[Experimental study on expression of connective tissue growth factor in viral myocarditis in mice]

To study the expression of connective tissue growth factor (CTGF) in the myocardial tissue of mice with viral myocarditis (VMC).

Balb/c mice were infected with coxsackie virus B3 (CVB3) to establish VMC model. The mice were divided into control group (n = 50) and VMC group (n = 50). on days 4, 7, 14 and 21 after infection, heart specimens of 8 mice were randomly taken and examined after HE staining for myocardial necrosis and cellular infiltration. The area of positive Masson stained myocardium collagen fibers was measured, and collagen volume fraction (CVF) was measured. Then the level of serum creatine phosphokinase-MB (CKMB) was determined. The levels of CTGF and TGF-β₁ were detected by streptavidin peroxidase immunoperoxidase technique. Expression of CTGF and TGF-β₁ were detected with reverse transcription-polymerase chain reaction (RT-PCR). At the same time, the correlations were analyzed.

(1) The level of CKMB peaked on day 7, and decreased afterwards (455.45 ± 37.95, 606.95 ± 35.64, 573.62 ± 42.90, 308.60 ± 20.49, respectively, 4 - 21 d points), in which 4, 7, 14 d points, there was significant difference compared with control group (t = 6.144, 12.558, 11.182, respectively, P < 0.01). (2) CVF increased significantly on day 14 (8.22 ± 1.95, t = 4.486, P < 0.01) and day 21 (9.46 ± 1.87, t = 4.486, P < 0.01) in VMC group. (3) Measured by streptavidin peroxidase immunoperoxidase technique, the levels of CTGF (171.50 ± 10.25, 141.70 ± 10.863, 110.35 ± 11.051, 81.05 ± 10.190, respectively, 4 - 21 d points) and TGF-β₁ (184.90 ± 11.480, 150.25 ± 9.915, 103.50 ± 10.455, 84.15 ± 9.848, respectively, 4 - 21 d points) increased after day 4 in VMC (P < 0.01). (4) Measured by RT-PCR, the expression of CTGF mRNA and TGF-β₁ increased in VMC group, and the increase was enhanced with the disease development (P < 0.01). (5) The expression of CTGF and TGF-β₁ was positively linearly correlated (r = 0.987, P < 0.01), the expression of CTGF was negatively correlated with CVF (r = -0.901, P < 0.01), but the expression of CTGF was detected earlier than myocardial fibrosis.

The increase of CTGF expression was associated with the severity of myocardial fibrosis in VMC. These results suggest that abnormal expression of CTGF may take part in the development of fibrosis in VMC.