Furthermore, the biological functions of miR-9 and SDC2 on aortic plaque area, proliferation of collagen fibers, Mac-3-labeled macrophages, inflammatory response, and levels of the focal adhesion kinase/extracellular signal-regulated kinase (FAK/ERK) signaling pathway-related proteins in atherosclerosis were evaluated after ectopic miR-9 expression or SDC2 depletion in ACS mice using oil red O staining, Masson’s trichrome staining, immunohistochemistry, and Western blot analysis, respectively. The gene discussed is MAPK1; the disease is atherosclerosis.