Coseeded Schwann cells myelinate neurites from differentiated neural stem cells in neurotrophin-3-loaded PLGA carriers

Yi Xiong^1,*, Ji-Xiang Zhu^2,*, Zheng-Yu Fang¹, Cheng-Guang Zeng², Chao Zhang¹, Guo-Long Qi³, Man-Hui Li¹, Wei Zhang¹, Da-Ping Quan², Jun Wan^1,4
1Biomedical Research Institute, Shenzhen-PKU-HKUST Medical Center, Shenzhen, ²DSAPM Lab, PCFM Lab, Institute of Polymer Science, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou, ³Department of Medical Information, Medical Collage of Jinan University, Guangzhou, ⁴Division of Life Science, the Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, People's Republic of China

*These authors contributed equally to this manuscript

Abstract: Biomaterials and neurotrophic factors represent promising guidance for neural repair. In this study, we combined poly-(lactic acid-co-glycolic acid) (PLGA) conduits and neurotrophin-3 (NT-3) to generate NT-3-loaded PLGA carriers in vitro. Bioactive NT-3 was released stably and constantly from PLGA conduits for up to 4 weeks. Neural stem cells (NSCs) and Schwann cells (SCs) were coseeded into an NT-releasing scaffold system and cultured for 14 days. Immunoreactivity against Map2 showed that most of the grafted cells (>80%) were differentiated toward neurons. Double-immunostaining for synaptogenesis and myelination revealed the formation of synaptic structures and myelin sheaths in the coculture, which was also observed under electron microscope. Furthermore, under depolarizing conditions, these synapses were excitable and capable of releasing synaptic vesicles labeled with FM1-43 or FM4-64. Taken together, coseeding NSCs and SCs into NT-3-loaded PLGA carriers increased the differentiation of NSCs into neurons, developed synaptic connections, exhibited synaptic activities, and myelination of neurites by the accompanying SCs. These results provide an experimental basis that supports transplantation of functional neural construction in spinal cord injury.

Keywords: PLGA, NT-3, neural stem cells, Schwann cells, myelin sheath