PCNA and Right ventricular hypertrophy: Consistent with previous studies,9 our results showed that hypoxia elevated calpain‐1 protein levels in both lung tissues of mice with HPH and PASMCs, significantly increased RVSP, right ventricular hypertrophy and vessel wall thickness, increased the expression of PCNA, Ki‐67, α‐SMA and the formation of collagen fibre in the lung tissues, and enhanced the proliferation and migration of PASMCs.