Loss of Neocortical Oligodendrocytes in Parkinson's Disease Patients-A Stereological Study

Parkinson's disease (PD) is a neurodegenerative disorder, clinically characterized by motor- and non-motor symptoms. Misfolding of alpha-synuclein into pathological substrates, followed by neuronal spread, seems to be a key event in the spatiotemporal course of the disease. Previously, few studies have yielded insight into altered cell numbers in post-mortem brains from PD patients. Beside nigral neuronal loss, no quantitative studies have reported significant loss of neurons in PD brains, suggesting that the neuropathological progress in PD have minor impact on neuronal survival outside of the substantia nigra. Reports further show impairment of intra- and inter-cortical white matter tracts, observations that signify a role of oligodendrocytes in PD pathogenesis. Hence, our objective of the present study was to investigate oligodendroglia morphology (total numbers and volumes) in the neocortex of post-mortem brains from PD patients and control subjects using stereological methods. Our findings show an explicit 34% reduction in the total number of oligodendrocytes in the frontal cortex of PD patients, with no such changes in the other cortical lobes. Furthermore, the results displayed no group differences in the mean volume of oligodendrocytes in the entire neocortex or its subregions. The reduction in frontal oligodendrocytes may be related to the demonstrated impairment of white matter tracts, however, further studies are needed to clarify the mechanistic and functional relevance of oligodendropathy in PD.