• Mei-Wei Chen, Xiang Zhang, Lie-Jing Lu, Fang Zhang, Xiao-Hui Duan, Chu-Shan Zheng, Yue-Yao Chen, and Jun Shen.
• Department of Radiology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, No.107 Yanjiang Road West, Guangzhou, 510120, China.
• Muscle Nerve. 2018 Feb 9.

IntroductionMacrophage recruitment is critical for nerve regeneration after an injury. The aim of this study was to investigate whether ultrasmall superparamagnetic iron oxide (USPIO) nanoparticle-based MRI could be used to monitor the enhanced macrophage recruitment by Toll-like receptor 4 (TLR4) activation in nerve injury.MethodsRats received intraperitoneal injections of either lipopolysaccharide (LPS) or phosphate buffered saline (PBS) or no injection (controls) after a sciatic nerve crush injury. After intravenous injection of the USPIOs (LPS and PBS groups) or PBS (control group), MRI was performed and correlated with histological findings.ResultsLPS group showed more remarkable hypointense signals on T2*-weighted imaging and lower T2 values in the crushed nerves than PBS group. The hypointense signal areas were associated with an enhanced recruitment of iron-loaded macrophages to the injured nerves.DiscussionUSPIO-enhanced MRI can be used to monitor the enhanced macrophage recruitment by means of TLR4 signal pathway activation in nerve injury. Muscle Nerve, 2018.© 2018 Wiley Periodicals, Inc.

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