Figure 2: miR-21 regulates osteoblastogenesis and maintains bone formation in vivo.
From: miR-21 deficiency inhibits osteoclast function and prevents bone loss in mice
(a,b) Bone marrow mesenchymal stem cells (BMMSCs) derived from miR-21−/− mice showed increased colony forming efficiency. Primary bone marrow cells were isolated from 3-month WT and miR-21−/− mice, seeded at 1 × 105 cells/cm2, cultured for 14 days, and stained with crystal violet. Colonies with over 50 cells were taken into account. Bars: 1 cm. (c) BMMSCs derived from miR-21−/− mice showed increased proliferation rate. 1st passaged BMMSCs isolated from 3-month WT and miR-21−/− mice were seeded at 2 × 103 cells/well in 96-well plates. Cell viability was determined by methyl thiazolyl tetrazolium (MTT) assay at indicated time points. (d) Toluidine blue staining (top) and calcein labeling (bottom) in histological sections of 3-month WT and miR-21−/− mice. Mice accepted double intraperitoneal injection of 20 mg/kg calcein at 16 days and 2 days prior to sacrifice. After sacrifice, tibiae were decalcified, embedded in paraffin, sectioned, and stained for toluidine blue. Femora were embedded in methyl methacrylate without decalcification, sectioned, and observed by a fluorescence microscope on the endosteum. Black arrows indicate osteoblasts analyzed on trabecular bone surfaces. Bars (top): 25 μm; Bars (bottom): 100 μm. (e,f) Corresponding parameters of toluidine blue staining showed comparable osteoblastogenesis in WT and miR-21−/− mice. N.Ob/BS, number of osteoblasts per bone surface (e). Ob.S/BS, osteoblast surface per bone surface (f). (g–i) Corresponding parameters detected by calcein labeling showed comparable bone formation in WT and miR-21−/− mice. MAR, mineral apposition rate (g). MS/BS, mineralized surface per bone surface (h). BFR, bone formation rate (i). (j) No significant difference was detected by the enzyme-linked immunosorbent assay (ELISA) on the concentrations of bone formation marker in serum of 3-month WT and miR-21−/− mice. P1NP, procollagen 1 N-terminal peptide. Data represents mean ± standard errors of the mean. n = 6/genotype. Statistical significance was evaluated by two-tailed Student’s t test. *P < 0.05. NS, not significant (P > 0.05).
