Prolonged human neural stem cell maturation supports recovery in injured rodent CNS
Paul Lu, … , Eileen Staufenberg, Mark H. Tuszynski
Paul Lu, … , Eileen Staufenberg, Mark H. Tuszynski
Published August 21, 2017
Citation Information: J Clin Invest. 2017;127(9):3287-3299. https://doi.org/10.1172/JCI92955.
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Prolonged human neural stem cell maturation supports recovery in injured rodent CNS

Abstract

Neural stem cells (NSCs) differentiate into both neurons and glia, and strategies using human NSCs have the potential to restore function following spinal cord injury (SCI). However, the time period of maturation for human NSCs in adult injured CNS is not well defined, posing fundamental questions about the design and implementation of NSC-based therapies. This work assessed human H9 NSCs that were implanted into sites of SCI in immunodeficient rats over a period of 1.5 years. Notably, grafts showed evidence of continued maturation over the entire assessment period. Markers of neuronal maturity were first expressed 3 months after grafting. However, neurogenesis, neuronal pruning, and neuronal enlargement continued over the next year, while total graft size remained stable over time. Axons emerged early from grafts in very high numbers, and half of these projections persisted by 1.5 years. Mature astrocyte markers first appeared after 6 months, while more mature oligodendrocyte markers were not present until 1 year after grafting. Astrocytes slowly migrated from grafts. Notably, functional recovery began more than 1 year after grafting. Thus, human NSCs retain an intrinsic human rate of maturation, despite implantation into the injured rodent spinal cord, yet they support delayed functional recovery, a finding of great importance in planning human clinical trials.

Authors

Paul Lu, Steven Ceto, Yaozhi Wang, Lori Graham, Di Wu, Hiromi Kumamaru, Eileen Staufenberg, Mark H. Tuszynski

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Figure 4

Axonal extension from H9-NSC grafts.

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Axonal extension from H9-NSC grafts. (A and B) Very large numbers of GFP...
(A and B) Very large numbers of GFP-labeled human axons extended from the lesion site (far left side of the image) caudally after 1 month. (A) Horizontal section and (B) C8 coronal section. NeuN labels gray matter. Inset images show higher magnification of axons extending caudally in white matter, 3 mm caudal to the graft. The second inset in A shows colocalization of GFP with the axonal marker Tuj1, indicating the identity of many GFP processes as axons at 1 month. (C) Axons persisted 3 months after grafting, although glial migration was also evident at this point, as identified by the human nucleus marker hNu (inset; see also Figure 5). Because NSCs did not migrate into host gray matter, axon numbers over time could be quantified in gray matter. (D) A larger number of NSC-derived axons were evident in C8 gray matter at 3 months compared with those seen at 1 month, as quantified in K. (E and F) Six months after grafting, axons remained detectable in white and gray matter caudal to the lesion site. (G and H) By 12 months, a reduction in axon numbers caudal to the lesion site was observed, as quantified in C8 gray matter in K. (I and J) Further attenuation of axon numbers was evident at 18 months. (K) Quantification of human NSC-derived axons in C8 gray matter. Data represent the mean ± SEM. P = 0.14, by ANOVA for 1 (n = 3), 3 (n = 3), 6 (n = 5), 12 (n = 3), and 18 months (n = 4). (L) Glial migration did not reach T12, thus GFP-labeled axon numbers could be reliably quantified over time at T12. A gradual reduction in axon numbers was evident. P < 0.05, by ANOVA; *P < 0.05 and **P < 0.01, by Fisher’s exact post-hoc test for 1 (n = 3), 3 (n = 3), 6 (n = 5), 12 (n = 3), and 18 months (n = 3). Scale bars: 800 μm (A, C, E, G, and I); 25 μm (B, D, F, H, and J). Original magnification: ×1200 for GFP-TUJ1 and ×600 for other inset images.