IRF9 is ubiquitously expressed and mediates the effects of IFNs, previous study showed that IRF9 played an important role in immunity and cell fate decision. Our recent study revealed that IRF9 involved in cardiac hypertrophy, hepatic steatosis and insulin resistance. However, the function of IRF9 in VSMC and neointima formation was largely unknown. We found that IRF9 expression was significantly increased in the VSMCs of mouse carotid artery. More importantly, we generated SMC-specific IRF9 overexpression transgenic mice (IRF9 TG) and found that IRF9 TG significantly increased VSMC proliferation, migration and neointima formation compared with NTG mice in response to injury. To evaluate the underlying mechanism by which IRF9 promotes VSMC proliferation and migration after vascular injury, IRF9 TG and NTG mice were subjected to wire-injury and the carotid arteries were collected at 14 days post-injury. We combined 3-5 vessels for one sample, and 3 samples for each phenotype. Subsequently, a total of 400ng RNA was used following Affymetrix instruction and 10 ug of cRNA were hybridized for 16 hr at 45. GeneChips were scanned using the Scanner 7G and the data was analyzed with Expression Console using Affymetrix default analysis settings and global scaling as normalization method. RMA analysis was employed to evaluate the gene expression.