Probing the influence of myelin and glia on the tensile properties of the spinal cord

Abstract

Although glia have been historically classified as the structurally supporting cells of the central nervous system, their role in tissue mechanics is still largely unstudied. The influence of myelin and glia on the mechanical properties of spinal cord tissue was examined by testing embryonic day 18 chick embryo spinal cords in uniaxial tension following disruption of the glial matrix using either ethidium bromide (EB) or an antibody against galactocerebroside (alphaGalC) in the presence of complement. Demyelination was confirmed by myelin basic protein immunoreactivity and quantified using osmium tetroxide staining. A substantial loss of astrocytes and oligodendrocytes concurrent with demyelination was observed following EB injection but not alphaGalC injection. No morphological changes were observed following injection of saline or IgG with complement as controls for EB and alphaGalC. Demyelinated spinal cords demonstrated significantly lower stiffness and ultimate tensile stress than myelinated spinal cords. No significant differences were observed in the tensile response between the two demyelinating protocols. The results demonstrate that the glial matrix provides significant mechanical support to the spinal cord, and suggests that myelin and cellular coupling of axons via the glial matrix in large part dictates the tensile response of the tissue.

How Klingler’s dissection permits exploration of brain structural connectivity? An electron microscopy study of human white matter

“…Indeed, even if it has been shown that both neurons and glial cells are very soft (Lu et al 2006), recent works have demonstrated that demyelination significantly lowers axonal stiffness and ultimate tensile stress (Shreiber et al 2008). It is then probable that myelin sheaths mechanically protect axons both during Klingler's preparation and dissection.…”

A computational model coupling mechanics and electrophysiology in spinal cord injury

“…The lack of protective myelin of the NRs (Shreiber et al 2009), recent findings highlighting the primordial role of blast-damaged ion channels in neurobehavioral deficits (Park et al 2013), and the Na v leak observed during trauma (Wang et al 2009) suggest the need for a strain-based damage criterion specific to the ion channels' properties. This Na v (and in this model, K v ) leak has been rationalized by a hyperpolarizing shift (or left-shift) of transient current operational range (Wang et al 2009) in the conductance of the ion channel.…”

“…Despite observations of stress concentrations at the NRs during stretch injury, the relation between axonal, myelin and glial stiffnesses, as well as the role of oligodendrocytes and paranodal axo-glial adhesions in the "glueing" of all three components remain largely controversial (Shreiber et al 2009). As a consequence and in the absence of more conclusive evidences, the case where all the strain is sustained equally by the NRs and the IRs is considered here (i.e., v = x).…”

Materials and technologies for soft implantable neuroprostheses

“…Even on a larger scale, this result seems to hold 61 . The difference between white and grey matter might stem from the lower cell density in the former 53 , which is structurally dependent on the oligodendrocyte connectivity, because demyelination in the rat spinal cord leads to lower stiffness and tensile stress 62 . Lower stiffness has also been reported for demyelinated regions in the murine brain parenchyma measured with magnetic resonance elastography (MRE) 63 .…”