Magnetic resonance tracking of transplanted microglia labeled with superparamagnetic iron oxide particles in the brain of normal rat and Alzheimer's disease model rat

Abstract

Objective To explore the methods of labeling exogenous microglia with superparamagnetie iron oxide(SPIO)particles,and to monitor the labeled cells after transplantation into the normal rat and Alzheimer's disease(AD)model rat with MR scanning.Methods Microglia was labeled with SPIO particles by using transfection agent,hemagglutinating virus of Japan envelope(HVJ-E).Then the microglias which were labeled with SPIO were injected into the internal carotid artery of normal rat (n=5)and AD model rat(n=5).Three days after transplantation,follow-up serial T2*-weighted gradient-echo MR imaging was performed at 7.0T MRI system.MR images were correlated with histological findings.Results In the brain of normal rat,the labeled microglias were demonstrated as several dotty signalintensity decrease on T2*-weighted MR images.The dotty spots were sporadic around the brain.Histological analysis showed that most prussian blue staining-positive cells were well correlated with the area where a signal intensity decrease was observed in MRI.MR could detect the signal intensity change caused by a few labeled cells.In the brain of AD model rat,MR scan showed a well-defined hypointensity area in the region of Aβ42 iniection.Signal intensity decrease was not obvious in the region of saline injection.The number of iron-positive cells(454±47)/mm2 at sites of Aβ42 injection was much higher than that(83±13)/mm2 of saline injection(P＜0.05). Conclusion MR can be used as a non-invasive means of detecting transplanted labeled microglia in vivo,with the potential for future clinical application in cell therapy of AD. Key words: Microglia; Alzheimer disease; Magnetic resonance imaging; Rats