ANTRAL FOLLICLES DEVELOP IN XENOGRAFTED CRYOPRESERVED AFRICAN ELEPHANT (LOXODONTA-AFRICANA) OVARIAN TISSUE

The preservation of germ plasm from endangered species could augment c aptive breeding programs aimed at maintaining genetic diversity. Mamma lian female germ plasm (oocytes) is extremely difficult to collect and cryopreserve; however, a promising alternative is the cryopreservatio n of ovarian tissue. In the present study, athymic nude (nu/nu) Balb/C mice were used to evaluate in vivo viability of cryopreserved ovarian tissue from Institute of Cancer Research genotype (ICR) mice or eleph ants. Female mice were ovariectomized prior to transplant of cryoprese rved-thawed ovarian tissue from ICR mice (n = 4) or elephants (n = 6), Control mice were sham operated (n = 4) or ovariectomized (n = 5). Tr ansplants were in the ovarian bursa, enabling in vivo ovulation and pr egnancies from allografts. Vaginal cytology was monitored daily, and t he intervals between and duration of epithelial cells present in smear s were evaluated. Appearance of epithelial cells in sham-operated and allografted mice were at intervals of 4.3 +/- 0.6 and 3.3 +/- 0.5 days , lasting for 1.4 +/- 0.1 and 1.6 +/- 0.2 days, respectively. Sporadic incidence of epithelial cells in ovariectomized animals occurred at l onger intervals (8.6 +/- 3.8 days). Females with xenografted elephant ovarian tissue demonstrated epithelial cells in vaginal smears at inte rvals of 4.5 +/- 1.0 days, for 2.5 +/- 0.5 days duration, which was si gnificantly longer than the other groups (P < 0.05). Histological eval uation of tissues at the time of epithelial cells in smears demonstrat ed well-developed antral follicles, although oocytes were of poor morp hological appearance or only cumulus-like complexes were seen. The nud e mouse model is effective for assessing cryopreserved ovarian tissue xenograft function which can support the development of antral follicl es. (C) 1998 Elsevier Science B.V. All rights reserved.