Titanium particle-challenged osteoblasts promote osteoclastogenesis and osteolysis in a murine model of periprosthestic osteolysis

摘要

The current study investigates the interactive behavior of titanium alloy particle-challenged osteoblastic bone marrow stromal cells (BMSCs) and macrophage lineage cells in a murine knee-prosthesis failure model. BMSCs were isolated from male BALB/c mice femurs and induced in osteogenic medium. At 24 h after isolation, BMSCs in complete induction medium were challenged with 1, 3 or 5 mg ml-1 titanium particles for 7 days. Culture media were collected at 2, 4 and 6 days and cells were harvested at 7 days for alkaline phosphatase (ALP) assay/stains. Cell proliferation in the presence of Ti particles was periodically evaluated by MTT assay. Mice implanted with titanium-pin tibial implants were given an intra-articular injection of 50 μl medium containing 5 × 105 Ti particles-challenged bone-marrow-derived osteoblastic cells, followed by a repeat injection at 2 weeks post-operation. Control mice with titanium-pin implants received a na?ve osteoblastic cell transfusion. After sacrifice at 4 weeks, the implanted knee joint of each group was collected for biomechanical pin-pullout testing, histological evaluation and reverse transcriptase polymerase chain reaction analysis of mRNA extracted from the joint tissues. Ti particles significantly stimulated the proliferation of BMSC-derived osteoblastic cells at both high and low particle concentrations (p 0.05), with no marked differences between the particle doses. ALP expression was diminished following Ti particle interactions, especially in the high-dose particle group (p 0.05). In addition, the culture media collected from short-term challenged (48 h) osteoblasts significantly increased the numbers of TRAP+ cells when added to mouse peripheral blood monocytes cultures, in comparison with the monocytes cells receiving na?ve osteoblasts media (p 0.05). Intra-articular introduction of the osteoblastic cells to the mouse pin-implant failure model resulted in reduced implant interfacial shear strength and thicker peri-implant soft-tissue formation, suggesting that titanium particles-challenged osteoblasts contributed to periprosthetic osteolysis. Comparison of the gene expression profiles among the peri-implant tissue samples following osteoblast injection did not find significant difference in RunX2 or Osterix/Sp7 between the groups. However, MMP-2, IL-1, TNF-α, RANKL, and TRAP gene expressions were elevated in the challenged-osteoblast group (p 0.05). In conclusion, titanium alloy particles were shown to interfere with the growth, maturation, and functions of the bone marrow osteoblast progenitor cells. Particle-challenged osteoblasts appear to express mediators that regulate osteoclastogenesis and peri-prosthetic osteolysis.