Influence of electrical stimulation on bone remodelling

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Electrical stimulation (ES) approaches are used in orthopaedics to enhance bone regeneration. A successful regenerative therapy is assumed by bone remodeling resulting from the interaction of osteoblasts and osteoclasts. Effects of bio-physical and electrical stimulation on either osteoblasts or osteoclasts have been reported in literature, however, the influence of alternating current fields on both cell types and the interaction of both in one ES set-up under similar stimulation conditions have not been described before. To investigate the influence of ES on bone remodeling and their effects on it, an already established in vitro system for ES will be adapted to stimulate the bone cells on hydroxyapatite (HA) coated glass and titanium. As HA is the main anorganic component of bone, it is a suitable substrate for the cultivation of both cell types, osteoblasts and osteoclasts. The HA coating will be achieved by body fluid simulation and the coating will be controlled by different analytic and imaging methods. At the beginning, the influence of ES on the viability of osteoblasts and osteoclasts will be investigated in separate experiments over 28 days in maximum. The time points for analyses are chosen due to cell-specific differentiation phases. By now, it is not known whether ES effects cellular differentiation. Moreover, it is unknown whether the differentiation phases are strongly separated or in fluent transitions. Therefore, the differentiation of both cell types induced by ES will be examined via analysis of the gene expression of selected markers and will be confirmed on protein level. Furthermore, the osteoblasts and osteoclasts will be cultivated with the cell culture supernatant generated by ES of the opposite cell type. The medium exchange allows the investigation of the interplay between both cell types through soluble factors independently from each other. The cell culture supernatants contain the total of all secreted factors necessary for bone cell interaction in vivo. It is already unknown whether the expression of soluble factors is regulated by ES which has to be examined in the presented proposal. Thus, supernatants will be analysed for composition and regulation of proteins specific for bone remodeling. The knowledge of cell cultivation with the conditioned medium will be used for the establishment of a co-culture of osteoblasts and osteoclasts for a simultaneous ES in the subsequent funding period. Within this project, fundamental knowledge about interactions between osteoblasts and osteoclasts under electrical stimulation will be acquired, allowing improved regeneration of bone tissue.