Nanofiber-induced hierarchically-porous magnesium phosphate bone cements accelerate bone regeneration by inhibiting Notch signaling.

Magnesium phosphate bone cements (MPC) have been recognized as a viable alternative for bone defect repair due to their high mechanical strength and biodegradability. However, their poor porosity and permeability limit osteogenic cell ingrowth and vascularization, which is critical for bone regeneration. In the current study, we constructed a novel hierarchically-porous magnesium phosphate bone cement by incorporating extracellular matrix (ECM)-mimicking electrospun silk fibroin (SF) nanofibers. The SF-embedded MPC (SM) exhibited a heterogeneous and hierarchical structure, which effectively facilitated the rapid infiltration of oxygen and nutrients as well as cell ingrowth. Besides, the SF fibers improved the mechanical properties of MPC and neutralized the highly alkaline environment caused by excess magnesium oxide. Bone marrow stem cells (BMSCs) adhered excellently on SM, as illustrated by formation of more pseudopodia. CCK8 assay showed that SM promoted early proliferation of BMSCs. Our study also verified that SM increased the expression of OPN, RUNX2 and BMP2, suggesting enhanced osteogenic differentiation of BMSCs. We screened for osteogenesis-related pathways, including FAK signaing, Wnt signaling and Notch signaling, and found that SM aided in the process of bone regeneration by suppressing the Notch signaling pathway, proved by the downregulation of NICD1, Hes1 and Hey2. In addition, using a bone defect model of rat calvaria, the study revealed that SM exhibited enhanced osteogenesis, bone ingrowth and vascularization compared with MPC alone. No adverse effect was found after implantation of SM in vivo. Overall, our novel SM exhibited promising prospects for the treatment of critical-sized bone defects.

Identification of allograft inflammatory factor-1 suppressing the progression and indicating good prognosis of osteosarcoma.

BACKGROUND: Osteosarcoma is one of the most common cancers worldwide. Intense efforts have been made to elucidate the pathogeny, but the mechanisms of osteosarcoma are still not well understood. We aimed to investigate the potential biomarker, allograft inflammatory factor-1 (AIF1), affecting the progression and prognosis of osteosarcoma. METHODS: Three microarray datasets were downloaded from GEO datasets and one was obtained from the TCGA dataset. The differentially expressed genes (DEGs) were identified. GO and KEGG functional enrichment analyses of overlapped DEGs were performed. The PPI network of overlapped DEGs was constructed by STRING and visualized with Cytoscape. Overall survival (OS) and Metastasis free survival (MFS) were analyzed from GSE21257. Finally, the effect of the most relevant core gene affecting the progression of osteosarcoma was examined in vitro. RESULTS: One hundred twenty six DEGs were identified, consisting of 65 upregulated and 61 downregulated genes. Only AIF1 was significantly associated with OS and MFS. It was found that AIF1 could be enriched into the NF-κB signaling pathway. GSEA and ssGSEA analyses showed that AIF1 was associated with the immune invasion of tumors. Cell experiments showed that AIF1 was underexpressed in osteosarcoma cell lines, while the malignant propriety was attenuated after overexpressing the expression of AIF1. Moreover, AIF1 also affects the expression of the NF-κB pathway. CONCLUSION: In conclusion, DEGs and hub genes identified in the present study help us understand the molecular mechanisms underlying the carcinogenesis and progression of osteosarcoma, and provide candidate targets for diagnosis and treatment of osteosarcoma.

Exploring the Osteogenic Potential of Zinc-Doped Magnesium Phosphate Cement (ZMPC): A Novel Material for Orthopedic Bone Defect Repair.

In orthopedics, the repair of bone defects remains challenging. In previous research reports, magnesium phosphate cements (MPCs) were widely used because of their excellent mechanical properties, which have been widely used in the field of orthopedic medicine. We built a new k-struvite (MPC) cement obtained from zinc oxide (ZnO) and assessed its osteogenic properties. Zinc-doped magnesium phosphate cement (ZMPC) is a novel material with good biocompatibility and degradability. This article summarizes the preparation method, physicochemical properties, and biological properties of ZMPC through research on this material. The results show that ZMPC has the same strength and toughness (25.3 ± 1.73 MPa to 20.18 ± 2.11 MPa), that meet the requirements of bone repair. Furthermore, the material can gradually degrade (12.27% ± 1.11% in 28 days) and promote osteogenic differentiation (relative protein expression level increased 2-3 times) of rat bone marrow mesenchymal stem cells (rBMSCs) in vitro. In addition, in vivo confirmation revealed increased bone regeneration in a rat calvarial defect model compared with MPC alone. Therefore, ZMPC has broad application prospects and is expected to be an important repair material in the field of orthopedic medicine.

Enhancing the mechanical properties and cytocompatibility of magnesium potassium phosphate cement by incorporating oxygen-carboxymethyl chitosan.

