Abstract: The endoplasmic reticulum (ER), one of the largest cellular organelles, serves as many
essential functions，including production of all components of cellular membranes, proteins, lipids, and steroids.
When unfold/mis-fold proteins were over -accumulated in ER, Endoplasmic reticulum stress (ERS) will be
induced. ERS, a self -defence mechanism, is a pathological condition of the functional disorder of ER. The
strong and long -lasting ERS could lead the irreversible cell injury, even apoptosis. The granulosa cells
abnormally apoptosis follicles of PCOS ovaries, which suggested that granulosa cells apoptosis by ERS may be
involved in PCOS pathogenesis.

Key words: Polycystic ovary syndrome, Endoplasmic reticulum, Stress, Granulosa cells, Apoptosis