Monocyte Subset Dynamics in Human Atherosclerosis Can Be Profiled with Magnetic Nano-Sensors

Monocytes are circulating macrophage and dendritic cell precursors that populate healthy and diseased tissue. In humans, monocytes consist of at least two subsets whose proportions in the blood fluctuate in response to coronary artery disease, sepsis, and viral infection. Animal studies have shown that specific shifts in the monocyte subset repertoire either exacerbate or attenuate disease, suggesting a role for monocyte subsets as biomarkers and therapeutic targets. Assays are therefore needed that can selectively and rapidly enumerate monocytes and their subsets. This study shows that two major human monocyte subsets express similar levels of the receptor for macrophage colony stimulating factor (MCSFR) but differ in their phagocytic capacity. We exploit these properties and custom-engineer magnetic nanoparticles for ex vivo sensing of monocytes and their subsets. We present a two-dimensional enumerative mathematical model that simultaneously reports number and proportion of monocyte subsets in a small volume of human blood. Using a recently described diagnostic magnetic resonance (DMR) chip with 1 µl sample size and high throughput capabilities, we then show that application of the model accurately quantifies subset fluctuations that occur in patients with atherosclerosis

Tumor microvascular changes in antiangiogenic treatment: Assessment by magnetic resonance contrast media of different molecular weights

Purpose: To test magnetic resonance (MR) contrast media of different molecular weights (MWs) for their potential to characterize noninvasively microvascular changes in an experimental tumor treatment model. Materials and Methods: MD-MBA-435, a poorly differentiated human breast cancer cell line, was implanted into 31 female homozygous athymic rats. Animals were assigned randomly to a control (saline) or drug treatment (monoclonal antibody vascular endothelial growth factor (MabVEGF) antibody) group. In both groups, dynamic MR imaging (MRI) was performed in each animal using up to three different contrast media on sequential days at baseline and follow-up examination. The MWs of the contrast media used ranged from 557 Da to 92 kDa. Using a bidirectional kinetic model, tumor microvessel characteristics, including the fractional plasma volume (fPV) and transendothelial permeability K-PS, were estimated for each contrast medium. These microvascular characteristics were compared between drug and control groups and between contrast media of different MWs. Results: Tumors grew significantly slower (P <0.0005) in the drug treatment group than in the control group. Mean K-PS and fPV values decreased significantly (P <0.05) in the Mab-VEGF antibody-treated group compared to baseline values using intermediate or macromolecular contrast media (MMCM), but did not change significantly using small molecular contrast media (SMCM). In the control groups, mean K-PS and mean fPV values did not reach statistical significance for any of the contrast media used. Conclusion: Therapeutic effects of a Mab-VEGF antibody on tumor microvessel characteristics can be monitored by dynamic MRI. Intermediate-size agents, such as Gadomer-17, offer a substantial dynamic range and are less limited by imaging precision and therefore should be considered a practical alternative to monitor antiangiogenesis treatment effects in a clinical setting