The impact of cumulus cell viability and pre-culture with the healthy cell mass on brilliant cresyl blue (BCB) staining assessment and meiotic competence of suboptimal porcine oocytes

• Published in: Theriogenology Vol. 226; pp. 158 - 166
• Main Authors: Fonseka, Wanniarachchige Tharindu Lakshitha, Do, Son Quang, Van, Phong Ngoc, Nguyen, Hai Thanh, Wakai, Takuya, Funahashi, Hiroaki
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15-09-2024
• Subjects: Brilliant cresyl blue; Cumulus cells; Meiotic competence; Oocytes; Meiotic competence; Brilliant cresyl blue; Oocytes; Cumulus cells
• ISSN: 0093-691X; 1879-3231; 1879-3231
• DOI: 10.1016/j.theriogenology.2024.06.012

Objectives of the present study were to investigate the characteristics including glucose-6-phosphate dehydrogenase activity, as determined by Brilliant Cresyl Blue (BCB) staining, of suboptimal porcine oocytes and to enhance the meiotic competence of those through pre-culture with cumulus cell masses (CCMs). Percentage of oocyte-cumulus complexes (OCCs) derived from small follicles (SF; <3 mm in diameter) containing the oocytes that were assessed as BCB-negative (BCB-) was significantly higher than those derived from medium follicles (MF; 3–6 mm in diameter). Degrees of dead cumulus cells were significantly higher in OCCs containing BCB- oocytes, regardless of the origin of OCCs (MF vs. SF), than those containing BCB-positive (BCB+) ones. Exposing OCCs containing BCB+ oocytes to the apoptosis inducer, carbonyl cyanide m-chlorophenylhydrazone, for 20 h significantly induced the transition to BCB- and meiotic progression of exposed OCCs were significantly reduced in both SF and MF derived ones. Transit of BCB- oocytes to BCB+ was induced when OCCs were pre-cultured with CCMs of MF derived OCCs containing BCB+ oocytes for 20 h before IVM. This pre-culture also significantly increased the meiotic competence of BCB- oocytes, particularly in SF derived ones. However, reactive oxygen species levels were significantly higher in BCB+ oocytes as compared with BCB- ones, regardless of pre-culture with CCMs, whereas no significant differences were found in the ATP contents among the treatment groups. In conclusion, the BCB result of oocytes could be regulated by the healthy status and content of surrounding cumulus cells and the meiotic competence of suboptimal BCB- porcine oocytes is improved by pre-culture with healthy CCMs.
•BCB assessment is effective to select SF-derived porcine oocytes with relatively high meiotic competence in vitro.•The incidence of BCB- oocytes increases when apoptosis of the oocyte-cumulus complexes is induced by CCCP.•Preculture of SF-derived BCB- oocytes results in the conversion of those to BCB+ and enhances their meiotic competence.