Glial cell responses to particles derived from spinal implant materials

Spinal implants have been successfully used to treat various spine conditions. However, concerns remain regarding the release of ions and particles that can cause adverse host responses. Moreover, the biological response from cells of the central nervous system to implant wear particles is not well documented. This research studied the interaction of silicon nitride, cobalt oxide, or chromium oxide particles with relevant glial cells, astrocytes and microglia, to assess their effects on viability and activation using a range of relevant concentrations. Astrocyte viability was not impaired by the particles, and expression levels of the astrocyte reactivity markers GFAP and vimentin were unaffected following 24 h of exposure. Moreover, the particles did not alter microglial phagocytic activity, or stimulate the release of the inflammatory cytokines TNF-α and IL-6. Together, these results suggest that the release of such particles from a spinal implant would not induce an inflammatory response in surrounding glial cells. Interestingly, high concentrations of SiN particles reduced microglial cell viability, potentially due to their tendency to form large agglomerates and/or their high dissolution rate. The present work highlights the importance of studying the potential effects of SiN particles on glial cells and encourages further investigations to fully understand the safety aspects of the use of SiN in spinal implants. • Glial cells were exposed to SiN, Co 3 O 4 , and Cr 2 O 3 particles, to assess effects of particle release from spinal implants. • None of the particles induced astrocyte reactivity or cytokine release from microglia. • High concentrations of SiN particles reduced microglial viability.