Labeling of primary human hepatocytes with micron-sized iron oxide particles in suspension culture suitable for large-scale preparation.

Labeling of hepatocytes with micron-sized iron oxide particles (MPIOs) enables cell detection using clinical magnetic resonance equipment. For clinical applications, large numbers of cells must be labeled in a simple and rapid manner and have to be applied in suspension. However, all existing protocols are based on adhesion culture labeling with subsequent resuspension, only suitable for small experimental settings. The aim of this study was to investigate the feasibility of preparing MPIO-labeled primary human hepatocytes in a temporary suspension culture. Human hepatocytes were isolated from 16 donors and labeled with MPIOs in suspension, using the Rotary Cell Culture System. Particle incorporation was investigated by light and electron microscopy. Cells were compared with adhesion culture-labeled and subsequently enzymatically resuspended cells. During a period of 5 days, hepatocyte-specific parameters of cell damage (aspartate aminotransferase and alanine aminotransferase) and metabolic activity (urea and albumin) were analyzed (n=7). Suspension cultures showed a higher outcome in cell recovery compared with the conventional labeling method. When incubated with 180 particles/viable cell for 4 h, the mean particle uptake was 28.8 particles/cell at a labeling efficiency of 95.1%. Labeling in suspension had no adverse effects on cell integrity or metabolic activity. We conclude that labeling of human hepatocytes in suspension is feasible and simple and may serve future large-scale processing of cells.

In vitro evaluation of magnetic resonance imaging contrast agents for labeling human liver cells: implications for clinical translation.

PURPOSE: Magnetic resonance imaging (MRI) is a promising approach for non-invasive monitoring after liver cell transplantation. We compared in vitro labeling of human liver cells with nano-sized (SPIO) and micron-sized iron oxide particles (MPIO). PROCEDURES: The cellular iron load was quantified and phantom studies were performed using 3.0-T MRI. Transferrin receptor and ferritin gene expression, reactive oxygen species (ROS) formation, transaminase leakage, and urea synthesis were investigated over 6 days. RESULTS: Incubation with MPIO produced stronger signal extinctions in MRI at similar iron loads within shorter labeling time. MPIO had no negative effects on the cellular iron homeostasis or cell performance, whereas SPIO caused temporary ROS formation and non-physiologic activation of the iron metabolic pathway. CONCLUSIONS: Our findings suggest that MPIO are suited for clinical translation of strategies for cellular imaging with MRI. Attention should be paid to iron release and oxidative stress caused by biodegradable contrast agents.