A model approach to show that monocytes can enter microporous β-TCP ceramics

Abstract β-TCP ceramics are versatile bone substitute materials and show many interactions with cells of the monocyte-macrophage-lineage. The possibility of monocytes entering microporous β-TCP ceramics has however not yet been researched. In this study, we used a model approach to investigate whether monocytes might enter β-TCP, providing a possible explanation for the origin of CD68-positive osteoclast-like giant cells found in earlier works. We used flow chambers to unidirectionally load BC, PRP, or PPP into slice models of either 2 mm or 6 mm β-TCP. Immunofluorescence for CD68 and live/dead staining was performed after the loading process. Our results show that monocytes were present in a relevant number of PRP and BC slices representing the inside of our 2 mm slice model and also present on the actual inside of our 6 mm model. For PPP, monocytes were not found beyond the surface in either model. Our results indicate the possibility of a new and so far neglected constituent in β-TCP degradation, perhaps causing the process of ceramic degradation also starting from inside the ceramics as opposed to the current understanding. We also demonstrated flow chambers as a possible new in vitro model for interactions between blood and β-TCP.