Background
The current murine models of peri-implant osseointegration failure are associated with wear particles. However, the current clinical osseointegration failure is not associated with wear particles. Here, we develop a murine model of osseointegration failure not associated with wear particles and validate it by comparing the cellular composition of interfacial tissues with human samples collected during total joint arthroplasty revision for aseptic loosening. Materials and
Conclusions
In this newly developed non-wear-particle-related murine osseointegration failure model, the cellular composition of human and murine interfacial tissue implicates specific populations of fibroblasts in fibrous tissue formation and implies that these cells may derive from mesenchymal stem cells.
Methods
Thirty-two 16-week-old female C57BL/6 mice underwent implantation with a press-fitted roughened titanium implant (Control, n = 11) to induce normal osseointegration and a press-fitted smooth polymethylmethacrylate implant (PMMA, n = 11), a loosely fitted smooth titanium implant (Smooth-Ti, n = 5) or a loosely fitted roughened titanium implant (Overdrill, n = 5) to induce osseointegration failure. Pullout testing was used to determine the strength of the bone-implant interface (n = 6 of each for Control and PMMA groups) at 2 weeks after implantation. Histology (n = 2/group) and immunofluorescence (n = 3/group) were used to determine the cellular composition of bone-implant interfacial tissue, and this was compared with two human samples.
Results
Osseointegration failure was confirmed with grossly loosening implants and the presence of fibrous tissue identified via histology. The maximum pullout load in the PMMA group was 87% lower than in the Control group (2.8 ± 0.6 N vs. 21 ± 1.5 N, p < 0.001). With immunofluorescence, abundant fibroblasts (PDGFRα+ TCF4+ and PDGFRα+ Pu1+) were observed in osseointegration failure groups and the human samples, but not in controls. Interestingly, CD146+PDGFRα+ and LepR+PDGFRα+ mesenchymal progenitors, osteoblasts (OPN+), vascular endothelium (EMCN+) cells were observed in all groups, indicating dynamic osteogenic activity. Macrophages, only M2, were observed in conditions producing fibrous tissue. Conclusions: In this newly developed non-wear-particle-related murine osseointegration failure model, the cellular composition of human and murine interfacial tissue implicates specific populations of fibroblasts in fibrous tissue formation and implies that these cells may derive from mesenchymal stem cells.