[Role of cytokine-matrix metalloproteinase axis on promoting vascular neointima hyperplasia in mice].

Objective: To observe the effects of tumor necrosis factor-α (TNF-α) and platelet derived growth factor (PDGF) on vascular neointimal hyperplasia on matrix metalloproteinase 9/2 gene knockout (MMP9/2(-/-)) mice and explore related mechanisms. Methods: Mice of control group, MMP9(-/-) group, MMP2(-/-) group and MMP9/2(-/-) group were studied. Femoral artery was injured by transluminal wire, the mRNA expression levels of TNF-α and PDGF on femoral artery were detected by RT-PCR; the protein expression of MMP9 and MMP2 were assessed by Western blot on day 0, 1, 3, 7, 14 and 28 post injury. Mice in control group received TNF-α(5 ng/ml, 0.10 ml), TNF-α(0.05 ml)+ MMP inhibitor SB-3CT(0.50 ng/ml, 0.05 ml) injection, or PDGF-bb (10 ng/ml, 0.10 ml)and PDGF-bb(0.05 ml)+ SB-3CT(0.05 ml)injection around injured artery, intimal hyperplasia at 2 and 4 weeks after injury was observed. Intimal hyperplasia at 2 and 4 weeks after injury was also observed in MMP9/2(-/-) mice. TNF-α(5 ng/ml, 0.10 ml)was injected to MMP2(-/-) mice, PDGF-bb (0.1 ml) was injected to MMP9(-/-) mice around injured artery, intimal hyperplasia at 2 and 4 weeks after injury was observed. The degree of neointimal hyperplasia were observed by the Elastica-van Gieson staining and the area of neointima and media of the arteries were measured by SigmaPlot and intima ratio was calculated. Vascular smooth muscle cell (VSMC) mediums of MMP9(-/-) and MMP2(-/-) mice were stimulated by TNF-α and PDGF-bb, respectively, and migration assay, and proliferation assay were performed, relative migration and proliferation cells numbers were counted. Results: (1) mRNA expression of TNF-α (235.33±23.68) and PDGF-bb (3.30±0.56) in femoral arteries peaked at 1 day after injury, while MMP9 or MMP2 protein expression peaked at 7 or 28 days after injury. (2)In control mice, TNF-α intervention significantly enhanced intimal hyperplasia at 2 weeks after injury (2.21±0.05 vs. 1.55±0.03 in blank control group, P<0.05), while PDGF-bb intervention significantly enhanced intimal hyperplasia at 4 weeks after injury (2.60±0.07 vs. 1.89±0.04, P=0.03). (3) Intima hyperplasia was significantly higher in control group than in MMP9/2(-/-) group at 2 weeks (1.63±0.05 vs. 0.46±0.01, P=0.008) and 4 weeks (2.24±0.06 vs. 0.51±0.01) after injury(P=0.005). (4) TNF-α intervention stimulated intimal hyperplasia in MMP2(-/-)mice (intimal ratio at 2 weeks after injury: 1.73±0.05 vs.1.23±0.03, P=0.02)and PDGF-bb intervention stimulated intimal hyperplasia in MMP9(-/-)mice(intimal ratio at 4 weeks after injury: 2.32±0.06 vs.1.35±0.03, P=0.03). (5) Reduced VSMC migration was evidenced in MMP9(-/-) mice post TNF-α stimulation (1.45±0.03 vs. 2.16±0.04 in control group, P=0.03), while reduced VSMC proliferation post PDGF was seen in MMP2(-/-) group (1.15±0.02 vs.1.82±0.04 in control group, P=0.03). Conclusions: TNF-α induced MMP9 activation plays a major role on promoting VSMC migration at the first 2 weeks after vascular injury, while PDGF induced MMP2 activation plays a crucial role on VSMC proliferation on the following 2 weeks after vascular injury in this mice model. Thus, the axis of TNF-α-MMP9-VSMC migration axis and PDGF-MMP2-VSMC proliferation axis are the two major working mechanisms responsible for intimal hyperplasia post vascular injury.