Upregulation of a disintegrin and metalloproteinase with thrombospondin motifs-7 by miR-29 repression mediates vascular smooth muscle calcification.

OBJECTIVE: Vascular calcification significantly increases cardiovascular morbidity and mortality. We recently reported that the deficiency of cartilage oligomeric matrix protein (COMP) leads to vascular mineralization. We characterized the COMP-degrading metalloproteinase, a disintegrin and metalloproteinase with thrombospondin motifs-7 (ADAMTS-7). Here, we tested whether ADAMTS-7 facilitates vascular calcification. METHODS AND
RESULTS: ADAMTS-7 expression was markedly upregulated in calcifying rat vascular smooth muscle cells (VSMCs) in vitro, calcified arteries of rats with chronic renal failure in vivo, and radial arteries of uraemic patients. Silencing of ADAMTS-7 markedly reduced COMP degradation and ameliorated VSMC calcification, whereas ectopic expression of ADAMTS-7 greatly enhanced COMP degradation and exacerbated mineralization. The transcriptional activity of ADAMTS-7 promoter was not altered by high phosphate. We used bioinformatics and quantitative polymerase chain reaction analysis to demonstrate that high-phosphate upregulated ADAMTS-7 mRNA and protein via miR-29a/b repression, which directly targeted the 3' untranslated region of ADAMTS-7 in VSMCs. MicroRNA (MiR)-29a/b mimic markedly inhibited but miR-29a/b inhibitor greatly enhanced high-phosphate-induced ADAMTS-7 expression, COMP degradation, and subsequent VSMC calcification. ADAMTS-7 silencing significantly diminished miR-29a/b repression-exaggerated VSMC calcification.
CONCLUSIONS: Our data reveal a novel mechanism by which ADAMTS-7 upregulation by miR-29a/b repression mediates vascular calcification, which may shed light on preventing cardiovascular morbidity and mortality.