Liposomal clodronate inhibition of osteoclastogenesis and osteoinduction by submicrostructured beta-tricalcium phosphate.
Bone graft substitutes such as calcium phosphates are subject to the innate inflammatory reaction, which may bear important consequences for bone regeneration. We speculate that the surface architecture of osteoinductive β-tricalcium phosphate (TCP) stimulates the differentiation of invading monocyte/macrophages into osteoclasts, and that these cells may be essential to ectopic bone formation. To test this, porous TCP cubes with either submicron-scale surface architecture known to induce ectopic bone formation (TCPs, positive control) or micron-scale, non-osteoinductive surface architecture (TCPb, negative control) were subcutaneously implanted on the backs of FVB strain mice for 12 weeks. Additional TCPs samples received local, weekly injections of liposome-encapsulated clodronate (TCPs + LipClod) to deplete invading monocyte/macrophages. TCPs induced osteoclast formation, evident by positive tartrate resistant acid phosphatase (TRAP) cytochemical staining and negative macrophage membrane marker F4/80 immunostaining. No TRAP positive cells were found in TCPb or TCPs + LipClod, only F4/80 positive macrophages and foreign body giant cells. TCPs stimulated subcutaneous bone formation in all implants, while no bone could be found in TCPb or TCPs + LipClod. In agreement, expression of bone and osteoclast gene markers was upregulated in TCPs versus both TCPb and TCPs + LipClod, which were equivalent. In summary, submicron-scale surface structure of TCP induced osteoclastogenesis and ectopic bone formation in a process that is blocked by monocyte/macrophage depletion.
MIRA Institute of Biomedical Technology and Technical Medicine, University of Twente, The Netherlands; Xpand Biotechnology B.V., The Netherlands. Electronic address: noel.davison@xpand-biotech.com.
Noel L
NL
Davison
INSERM UMR 957, Department of Pathophysiology of Bone Resorption, University of Nantes, France.
Anne-Laure
AL
Gamblin
INSERM UMR 957, Department of Pathophysiology of Bone Resorption, University of Nantes, France.
Pierre
P
Layrolle
MIRA Institute of Biomedical Technology and Technical Medicine, University of Twente, The Netherlands; Xpand Biotechnology B.V., The Netherlands.
Huipin
H
Yuan
MIRA Institute of Biomedical Technology and Technical Medicine, University of Twente, The Netherlands; Xpand Biotechnology B.V., The Netherlands; School of Engineering and Materials Science (SEMS), Queen Mary University of London, United Kingdom.
Joost D
JD
de Bruijn
Xpand Biotechnology B.V., The Netherlands.
Florence
F
Barrère-de Groot
D000818:Animals; D002130:Calcium Phosphates / Q000494:pharmacology*; D002478:Cells, Cultured; D004002:Clodronic Acid / Q000737:chemistry* / Q000494:pharmacology*; D008081:Liposomes / Q000737:chemistry*; D008297:Male; D051379:Mice; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects*
D002130:Calcium Phosphates; D008081:Liposomes; C485817:beta-tricalcium phosphate; D004002:Clodronic Acid
Calcium phosphate; Foreign body response; Osteoclasts; Osteoimmunology; Osteoinduction; Surface microstructure