The immunomodulator decoy receptor 3 improves locomotor functional recovery after spinal cord injury.
Spinal cord injury (SCI) causes loss of neurons and axons and results in motor and sensory function impairments. SCI elicits an inflammatory response and induces the infiltration of immune cells, predominantly macrophages, to the injured site. Decoy receptor 3 (DcR3), also known as tumor necrosis factor receptor superfamily member (TNFRSF)-6B, is a pleiotropic immunomodulator capable of inducing macrophage differentiation into the M2 phenotype and enhancing angiogenesis. Because M2 macrophages are crucial for the recovery of impaired motor functions, we ask whether DcR3 is beneficial for the functional recovery of locomotion in Sprague-Dawley (SD) rats after SCI.



Contusion injury of the spinal cord was performed using a New York University impactor at the ninth thoracic vertebrae, followed by intrathecal injection of 15 μg recombinant protein comprising DcR3 (DcR3.Fc) in 5 μl of normal saline as the treatment, or 5 μl of normal saline as the control, into the injury epicenter. Functional recovery was evaluated using an open-field test weekly up to 6 weeks after injury. The cavity size and myelin sparing in the rostral-to-caudal region, including the epicenter of the injury, were then examined in SCI rats by histological staining. The expression of anti-inflammatory cytokines and the presence of M2 macrophages were determined by quantitative real-time polymerase chain reaction (qPCR) and immunohistochemistry at 7 day after SCI. Statistical analysis was performed using a two-tailed Student's t test.



Intrathecal administration of DcR3.Fc significantly improved locomotor function and reduced secondary injury with a smaller wound cavity and increased myelin sparing at the lesion site. Compared with the control group, DcR3.Fc-treated rats had increased vascularization at the injury epicenter along with higher levels of interleukin (IL)-4 and IL-10 and lower level of IL-1β on DcR3.Fc-treated rats at day 7 after SCI. Moreover, higher levels of arginase I (Arg I) and CD206 (M2 macrophage markers) and RECA-1 (endothelial marker) were observed in the epicenter on day 7 after SCI by immunofluorescence staining.



These results indicated that DcR3.Fc may promote the M2 macrophage infiltration and enhanced angiogenesis at the lesion site, thus preserving a greater amount of spinal cord tissues and enhancing functional recovery after SCI.
Department and Institute of Pharmacology, National Yang-Ming University, Taipei, 11221, Taiwan.|Neural Regeneration Laboratory, Taipei, 11217, Taiwan.
Chuan-Wen
CW
Chiu
Department and Institute of Pharmacology, National Yang-Ming University, Taipei, 11221, Taiwan.|Neural Regeneration Laboratory, Taipei, 11217, Taiwan.
Wen-Hung
WH
Huang
Neural Regeneration Laboratory, Taipei, 11217, Taiwan.
Shao-Ji
SJ
Lin
Neural Regeneration Laboratory, Taipei, 11217, Taiwan.
May-Jywan
MJ
Tsai
Division of Plastic and Reconstructive Surgery, Department of Surgery, Taipei Veterans General Hospital, Taipei, 11217, Taiwan.
Hsu
H
Ma
Genomics Research Center, Academia Sinica, Taipei, Taiwan. slhsieh@gate.sinica.edu.tw.|Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan. slhsieh@gate.sinica.edu.tw.|Department of Medical Research, Taipei Veterans General Hospital, Taipei, Taiwan. slhsieh@gate.sinica.edu.tw.
Shie-Liang
SL
Hsieh
Department and Institute of Pharmacology, National Yang-Ming University, Taipei, 11221, Taiwan. hc_cheng@vghtpe.gov.tw.|Neural Regeneration Laboratory, Taipei, 11217, Taiwan. hc_cheng@vghtpe.gov.tw.|Center for Neural Regeneration, Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, Taipei, 11217, Taiwan. hc_cheng@vghtpe.gov.tw.
Henrich
H
Cheng
D000818:Animals; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D008124:Locomotion / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D053323:Receptors, Tumor Necrosis Factor, Member 6b / Q000494:pharmacology / Q000627:therapeutic use*; D020127:Recovery of Function / Q000187:drug effects / Q000502:physiology*; D013119:Spinal Cord Injuries / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology
D053323:Receptors, Tumor Necrosis Factor, Member 6b; C505911:TNFRSF6B protein, human
Alternatively activated macrophage; DcR3; Spinal cord injury