The synthesis of the myelin sheath by Schwann cells in the peripheral nervous system is controlled by several transcription factors including Early Growth Response 2 gene (Egr2). This latter factor is also involved in the maintenance of peripheral myelin. The current study was aimed to set up a new method to study the involvement of various genes in peripheral myelin maintenance. Modified self-delivery small interfering RNAs (siRNAs) are used to silence candidate genes in vitro, without using transfection reagents. These siRNAs were used on organotypic cocultures of neurons and Schwann cells contained in dorsal root ganglia (DRG).
DRG were extracted from embryonic rat. Control non-targeting siRNAs tested did not induce significant demyelination in cocultures. Anti-Egr2 siRNAs down-regulated in vitro their target gene expression by 60%. Furthermore, treatment with anti-Egr2 siRNAs resulted in abnormalities of the myelin sheaths in cocultures. The current results are in line with previous findings involving Egr2 in active myelin maintenance, which were obtained using conditional knockout experiments in mice. The results obtained constitute a proof of concept for the use of self-delivery siRNAs to investigate the molecular mechanisms of myelin maintenance in vitro.

Dorsal root ganglion, cell culture, Schwann cells, myelin maintenance