Interaction of macrophages with fibrous materials in vitro.

Fibrous materials have the potential of being used for tissue scaffolding. The interaction of macrophages with fibres of various compositions and sizes was observed in vitro. The following materials were tested: individual gold fibres; woven fibres of polyester and nylon; non-woven fibres of polybutylene/polypropylene 80:20 and polyester. All fibres had diameters between 2 and 40 microns. At the end of the 24 h incubation time, culture media were retrieved for the assay of tumour necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6), two cytokines secreted by activated macrophages. Fibre samples were processed for scanning electron microscopy (SEM), or for immunofluorescence labelling of the MAC-1 and ICAM-1 cell surface markers. Confocal microscopy was used for the latter, which was performed with the woven and non-woven samples. None of the fibre samples induced significant amounts of TNF-alpha or IL-6 secretion in the culture medium, suggesting that the cells did not activate this pathway. SEM on individual gold fibres showed that the fibre diameter had an effect on the morphology of the cells, namely on their extent of spreading. Larger fibres had a higher number of cells, which tended to cluster together without spreading extensively. When comparing woven and non-woven fibres, SEM showed that cells spread extensively on the woven fibres, whereas they tended to maintain their spherical shape on the non-woven fibres. Confocal microscopy demonstrated a difference between materials in the number of MAC-1 and ICAM-1 positive cells. These results demonstrate that a combination of morphological, immune and biochemical markers can be used to distinguish the response of elicited macrophages to various materials. The cells appeared to be only moderately activated on all materials tested, with changes in their morphology but without increased secretion of cytokines. The measured responses imply interactions between nominal fibre composition and fibre diameter.