The effects of strontium-substituted bioactive glasses on osteoblasts and osteoclasts in vitro

Bioactive glasses (BC) which contain strontium have the potential to combine the known bone regenerative properties of BC with the anabolic and anti-catabolic effects of strontium cations. Here we created a BC series (SiO2-P2O5-Na2O-CaO) in which 0-100% of the calcium was substituted by strontium and tested their effects on osteoblasts and osteoclasts in vitro. We show that ions released from strontium-substituted BC enhance metabolic activity in osteoblasts. They also inhibit osteoclast activity by both reducing tartrate resistant acid phosphatase activity and inhibiting resorption of calcium phosphate films in a dose-dependent manner. Additionally, osteoblasts cultured in contact with BC show increased proliferation and alkaline phosphatase activity with increasing strontium substitution, while osteoclasts adopt typical resorption morphologies. These results suggest that similarly to the osteoporosis drug strontium ranelate, strontium-substituted BC may promote an anabolic effect on osteoblasts and an anti-catabolic effect on osteoclasts. These effects, when combined with the advantages of BC such as controlled ion release and delivery versatility, may make strontium-substituted BC an effective biomaterial choice for a range of bone regeneration therapies. (C) 2010 Elsevier Ltd. All rights reserved.