Osteogenesis of mesenchymal stem cells (MSCs) has played a necessary role in the repair of bone. According to some reports, microRNAs participate in different physiological activity of the cells, including cell differentiation. This study investigated the function that miR-139-5p plays in the osteogenic differentiation of human bone marrow MSCs (hBMSCs). In addition to miR-139-5p, the effects of alkaline phosphatase (ALP), a membrane-bound metalloenzyme that is considered an early osteogenic differentiation marker, have also been investigated. Calcium-rich deposit (mineralization) is also a typical osteogenic differentiation marker that could be visualized by alizarin red S (ARS) staining. Inhibiting miR-139-5p notably promotes the hBMSC osteoblast differentiation, which, however, will be reduced by overexpressed miR-139-5p. This result has been made based on the alternations of ALP activity, ARS staining, as well as expression of osteogenic genes, including runt-related gene-2 (Runx2), collagen I (Col-1), and osteocalcin (OCN). miR-139-5p exerts its role in BMSC osteogenesis most probably through the Wnt/β-catenin pathway, by direct targeting CTNNB1 and frizzled 4 (FZD4), essential factors of Wnt/β-catenin pathway. In conclusion, according to the present study, inhibiting miR-139-5p could be a promising strategy in hBMSC osteogenesis.

The mTOR/p70S6K signal transduction pathway plays a key role in the regulation of cancer cells' survival and proliferation. However, its roles in osteosarcoma, which is one of the most rapidly growing sarcomas, remain unknown. This study investigated for the first time the correlation between the mTOR/p70S6K signal transduction pathway in human osteosarcoma and patients' prognosis. The expression patterns of mTOR and p70S6K in paraffin-embedded specimens gathered from 65 patients with primary osteosarcoma were detected by the method of immunohistochemistry using antibodies against mTOR and p70S6K. Kaplan-Meier survival and Cox regression analyses were performed to evaluate the prognosis of patients. Immunostaining revealed that the mTOR/p70S6K signal transduction pathway is activated in human osteosarcoma. Additionally, positive expression of mTOR and p70S6K proteins was significantly correlated with surgical stage, metastasis pattern and percentage of dead cells of osteosarcoma. Moreover, in univariate analysis, surgical stage, metastasis pattern and percentage of dead cells, mTOR and p70S6K expression showed significant influence on overall survival (OS) and disease-free survival (DFS). In multivariate analysis, surgical stage (IIA vs. IIB/III), metastasis pattern (without vs. with), percentage of dead cells (≥90 vs. <90%), mTOR expression pattern (negative vs. positive) and p70S6K expression pattern (negative vs. positive) were significant for DFS and OS. Our results demonstrate the correlation of mTOR and p70S6K expression patterns with the oncological progression of osteosarcoma patients, suggesting the prognostic significance of the mTOR/p70S6K signal transduction pathway in osteosarcoma patients, which may lay a foundation for making further investigations on the mTOR/p70S6K signal transduction pathway as a potential target for osteosarcoma therapy.

The osteogenic differentiation of human bone mesenchymal stromal cells (BMSCs) has been considered as a central issue in fracture healing. Wnt signaling could promote BMSC osteogenic differentiation through inhibiting PPARγ. During atrophic nonunion, Wnt signaling-related factors, WNT5A and FZD3 proteins, were significantly reduced, along with downregulation of Runx2, ALP, and Collagen I and upregulation of PPARγ. Here, we performed a microarray analysis to identify differentially expressed miRNAs in atrophic nonunion tissues that were associated with Wnt signaling through targeting related factors. Of upregulated miRNAs, miR-381 overexpression could significantly inhibit the osteogenic differentiation in primary human BMSCs while increase in PPARγ protein level. Through binding to the 3′UTR of WNT5A and FZD3, miR-381 modulated the osteogenic differentiation via regulating β-catenin nucleus translocation. Moreover, PPARγ, an essential transcription factor inhibiting osteogenic differentiation, could bind to the promoter region of miR-381 to activate its expression. Taken together, PPARγ-induced miR-381 upregulation inhibits the osteogenic differentiation in human BMSCs through miR-381 downstream targets, WNT5A and FZD3, and β-catenin nucleus translocation in Wnt signaling. The in vivo study also proved that inhibition of miR-381 promoted the fracture healing. Our finding may provide a novel direction for atrophic nonunion treatment.

The ET-1/ET(A) pathway may represent an important target for treating OS, because blocking the ET(A) receptor with a selective antagonist can inhibit OS cell invasion and potentiate a chemotherapeutic agent's effect on OS.

Magnesium (Mg) alloy is gaining more interest because of its degradability and osteogenic potential. Still, it has some deficiencies, such as its rapid degradation rate, insufficient mechanical property. This research aimed to design a novel biodegradable Mg-argentum (Ag)-yttrium (Y) alloy, and Y was added to improve degradable and mechanical property. Mg-Ag-Y alloys were characterized for mechanical features, practicabilities in vitro and in vivo. The mechanical features results shown that this novel component was similar to native bone tissue in elastic moduli, tensile, and compressive stress. Then mesenchymal stem cells (MSCs) were seeded in alloys to assess cell toxicity in vitro. The results showed that its aqueous extract was suitable for MSCs adhesion and proliferation. Then the alloy was evaluated for biomedical applications in nonfractured distal femora of Sprague Dawley rats for 6 weeks, compared with those of pure-Mg and stainless steel groups. All rats survived, and hematological and histological evaluation showed no abnormal physiology 6 weeks postimplantation, and measurements of serum Mg concentration were within normal levels. X-ray scanning, microcomputed tomography, and histological examinations were performed to evaluate the degradability and osteogenic potential. The results indicated that the degradation rate of alloy was 0.91 mm per year, (range 0.77-1.22 mm), and pure-Mg 1.80 mm per year (1.43-2.26 mm). The new bone quantity was 3.18 mm (1.46-4.44 mm ) in Mg-Ag-Y alloys group, 1.39 mm (0.54-2.32 mm ) in pure-Mg group, and none in stainless steel group. These promising results suggest potential clinical application of Mg-Ag-Y alloys for use as resorbable bone fixation implant. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2059-2069, 2018.