In vitro distinction between proinflammatory and antiinflammatory macrophages with gadolinium-liposomes and ultrasmall superparamagnetic iron oxide particles at 3.0T.

BACKGROUND: Inflammation involves a heterogeneous macrophage population, for which there is no readily available MR assessment method. PURPOSE: To assess the feasibility of distinguishing proinflammatory M1 and antiinflammatory M2 macrophages at MRI enhanced with gadolinium liposomes or ultrasmall superparamagnetic iron oxide particles. STUDY TYPE: In vitro. SPECIMEN: We employed cultured RAW macrophages. M0 macrophages were polarized with lipopolysaccharide (LPS) or interleukin-4 (IL-4), resulting in M1 or M2 macrophages. The macrophages were incubated with gadolinium (±rhodamine) liposomes or iron oxide particles and cell pellets were prepared for MRI. FIELD STRENGTH/SEQUENCE: Transverse relaxation rates and quantitative susceptibility were obtained at 3.0T with multiecho turbo spin echo and spoiled gradient echo sequences. ASSESSMENT: MRI results were compared with confocal microscopy, flow cytometry, and expression of endocytosis, M1 and M2 genes. STATISTICAL TESTS: Mann-Whitney and Kruskal-Wallis tests were performed. RESULTS: Higher transverse relaxation rates and susceptibility were observed in M1 than in M2 and M0 macrophages (P < 0.01 both with liposomes and USPIO) and significantly different susceptibility in M2 and M0 macrophages (P < 0.01 both with liposomes and USPIO). These MRI results were confirmed at confocal microscopy and flow cytometry. LPS macrophages displayed M1 gene expression, whereas IL-4 macrophages showed M2 polarization and lower endocytosis gene expression rates. DATA CONCLUSION: These in vitro results show that it is feasible to distinguish between proinflammatory M1 and antiinflammatory M2 macrophages according to their level of contrast agent uptake at MRI. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:1166-1173.

Bioinspired Multi-Activities 4D Printing Objects: A New Approach Toward Complex Tissue Engineering.

4D printing is an innovative approach which might in a near future lead to the achievement of highly complex smart materials. The authors describe a new strategy for the achievement of 4D printed objects with multiple biological activities. These activities are generated through the entrapment, during 3D printing, of two distinct enzymes (alkaline phosphatase and thrombin). These two enzymes give then the ability to the 4D printed object to generate bioactivities useful for in vitro tissue engineering. Indeed, it is shown that the entrapped alkaline phosphatase enables the localized and pre-programmed calcification of some 3D object parts while the diffusion of thrombin from the object permits the formation of fibrin biofilm (including living cells) directly at the surface of 3D object. Both activities and enzyme behavior within the 4D printed hydrogel are characterized through enzymatic measurements, microscopy, magnetic resonance imaging (MRI), and cell seeding.