An in vitro model to study myelin maintenance using small interfering ribonucleic acid in co-cultures of neurons and Schwann cells.

Résumé

The synthesis of the myelin sheath by Schwann cells in the peripheral nervous system is under the control of several transcription factors including Egr2. This latter factor is also involved in the maintenance of peripheral myelin. The present study was aimed to set up a new method to study the involvement of various genes in peripheral myelin maintenance.  We used modified self-delivery small interfering RNAs (siRNAs) to silence candidate genes in vitro, without using transfection reagents. These siRNAs were used on organotypic co-cultures of dorsal root ganglia (DRG) from embryonic rat. Control non-targeting siRNAs did not induce significant demyelination in co-cultures. 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 co-cultures. These results are in line with previous findings involving Egr2 in active myelin maintenance, which were obtained using conditional knockout experiments in mice. Our results constitute a proof of concept for the use of self-delivery siRNAs to investigate the molecular mechanisms of myelin maintenance in vitro.