Bone morphogenetic protein 6 expression in cumulus cells is negatively associated with oocyte maturation

Abstract

Bone morphogenetic protein 6 (BMP6) is a regulatory peptide secreted by oocytes and granulosa cells that locally regulates folliculogenesis and follicular development. To determine BMP6 location, we studied BMP6 expression in human follicles using immunohistochemistry, real-time polymerase chain reaction (RT-PCR) and western blot analysis. RT-PCR was performed on 354 individual cumulus cell (CC) masses from 48 women to investigate the relationship between BMP6 mRNA expression in CCs and oocyte developmental potential. Results showed that BMP6 protein was mainly located in oocytes from preantral follicles and in granulosa cells from antral follicles. BMP6 mRNA expression was much higher in oocytes than in CCs and mural granulosa cells (mGCs) from preovulatory follicles (p < 0.01), and BMP6 protein level was higher in CCs than in mGCs (p < 0.05). BMP6 mRNA expression was higher in CCs from immature oocytes than in those from mature oocytes (p < 0.05). However, BMP6 mRNA expression in CCs was not associated with oocyte fertilization, embryo morphological grading, or implantation. In conclusion, BMP6 was mainly expressed in oocytes at all human follicular developmental stages and BMP6 mRNA expression in CCs may be negatively correlated with oocyte maturation. BMP6 expression could therefore be used as a biomarker of oocyte maturation.

Keywords:

• Bone morphogenetic protein 6
• follicles
• oocytes
• cumulus cells
• mural granulosa cells

Acknowledgments

The authors thank Doctor Xiaorong Peng for providing paraffin-embedded ovary tissue samples and Diane Williams from Liwen Bianji, Edanz Group China (www.liwenbianji.cn/ac) for editing the English text of a draft of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by the National Youth Science Foundation Project Fund (No. 81000274) and the Fundamental Research Funds for the Central Universities (HUST: 2012QN090).