Because Boucher et al. reported that LRP1 is tightly involved in the pathogenesis of atherosclerosis by regulating signaling of TGFβ and PDGF, and their receptors [27], [28], knockdown analysis using LRP1 siRNAs was perfomed to examine the role of LRP1 in the regulatory effect of PDGF-induced Col4 expression and PDGF-activated TGFβ signaling pathway in MCs. Here, TGFB1 is linked to atherosclerosis.