Comprehensive study on the roles of released ions from biodegradable Mg-5 wt% Ca-1 wt% Zn alloy in bone regeneration.

We report here the effect of micro-environmental changes from biodegradable magnesium alloys on the activities of cells - osteoblasts, osteoclasts and macrophages - which play critical roles in each phase of the bone-regeneration process. Despite positive bone formation effects from several in vivo studies, minimal progress has been made in identifying underlying mechanisms through in vitro studies, which are currently concentrated on osteoblastic activities. The observed in vitro and in vivo results indicated that alkaline pH and released magnesium and zinc ions derived from Mg-5 wt% Ca-1 wt% Zn alloy biodegradation promote the progress of bone formation. In contrast, alkaline pH and magnesium ions remarkably suppressed osteoclastic activities and pro-inflammatory cytokine production, closely related to osteolysis and prosthesis failure. Findings from the present study conclude that the degradation of Mg-5 wt% Ca-1 wt% Zn alloys can promote new bone formation by simultaneously affecting the complex combination of variable cellular activities and phases.