A three-dimensional human nerve model reveals how the myelin sheath relates to impulse conduction velocity

A three-dimensional human nerve model reveals how the myelin sheath relates to impulse conduction velocity

On 26 August, researchers described HydroMEA in an article. This chip allows human sensory neurons to grow in a gel alongside Schwann cells. These peripheral nervous system cells produce myelin, the sheath that surrounds the long projections of neurons, known as axons. A microelectrode array made it possible to measure impulse conduction velocity.

In a 2025 study, some of the HydroMEA authors had already used microchannels and electrodes to isolate responses from individual human sensory axons. In the new model, they added a three-dimensional gel with a stiffness close to that of nerve tissue, along with Schwann cells.

The researchers placed neurons in the center of the chip and Schwann cells on either side. Narrow channels kept the neuronal cell bodies in the central compartment and guided the axons over the electrodes. One electrode stimulated the end of the axon bundle, while the others recorded the arrival of the response. The researchers calculated conduction velocity by dividing the path length by the delay.

At the final timepoint, mean conduction velocity was 0,8 m/s in the culture containing Schwann cells and 0,5 m/s in the culture containing neurons alone. Images of the system show myelin sheaths surrounding the axons.

The authors exchanged the media between the cultures. The difference in conduction velocity remained. They therefore attribute it to direct interactions between the cells and to changes around the axon, while attributing the later increase in velocity to myelination.

The authors next propose using this system to model myelin loss and to compare drugs or electrical stimulation by measuring conduction velocity. This approach would make it possible to relate the visible sheath to the axon's ability to conduct an impulse.