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Review
. 2017 Jun 23:652:41-49.
doi: 10.1016/j.neulet.2016.11.003. Epub 2016 Nov 3.

The age factor in axonal repair after spinal cord injury: A focus on neuron-intrinsic mechanisms

Cédric G Geoffroy  1 , Jessica M Meves  2 , Binhai Zheng  3
Affiliations
Review

The age factor in axonal repair after spinal cord injury: A focus on neuron-intrinsic mechanisms

Cédric G Geoffroy et al. Neurosci Lett. .

Abstract

Age is an important consideration for recovery and repair after spinal cord injury. Spinal cord injury is increasingly affecting the middle-aged and aging populations. Despite rapid progress in research to promote axonal regeneration and repair, our understanding of how age can modulate this repair is rather limited. In this review, we discuss the literature supporting the notion of an age-dependent decline in axonal growth after central nervous system (CNS) injury. While both neuron-intrinsic and extrinsic factors are involved in the control of axon growth after injury, here we focus on possible intrinsic mechanisms for this age-dependent decline.

Keywords: Aging; Axon growth; Axon regeneration; CNS injury; Neuron-intrinsic; Spinal cord injury.

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Figures

Figure 1
Figure 1. Spinal Cord Injury and Age
A: Average Age of Incidence for SCI increased from ~29 in the 1970s to ~42 since 2010 in the US (from National Spinal Cord Injury Statistical Center); B–C: Age distribution for people who live with a paralyzing spinal cord injury in the US. (Adapted From One Degree of Separation, 2009, Christopher and Dana Reeve Foundation).
Figure 2
Figure 2. Age-dependent decline in axon regeneration after spinal cord injury
Age at the time of PTEN deletion influences axon regeneration of the CST 6 weeks after T8 dorsal hemisection. In 12-month old WT animals (B) few CST axons are found at close proximity of the injury, similar to young WT animals (A). After PTEN deletion (C–D), a high number of CST axons grow rostral to the lesion all the way to the injury border, independently of the age PTEN deletion occurs. However, only animals with PTEN deleted at a young age (C) present strong regeneration caudal to the lesion site (Adapted from Geoffroy et al. 2016).
Figure 3
Figure 3. Neuronal intrinsic changes occurring with age
Diagram of known or speculated intrinsic changes occurring with aging in neurons that may contribute to the age-dependent decline in axon growth. These changes include, but are not limited to, differences in signaling pathways, cytoskeleton composition, axonal transport and mitochondria activity.
Figure 4
Figure 4. Schematic representation of possible molecular pathways involved in the age-dependent regeneration decline
Simplified diagram of molecular pathways known or speculated to alter with aging, and potential interactions between them.
See this image and copyright information in PMC

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