Effect of connective tissue growth factor (CTGF) expression on radiation pulmonary fibrosis in rats

Objective To explore the effect of connective tissue growth factor(CTGF) on initiation of radiation pulmonary fibrosis (RPF) and the relation to α_smooth muscle actin (α_SMA). Methods The promotive effect of CTGF on proliferation of human lung fibroblasts (HLF) by 5 Gy of ()~(60)Co γ_rays was determined by MTT colorimetry.The expressions of CTGF and α_SMA in HLF were observed by Western blot.Changes of collagen Ⅰ and Ⅲ in rat lungs were determined by Sirius red staining and polarization microscopy.Expressions of CTGF and α_SMA in RPF were observed with immuneohisto_chemistry and analysis. Results Expressions of CTGF and α_SMA were increased.CTGF reached its peak at 24 h after irradiation,whereas α_SMA still kept at a highlevel 72 h after irradiation.A small amount of collagen was produced in rat lung one month after irradiation,in which type Ⅲ collagen was the primary component.However,a large amount of collagen was produced in rat lung 3_6 months after irradiation,in which type Ⅰ was dominant.CTGF began to expression 1 week after irradiation in proliferative fibroblasts of rat lung,and it was most evident 3 months after irradiation.α_SMA began to express in proliferative myofibroblasts 1 week after irradiation, and the high peek was reached at 3 months after irradiation. Conclusion Irradiation can induce expression of CTGF in pulmonary tissue and the later can promote the transformation of fibroblasts to myofibroblasts,strengthen the ability of synthesis and secretion of type Ⅰ and Ⅲ collagen.;