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Chronic enhancement of the intrinsic growth capacity of sensory neurons combined with the degradation of inhibitory proteoglycans allows functional regeneration of sensory axons through the dorsal root entry zone in the mammalian spinal cord
Journal article   Open access   Peer reviewed

Chronic enhancement of the intrinsic growth capacity of sensory neurons combined with the degradation of inhibitory proteoglycans allows functional regeneration of sensory axons through the dorsal root entry zone in the mammalian spinal cord

Michael P Steinmetz, Kevin P Horn, Veronica J Tom, Jared H Miller, Sarah A Busch, Dileep Nair, Daniel J Silver and Jerry Silver
The Journal of neuroscience, v 25(35), pp 8066-8076
31 Aug 2005
PMID: 16135764
url
https://doi.org/10.1523/JNEUROSCI.2111-05.2005View
Published, Version of Record (VoR) Open

Abstract

Neurons, Afferent - drug effects Neurons, Afferent - cytology Spinal Cord - drug effects Spinal Cord - growth & development Nerve Regeneration - physiology Cells, Cultured Axons - drug effects Proteoglycans - metabolism Rats Axons - physiology Ganglia, Spinal - cytology Neurons, Afferent - physiology Rats, Sprague-Dawley Zymosan - pharmacology Animals Nerve Regeneration - drug effects Female Ganglia, Spinal - growth & development Spinal Cord - cytology Ganglia, Spinal - drug effects
Peripherally conditioned sensory neurons have an increased capacity to regenerate their central processes. However, even conditioned axons struggle in the presence of a hostile CNS environment. We hypothesized that combining an aggressive conditioning strategy with modification of inhibitory reactive astroglial-associated extracellular matrix could enhance regeneration. We screened potential treatments using a model of the dorsal root entry zone (DREZ). In this assay, a gradient of inhibitory chondroitin sulfate proteoglycans (CSPGs) stimulates formation of dystrophic end bulbs on adult sensory axons, which mimics regeneration failure in vivo. Combining inflammation-induced preconditioning of dorsal root ganglia in vivo before harvest, with chondroitinase ABC (ChABC) digestion of proteoglycans in vitro allows for significant regeneration across a once potently inhibitory substrate. We then assessed regeneration through the DREZ after root crush in adult rats receiving the combination treatment, ChABC, or zymosan pretreatment alone or no treatment. Regeneration was never observed in untreated animals, and only minimal regeneration occurred in the ChABC- and zymosan-alone groups. However, remarkable regeneration was observed in a majority of animals that received the combination treatment. Regenerated fibers established functional synapses, as demonstrated electrophysiologically by the presence of an H-reflex. Two different postlesion treatment paradigms in which the timing of both zymosan and ChABC administration were varied after injury were ineffective in promoting regeneration. Therefore, zymosan pretreatment, but not posttreatment, of the sensory ganglia, combined with ChABC modification of CSPGs, resulted in robust and functional regeneration of sensory axons through the DREZ after root injury.

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Domestic collaboration
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Neurosciences
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