Background: The proliferation and osteogenic differentiation of human bone marrow mesenchymal stem cells (HBMScs) are modulated by a variety of microRNAs (miRNAs). SATB homeobox 2 (SATB2) is a critical transcription factor that contributes to maintain the balance of bone metabolism. However, it remains unclear how the regulatory relationship between miR-103 and SATB2 on HBMScs proliferation and osteogenic differentiation.
Methods: HBMScs were obtained from Cyagen Biosciences and successful induced osteogenic differentiation. The proliferation abilities of HBMScs after treatment with agomiR-103 and antagomiR-103 were assessed using a cell counting Kit-8 (CCK-8) assay, and osteogenic differentiation was determined using alizarin red S staining and alkaline phosphatase (ALP) activity assay. The expression levels of miR-103, SATB2, and associated osteogenic differentiation biomarkers, including RUNX family transcription factor 2 (RUNX2), bone gamma-carboxyglutamate protein (BGLAP), and secreted phosphoprotein 1 (SPP1), were evaluated using real-time qPCR and Western blot. The regulatory sites of miR-103 on SATB2 were predicted using bioinformatics software and validated using a dual luciferase reporter assay. The underlying mechanism of miR-103 on SATB2-medicated HBMScs proliferation and osteogenic differentiation were confirmed by co-transfection of antagomiR-103 and SATB2 siRNA.
Results: The expression of miR-103 in HBMScs after induction of osteogenic differentiation was reduced in a time-dependent way. Overexpression of miR-103 by transfection of agomiR-103 suppressed HBMScs proliferation and osteogenic differentiation, while silencing of miR-103 by antagomiR-103 abolished these inhibitory effects. Consistently, RUNX2, BGLAP and SPP1 mRNA and protein expression were decreased in agomiR-103 treated HBMScs compared with those in agomiR-NC group. Meanwhile, antagomiR-103 upregulated the mRNA and protein expression levels of RUNX2, BGLAP and SPP1 in HBMScs. Further studies revealed that SATB2 was a direct target gene of miR-103. BMSCs transfected with agomiR-103 exhibited significantly downregulated protein expression level of SATB2, whereas knockdown of miR-103 promoted it. Additionally, rescue assays confirmed that silencing of SATB2 partially reversed the effects of antagomiR-103 induced HBMScs proliferation and osteogenic differentiation.
Conclusions: The present results suggested that miR-103 negatively regulates SATB2 to serve an inhibitory role in the proliferation and osteogenic differentiation of HBMScs, which sheds light upon a potential therapeutic target for treating bone-related diseases.