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Acta sci. vet. (Impr.); 38(supl.2): s425-s435, 2010. ilus

Artigo em Inglês | VETINDEX | ID: biblio-1411721

Resumo

The use of cryobiology has been of extreme importance for the preservation of genetic material from males and females for subsequent use in assisted reproduction programs. Especially to cryopreservation of ovarian tissue the goal is to ensure the follicular viability, notably, preantral follicles, which represent 95% of the shares present in follicular ovarian cortex. In addition, cryopreservation procedures must maintain the integrity of tissue compartments and the cell-to-cell contacts. Researching for an ideal protocol for cryopreservation of ovarian cortex has been widely performed in animals such as mice and some production species such as goat and sheep. Studies carried out in those species are of great importance for the preservation and enjoyment of the maximum reproductive potential of goats and sheep of valuable genetic, economic and social development for the Northeast of Brazil. Moreover, the similarities observed between ovarian tissue and folliculogenesis between small ruminants and humans shows that the application of cryopreservation of ovarian fragments in sheep and goats can be potentially applied to humans. Therefore, the use of cryopreservation of oocytes enclosed in ovarian preantral follicles has been shown as a complementary tool for reproductive biotechnology aimed at maximizing the reproductive potential of animals of high genetic value even after the death or programmed disposal. Preantral follicles can be cryopreserved in situ or isolated, i.e. included or free of the ovarian cortex, respectively. Although results of ovarian tissue cryopreservation have been promising, this technique has disadvantages: difficulties in assessment of the quality or quantity of the follicular population in the tissue, the possibility of transmission of disease or infection present in the tissue to the graft recipient, and the possible presence of chromosomal defects or autoimmune conditions that affect the whole ovary. Furthermore, cryopreservation of isolated preantral follicles is less practical, the chances of losing them during the different stages of cryopreservation are larger. Moreover, there is not established a culture system that ensures the fully growth and maturation of these follicles in vitro, ensuring thus the production of viable embryos. Regardless, one way or another, the application of cryopreservation of preantral follicles, isolated or enclosed in ovarian tissue, will allow the establishment of animal/human germplasm banks in order to preserve the genetic heritage and hence the preservation and maintenance of female fertility. Several studies in different species, especially humans, have demonstrated the resumption of reproductive function including reporting the birth of healthy offspring after transplantation of cryopreserved ovarian tissue. However, in small ruminants, especially goats, advances are still limited. In this review, will present the main results obtained with the cryopreservation of preantral follicles, emphasizing the efforts that have been performed by our team in the Laboratory of Manipulation of Oocytes and Ovarian Preantral Follicles (LAMOFOPA) for the ovarian tissue banking from goats and sheep. Our findings have allowed us to conclude that further studies are required in order to define a protocol (slow frozen or vitrification) to ensure the viability and ovarian function and follicular normal after thawing/warming.

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