Pro-osteoclastic In Vitro Effect of Polyethylene-like Nanoparticles: Involvement in the Pathogenesis of Implant Aseptic Loosening.

Polyethylene micro-sized wear particles released from orthopaedic implants promote inflammation and osteolysis; however, less is known about the bioactivity of polyethylene nano-sized wear particles released from the last generation of polymer-bearing surfaces. We aim to assess the internalization of fluorescent polyethylene-like nanoparticles by both human macrophages and osteoclasts and also, to determine their effects in osteoclastogenesis in vitro. Human macrophages and osteoclasts were incubated with several ratios of fluorescent polyethylene-like nanoparticles between 1-72 hours, and 4 hours, 2, 4, 6 and 9 days respectively. The internalization of nanoparticles was quantified by flow cytometry and followed by both confocal and video time-lapse microscopy. Osteoclast differentiation and activity was semi-quantified by Tartrate-Resistant Acid Phosphatase (TRAP) staining, TRAP mRNA relative expression and pit resorption assay respectively. Macrophages, osteoclast precursors and mature osteoclasts internalized nanoparticles in a dose- and time-dependent manner and maintained their resorptive activity. In addition, nanoparticles significantly increased the osteoclastogenesis as shown by up-regulation of the TRAP expressing cell number. We conclude that polyethylene-like nano-sized wear particles promote osteoclast differentiation without alteration of bone resorptive activity of mature osteoclasts and they could be considered as important actors in periprosthetic osteolysis of the last new generation of polymer-bearing surfaces. This article is protected by copyright. All rights reserved.