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 beta 3 in these cells. The miRNA expression profile was determined by miRNA PCR array and real-time PCR. Protein expression of integrin beta 3 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 beta 3, 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 beta 3. Investigation of the regulatory mechanisms of tissue fibrosis by miR-150 could lead to development of new diagnostic tools and new treatments using miRNA. (Am J Pathol 2013, 182: 206-216; http://dx.doi.org/10.1016/j.ajpath.2012.09.023)