miR-150 Down-Regulation Contributes to the Constitutive Type I Collagen Overexpression in Scleroderma Dermal Fibroblasts via the Induction of Integrin β3

Overexpression of integrins in dermal fibroblasts is thought to play a key role in the pathogenesis of systemic sclerosis (SSc), but the mechanism is unknown. We evaluated the possibility that microRNAs (miRNAs) are involved in the regulation of integrin β3 in these cells. The miRNA expression profile was determined by miRNA PCR array and real-time PCR. Protein expression of integrin β3 was determined by immunoblotting. In vivo detection of miRNA in paraffin section was performed by in situ hybridization. miR-150 expression was decreased in SSc fibroblasts both in vivo and in vitro. The transfection of miR-150 inhibitor into normal fibroblasts induced expression of integrin β3, phosphorylated Smad3, and type I collagen, whereas forced overexpression of the miRNA resulted in their down-regulation in SSc fibroblasts. Treatment of SSc fibroblasts with 5-AdC revealed that miR-150 down-regulation in these cells is caused by DNA methylation. In addition, we found that miR-150 is detectable and quantitative in serum. Serum miR-150 levels were decreased in SSc patients, and the SSc patients with lower serum miR-150 levels tended to have more severe clinical manifestations. miR-150 may play an important role in the pathogenesis of SSc via overexpression of integrin β3. Investigation of the regulatory mechanisms of tissue fibrosis by miR-150 could lead to development of new diagnostic tools and new treatments using miRNA.