Fig 2: Expression of miR-144, Sfrp1 and TNF-α in clinical samples. (A) Expression of miR-144 was detected by reverse transcription-quantitative polymerase chain reaction analysis. Serum levels of (B) Sfrp1 and (C) TNF-α were detected by ELISA. (D) Correlation analysis was performed to examine the relationship between miR-144 and Sfrp1. Data represent the mean ± SEM. **P<0.01 and ***P<0.001. OP, osteoporosis; miR, microRNA; Sfrp1, secreted frizzled-related protein 1.

Fig 3: miR-144 promotes the proliferation and differentiation of BMSCs by downregulating the expression of Sfrp1. (A) A luciferase reporter assay was used to examine the direct interaction between miR-144 and Sfrp1. The group of BMSCs were co-transfected with WT Sfrp1 plasmid and miR-144 mimic was compared with the other three groups. BMSCs were transfected with Sfrp1 siRNA, and the interference efficiency was analyzed by (B) reverse transcription-quantitative polymerase chain reaction and (C) western blot analysis, respectively. (D) A colony formation assay was used to determine how Sfrp1 affected the ability of miR-144 to promote BMSC proliferation, and (E) quantified. (F) Alizarin red staining was performed following 3 weeks of osteogenic differentiation to detect the calcium nodi in BMSCs (magnification, ×200), with (G) quantification of staining. (H) ALP activity assays were performed following 14 days of osteogenic differentiation. The group of BMSCs co-transfected with the miR-144 inhibitor and NC siRNA was compared with other two groups. (I) Protein expression levels of Sfrp1, Runx2, CDK4, Wnt1 and β-catenin were analyzed by western blot analysis. GAPDH was used as an internal control. Data represent the mean ± SEM. **P<0.01 and ***P<0.001. miR, microRNA; BMSCs, bone marrow-derived mesenchymal stem cells; WT, wild-type; MUT, mutant; siRNA, small interfering RNA; NC, negative control; ALP, alkaline phosphatase; Sfrp1, secreted frizzled-related protein 1; Runx2, Runt-related transcription factor 2; CDK4, cyclin-dependent kinase 4.