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Yong Li,1,* Sheng-Chun Fang,2,* Lan Zhou,1 Xue-Mei Mo,3 Hao-Dong Guo,3 Yan-Bo Deng,3 Hong-Hao Yu,1 Wei-Yi Gong3 1College of Biotechnology, Guilin Medical University, Guilin, Guangxi, 541100, People’s Republic of China; 2Department of Anesthesiology, Wuhan Children’s Hospital (Wuhan Maternal and Child Healthcare Hospital), Tongji Medical College of Huazhong University of Science and Technology, Wuhan, Hubei, 430015, People’s Republic of China; 3Department of Pain Management, Affiliated Hospital of Guilin Medical University, Guilin, Guangxi, 541000, People’s Republic of China*These authors contributed equally to this workCorrespondence: Hong-Hao Yu, College of Biotechnology, Guilin Medical University, Guilin, Guangxi, 541100, People’s Republic of China, Email geneyhh@126.com Wei-Yi Gong, Department of Pain Management, Affiliated Hospital of Guilin Medical University, Guilin, 541000, Guangxi, People’s Republic of China, Email 942261597@qq.comBackground: Neuropathic pain (NP) after spinal cord injury (SCI-evoked NP) is clinically challenging; the underlying mechanisms are not fully understood, leading to a lack of promising treatment options. NP occurs in only a subset of patients with SCI. The injured spinal cord exhibits a series of histopathological changes, and the complement system has been shown to play an important role in these processes. In addition, NMDA receptor subunit 2B (NR2B) is involved in the development and maintenance of NP. This preliminary study was performed to investigate the correlations of the complement receptor 3/complement component 3 (CR3/C3) pathway and NR2B with SCI-evoked NP.Methods: A trauma-induced SCI animal model was established and SCI-evoked NP was evaluated by behavioural analysis. Transcriptome analysis was performed to identify genes in the CR3/C3 pathway related to synaptic modification, while the expression and distribution of NR2B in the injured spinal cord, and the relation to NP, were examined by immunohistochemical analysis.Results: Nine of seventeen SCI rats (52.9%) developed NP. C3 mRNA expression was significantly decreased in SCI-evoked NP rats and significantly increased in the non-NP SCI rats. C1q mRNA and CR3 mRNA expression were significantly increased in all SCI rats, but higher levels of expression were observed in the non-NP SCI rats. NR2B mRNA expression was significantly increased in the SCI-evoked NP rats and significantly decreased in the non-NP SCI rats. In addition, significantly elevated expression of NR2B-positive cells was seen in lamina II of the superficial dorsal horn in SCI-evoked NP rats in comparison with non-NP SCI rats.Conclusion: NP occurred in only a subset of SCI rats, and the CR3/C3 pathway and NR2B were involved in SCI-evoked NP. Further studies are required to determine the mechanisms underlying the SCI-evoked NP associated with the CR3/C3 pathway and NR2B.Keywords: spinal cord injury, neuropathic pain, complement receptor 3, complement component 3, NMDA receptor 2B subunit

Xiao-Ai Chen1,5*, Li-Jun Zhang2*, Zhi-Jie He3, Wei-Wei Wang4, Bo Xu1, Qian Zhong1, Xin-Tao Shuai4, Li-Qun Yang4, Yu-Bin Deng11Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China; 2Futian Affiliated Hospital, Guangdong Medical College, Shenzhen, China; 3Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China; 4Institute of Polymer Science, School of Chemistry and Chemical Engineering, BME Center, State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou, China; 5Yunnan Cancer Hospital, The Third Affiliated Hospital, Kunming Medical College, Kunming, China*Both authors contributed equally to this workBackground: Mesenchymal stem cell transplantation is a promising method in regenerative medicine. Gene-modified mesenchymal stem cells possess superior characteristics of specific tissue differentiation, resistance to apoptosis, and directional migration. Viral vectors have the disadvantages of potential immunogenicity, carcinogenicity, and complicated synthetic procedures. Polyethylene glycol-grafted polyethylenimine (PEG-PEI) holds promise in gene delivery because of easy preparation and potentially targeting modification.Methods: A PEG8k-PEI25k graft copolymer was synthesized. Agarose gel retardation assay and dynamic light scattering were used to determine the properties of the nanoparticles. MTT reduction, wound and healing, and differentiation assays were used to test the cytobiological characteristics of rat mesenchymal stem cells, fluorescence microscopy and flow cytometry were used to determine transfection efficiency, and atomic force microscopy was used to evaluate the interaction between PEG-PEI/plasmid nanoparticles and mesenchymal stem cells.Results: After incubation with the copolymer, the bionomics of mesenchymal stem cells showed no significant change. The mesenchymal stem cells still maintained high viability, resettled the wound area, and differentiated into adipocytes and osteoblasts. The PEG-PEI completely packed plasmid and condensed plasmid into stable nanoparticles of 100–150 nm diameter. After optimizing the N/P ratio, the PEG-PEI/plasmid microcapsules delivered plasmid into mesenchymal stem cells and obtained an optimum transfection efficiency of 15%–21%, which was higher than for cationic liposomes.Conclusion: These data indicate that PEG-PEI is a valid gene delivery agent and has better transfection efficiency than cationic liposomes in mesenchymal stem cells.Keywords: stem cells, gene delivery, nanoparticles, atomic force microscopy