MicroRNA‑92a overexpression promotes the osteogenic differentiation of bone mesenchymal stem cells by impeding Smad6‑mediated runt‑related transcription factor 2 degradation.

Bone mesenchymal stem cells (BMSCs) are an important source of stem cells for tissue repair and regeneration; therefore, understanding the mechanisms that regulate stem cell differentiation in a specific lineage is critical. Runt‑related transcription factor 2 (Runx2) is a bone‑specific transcription factor that serves an important role in promoting osteogenic differentiation. However, Runx2 protein levels are regulated by the ubiquitin‑proteasome pathway. Previous research has identified that Smad6 can interact with Runx2 and enhance Smurf1‑induced Runx2 degradation in a ubiquitin‑proteasome‑dependent manner. Bioinformatics analysis demonstrated that miR‑92a can target Smad6. To characterize the regulatory effect of miR‑92a on osteogenic differentiation of BMSCs and assess the interactive association between Smad6 and miR‑92a, BMSCs were obtained from mice and miR‑92a or Smad6 overexpression vectors were constructed. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blots were used to analyze the expression of miR‑92a and Smad6, and the luciferase reporter assay was used to examine the interaction between miR‑92a and Smad6. BMSCs were induced in osteogenic differentiation media for 21 days. The alkaline phosphatase activity was assessed and Alizarin Red histochemical staining was also performed. The results suggested that the expression of miR‑92a suppressed Smad6‑mediated Runx2 degradation by direct integration with the 3'‑UTR of Smad6 mRNA, which was confirmed by a luciferase reporter assay. In addition, the expression of miR‑92a promoted the osteogenic differentiation of BMSCs. However, the regulatory effect of miR‑92a was inhibited by overexpression of Smad6. Taken together, the results suggest that miR‑92a expression inhibits the osteogenic differentiation of BMSCs by targeting Smad6.