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

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

Acknowledgments

We thank the Chinese National Natural Science Foundation (30900774 to Y Xiong; 81000465 to J Wan; U1134007, 20974128 and 51073178 to DP Quan), Shenzhen-Hong Kong Innovation Foundation (08fz-08) and the China Postdoctoral Science Foundation (20090460788) for financial support. We also thank Shenzhen Biomedical Research Support Platform for the technical help. We thank Dr Kepeng Wang for revising our manuscript.

Disclosure

The authors declare no conflicts of interest in this work.

Supplementary figure

Figure S1 NSCs and SCs were cultured in the scaffold for 14 days. Cells were immunostained in (A) PLGA only; (B) PLGA-SF; (C) PLGA-SF-NT-3 group with markers for astrocytes (GFAP; star; red), and oligodendrocytes (O4; arrow; green). Nuclei were stained by DAPI (blue); (D) Cells with staining of O4 were manually counted. There was no statistical difference among groups (P > 0.05; n = 3 for each group).

Note: Scale bar = 20 μm in A–C.

Abbreviations: NSCs, neural stem cells; SCs, Schwann cells; PLGA, poly-(lactic acid-co-glycolic acid); SF, silk fibroin; NT-3, neurotrophin-3; GFAP, glial fibrillary acidic protein; DAPI, 4′,6-diamidino-2-phenylindole.