Expression of PCNA in rat ASMC of each group. Representative images of immunocytochemistry for PCNA in rat ASMCs of control group (A), chronic asthma group (B) and SMI group (C). The positive staining of PCNA was brown color, mainly located in the nucleus. Bar = 100 μm. D. Summarized data of PCNA protein expression of ASMC of each group. Set the relative value of OD of the control group as 1.0, and the relative value of OD of other two groups was normalized to the control group. **P < 0.01 vs. the control group. # #P < 0.01 vs. the asthma group.