Phagocytosis of different particulate dermal filler substances by human macrophages and skin cells

BACKGROUND. Foreign substances have been introduced into the human body with varying degrees of success. Polymethylmethacrylate (PMMA) microspheres of different sizes recently have been manufactured for use as a filler substances in the skin and other organs. OBJECTIVE. To establish whether the size of PMMA microspheres determines whether various cell types initiate phagocytosis. METHODS. The capacity of three different cell lines-U-937 cells, XS 106 and XS 52 Langerhans cells, and HaCaT keratinocytes-to phagocytose microspheres of varying sizes was examined using light and confocal microscopy as well as fluorescence-activated cell sorter (FACS) analysis. Tumor necrosis factor (TNF)-alpha secretion was also determined. RESULTS. The U-937 cells, keratinocytes, and Langerhans cells could phagocytose PMMA particles of 20 mum or smaller. Microspheres larger than 20 mum were not ingested by any of the cells. CONCLUSION. Microspheres larger than 20 mum have a lower likelihood of being phagocytosed. Thus this study suggests that microspheres 40-50 mum in diameter are less likely to initiate an inflammatory reaction when injected into the dermis and subdermis as a filler substance. On the other hand, microparticles made of silicone and polymethacrylate were phagocytosed, possibly because of their different structure.