Cholesterol Depletion Regulates Axonal Growth and Enhances Central and Peripheral Nerve Regeneration

Abstract

Axonal growth during normal development and axonal regeneration rely on the action of many receptor signaling systems and complexes, most of them located in specialized raft membrane microdomains with a precise lipid composition. Cholesterol is a component of membrane rafts and the integrity of these structures depends on the concentrations present of this compound. Here we explored the effect of cholesterol depletion in both developing neurons and regenerating axons. First, we show that cholesterol depletion in vitro in developing neurons from the central and peripheral nervous systems increases the size of growth cones, the density of filopodium-like structures and the number of neurite branching points. Next, we demonstrate that cholesterol depletion enhances axonal regeneration after axotomy in vitro both in a microfluidic system using dissociated hippocampal neurons and in a slice-coculture organotypic model of axotomy and regeneration. Finally, using axotomy experiments in the sciatic nerve, we also show that cholesterol depletion favors axonal regeneration in vivo . Importantly, the enhanced regeneration observed in peripheral axons also correlated with earlier electrophysiological responses, thereby indicating functional recovery following the regeneration. Taken together, our results suggest that cholesterol depletion per se is able to promote axonal growth in developing axons and to increase axonal regeneration in vitro and in vivo both in the central and peripheral nervous systems.

Changes in the transcriptional fingerprint of satellite glial cells following peripheral nerve injury

“…Supporting this hypothesis, Amsalem, Poilbout, Ferracci, Delmas, and Padilla () demonstrated how inflammation lowers the cholesterol content in DRG neuron cultures and that pharmacological depletion of neuronal cholesterol causes sensitization of nociceptive neurons, promoting mechanical and thermal hyperalgesia by activation of voltage‐gated Nav1.9 channels. Furthermore, it was recently described how depletion of cholesterol promotes growth in developing neurons and increases axonal regeneration in the peripheral nervous systems (Roselló‐Busquets et al, ). It may, therefore, be speculated that reduced cholesterol synthesis by SGC contributes to lowering cholesterol levels in injured sensory neurons with the purpose of promoting neuronal repair and axonal regeneration, however at the cost of increasing nociceptive activity.…”

Nystatin Regulates Axonal Extension and Regeneration by Modifying the Levels of Nitric Oxide

“…Previous results showed that Nystatin increases axon regeneration post-axotomy in primary cell cultures of hippocampal neurons (Roselló-Busquets et al, 2019). The ability of axons to regenerate is lost in adult CNS neurons (He and Jin, 2016;Curcio and Bradke, 2018;Fawcett, 2019).…”

“…Consistent with the lack of action on NO production, the effect of highest doses of Nystatin (10 µM and 25 µM) on growth cone area and filopodia density is independent of NOS inhibition (Figures 6E-H). Methyl-betacyclodextrin (MβCD) is a compound that, similar to Nystatin, extracts cholesterol from cell membranes, increasing growth cone area and filopodia number (Roselló-Busquets et al, 2019).…”

“…As a consequence, Nystatin has been widely used to disrupt and study the cellular function of lipid rafts. Lipid rafts are membrane microdomains enriched in cholesterol and sphingolipids, that facilitate the compartmentalization of signaling proteins, working as platforms for spatial and temporal regulation of the cytoskeleton, membrane anchoring, and cell adhesion, controlling the motility of growth cones (Guirland and Zheng, 2007), and the regenerative properties of lesioned axons (Tassew et al, 2014;Roselló-Busquets et al, 2019). The extended clinical use of Nystatin, together with its ability to affect the organization of lipid rafts, makes it an ideal candidate to explore its function as a possible therapeutic agent for the treatment of spinal cord lesions.…”

Neuromuscular Activity Induces Paracrine Signaling and Triggers Axonal Regrowth after Injury in Microfluidic Lab-On-Chip Devices

“…Additionally, some studies have also reported different ways to lesion axons on lab-on-chip devices (i.e., [7]). However, these studies mainly used the devices to support in vivo experimentation and did not take advantage of the full potential of these platforms (see [8] for a recent example). Concerning PN-modelling, several methods were developed to generate contractile myotubes on lab-on-chip devices (i.e., [9][10][11]).…”