Netrin1-carrying magnetic microspheres with magnetic field activate neurotrophin factors to guide neuronal outgrowth in vitro and in vivo

Abstract

Nerve injuries often result in the failure of functional synapses connections, primarily due to the absence of neurotrophic factors and guidance at the injury sites. In response to this challenge, an effective approach involving magnetic microspheres carrying axonal guidance cue (Netrin1) was presented. These microspheres were prepared using Fe3O4 and PLGA via electrospray. Netrin1 was incorporated into structural particles that could be oriented in a magnetic field and released at the injury sites. In this study, oriented and longer axons were observed in the cortical neurons after 10 μg/mL magnetic microspheres (MMSs) treatment. Under an applied magnetic field of 5 mT, Netrin1-carrying magnetic microspheres (N@MMSs) demonstrated a more significant increase in cell viability, mitochondrial membrane potential, mRNA expressions of BDNF and NGF compared to MMSs. These findings were assessed using the cell counting kit-8, tetramethyl rhodamine fluorescence, and real time PCR assay, respectively. Furthermore, N@MMSs demonstrated significant protection against glutamate-induced neuronal oxidative toxicity, as evaluated by mitochondrial respiratory function and glycolysis stress using the Seahorse Extracellular Flux analyzer. Subsequently, N@MMSs and a magnetic field were applied to adult mice after sciatic nerve injury. Behavior analysiss, including the open field test, indicated that N@MMSs typically increased motor activity under the magnetic field and significantly decreased paw licking latency on the 14th day. Finally, both BDNF and NGF expressions increased compared to the injury group. In conclusion, N@MMSs show promise as alternative particles for nerve regeneration.