Modeling myelin: A toolkit for exploring myelin's mysteries in vitro

Abstract

In the myelin field, there is a lack of reliable in vitro tools to study myelination, especially using human cells. In this issue of Developmental Cell, James et al. present a guide to generating human iPSC-derived "myelinoids"-3D models of myelination that reliably achieve mature myelin formation.

Figure 1.. Modeling mature myelin with myelinoids

(A) (Left) Schematic representing the architecture of a myelinated axon: node of Ranvier between myelinated segments (pink), paranode at the periphery of each myelin sheath (blue), and the intervening internode under the myelin sheath (green). Overlying myelin is yellow. (Right) Cross section of internode showing multiple myelin layers encircling an axon. The g-ratio is measured as the ratio of the diameter of the axon (d) to the diameter of the entire fiber (D). (B) Graphical summary depicting examples of outstanding questions that could be explored with the myelinoid model. From the top, clockwise around the “myelinoid” at the center: timeline of myelin formation in human cells, effects of genetic mutations affecting myelin, therapeutic compounds that promote remyelination, impact of environmental exposure on myelin, adaptive myelination, effects of other cell types on myelin, and role of myelin damage in neuron degeneration. Graphics created with BioRender.