Follicular development in cryopreserved Common Wombat ovarian tissue xenografted to Nude rats

The Northern Hairy-nosed Wombat (Lasiorhinus krefftii) is a highly endanger ed marsupial species and every possible option for sustaining the species n eeds to be explored. One important approach may be the development of assis ted reproductive technologies in the non-endangered Common Wombat (Vombatus ursinus) and Southern Hairy-nosed Wombat (Lasiorhinus latifrons) for appli cation in breeding the Northern Hairy-nosed Wombat. In this study, it was examined whether cryopreserved Wombat ovarian tissue would develop following xenografting to immunologically deficient rats. Ova rian tissue was collected from Common Wombats (n = 3) and cryopreserved as small cortical pieces. After thawing the cortical pieces were grafted under neath the kidney capsule of Nude rats (n = 16). The grafts were recovered a t 2, 4, and 10 weeks after transplantation and their gross and histological appearance investigated. Two weeks after grafting (n = 2), the tissue was revascularized and healthy primordial follicles were present. At week 4 (n = 2), some follicular development was present. At week 10, six rats receive d human chorionic gonadotrophin (hCG) to trigger follicle and oocyte matura tion while another six rats were not given any treatment. The administratio n of hCG did not induce preovulatory follicles and oocyte maturation althou gh type 5 follicles were present in ovarian tissue collected 10 weeks postt ransplantation in both treated and untreated groups. This study demonstrate s for the first time that Wombat ovarian tissue can survive and function wh en grafted into immunocompromized rats and that Wombat ovarian follicles ca n be recruited to growth and development in an ovarian xenograft. This mode l system has the potential to produce mature oocytes from endangered specie s for use in assisted reproductive technologies such as in vitro fertilizat ion (IVF), intracytoplasmic sperm injection (ICSI), and mature oocytes from non-endangered species for nuclear transfer which may be necessary for the preservation of critically endangered species. (C) 2001 Published by Elsev ier Science B.V.