Adenovirus-mediated expression of vascular endothelial growth factor-a potentiates bone morphogenetic protein9-induced osteogenic differentiation and bone formation.

Mesenchymal stem cells (MSCs) are suitable seed cells for bone tissue engineering because they can self-renew and undergo differentiation into osteogenic, adipogenic, chondrogenic, or myogenic lineages. Vascular endothelial growth factor-a (VEGF-a), an angiogenic factor, is also involved in osteogenesis and bone repair. However, the effects of VEGF-a on osteogenic MSCs differentiation remain unknown. It was previously reported that bone morphogenetic protein9 (BMP9) is one of the most important osteogenic BMPs. Here, we investigated the effects of VEGF-a on BMP9-induced osteogenesis with mouse embryo fibroblasts (MEFs). We found that endogenous VEGF-a expression was undetectable in MSCs. Adenovirus-mediated expression of VEGF-a in MEFs potentiated BMP9-induced early and late osteogenic markers, including alkaline phosphatase (ALP), osteocalcin (OCN), and osteopontin (OPN). In stem cell implantation assays, VEGF-a augmented BMP9-induced ectopic bone formation. VEGF-a in combination with BMP9 effectively increased the bone volume and osteogenic activity. However, the synergistic effect was efficiently abolished by the phosphoinositide 3-kinase (PI3K)/AKT inhibitor LY294002. These results demonstrated that BMP9 may crosstalk with VEGF-a through the PI3K/AKT signaling pathway to induce osteogenic differentiation in MEFs. Thus, our findings demonstrate the effects of VEGF-a on BMP9-induced bone formation and provide a new potential strategy for treating nonunion fractures, large segmental bony defects, and/or osteoporotic fractures.

IGF1 potentiates BMP9-induced osteogenic differentiation in mesenchymal stem cells through the enhancement of BMP/Smad signaling.

Engineered bone tissue is thought to be the ideal alternative for bone grafts in the treatment of related bone diseases. BMP9 has been demonstrated as one of the most osteogenic factors, and enhancement of BMP9-induced osteogenesis will greatly accelerate the development of bone tissue engineering. Here, we investigated the effect of insulin-like growth factor 1 (IGF1) on BMP9-induced osteogenic differentiation, and unveiled a possible molecular mechanism underling this process. We found that IGF1 and BMP9 are both detectable in mesenchymal stem cells (MSCs). Exogenous expression of IGF1 potentiates BMP9-induced alkaline phosphatase (ALP), matrix mineralization, and ectopic bone formation. Similarly, IGF1 enhances BMP9-induced endochondral ossification. Mechanistically, we found that IGF1 increases BMP9-induced activation of BMP/Smad signaling in MSCs. Our findings demonstrate that IGF1 can enhance BMP9-induced osteogenic differentiation in MSCs, and that this effect may be mediated by the enhancement of the BMP/Smad signaling transduction triggered by BMP9. [BMB Reports 2016; 49(2): 122-127].

Evodiamine inhibits the proliferation of human osteosarcoma cells by blocking PI3K/Akt signaling.

Osteosarcoma (OS) is the most common non-hematologic primary malignancy of bone, and multiple chemotherapeutic agents have been applied in the treatment of OS for over 40 years. Nevertheless, due to the poor prognosis of OS, it is essential to develop a novel treatment strategy. Evodiamine (EVO), a quinolone alkaloid extracted from the fruit of Evodia rutaecarpa, has been demonstrated to inhibit tumor cell proliferation. Thus, the main aim of the present study was to investigate the anti-proliferative and apoptosis-inducing effects of evodiamine (EVO) on human OS 143B cells, but also the possible mechanisms underlying these effects. The results of crystal violet staining, flow cytometry, western blot analysis and an in vivo experiment demonstrated that EVO exhibits significant inhibitory effects on cell proliferation, exhibits apoptosis-inducing effects and arrests the cell cycle in 143B cells. According to our findings of polymerase chain reaction (PCR), western blot analysis and recombinant adenoviral transfection, we confirmed that EVO upregulates both the protein and gene levels of phosphatase and tensin homolog (PTEN) in a concentration-dependent manner in 143B cells. Overexpression of PTEN reinforced the anti-proliferative effect of EVO in the 143B cells, while knockdown of PTEN upregulated PI3K/Akt signaling transduction and reversed the inhibitory effect of EVO on 143B cell proliferation. Further analysis indicated that EVO upregulated the expression of PTEN by inactivating PI3K/Akt signaling by decreasing phosphorylated Akt1/2. Based on the above results, we conclude that PTEN/PI3K/Akt signaling is involved in the inhibitory effect on human OS 143B cell proliferation by EVO.

The role of COX-2 in mediating the effect of PTEN on BMP9 induced osteogenic differentiation in mouse embryonic fibroblasts.

Mouse embryonic fibroblasts (MEFs) are multi-potent progenitor cells (MPCs), can differentiate into different lineages, such as osteogenic, and adipogenic. PTEN, a tumor suppressor, may be involved in regulating bone development through interacting with COX-2. BMP9, the most potent osteogenic BMPs, can up-regulate COX-2 in MPCs. Whether PTEN is involved in BMP9 induced osteogenic differentiation in MPCs remains unknown. The goal of this investigation is to identify the effect of PTEN on BMP9-induced osteogenic differentiation in MPCs and dissect the possible mechanism underlay this. We found that BMP9 down-regulates PTEN, and PTEN inhibitor (VO) effectively increases different osteogenic markers induced by BMP9 in MEFs. Exogenous expression of PTEN inhibits BMP9 induced ectopic bone formation apparently. Mechanistically, we found that VO can enhance BMP9 induced BMPs/Smads signaling prominently without no substantial effects on cell cycle. Further analysis indicates that VO can promote BMP9-induced expression of COX-2 in MEFs, which can be eliminated by PI3K inhibitor. Additionally, COX-2 knockdown abolishes the effect of VO on BMP9-induced ALP activities in MEFs. Our findings suggest that PTEN plays an important role in regulating BMP9 induced osteogenic differentiation in MPCs, which may be mediated by PTEN/PI3K/Akt signaling to modulate the expression of COX-2.