Effects of miR-221-5p inhibition on the osteogenic differentiation of MBD-MSCs. (A) RT-qPCR was used to quantify the expression levels of miR-221-5p in N-MSCs and MBD-MSCs prior to and following osteoblast induction. (B) RT-qPCR was used to quantify the expression levels of miR-221-5p in MBD-MSCs following transfection with miR-221-5p mimic or inhibitor. (C) Expression levels of marker genes of osteogenic differentiation were detected by RT-qPCR following transfection. (D) Western blotting was performed to detect the protein expression levels of ALP, OPN and OC following transfection. (E) Relative band intensity of ALP, OPN and OC protein. *P<0.05, **P<0.01 vs. NC-mimic, unless indicated otherwise. #P<0.05, ##P<0.01 vs. NC-inhibitor. ALP, alkaline phosphatase; MBD, myeloma bone disease; miR-221-5p, microRNA-221-5p; MSC, mesenchymal stem cell; N, normal; NC, negative control; OC, osteocalcin; OPN, osteopontin; RT-qPCR, reverse transcription-quantitative PCR.