Biological response to micron‐ and nanometer‐sized particles known as potential wear products from artificial hip joints: Part II: Reaction of murine macrophages to corundum particles of different size distributions

Abstract

Macrophages play a pivotal role in tissue reaction and immune response. They recognize, phagocytose particles and generate cytokines to influence local cellular reactions. Friction and wear of implant components usually generates microparticles (MP) in a size range of 1-10 mum and nanoparticles (NP) in the range of 10-1000 nm. To investigate the possible impact of MP or NP on cellular reactions, we exposed murine macrophages (RAW264.7) to corundum MP and NP. The same mass was used in both NP and MP cell culture solutions, i.e. there were more NP than MP per identical volumes of culture solution. After 4, 24, 48, 72, and 96 h aliquots of cell culture supernatants were tested for different cytokines, growth factors and nitric oxide. Macrophages were stained with MGG (May-Grünwald Giemsa), counted and morphologically characterized by scanning electron microscopy and transmission electron microscopy. Particles were attached to cell surfaces and phagocytosed within cells. Cells stimulated with particles or lipopolysaccharides for positive controls showed surface modifications indicating enhanced function. Although only marginal differences between negative controls and particle-stimulated cells were observed in respect to cytokine production, exposure to corundum particles led to a decrease in the number of vital macrophages and to an increase in the number of giant cells. Corundum NP formed micron-sized aggregates in the cell culture medium and led to the production of more giant cells than MP. Sodiumdodecylsulfate polyacrylamide gel electrophoresis of the cell culture medium with particles proved the adsorption of proteins to particles.

Comparison of the cytotoxic and inflammatory responses of titanium particles with different methods for endotoxin removal in RAW264.7 macrophages

“…This cell line has been used by previous investigators performing similar assays [30][31][32] and has the advantages of being a robust, stable, established cell line with predictable uniform cytokine responses. The RAW264.7 cells were grown, maintained, and assayed in DMEM with 10% heat-inactivated fetal bovine serum.…”

Interaction of materials and biology in total joint replacement – successes, challenges and future directions

“…Larger particles (>7μm) were shown to have no effect on bone resorption and cytokine production. In another study using mouse RAW264.7 macrophages, corundum particles in the nanometer size induced higher pro-inflammatory cytokine production and more giant cell formation than micrometer sized particles 48 . Human THP1 macrophage cells exposed to conventional or highly cross-linked UHMWPE particles induced significant pro-inflammatory cytokine production when the particles were of a larger size (>10μm); cells exposed to conventional UHMWPE particles showed higher cytotoxicity with small particles (0.7μm) 47 .…”

“…The biological response of immune cells to wear particles is dependent on the particle composition 43 , dose 44 , 45 , size 44 , 46-48 , shape, and surface chemistry, energy and topography 49 . In one study, periprosthetic tissues from patients with aseptic loosening of implants were transplanted into the muscles of immunodeficient mice.…”

Self‐healing biomaterials

“…Attempts by the immune system to consume and remove these wear particles often leads to a state of a chronic inflammation. It has also been observed that wear debris cleared from the joint space by lymph or blood flow collects in the lymph nodes and other organs of the immune system 42, 44, 45…”