Effects of electroacupuncture and the retinoid X receptor (RXR) signalling pathway on oligodendrocyte differentiation in the demyelinated spinal cord of rats

OBJECTIVES In spinal cord demyelination, some oligodendrocyte precursor cells (OPCs) remain in the demyelinated region but have a reduced capacity to differentiate into oligodendrocytes. This study investigated whether 'Governor Vessel' (GV) electroacupuncture (EA) would promote the differentiation of endogenous OPCs into oligodendrocytes by activating the retinoid X receptor γ (RXR-γ)-mediated signalling pathway. METHODS Adult rats were microinjected with ethidium bromide (EB) into the T10 spinal cord to establish a model of spinal cord demyelination. EB-injected rats remained untreated (EB group, n=26) or received EA treatment (EB+EA group, n=26). A control group (n=26) was also included that underwent dural exposure without EB injection. After euthanasia at 7 days (n=5 per group), 15 days (n=8 per group) or 30 days (n=13 per group), protein expression of RXR-γ in the demyelinated spinal cord was evaluated by immunohistochemistry and Western blotting. In addition, OPCs derived from rat embryonic spinal cord were cultured in vitro, and exogenous 9-cis-RA (retinoic acid) and RXR-γ antagonist HX531 were administered to determine whether RA could activate RXR-γ and promote OPC differentiation. RESULTS EA was found to increase the numbers of both OPCs and oligodendrocytes expressing RXR-γ and RALDH2, and promote remyelination in the remyelinated spinal cord. Exogenous 9-cis-RA enhanced the differentiation of OPCs into mature oligodendrocytes by activating RXR-γ. CONCLUSIONS The results suggest that EA may activate RXR signalling to promote the differentiation of OPCs into oligodendrocytes in spinal cord demyelination.