A novel form of electrical stimulation increases osteoblast activity: potential implications for enhanced fracture healing

Abstract

Delayed facture repair and bony non-unions pose a clinical challenge. Understandably, novel methods to enhance bone healing have been studied by researchers worldwide. Electrical stimulation (ES) has shown to be effective in enhancing bone healing, however the best wave form and mechanism by which it stimulates osteoblasts remains unknown. Interestingly, it is considered that osteoblast activity depends on specific waveforms applied. Therefore, the aim of this study was to evaluate whether particular waveforms have a differential effect on osteoblast activity. An osteoblast cell line was electrically stimulated with either capacitive coupling (CC) or a novel degenerate wave (DW) using a unique in vitro ES system. Following application of both waveforms, the extent of cytotoxicity, proliferation, differentiation and mineralisation of the osteoblasts were assessed using various assays. Differentiation and mineralisation were further analysed using quantitative real-time PCR (qRT PCR) and immunocytochemistry (ICC). DW stimulation significantly enhanced the differentiation of the osteoblasts compared to CC stimulation, with increased protein and gene expression of alkaline phosphatase and type 1 collagen at 28 hours (p < 0.01). DW significantly enhanced the mineralisation of the osteoblasts compared to CC with greater Alizarin Red S staining and gene expression of osteocalcin, osteonectin, osteopontin and bone sialoprotein at 28 hours (p < 0.05). Moreover, immunocytochemical assays showed higher osteocalcin expression after DW stimulation compared to CC at 28 hours. In conclusion we have shown that ES waveforms enhanced osteoblast activity to different extent but importantly demonstrate for the first time that DW stimulation has a greater effect on differentiation and mineralisation of osteoblasts than CC stimulation. DW stimulation has potential to provide a secure, controlled and effective application for bone healing. These findings have significant implications in the clinical management of fracture repair and bone non-unions.