Objective: To evaluate effects of sirolimus on collagen synthesis and collagen type I and type III mRNA expression in vascular smooth muscle cells (VSMCs).
Methods: Rat VSMCs from thoracic aorta were cultured and added with sirolimus of the concentrations of 0, 0.1, 1.0, 10, and 100 ng/ml respectively for 24 h, then co-cultured with L-(3)H-proline for 12 h. L-(3)H-proline incorporation was monitored by liquid scintillation counting. RT-PCR was used to detect the mRNA expression of collagen type I and collagen type III. Logarithmic phase VSMC were treated with sirolimus by 0 ng/ml, 0.1 ng/ml, 1 ng/ml, 10 ng/ml and 100 ng/ml respectively for 24 h prior to 12 h exposure to L-(3)H-proline.
Results: The proline incorporation values were 1369 +/- 186, 1211 +/- 157, 1037 +/- 139, 910 +/- 144, and 741 +/- 160 cpm respectively of the 0, 0.1, 1, 10, and 100 ng/ml sirolimus groups. Paired t-test analysis showed that the proline incorporation value of the group with higher sirolimus concentration was significantly lower than that of the group with lower sirolimus concentration (F = 18.936, P < 0.001), except between the 0.1 ng/ml group and 0 ng/ml group (control group) and between the 1 ng/ml group and 10 ng/ml group (P = 0.057, P = 0.12). RT-PCR showed that the collagen I levels were 112 +/- 23, 140 +/- 23, 152 +/- 12, 166 +/- 22, and 179 +/- 18 respectively in the groups of sirolimus of the concentrations of 100, 10, 1, 0.1, and 0 ng/ml respectively, the higher the concentration of sirolimus the lower the collagen I level (all P < 0.05), however, there was no significant difference in the collagen I level between the 0.1 mg/ml group and the control group (P = 0.236). There was no significant difference in the collagen III level among the groups of sirolimus of different concentrations (F = 2.409, P = 0.070).
Conclusion: Sirolimus inhibits the collagen synthesis in the VSMCs and attenuates the mRNA expression of type I collagen concentration-dependently.