Osteoclastogenesis and osteoclastic resorption of tricalcium phosphate: Effect of strontium and magnesium doping

Bone substitute materials are required to support the remodeling process, which consists of osteoclastic resorption and osteoblastic synthesis. Osteoclasts, the bone-resorbing cells, generate from differentiation of hemopoietic mononuclear cells. In the present study, we have evaluated the effects of 1.0 wt % strontium (Sr) and 1.0 wt % magnesium (Mg) doping in beta-tricalcium phosphate (beta-TCP) on the differentiation of mononuclear cells into osteoclast-like cells and its resorptive activity. In vitro osteoclast-like cell formation, adhesion, and resorption were studied using osteoclast precursor RAW 264.7 cell, supplemented with receptor activator of nuclear factor ?beta ligand (RANKL). Osteoclast-like cell formation was noticed on pure and Sr-doped beta-TCP samples at day 8, which was absent on Mg-doped beta-TCP samples indicating decrease in initial osteoclast differentiation due to Mg doping. After 21 days of culture, osteoclast-like cell formation was evident on all samples with osteoclastic markers such as actin ring, multiple nuclei, and presence of vitronectin receptor av beta 3 integrin. After osteoclast differentiation, all substrates showed osteoclast-like cell-mediated degradation, however, significantly restricted for Mg-doped beta-TCP samples. Our present results indicated that substrate chemistry controlled osteoclast differentiation and resorptive activity, which can be used in designing TCP-based resorbable bone substitutes with controlled degradation properties. (c) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 100A: 24502461, 2012.