Engineered micropillars to unveil oligodendrocyte responses to physical cues

Destruction of myelin internodes, oligodendrocyte (OL) apoptosis, and axonal degeneration characterize diseased or aged central nervous systems. While OLs can partially regenerate myelin sheaths, the remyelination process ultimately fails. Tissue mechanical and physical properties, such as stiffness and axonal curvature, play a role in this process. However, the complexity of existing models has hindered studies of OL mechanobiology. Here, a tissue-engineered model is presented to investigate the impact of stiffness and axonal diameter on OL myelination. The model consists of poly(dimethylsiloxane) micropillars with biologically relevant diameters (1-5 {micro}m), tunable rigidity, and amenable for surface functionalization. The optimized method enables the production of high-aspect-ratio, transparent micropillar arrays, in a reproducible and scalable system, serving as surrogate axons. Additionally, new protocols for quantifying myelin formation are introduced, which can be adapted to any myelination studies. Softer micropillars accelerate OL differentiation, while rigid ones promote the maintenance of mature OL states. Wrapping of OLs increased with micropillar diameter on rigid substrates, but not on softer ones, suggesting a complex interplay between curvature and rigidity. These processes involve calcium-sensitive channels, histone deacetylases, and microtubules dynamics. The proposed platform constitutes a versatile and user-friendly system, with applications from fundamental myelin research to drug discovery.