YAP is the key regulator in ECM stiffness‐induced hBdSMCs proliferation. (A) Proliferating cell nuclear antigen (PCNA) protein of cells with YAP knocked down under different stiffness was detected by western blot, n = 3. KD‐YAP, Knock down of YAP. Scrambled1 is for KD‐YAP. (B) PCNA was detected by Western blot under 32 kPa in rescue experiment, n = 3. Ad‐YAP, over‐expression of YAP. Scrambled1 is for KD‐YAP, Scrambled2 is for Ad‐YAP. (C) EdU assay of KD‐YAP under different stiffness, scale bar = 200 µm. (D) Quantification of EdU assay in (C) is the mean ± SEM, n = 10, **P < 0.01, ****P < 0.0001. (E) EdU assay of rescue experiment under 32 kPa was performed to detect the DNA replication, scale bar = 200 µm. Scrambled1 is for KD‐YAP, Scrambled2 is for Ad‐YAP. (F) Quantification of the EdU assay in (E) is the mean ± SEM, n = 5, *P < 0.05, ****P < 0.0001