Brilliant cresyl blue staining enhances the morphological quality evaluation of porcine oocytes-a preliminary study

Brilliant cresyl blue (BCB) staining is a method used for selection of developmentally competent porcine oocytes, in addition to the standard morphological classification. The aim of the current study was to assess the relationship between BCB staining in porcine oocytes with high and low morphological characteristics and its maturation rate. In the first part of the study, cumulus-oocytes complexes (COCs) (n=434) were aspirated from 60 ovaries. According to the morphological classification and BCB staining, they were divided in 4 groups: COC+/BCB+, COC-/BCB+, COC+/BCB-, and COC-/BCB-. In the second experiment, COCs (n=445) were categorized into 3 groups: control, BCB+, and BCB-. Significant differences in the maturation rate were observed between COC+/BCB+ and COC-/BCB- (66% vs. 23%), and between COC+/BCB+ and COC-/BCB+ (66% vs. 38%) (p<0.0001). Significant differences were also registered between COC-/BCB+ and COC-/BCB-(38% vs. 23%) and between COC+/BCB- and COC-/BCB- (53% vs. 23%) (p<0.01). Results from the second experiment showed that only BCB- oocytes had a significantly lower maturation rate (28%) compared to the control (63%) and BCB+ oocytes (59%) (p<0.001). These findings showed that COCs with high morphological characteristics had higher developmental ability compared to COCs with low morphology. The BCB-staining in high-quality oocytes did not have a significant impact on their maturation ability compared to a control group, but it might be useful for selecting developmentally competent oocytes with low morphology characteristics.