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The aim of the present study was to take osteopontin (OPN) as molecular target to study its effects on injured intima model of carotid artery in rat using perivascular transfer of OPN-small interference RNA (siRNA). OPN mRNA in cultured VSMCs was quantified by real-time RT-PCR, and OPN-siRNA-002 was determined as the most sensitive sequence and used as transfected siRNA in the subsequent animal experiments. We established rat carotid arterial intima-injured model with balloon-injured method, and then perivascularly transfected OPN-siRNA-002 to study the role of OPN-siRNA in regulating several related genes including proliferating cell nuclear antigen (PCNA), transforming growth factor β1(TGF-β1), matrix metalloproteinase-2 (MMP-2), and matrix metalloproteinase-14 (MMP-14), as well as its role in neointimal formation. OPN mRNA and protein decreased about 50 % with corresponding decrease in intima thickness after transfecting with specific OPN-siRNA-002 compared with Pluronic control group and OPN-SCR-siRNA group on each time point (n = 6, p < 0.001), and this inhibiting effects persisted up to 14 days after balloon injury. PCNA, TGF-β1, MMP-2, and MMP-14 mRNA and protein correlated directly with the respective levels of OPN, suggesting its functions via regulating these downstream factors (n = 6, p < 0.001). OPN may be a potential target gene in reducing the risk for arterial restenosis after vascular intervention.

Early growth response factor-1 (Egr-1) and osteopontin (OPN) play important roles in the migration and proliferation of vascular smooth muscle cells (VSMC), but little is known about their relationship. Therefore, we transfected VSMCs with either Egr-1 cDNA, Opn cDNA, a DNA enzyme designed to target Egr-1 (ED5), or antisense Opn oligodeoxynucleotides and examined changes in Egr-1 and OPN expression at the mRNA and protein levels. OPN expression levels were increased in cells that were stably transfected with Egr-1 cDNA. By contrast, both Egr-1 and OPN expression were reduced when ED5 was transfected into Egr-1-expressing cells. Similarly, Opn transfection upregulated Egr-1 levels, while Opn anti-sense oligodeoxynucleotide transfection decreased Egr-1 expression. ChIP analysis showed that Egr-1 binds to the Opn gene promoter. Furthermore, treatment with the extracellular-regulated protein kinase (ERK) inhibitor PD98059 inhibited the upregulation of Egr-1 by OPN. We find that Egr-1 and OPN positively regulate each other in VSMCs.

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