Effect of Bone Marrow Stromal Cells Derived miR-26b on Chondrocytes of Osteoporosis Rats.

Objective: Osteoporosis is a common bone disease. miR-26b regulates OA-induced osteogenesis and induces osteoporosis. miR-26b is elevated in bone marrow stromal cells (BMSCs) during bone formation; however, we haven't fully revealed whether it is directly involved in this process, which was the aim of this study.

Methods: An oophorectomized rat model of osteoporosis was used. BMSCs were detected by electron microscopy of exosomes, and mir-26b levels were detected by RT-PCR. The correlation between mir-26b and sirt2 was detected by bioinformatics and luciferase activity analysis. Bone microstructure and cartilage moisture content were also measured. The proliferation ability of mir-26b and sirt2 on chondrocytes was detected by cell viability test and flow cytometry.

Results: Western blotting further proved that the surface markers of isolated granular exosomes were positive for CD63 and CD81. Further analysis showed that exosomes' diameters ranged from 50 to 150 nm. Mir-26b is elevated in BMSC, and its mimics can promote proliferation. Luciferase showed that mir-26b targets sirt2 and the effect of elevated mir-26b on chondrocytes was completely reversed by silencing sirt2. The proliferation ability of C28/I2 chondrocytes in Mir MICs group was lower than other two groups, while that in Mir inhibition group had stronger proliferation ability than in the Mir NC group. mir-26b was highly expressed in BMSC, indicating that mir-26b comes from secretion of BMSC.

Conclusion: Mir-26 is highly expressed in OP. mir-26b can therefore target sirt2 to promote proliferation and inhibit apoptosis of OP chondrocytes. It may offer a possibility of a treatment of OP in the future.