Neurofilament Transport in Axonal Regeneration

Abstract Introduction Stem cell therapy using neural progenitor cells (NPCs) shows promise in mitigating the debilitating effects of spinal cord injury (SCI). Notably, myelin stimulates axonal regeneration from mammalian NPCs. This led us to hypothesize that myelin-associated proteins may contribute to axonal regeneration from NPCs. Methods We conducted an R-based bioinformatics analysis to identify key gene(s) that may participate in myelin-associated axonal regeneration from murine NPCs, which identified the serine protease myelin basic protein (Mbp). We employed E12 murine NPCs, E14 rat NPCs, and human iPSC-derived Day 1 NPCs (D1 hNPCs) with or without CRISPR/Cas9-mediated Mbp knockout in combination with rescue L1-70 overexpression, constitutively-active VP16-PPARγ2, or the PPARγ agonist ciglitazone. A murine dorsal column crush model of SCI utilizing porous collagen-based scaffolding (PCS)-seeded murine NPCs with or without stable Mbp overexpression was used to assess locomotive recovery and axonal regeneration in vivo. Results Myelin promotes axonal outgrowth from NPCs in an Mbp-dependent manner and that Mbp’s stimulatory effects on NPC neurite outgrowth are mediated by Mbp’s production of L1-70. Furthermore, we determined that Mbp/L1-70’s stimulatory effects on NPC neurite outgrowth are mediated by PPARγ-based repression of neuron differentiation-associated gene expression and PPARγ-based Erk1/2 activation. In vivo, PCS-seeded murine NPCs stably overexpressing Mbp significantly enhanced locomotive recovery and axonal regeneration in post-SCI mice. Conclusions We discovered that Mbp supports axonal regeneration from mammalian NPCs through the novel Mbp/L1cam/Pparγ signaling pathway. This study suggests that bioengineered, NPC-based interventions can promote axonal regeneration and functional recovery post-SCI.

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Chemotropic guidance facilitates axonal regeneration and synapse formation after spinal cord injury

Nature Neuroscience ◽

10.1038/nn.2365 ◽

2009 ◽

Vol 12 (9) ◽

pp. 1106-1113 ◽

Cited By ~ 142

Author(s):

Laura Taylor Alto ◽

Leif A Havton ◽

James M Conner ◽

Edmund R Hollis II ◽

Armin Blesch ◽

...

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Axonal Regeneration ◽

Synapse Formation ◽

Cord Injury

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Descending propriospinal neurons mediate restoration of locomotor function following spinal cord injury

Journal of Neurophysiology ◽

10.1152/jn.00544.2016 ◽

2017 ◽

Vol 117 (1) ◽

pp. 215-229 ◽

Cited By ~ 10

Author(s):

Katelyn N. Benthall ◽

Ryan A. Hough ◽

Andrew D. McClellan

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Axonal Regeneration ◽

Central Pattern Generators ◽

Burst Activity ◽

Compensatory Mechanism ◽

Spinal Lesions ◽

Cord Injury ◽

Recovery Times ◽

Indirect Activation

Following spinal cord injury (SCI) in the lamprey, there is virtually complete recovery of locomotion within a few weeks, but interestingly, axonal regeneration of reticulospinal (RS) neurons is mostly limited to short distances caudal to the injury site. To explain this situation, we hypothesize that descending propriospinal (PS) neurons relay descending drive from RS neurons to indirectly activate spinal central pattern generators (CPGs). In the present study, the contributions of PS neurons to locomotor recovery were tested in the lamprey following SCI. First, long RS neuron projections were interrupted by staggered spinal hemitransections on the right side at 10% body length (BL; normalized from the tip of the oral hood) and on the left side at 30% BL. For acute recovery conditions (≤1 wk) and before axonal regeneration, swimming muscle burst activity was relatively normal, but with some deficits in coordination. Second, lampreys received two spaced complete spinal transections, one at 10% BL and one at 30% BL, to interrupt long-axon RS neuron projections. At short recovery times (3–5 wk), RS and PS neurons will have regenerated their axons for short distances and potentially established a polysynaptic descending command pathway. At these short recovery times, swimming muscle burst activity had only minor coordination deficits. A computer model that incorporated either of the two spinal lesions could mimic many aspects of the experimental data. In conclusion, descending PS neurons are a viable mechanism for indirect activation of spinal locomotor CPGs, although there can be coordination deficits of locomotor activity. NEW & NOTEWORTHY In the lamprey following spinal lesion-mediated interruption of long axonal projections of reticulospinal (RS) neurons, sensory stimulation still elicited relatively normal locomotor muscle burst activity, but with some coordination deficits. Computer models incorporating the spinal lesions could mimic many aspects of the experimental results. Thus, after disruption of long-axon projections from RS neurons in the lamprey, descending propriospinal (PS) neurons appear to be a viable compensatory mechanism for indirect activation of spinal locomotor networks.

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Nerve Growth Factor Enhances Nerve Regeneration through Fibronectin Grafts

Journal of Hand Surgery (European Volume) ◽

10.1016/s0266-7681(96)80058-1 ◽

1996 ◽

Vol 21 (4) ◽

pp. 514-522 ◽

Cited By ~ 77

Author(s):

I. H. WHITWORTH ◽

R. A. BROWN ◽

C. J. DORÉ ◽

P. ANAND ◽

C. J. GREEN ◽

...

Keyword(s):

Image Analysis ◽

Nerve Growth Factor ◽

Growth Factor ◽

Schwann Cell ◽

Nerve Regeneration ◽

Axonal Regeneration ◽

Cell Regeneration ◽

Nerve Growth ◽

Computerized Image Analysis ◽

Immunohistochemical Techniques

Soluble fibronectin and nerve growth factor (NGF) promote axonal regeneration when placed in silicone tubes. We investigated the ability of orientated fibronectin mats to bind and release bioactive NGF and the possibility of augmenting axonal regeneration following axotomy by using fibronectin conduits impregnated with NGF. The release of NGF was quantified using a fluorometric ELISA and bioactivity confirmed with a neuronal culture bioassay. Immunohistochemical techniques and computerized image analysis were used to assess the rate and volume of axonal and Schwann cell regeneration. The delivery of NGF to the site of injury produced an increase in the rate ( P≤0.007) and volume ( P≤0.004) of both axonal and Schwann cell regeneration when compared to conduits of plain fibronectin. We conclude that the local delivery of NGF by impregnated fibronectin conduits enhances axonal regeneration.

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