Figure 1. S100A9 induces cellular senescence in bone marrow stromal cells. (A) S100A9 expression in BM-MNCs isolated from MDS patient specimens (n = 19 LR-MDS, and n = 13 HR-MDS) compared with the expression in normal control BM-MNCs (n =20) as determined with qPCR (left). S100A9 levels in bone marrow supernatant from MDS patient specimens (n = 16 LR-MDS, and n = 8 HR-MDS) compared with the levels in normal BM-MNCs (n =10) as measured with ELISA (right). (B) HS-27a cells and MSCs were co-cultured with normal control BM-MNCs and MDS BM-MNCs. Senescent cells (green) were tested after 72 h. The number of senescent cells from at least 500 cells in 10 randomly chosen fields was used to calculate their percentage (40 × magnification). (C) Cells were treated with rhS100A9 (200 ng/ml for HS-27a, 500 ng/ml for MSC) for 72h. Subsequently, senescent cells were counted and presented in graphs (40 × magnification). Finally, p53, p21, and p16 levels were measured using qPCR and western blot. Data are expressed as mean ± SD from three experiments. *P<0.05, **P<0.01, and ***P<0.001.