Strontium enhances BMP-2 mediated bone regeneration in a femoral murine bone defect model.

The application of strontium is one option for the clinical treatment of osteoporosis-a disease characterized by reduced bone density and quality-in order to reduce the risk of vertebral and nonvertebral fractures. Unlike other drugs used in osteoporosis therapy, strontium shows a dual effect on bone metabolism by attenuating cellular resorption and simultaneously enhancing new bone tissue formation. Current concerns regarding the systemic application of highly dosed strontium ranelate led to the development of strontium-modified scaffolds based on mineralized collagen (MCM) capable to release biologically active Sr2+ ions directly at the fracture site. In this study, we investigated the regenerative potential of these scaffolds. For in vitro investigations, human mesenchymal stromal cells were cultivated on the scaffolds for 21 days (w/ and w/o osteogenic supplements). Biochemical analysis revealed a significant promoting effect on proliferation rate and osteogenic differentiation on strontium-modified scaffolds. In vivo, scaffolds were implanted in a murine segmental bone defect model-partly additionally functionalized with the osteogenic growth factor bone morphogenetic protein 2 (BMP-2). After 6 weeks, bridging calluses were obtained in BMP-2 functionalized scaffolds; the quality of the newly formed bone tissue by means of morphological scores was clearly enhanced in strontium-modified scaffolds. Histological analysis revealed increased numbers of osteoblasts and blood vessels, decreased numbers of osteoclasts, and significantly enhanced mechanical properties. These results indicate that the combined release of Sr2+ ions and BMP-2 from the biomimetic scaffolds is a promising strategy to enhance bone regeneration, especially in patients suffering from osteoporosis. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:174-182, 2020.

Evaluation of topographical and chemical modified TiAl6V4 implant surfaces in a weight-bearing intramedullary femur model in rabbit.

For cementless total joint replacement implants, the biological response to physicochemical surface characteristics is crucial for their success that depends on fixation by newly formed bone. In this study, the surface of TiAl6V4 (Tilastan®) implants was modified by (a) corundum blasting, (b) corundum blasting followed by electrochemical calcium phosphate (CaP) deposition, and (c) titanium plasma spraying followed by electrochemical CaP deposition. All modifications resulted in a surface roughness suitable to enhance primary implant stabilization and to favor osteoblast adhesion and function; the thin, biomimetic CaP coating is characterized by fast resorbability and served as chemical cue to stimulate osteogenesis. After implantation in a full weight-bearing rabbit intramedullary distal femur model, osseointegration was investigated after 3, 6, and 12 weeks. For all modifications, new bone formation, occurring from the endosteum of the femoral cortical bone, was observed in direct contact to the implant surface after 3 weeks. At the later time points, maturation of the woven bone into lamellar bone with clearly defined osteons was visible; the remodeling process was accelerated by the CaP coating. The ingrowth of newly formed bone into the pores of the titanium plasma sprayed surfaces indicates a strong interlock and finally implant fixation. Our findings indicate a positive impact of the tested surface modifications on osseointegration.