International Journal of Nanomedicine (Jul 2024)

Magnetic Stimulation of Gigantocellular Reticular Nucleus with Iron Oxide Nanoparticles Combined Treadmill Training Enhanced Locomotor Recovery by Reorganizing Cortico-Reticulo-Spinal Circuit

  • Li J,
  • Zhou T,
  • Wang P,
  • Yin R,
  • Zhang S,
  • Cao Y,
  • Zong L,
  • Xiao M,
  • Zhang Y,
  • Liu W,
  • Deng L,
  • Huang F,
  • Sun J,
  • Wang H

Journal volume & issue
Vol. Volume 19
pp. 7473 – 7492

Abstract

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Juan Li,1,* Ting Zhou,1,* Pei Wang,1,* Ruian Yin,1 Shengqi Zhang,1 Yile Cao,1 Lijuan Zong,1 Ming Xiao,2 Yongjie Zhang,3 Wentao Liu,4 Lingxiao Deng,5 Fei Huang,6 Jianfei Sun,7,* Hongxing Wang1,* 1Department of Rehabilitation Medicine, Zhongda Hospital Southeast University, Nanjing, 210024, People’s Republic of China; 2Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, 211166, People’s Republic of China; 3Department of Human Anatomy, Nanjing Medical University, Nanjing, 211166, People’s Republic of China; 4Department of Pharmacology, Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, 211166, People’s Republic of China; 5Department of Neurological Surgery, Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Indianapolis, IN, 46202-2266, USA; 6Institute of Neurobiology, Binzhou Medical University, Yantai, 264003, People’s Republic of China; 7State Key Laboratory of Bioelectronics, Jiangsu Key Laboratory of Biomaterials and Devices, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210009, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jianfei Sun, State Key Laboratory of Bioelectronics, Jiangsu Key Laboratory of Biomaterials and Devices, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210009, People’s Republic of China, Email [email protected] Hongxing Wang, Department of Rehabilitation Medicine, Southeast University Zhongda Hospital, Nanjing, 210024, People’s Republic of China, Email [email protected]: Gigantocellular reticular nucleus (GRNs) executes a vital role in locomotor recovery after spinal cord injury. However, due to its unique anatomical location deep within the brainstem, intervening in GRNs for spinal cord injury research is challenging. To address this problem, this study adopted an extracorporeal magnetic stimulation system to observe the effects of selective magnetic stimulation of GRNs with iron oxide nanoparticles combined treadmill training on locomotor recovery after spinal cord injury, and explored the possible mechanisms.Methods: Superparamagnetic iron oxide (SPIO) nanoparticles were stereotactically injected into bilateral GRNs of mice with moderate T10 spinal cord contusion. Eight-week selective magnetic stimulation produced by extracorporeal magnetic stimulation system (MSS) combined with treadmill training was adopted for the animals from one week after surgery. Locomotor function of mice was evaluated by the Basso Mouse Scale, Grid-walking test and Treadscan analysis. Brain MRI, anterograde virus tracer and immunofluorescence staining were applied to observe the tissue compatibility of SPIO in GRNs, trace GRNs’ projections and evaluate neurotransmitters’ expression in spinal cord respectively. Motor-evoked potentials and H reflex were collected for assessing the integrity of cortical spinal tract and the excitation of motor neurons in anterior horn.Results: (1) SPIO persisted in GRNs for a minimum of 24 weeks without inducing apoptosis of GRN cells, and degraded slowly over time. (2) MSS-enabled treadmill training dramatically improved locomotor performances of injured mice, and promoted cortico-reticulo-spinal circuit reorganization. (3) MSS-enabled treadmill training took superimposed roles through both activating GRNs to drive more projections of GRNs across lesion site and rebalancing neurotransmitters’ expression in anterior horn of lumbar spinal cord.Conclusion: These results indicate that selective MSS intervention of GRNs potentially serves as an innovative strategy to promote more spared fibers of GRNs across lesion site and rebalance neurotransmitters’ expression after spinal cord injury, paving the way for the structural remodeling of neural systems collaborating with exercise training, thus ultimately contributing to the reconstruction of cortico-reticulo-spinal circuit. Keywords: gigantocellular reticular nucleus, locomotion, magnetic stimulation, spinal cord injury, superparamagnetic iron oxide nanoparticles, treadmill training

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