Expression of SIRT1 protein in human GCs. Immunohistochemical detection of SIRT1 in the human ovary (A, primary follicle; B, tertiary follicle; C, preovulatory follicle). Representative data from five specimens were shown. Nuclei of GCs were positively stained with anti-SIRT1 antibody at various stages of follicular development. Bars indicate (A) 50 μm, (B) 200 μm, and (C) 50 μm in high-power field and 200 μm in low-power field. SIRT1 was detected in primary (A), tertiary (B), and preovulatory (C) follicles of granulosa cells. Note that a part of the theca cells and oocyte nucleus are stained. Negative controls included a section incubated with preimmune rabbit IgG. (D) Western blotting revealed the presence of SIRT1 in KGN cells, human GCs, and HeLa cells (positive control).