Use of oocytes selected by brilliant cresyl blue staining enhances rabbit cloned embryo development in vitro

SummaryRabbits play an important role in people's lives due to their high nutritional value and high-quality hair that can be used as raw material for textiles. Furthermore, rabbits are an important animal model for human disease, as genome-edited animals are particularly valuable for studying gene functions and pathogenesis. Somatic cell nuclear transfer (SCNT) is an important technique for producing genome-edited animals and it has great value in saving endangered species and in clone stem cell therapy. However, the low efficiency of SCNT limits its application, with the selection of suitable rabbit oocytes being crucial to its success. In the present study, we collected oocytes from ovarian follicles and stained them with 26 μM brilliant cresyl blue (BCB). We then matured the oocytes in vitro and used them for SCNT. Comparison of the BCB-positive oocytes with BCB-negative oocytes and the control group showed that the BCB-positive group had a significantly higher maturation rate (81.4% vs. 48.9% and 65.3% for the negative and control groups, respectively), cleavage rate (86.6% vs. 67.9% and 77.9%), blastocyst rate (30.5% vs. 12.8% and 19.6%), total number of blastocysts (90±7.5 vs. 65.3±6.3 and 67.5±5.7), and inner cell mass (ICM)/ trophectoderm (TE) index (42.3±4.2 vs. 30.2±2.1 and 33.9±5.1) (P<0.05). The BCB-positive group had a significantly lower apoptosis index (2.1±0.6 vs. 8.2±0.9 and 6.7±1.1 for the negative and control groups, respectively) (P<0.05). These findings demonstrate that BCB-positive oocytes have a higher maturation ability and developmental competence in vitro, indicating that BCB staining is a reliable method for selecting oocytes to enhance the efficiency of SCNT.