Involvement of clusterin in 15-deoxy-Δ^12,14-prostaglandin J₂-induced vascular smooth muscle cell differentiation

To establish an in vitro model of vascular smooth muscle cell (VSMC) differentiation, we examined the effect of 15-deoxy-Δ^12,14- prostaglandin J₂ (15d-PGJ₂) on the expression of VSMC differentiation markers. After the addition of 15d-PGJ₂ to confluent human umbilical artery smooth muscle cells synchronized in the G₀ phase, cells showed a "hill and valley" appearance and thereafter aggregated and formed macroscopic nodules. Cells forming nodules expressed high levels of SM2, the most specific VSMC differentiation marker, comparable to medial VSMCs in vivo. 15d-PGJ₂ significantly increased the mRNA and protein expression levels of clusterin, a secreted glycoprotein reported to induce nodule formation and differentiation of VSMCs. Moreover, addition of an anti-clusterin antibody completely inhibited the nodule formation induced by 15d-PGJ₂ and induced apoptosis. Our results suggested that clusterin is involved in 15d-PGJ₂-induced nodule formation and cell differentiation in VSMCs.