Oligodendroglial Response in the Spinal Cord in TDP-43 Proteinopathy with Motor Neuron Involvement

<b><i>Background:</i></b> TDP-43 proteinopathies represent a spectrum of neurodegenerative disorders. Variable clinical presentations including frontotemporal dementia, amyotrophic lateral sclerosis (ALS) and mixed forms are associated with the spatial heterogeneity of the TDP-43 pathology. Recent studies have emphasized the role of oligodendrocytes in the pathogenesis of ALS. <b><i>Objective:</i></b> To evaluate whether TDP-43 proteinopathies are associated with an oligodendroglial response. <b><i>Methods:</i></b> We performed a study on 7 controls and 10 diseased patients with spinal cord involvement. Using the oligodendroglia-specific antibody TPPP/p25, we assessed oligodendrocyte density in the lateral corticospinal tracts (LCSs) along with the presence of perineuronal oligodendrocytes (PNOGs) in the anterior horns. We performed a densitometry of myelin basic protein (MBP) immunoreactivity. The numbers of TDP-43 and p62 immunoreactive inclusions were counted in both the LCSs and the anterior horns. <b><i>Results:</i></b> Double immunolabeling confirmed that oligodendrocytes harbor TDP-43 inclusions. In the LCSs, MBP density, but not the number of oligodendrocytes, was decreased in the diseased group. However, oligodendrocyte counts in the LCS correlated positively, and the density of MBP inversely, with the number of neuronal inclusions in the anterior horn, suggestive of a compensatory response of oligodendrocytes. The number of neurons with PNOGs correlated with the amount of inclusions. <b><i>Conclusion:</i></b> Our study further emphasizes the importance of oligodendroglia in the pathogenesis of TDP-43 proteinopathies with spinal cord involvement.