Insulin receptor substrate‐1 time‐dependently regulates bone formation by controlling collagen Iα2 expression via miR‐342

ABSTRACT Insulin promotes bone formation via a well‐studied canonical signaling pathway. An adapter in this pathway, insulin‐receptor substrate (IRS)‐1, has been implicated in the diabetic osteopathy provoked by impaired insulin signaling. To further investigate IRS‐1's role in the bone metabolism, we generated Irs‐1‐deficient Irs‐1smla/smla mice. These nullmice developed a spontaneousmutation that led to an increase in trabecular thickness (Tb. Th) in12‐mo‐old, butnot in 2‐mo‐oldmice. Analyses of the bonemarrowstromal cells (BMSCs) fromthese mice revealed their differential expression of osteogenesis‐related genes and miRNAs. The expression of miR‐342, predicted and then proven to target the gene encoding collagen type Ia2 (COL1A2), was reduced in BMSCs derived fromIrs‐1‐nullmice. COL1A2expressionwas thenshowntobe agedependent in osteoblasts and BMSCsderivedfrom Irs‐1smla/smla mice. After the induction of osteogenesis in BMSCs, miR‐342 expression correlated inversely with that of Col1a2. Further, Col1a2‐specific small interfering RNA (siRNA) reduced alkaline phosphatase (ALP) activity and inhibited BMSCdifferentiation into osteocyte‐like cells, both inwild‐type (WT) and Irs‐1smla/smla mice. Conversely, in Irs‐1smla/smla osteocytes overexpressing COL1A2, ALP‐positive staining was stronger than in WT osteocytes. In summary, we uncovered a temporal regulation of BMSC differentiation/bone formation, controlled via Irs‐1/miR‐ 342 mediated regulation of Col1a2 expression.—Guo, Y., Tang, C.‐Y., Man, X.‐F., Tang, H.‐N., Tang, J., Wang, F., Zhou, C.‐L., Tan, S.‐W., Feng, Y.‐Z., Zhou, H.‐D. Insulin receptor substrate‐1 time‐dependently regulates bone formation by controlling collagen Iα2 expression via miR‐342. FASEB J. 30, 4214–4226 (2016). www.fasebj.org