoprotectants without freezing. The assessed parameters were: number of immature oocytes retrieved per ovary, allocation of the oocytes to different classes regarding antral follicle size and oocyte-granulosa cell adhesion, and the relative density of transzonal processes containing filamentous actin (TZPs-Act).

Although cryopreservation reduces the average number of oocytes retrieved per ovary, it increases the relative distribution of granulosa-free oocytes while decreasing that of granulosa-enclosed ones. Additionally, a post-thaw decrease in TZPs-Act density was recorded. This decrease was also observed after cryoprotectant exposure without freezing, although at a lower level. For the assessed parameters, DMSO was more effective than glycerol as a cryoprotectant.

In situ cryopreservation of granulosa-oocyte complexes with current protocols disrupts the granulosa-oocyte interface. The different patterns of granulosa cell adhesion and interaction in oocytes derived from different-sized antral follicles further suggests that the granulosa-oocyte interface may be developmentally regulated.