Migration of bone cells and precursor cells to the site of a bone defect can accelerate bone regeneration. Therefore, guidance of these cells by direct current (DC) is an interesting approach to improve implant ingrowth or fracture healing. To allow a better understanding of DC-induced directed migration, a specific stimulation chamber was established and the influence of DC on calcium channel expression in osteoblasts was investigated. Human osteoblasts were isolated from femoral heads of patients undergoing total hip arthroplasty after patient”s consent. The study was approved by the local ethical committee (AZ: 2010–10). Differentiation into osteoblasts was ensured by cultivation in standard cell culture medium enriched with β-glycerophosphate, ascorbic acid and dexamethasone. 2×103 osteoblasts were seeded into custom-made chambers for DC field application. After 12 h DC was applied to chambers via Ag/AgCl electrodes set into separate reservoirs coupled to cell culture area by 2% agarose bridges in order to prevent cytotoxic impact of electrochemical reactions proceeding at the electrodes. Electric fields ranging from 150 to 450 V/m were applied to cells for 7 h. Several cell images were taken over time and used for evaluation of migration direction and speed with ImageJ software. Subsequently, cells were lysed in Trizol for RNA isolation and semiquantitative real-time polymerase chain reaction of voltage-gated calcium channels Cav1.4 and Cav3.2 as well as stretch-activated magnesium and calcium channel TRPM7 was performed.Introduction
Methods
Enhanced micromotions between the implant and surrounding bone can impair osseointegration, resulting in fibrous encapsulation and aseptic loosening of the implant. Since the effect of micromotions on human bone cells is sparsely investigated, an Micromotions ranging from 25 µm to 100 µm were applied as sine or triangle signal with 1 Hz frequency to human osteoblasts seeded on collagen scaffolds. Micromotions were applied for six hours per day over three days. During the micromotions, a static pressure of 527 Pa was exerted on the cells by Ti6Al4V cylinders. Osteoblasts loaded with Ti6Al4V cylinders and unloaded osteoblasts without micromotions served as controls. Subsequently, cell viability, expression of the osteogenic markers collagen type I, alkaline phosphatase, and osteocalcin, as well as gene expression of osteoprotegerin, receptor activator of NF-κB ligand, matrix metalloproteinase-1, and tissue inhibitor of metalloproteinase-1, were investigated.Objectives
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