Node of Ranvier formation on motoneurons in vitro.

One of the most significant interactions between Schwann cells and neurons is myelin sheath formation. Myelination is a vertebrate adaptation that enables rapid conduction of action potentials without a commensurate increase in axon diameter. In vitro neuronal systems provide a unique modality to study both factors influencing myelination and diseases associated with myelination. Currently, no in vitro system for motoneuron myelination by Schwann cells has been demonstrated. This work details the myelination of motoneuron axons by Schwann cells, with complete Node of Ranvier formation, in a defined in vitro culture system. This defined system utilizes a novel serum-free medium in combination with the non-biological substrate, N-1[3 (trimethoxysilyl) propyl] diethylenetriamine (DETA). The myelinated segments and nodal proteins were visualized and quantified using confocal microscopy. This defined system provides a highly controlled, reproducible model for studying Schwann cell interactions with motoneurons as well as the myelination process and its effect on neuronal plasticity. Furthermore, an in vitro system that would allow studies of motoneuron myelination would be beneficial for understanding peripheral demyelinating neuropathies such as diabetes induced peripheral neuropathy and could lead to a better understanding of CNS demyelinating diseases like multiple sclerosis, as well as neuromuscular junction maturation and maintenance.