Abstract: Objective To investigate the expression of connective tissue growth factor(CTGF) mRNA in the sclerotic skin of mice with bleomycin (BLM)-induced scleroderma.Methods Twenty-four SPF female BALB/c mice were randomly divided into the model group and the control group.The model mice were subcutaneously injected on the back with 0.1 mL of BLM (300 μg/mL,diluted in saline) daily for 4 weeks,while the controls were injected with saline in the same manner.After the final injection the skin section in the injected area was collected for histological examination,measurement of dermis thickness,determination of hydroxyproline contents by a colorimetric method,detection of CTGF mRNA expression by in situ hybridization and measurement of CTGF and pro-collagen α1(pro-COL1A1) mRNA expression by semiquantitative RT-PCR.Results Compared with the control mice,the model mice showed typical scleroderma histologically.The dermis was significantly thicker and the skin hydroxyproline content was significantly higher in the model group than that in the controls (both P<0.01).The positive signals for CTGF mRNA were mainly distributed in the cytoplasm of the fibroblasts in the dermis.The mRNA expression of both CTGF and pro-COL1A1 in the model mice was significantly up-regulated (P<0.05,P<0.01,respectively) than that in the controls.The hydroxyproline content in the skin of model mice correlated positively with the expression of pro-COL1A1 mRNA (P<0.05),meanwhile the latter correlated positively with the mRNA expression of CTGF (P<0.01).Conclusion BLM may increase the expression of pro-COL1A1 by up-regulating CTGF mRNA expression,which finally leads to the increase of the collagen content in the skin.

Key words: Scleroderma, Animal model, CTGF, mRNA