Incorporating bioactive substances into synthetic bioceramic scaffolds is challenging. In this work, oxygen-carboxymethyl chitosan (O-CMC), a natural biopolymer that is nontoxic, biodegradable and biocompatible, was introduced into magnesium potassium phosphate cement (K-struvite) to enhance its mechanical properties and cytocompatibility. This study aimed to develop O-CMC/magnesium potassium phosphate composite bone cement (OMPC), thereby combining the optimum bioactivity of O-CMC with the extraordinary self-setting properties and mechanical intensity of the K-struvite. Our results indicated that O-CMC incorporation increased the compressive strength and setting time of K-struvite and decreased its porosity and pH value. Furthermore, OMPC scaffolds remarkably improved the proliferation, adhesion and osteogenesis related differentiation of MC3T3-E1 cells. Therefore, O-CMC introduced suitable physicochemical properties to K-struvite and enhanced its cytocompatibility for use in bone regeneration.

An injectable bioactive magnesium phosphate cement incorporating carboxymethyl chitosan for bone regeneration.

Magnesium phosphate cement (MPC) can be injected to form an in situ scaffold to repair bone defects. Here we synthesized novel injectable bioactive cements (CMPCs) by incorporating different ratios of carboxymethyl chitosan (CMC, 0-10%) into MPC. The physiochemical properties, compositions, and microstructures of CMPCs were evaluated. The in vitro cellular responses of pre-osteoblast MC3T3-E1 cells to CMPCs including adhesion, proliferation, and differentiation were quantified and the underlying cellular mechanisms investigated. CMPCs had longer setting times and lower setting temperatures. CMPC injectability was enhanced by the addition of CMC. The CMPC containing 5% CMC had the highest compressive strength and washout resistance. CMPCs had a more neutral pH compared to MPC at four weeks. Furthermore, CMPC samples showed similar degradability and Mg2+ release to MPC in Tris-HCl buffer. Osteoblasts (MC3T3-E1) showed significantly greater adherence, proliferation, and differentiation on CMPC specimens than on MPC. Finally, CMPCs effectively increased the adsorption of fibronectin and activated integrin signaling as indicated by enhanced FAK and ERK phosphorylation. Our novel CMPC composites have improved physicochemical properties and cellular responses and represent a promising material for bone regeneration.

The Notch Pathway Promotes Osteosarcoma Progression through Activation of Ephrin Reverse Signaling.

Despite significant advancements in the diagnosis and treatment of osteosarcoma, the molecular mechanisms underpinning disease progression remain unclear. This work presents strong clinical and experimental evidence demonstrating that Notch signaling contributes to osteosarcoma progression. First, using a cohort of 12 patients, Notch genes were upregulated in tumors compared with adjacent normal tissue, and high tumor expression of Notch1 intercellular domain (NICD1) and the Notch target gene Hes1 correlated with poor chemotherapy response. Data mining of publicly available datasets confirmed that expression of Notch pathway genes is related to poor prognosis in osteosarcoma. On the basis of in vitro analysis, Notch signaling promoted osteosarcoma proliferation, enhanced chemoresistance, facilitated both migration and invasion, and upregulated stem cell-like characteristics. Xenograft models demonstrated that Notch signaling promotes primary tumor growth and pulmonary metastasis, and Notch inhibition is effective in reducing tumor size and preventing metastasis. Mechanistically, activated Notch signaling induces the expression of ephrinB1 and enhances the tumor-promoting ephrin reverse signaling. Overall, these findings provide functional evidence for Notch pathway genes as candidate biomarkers to predict prognosis in patients with osteosarcoma, and suggest a mechanistic rationale for the use of Notch inhibitors to treat osteosarcoma. IMPLICATIONS: The study provides preclinical evidence for Notch pathway as a molecular marker to predict osteosarcoma prognosis and as a therapeutic target against osteosarcoma. In addition, we identified a novel mechanism that ephrin reverse signaling acts as a key mediator of Notch pathway.

miR-143-3p inhibits the proliferation, migration and invasion in osteosarcoma by targeting FOSL2.

Osteosarcoma (OS) is the most common type of primary malignant bone tumor and mainly occurs in children and adolescent. Because of its early migration and invasion, OS has a poor prognosis. It has been reported that mircoRNAs (miRNAs) play a crucial role in the occurrence and development of multiple tumors. In this study, we identified the aberrant-expression of miR-143-3p in osteosarcoma and examined the role of miR-143-3p in OS development. Further, we searched the miR-143-3p target gene and verified its accuracy by luciferase experiments. Finally, we explored the relationship between miR-143-3p and FOS-Like antigen 2 (FOSL2). Our data indicated that miR-143-3p expression was substantially lower in OS tissues and cell-line compared with normal tissues, and was lower in patients with poor prognosis. In addition miR-143-3p inhibited OS cell proliferation and metastasis while promoting apoptosis. We next showed that FOSL2 was directly targeted by miR-143-3p and could reverse the inhibition caused by miR-143-3p. Finally, we found FOSL2 expression in OS cells was significantly higher compared with normal cells and negatively correlated with miR-143-3p. Thus, miR-143-3p directly and negatively targets FOSL2 to affect OS characteristics. This provides a new target for the treatment of OS and deserves further study.