In some aspects, the invention provides a method of treating atherosclerosis in a subject. The method comprises administering to the subject an agent that increases the activity or level of a let-7 miRNA or an agent that decreases activity or level of a TGFβ signaling polypeptide in an endothelial cell in the subject. In some embodiments, the subject is administered an additional agent comprising a therapeutically effective amount of rapamycin or any derivative thereof. In some embodiments, the agent is a let-7 miRNA. In some other aspects, the invention provides a pharmaceutical composition comprising a let-7 miRNA. In some embodiments, the let-7 miRNA is encapsulated in a nanoparticle formulated for selective delivery to an endothelial cell.