Advances in mammalian ovarian tissue cryopreservation

In mammals, the ovum is one of the largest cells with a relatively small ratio of surface area to cytoplasm and unique biological characteristics. The quantity of ova in the ovary is very limited and will decreases dramatically along with female development. Ovarian tissue cryopreservation (OTC) significantly contributes to the preservation of genetic material from the endangered and rare species, animals with special economic value, emotional pets, and excellent police/military dogs. Additionally, it offers the potential for long-term storage of female germplasm resources. Consequently, it is crucial to cryopreserve ovarian tissue and oocytes. During the cryopreservation process, cryoprotectant agents are vital in reducing the fatal or reversible cryogenic damage. In recent years, slow freezing and vitrification are the main methods of mammalian OTC. Currently, challenges of mammalian OTC include the damage of ovarian cells (particularly oocytes) caused by freezing techniques and the subsequent development of transplanted ovarian tissue after freezing and thawing. Thus, further research is required to optimize and enhance the freezing technology or develop novel freezing equipment to improve the efficiency of mammalian OTC. This review encompasses the cryopreservation progress of mammalian ovarian tissue and its prospects.