X.Y.Cai1, G.A.Chen1,2, Y.Lian1, X.Y.Zheng1 and H.M.Peng1

BACKGROUND: Vitrification is assumed to be a promising method to cryopreserve human oocytes but still needs optimization. In this study, rabbit oocytes (fertilized by ICSI) were vitrified with cryoloops, and the effect of three different cryopreservation protocols on spindle configuration and embryo quality was assessed. METHODS: Meta-phase II rabbit oocytes were randomly assigned to one of four groups: (i) control; (ii) E40 [40 % ethylene glycol (EG)]; (iii) ED20 [20 % EG 1 20 % dimethylsulphoxide (DMSO)]; and (iv) ED20 1M (20 % EG 1 20% DMSO 1 vitrification machine). After warming, one part of each group was fertilized by ICSI to examine the fer-tilization and embryo cleavage ability, and the others were immunostained for tubulin and chromatin before visu-alization using confocal microscopy. RESULTS: The survival rates after warming were 79.1, 83.1 and 82.3%, respectively. In protocols E40 and ED20, the spindles were severely injured and the embryo quality not good com-pared with those in the ED20 1M group. CONCLUSIONS: The fastest cooling rate in combination with EG and DMSO as cryoprotectants had the fewest adverse effects on the spindle configuration of rabbit oocytes and embryo development. Key words: cryoloop/cryopreservation/oocyte/rabbit/spindle/vitrificatio