Ricerc@Sapienza

Aim of the study was to evaluate USPIO labeling in different macrophage populations using a clinical 3.0T MR unit with optical and electron microscopy as the gold standard. Human monocytic cell line THP-1 cells were differentiated into macrophages. Afterwards, M0 macrophages were incubated with IL-4 and IL-13 in order to obtain M2 polarized macrophages or with IFN-gamma and LPS for classical macrophage activation (M1). These groups were incubated with USPIO-MR contrast agent (P904) for 36?hr; M0, M0?+?P904, M1?+? P904, and M2?+?P904 were analyzed in gel phantoms with a 3.0T MR scanner. m-RNA of M1 and M2 markers confirmed the polarization of THP-1-derived macrophages. M2?+?P904 showed a much higher T1 signal (p?<? 0.0001), a significantly lower (p?<?0.0001) T2* signal, and significantly higher R* (p?<?0.0001) compared to the other populations. Hystological analysis confirmed higher iron content in the M2-polarized population compared to both M1-polarized (p?=?0.04) and M0-P904 (p?=?0.003). Ultrastructure analysis demonstrated ubiquitous localization of P904 within the cellular compartments. Our results demonstrate that a selective USPIO-labeling of different macrophage populations can be detected in vitro using the 3.0T clinical scanner.