LPS increases biomaterial degradation by human monocytes in vitro.

Different cell lines are involved during an immunological reaction, principally lymphocytes and monocytes. Monocyte/macrophage cells, which are among the first to appear in wound-healing and infection sites, are largely implicated in phagocytosis and could be involved in calcium-phosphate degradation. Their role in these processes may relate to cytokine secretions and/or their sensitivity to certain cytokines. We tested the behavior of human monocytes placed on the surface of biphasic calcium-phosphate (BCP) tablets in the presence of two lipopolysaccharide (LPS) concentrations. After short-term culture (48 h), cytokine release (IL-1beta, IL-6) was measured by ELISA, and morphological cell events and biomaterial degradation were observed in scanning electron microscopy. BCP surface pits were noted near cells stimulated by 0.5 microg/mL LPS but were not apparent with 10 microg/mL LPS. The number of lacunae on BCP was increased after LPS treatment of human monocytes. An upmodulation of IL-1beta and IL-6 (in culture medium) released by LPS-activated human monocytes was observed, indicating good cell stimulation. This study demonstrates that LPS-activated human monocytes can degrade the surface of calcium-phosphate ceramic and confirms the role of human monocytes in biomaterial degradation.