White matter injury induced by perinatal exposure to glutaric acid

Glutaric acid (GA) is a neurotoxic metabolite that accumulates in the CNS of patients with glutaric acidemia-I (GA-I), a neurometabolic disease caused by deficient activity of glutaryl-CoA dehydrogenase. Most GA-I patients display characteristic CNS lesions, mainly in the gray and white matter of basal ganglia and cerebral cortex. Neurons and astrocytes are believed to be vulnerable to millimolar concentrations of GA. However, little is known about the effects of GA on oligodendrocytes (OL) and the myelination process in the postnatal brain. Here, we show that a single intracerebroventricular administration of GA to rat neonatal pups induced a selective and long-lasting myelination failure in the striatum but no deleterious effect in the myelination of the corpus callosum. At 45 days post-GA injection, the myelinated area of striatal axonal bundles was decreased by 35 %, and the expression of myelin basic protein and myelin-associated glycoprotein (MAG) reduced by 25 and 60 %, respectively. This was accompanied by long lasting cytopathology features in MAG and CC-1-expressing OLs, which was confirmed by transmission electron microscopy. Remarkably, GA did not induce acute loss of pre-OLs in the striatum as assessed by NG2 or PDGFRα immunohistochemistry, suggesting an indirect and progressive mechanism for OL damage. In accordance, GA-induced white matter injury was restricted to the striatum and associated to GA-induced astrocytosis and neuronal loss. In conclusion, the current evidence indicates a pathogenic mechanism by which GA can permanently affect myelin status.