To study the effects of miR-22 on the proliferation and the apoptosis of osteosarcoma MG-63 cell line and to explore the potential molecular mechanism that miR-22 regulates this biological process. Quantitive real-time polymerase chain reaction (RT-qPCR) was performed to explore the miRNA level of miR-22. The MG-63 cell line was infected with miR-22 mimics for establishment of miR-22 overexpression. Non-infected cells were in blank group and cells infected with empty vector were served as negative control (NC group). MTT assay was conducted to measure cell viability. The cell cycle and apoptosis were explored using flow cytometry and the apoptosis-related markers were detected by western blotting. RT-qPCR results revealed that the miR-22 miRNA level in the MG-63 cells was significantly lower than that in osteoblasts (P<0.05). MTT assay showed that the MG-63 cells infected with miR-22 mimics exhibited markedly decreased proliferation ability compared with blank and empty vector (NC) groups. Next, we found that overexpression of miR-22 remarkably increased the apoptosis of the MG-63 cells, evidenced from the flow cytometry results and elevated Bax and reduced Bcl-2. Furthermore, results revealed that percentage of the cells at G0/G1 phase in miR-22 mimic group (66.75±3.67%) was significantly higher than blank (52.9±2.58%) and NC (50.5±2.45%) groups. miR-22 attenuated the proliferation and induced the apoptosis of the MG-63 cells via promoting G0/G1 cell cycle arrest. Thus, miR-22 may have the potential to be a novel therapeutic in treatment of osteosarcoma.

Mesenchymal stem cells (MSCs) are used to investigate regeneration and differentiation. MicroRNA-204 (miR-204) in involved in the Runt-related transcription factor 2/alkaline phosphatase/bone morphogenic protein 2 (Runx2/ALP/BMP2) signaling pathway that regulates bone marrow mesenchymal stem cell (BMSC) differentiation; however, the mechanisms underlying the effects of miR-204 are yet to be determined. The aim of the present study was to investigate the effects of miR-204 on BMSC differentiation. BMSCs were derived from rat bone marrow. The expression levels of Runx2, ALP and BMP2 were measured via reverse transcription-quantitative polymerase chain reaction and western blot analyses following transfection of BMSCs with miR-204 agomir or BMP2 expression vector. The ability of the miR-204 gene to directly bind BMP2 mRNA was assessed using dual-luciferase assays. Ossification was measured via alizarin red stain assays. It was observed that the expression levels of Runx2 and ALP increased over time, whereas those of miR-204 decreased; additionally, miR-204 agomir upregulation inhibited the expression of Runx2, ALP and BMP2 in BMSCs. It was revealed that miR-204 directly interacted with BMP2 mRNA, and that transfection with miR-204 agomir suppressed ossification in BMSCs by targeting the BMP2/Runx2/ALP signaling pathway.

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Estradiol (E2) serves an important role in the changes of postmenopausal bone turnover rate and the development of osteoporosis. The present study aimed to investigate the effects of E2 on high glucose (HG)-induced osteoblast injury. Cell Counting Kit-8 was used to determine cell viability. Reverse transcription-quantitative PCR (RT-qPCR) and western blotting was used to analyze the mRNA and protein expression levels of osteocalcin, Runt-related transcription factor 2 (Runx2), nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO1). Flow cytometry was performed to analyze apoptosis. The results revealed that cell viability was lower in cells treated with HG (100, 200 or 300 mg/dl) compared with the control group. Cell viability was decreased in cells treated with 200 mg/dl HG on days 3, 5 and 7. In addition, cell viability was increased by 0.1 µM E2. E2 with HG co-treatment increased cell viability, osteocalcin and Runx2 mRNA expression levels and nuclear Nrf2 and HO1 protein expression levels compared with the HG-only group. All these changes, with the exception of Runx2, were reversed by silencing Nrf2 expression using small interfering (si)RNA (siNrf2). Additionally, apoptosis was reduced by E2 in HG-treated cells, which was reversed by siNrf2 transfection. These results demonstrated that E2 may prevent HG-induced osteoblast injury by activating Nrf2/HO1 signaling pathways.

Spleen tyrosine kinase (SYK) has an important role in immunoreceptor signaling, and SYK inhibition has accordingly attenuated immune-mediated injury in several models. Therefore, the present study examined the effect of SYK inhibition with the selective spleen tyrosine kinase inhibitor P505-15 in experimental rheumatoid arthritis (RA) using a murine model of collagen-induced arthritis (CIA). Treatment with the selective SYK inhibitor P505-15, a small molecule kinase inhibitor selective for SYK, led to a reduction in arthritis score and attenuated histological damage. P505-15 reduced cartilage destruction and macrophage infiltration in CIA mice. In addition, P505-15-treated mice showed lower circulating levels of type II-collagen immunoglobulin (Ig)G1 and IgG2 and pro-inflammatory cytokines. Importantly, P505-15 treatment markedly reduced the interleukin 1β-stimulated inflammatory response in human RA synovial cells. Given these encouraging results, a key function for SYK in the development of RA was identified, highlighting that SYK may be a potential therapeutic target for human RA.