gms | German Medical Science

Objective: Superparamagnetic iron oxide nanoparticles (SPIOs) have been used as contrast agents in magnetic resonance imaging (MRI) and are of special interest for diagnostic and therapy of central nervous system (CNS) diseases. Currently, particular focus lies on the use of SPIOs to specifically influence neuronal regeneration after injury due to their unique composition, including size, surface coating and charge. The resulting increased interaction with and accumulation by brain cells make them ideal tools to act at the molecular level. Therefore, we sought to investigate the activation of intracellular signaling pathways as well as the cytokine/chemokine secretion profile responsible for SPIO-induced neurite outgrowth, which we have reported before.

Methods: Microglia and astrocytes from C57Bl6/J pups (P0-P2) and hippocampal neurons from mice embryos (E18) were cultured separately and in a co-culture. Very Small Iron Oxide Particles (VSOP-R1/-R2), differing in size or the clinically proven polymer coated Resovist^® (Bayer Schering Pharma AG) or Feraheme^® (AMAG Pharmaceuticals, Inc.), were added at 0,5mM for 24 hours. We analyzed arrays to identify up- und down regulated cytokines and chemokines. We performed ELISA to identify proteins and factors that mediate SPIO actions to investigate the underlying signaling pathways. We localized SPIOs and evaluated the degree of cellular uptake. Western blotting was used to analyze intracellular signaling cascades.

Results: Previous results showed that SPIOs induce degeneration of primary neurons, but stimulate neurite outgrowth in neuronglia co-cultures in a particle- and concentration-dependent manner. SPIOs modify and activate growth promoting intracellular signaling pathways in primary neurons in different cell cultures, depending on the microglia surrounding.

Conclusion: VSOPs, Resovist^® and Feraheme^® have so far not been thoroughly reviewed in terms of interactions with CNS tissue and potential adverse effects. Our experiments show, that there are considerable interferences between primary murine CNS cells and applied SPIOs as well as differences for the evaluated SPIOs. We just start to shed light on the influence of SPIO´s on intracellular signaling cascades. The analysis of particle interactions and subsequent effects substantially contribute to the assessment of chances of SPIOs for the regeneration of spinal cord injury and limits in applications of SPIOs for diagnostics (e.g. MRI) in humans.