Interstitial cells subjacent to the entorhinal region expressing somatostatin-28 immunoreactivity are susceptible to development of Alzheimer's disease-related cytoskeletal changes

Abstract

Interstitial cells are isolated neurons located in the infracortical white matter that are known to express neuropeptides. Twenty-four cases selected for the absence, slight (Braak stages I-II), moderate (Braak stages III-IV), or serious degree (Braak stages V-VI) of cortical neurofibrillary pathology were studied for the presence of Alzheimer's disease-related abnormal tau in interstitial cells of the entorhinal region. AT8-immunoreactive white matter neurons were observed in all Braak stages of cortical neurofibrillary pathology. Both normal-appearing neurons and neurons with degenerative changes in the cellular processes were observed. Normal-appearing cells were predominantly found in stages I and II, whereas degenerative interstitial cells numerically increased from stage I onwards. The normal-appearing cells were medium-sized (10-25 micro m), with ovoid, fusiform, triangular or multipolar cell bodies, and showed an extensive dendritic field, which was oriented perpendicular to the direction of the perforant pathway. Since the morphology of the AT8-immunopositive normal-appearing cells was similar to that reported on somatostatinergic interstitial cells subjacent to the entorhinal region, double-labeling with AT8 and anti-somatostatin-28 (S309) was performed. All AT8-immunoreactive normal-appearing interstitial cells revealed co-staining with somatostatin-28 antiserum, whereas some of the AT8-immunopositive cells with degenerative processes reacted positively and others negatively with S309. In summary, a distinctive interstitial cell type characterized by extensive arborization oriented perpendicular to the course of the perforant pathway and showing somatostatin expression is susceptible to developing the Alzheimer's disease-related cytoskeletal changes. Progression in cytoskeleton change is accompanied by loss of somatostatin.