Effects of neural stem cells transplantation and FK506 on pathologic and ultrastructural changes of injured spinal cord

Objective To investigate the impacts of neural stem cells (NSCs) transplantation on spinal pathology and ultrastructure after spinal cord injury (SCI) in rats and probe into the protective role of tacrolimus (FK506) on neural regeneration. Methods Compressive SCI at T8 was induced in the adult SD rats,which were randomly assigned to the control group,FK506 group,NSCs group and NSCs + FK506 group.The differences of neural regeneration in each group were compared at days 7,14,28 and 56 after injury by motor evoked potentials ( MEP),HE staining,immunohistochemical staining,ultrastructure observation and image analysis of the myelinated fiber. Results The MEP latency in the NSCs + FK506 group was significantly shorter than that in other groups at day 28 ( P ＜ 0.05 ).HE staining revealed that only local necrosis presented in the NSCs + FK506 group at day 56.More BrdU and NF-200 positive cells were detected with immunohistochemical staining in the other three groups as compared with the control group.Moreover,the positive cells in the NSCs + FK506 group also outnumbered the FK506 group and NSCs group.Electron microscope scan showed edema under the membrane of large myelin sheath in the control group,and classic new myelin sheath and neuraxis in the NSCs + FK506 group at day 56.The regeneration of the nerve fiber in the NSCs + FK506 group was better than that of other three groups (P ＜0.01 ). Conclusion After NSCs transplantation for SCI rats,the early combination use of FK506 can improve the pathology and ultrastructure of the regenerative nerve fiber and is conducive to nerve regeneration. Key words: Spinal cord injuries;  Tacrolimus binding proteins;  Stem cell transplantation; Pathology;  Ultrastructure