MKI67 and Myocardial fibrosis: Our results showed that compared with the normoxia group; the cell numbers; hydroxyproline content; expression of sensitive markers for cell proliferation, including α-SMA, Ki67, PCNA, and EdU positive cells, were significantly increased, indicating that hypoxia successfully induced primary cardiac fibroblast proliferation, which effectively imitated the pathological properties of hypoxia-related myocardial fibrosis in vitro.