Search

The purpose of this work is to study the action of fluoride on osteoblastic function through knocking down double-stranded RNA-activated protein kinase (PKR)-like ER kinase (PERK) mRNA in OS732 cells (human osteoblast-like cell line). The previous researches had demonstrated that fluoride induced endoplasmic reticulum (ER) stresses in other cells or tissues. PERK as one branch of UPR to combat ER stress played a role in mediating the proliferation and differentiation of osteoblast. The mechanism of skeletal fluorosis by which fluoride regulated osteoblast was not fully defined. We used the real-time PCR and small interfering RNA techniques to determine the expression PERK signaling and osteoblastic and osteoclastic differentiation-related factors and investigated the role of PERK signaling in fluoride-stimulated osteoblastic function. Cells transfected with 50 nM small interfering RNA (siRNA)-PERK showed effectively decreased protein and gene expression of PERK and reduced protein expression of nuclear factor erythroid 2-related factor 2 (Nrf2). Meantime, cells transfected with siRNA significantly decreased the protein level of alkaline phosphatase (ALP) and nuclear factor kappa B ligand (RANKL) in cells under fluoride exposure. It suggested that knockdown of PERK expression hardly stimulated osteoblastic and osteoclastic early differentiation induced by fluoride. Conversely, there were littler effect of siRNA PERK on expression of Runt-related transcription factor 2 (RUNX2) and osteoprotegerin (OPG) in cells, but fluoride exposure markedly stimulated their expression. This study proved that the mechanism underlying fluoride induced osteoblastic and osteoclastic differentiation possible was due to activation of ALP and RANKL mediated by PERK in OS732 cells.

Polyetheretherketone (PEEK) is a promising biomedical material for orthopedic and dental applications owing to its excellent mechanical properties, near absence of immune toxicity, and X-radiolucency but suffers from bioinertness and inferior osteo-conduction. Surface modification of PEEK can effectively overcome these problems, while retaining most of its advantageous properties. In this study, the dual growth factors IGF-1 and BMP-2 were immobilized onto the porous surface of PEEK materials using polydopamine (pDA) coating to construct a bioactive interface. The surface characteristics of modified PEEK were evaluated by scanning electron microscopy and X-ray photoelectron spectroscopy. The pore size, generally distributed between 0.24 and 0.74 µm, was evaluated using ImageJ software. Hydrophilicity and BSA protein adsorption capacity were significantly enhanced after pDA coating. IGF-1 and BMP-2 were successfully immobilized onto the porous surface via pDA coating, and the immobilization efficiency was determined by ELISA. In vitro, samples treated with 50 ng/ml IGF-1 and 50 ng/ml BMP-2 showed better cytocompatibility for cell proliferation. The in vitro studies revealed that PEEK immobilized with dual growth factors could significantly improve cell attachment, spreading, proliferation, extracellular matrix secretion, alkaline phosphatase activity, and mineralization of MC3T3-E1 cells. [ABSTRACT FROM AUTHOR]

P15, a synthetic 15 amino acid peptide, mimics the cell-binding domain within the alpha-1 chain of human collagen is being tested in clinical trials to determine if it enhances bone formation in spinal fusions. We hypothesize that covalent attachment of P15 to titanium implants may also serve to promote osseointegration. To test this hypothesis, we measured osteoblast and mesenchymal cell adhesion, proliferation, and maturation on P15 tethered to a titanium (Ti-P15) surface. P15 peptide was covalently bonded to titanium alloy surfaces and incubated with osteoblast like cells. Cell toxicity, adhesion, spreading, and differentiation was then evaluated. Real-time quantitative PCR, Western blot analysis, and fluorescent immunohistochemistry was performed to measure osteoblast gene expression and differentiation. There was no evidence of toxicity. Significant increases in early cell attachment, spreading, and proliferation were observed on the Ti-P15 surface. Increased filapodial attachments, α2 integrin expression, and phosphorylated focal adhesion kinase immunostaining indicated activation of integrin signaling pathways. qRT-PCR analysis indicated there was significant increase in osteogenic differentiation markers in cells grown on Ti-P15 compared to control-Ti. Western blotting confirmed these findings. Surface modification of titanium with P15 significantly increased cell attachment, spreading, osteogenic gene expression, and differentiation. Results of this study suggest that Ti-P15 has the potential to safely enhance bone formation and promote osseointegration of titanium implants. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1626-1633, 2012 [ABSTRACT FROM AUTHOR]