Influence of the zinc concentration of sol–gel derived zinc substituted hydroxyapatite on cytokine production by human monocytes in vitro

A possible complication associated with the implantation of hydroxyapatite (HA)-based prosthesis is the release of particles. These particles can be phagocyted by monocytes that are among the first cells to colonize the inflammatory site. The activated monocytes produce inflammatory mediators such as cytokines that cause osteoclasts activation. The present work, describes studies on the effect of sol–gel derived zinc-substituted HA particles with various zinc substitution percentages (0.5–2%) on cytokine production (TNF-α, IL-1β, IL-6, IL-10, and IL-8) by both LPS-stimulated or unstimulated human monocytes. Our data demonstrates that the zinc has an effect on cytokines production. It decreases the production of TNF-α and increases the production of IL-8 by unstimulated cells. Using LPS-stimulated cells, it decreases the production of inflammatory cytokines and increases the production of anti-inflammatory cytokine (IL-10), indicating that zinc-substituted hydroxyapatite has favourable effects on the cytokines production by monocytes.