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USPIO-labeling in M1 and M2-polarized macrophages: An in vitro study using a clinical magnetic resonance scanner
Chiara Zini1, Mary A Venneri2, Selenia Miglietta3
1Faculty of Medicine and Dentistry, Department of Radiological Sciences, Oncology and Pathology, University of Rome "Sapienza", Latina, Italy.
Abstract:
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.
Insights
This study shows that ultrasmall iron oxide nanoparticles (USPIOs) can selectively label different macrophage types. This selective USPIO labeling is detectable in vitro using a clinical 3.0T MRI scanner.
Area of Science:
- Biomedical Imaging
- Cell Biology
- Nanotechnology
Background:
- Macrophage polarization plays a crucial role in various physiological and pathological processes.
- Ultrasmall iron oxide nanoparticles (USPIOs) are promising contrast agents for magnetic resonance imaging (MRI).
- Differentiating and tracking macrophage populations in vivo remains a challenge.
Purpose of the Study:
- To evaluate the selective labeling of different macrophage populations (M0, M1, M2) with USPIOs.
- To assess the detectability of USPIO labeling using a clinical 3.0T MRI scanner.
- To correlate MRI findings with optical and electron microscopy for gold-standard validation.
Main Methods:
- Human monocytic THP-1 cells were differentiated into M0, M1 (IFN-gamma/LPS stimulated), and M2 (IL-4/IL-13 stimulated) macrophages.
- Macrophages were incubated with the USPIO contrast agent P904 for 36 hours.
- Labeled macrophage populations were analyzed using a 3.0T MRI scanner and validated with histological and ultrastructural analyses.
Main Results:
- M2-polarized macrophages exhibited significantly higher T1 signal and lower T2* signal compared to M0 and M1 macrophages after USPIO incubation.
- Histological analysis confirmed a higher iron content in M2-polarized macrophages.
- MRI detected selective USPIO labeling of different macrophage populations in vitro.
Conclusions:
- Selective USPIO labeling of distinct macrophage populations is achievable in vitro.
- A clinical 3.0T MRI scanner can detect these selective USPIO-labeling differences.
- This technique holds potential for non-invasively tracking macrophage polarization in clinical settings.
