Does endoplasmic reticulum stress stimulate the apoptosis of granulosa cells in polycystic ovary syndrome?

The aim of this study was to determine whether endoplasmic reticulum (ER) stress is involved in the apoptosis of granulosa cells in patients with polycystic ovary syndrome (PCOS). A total of 116 patients undergoing in vitro fertilization/intracytoplasmic sperm injection cycles at the Binzhou Medical University Hospital IVF Center between September 2019 and January 2020 were enrolled in the study. Apoptosis of the granulosa cells in each patient was analyzed using flow cytometry, and progesterone and estrogen levels in the cell-culture fluid were measured by enzyme-linked immunosorbent assay. The expressions of X-box-binding protein 1 (XBP1(s)), activating transcription factor 6 (ATF6), C/EBP homologous protein (CHOP), B-cell CLL/lymphoma 2 protein (Bcl-2), and Bcl-2 associated X protein (Bax) at the gene or protein level were analyzed using quantitative real-time polymerase chain reaction and Western blotting, respectively. In patients with PCOS, body mass index and basal serum concentrations of luteinizing hormone, testosterone (T), and anti-Mullerian hormone significantly increased (P < 0.05). The number of oocytes retrieed and the rate of clinical pregnancy after the first frozen embryo transfer also significantly increased (P < 0.05). Although apoptosis rate in the granulosa cells significantly increased in patients with PCOS, progesterone (P) and estrogen (E) levels in the cell-culture fluid significantly decreased (P < 0.05). The apoptosis of granulosa cells was also found to affect blastocyst formation. Furthermore, the messenger ribonucleic acid (mRNA) expressions of XBP1(s), ATF6, CHOP, and Bax significantly increased in patients with PCOS, while that of Bcl-2 significantly decreased (P < 0.05). The protein expressions of CHOP and Bax significantly increased in patients with PCOS, while that of Bcl-2 significantly decreased (P < 0.05). After treatment of the granulosa cells with tauroursodeoxycholic acid, apoptosis rate and mRNA or protein expressions of XBP1(s), CHOP, and Bax significantly decreased, while the expression of Bcl-2 and levels of progesterone and estrogen significantly increased (P < 0.05). We conclude that ER stress could induce the apoptosis of granulosa cells in patients with PCOS. Cell apoptosis may decrease the number of blastocysts formed.