Histological and Immunohistochemical Observations of the Hippocampus in Clinically Established Neurodegenerative Disorders linked to Cause of Death

Moultrie, GA

Introduction: Neurodegeneration remains a very important subject of neuroscience research. While experimental studies have modeled conditions and attempted to provide insights, special opportunities exist in situations where clinically established conditions in the actual human brain can be investigated for the neurological, glial and molecular changes that characterize brain changes that produce pathological and neuronal aberrations that are manifested in these conditions. This study considers hippocampi in brains that have suffered clinically established neurodegeneration leading to death.

Methods: Twelve hippocampus samples [N=12] were obtained from 6 brains with clinically established cause of death being neurodegenerative disorders. In each case, whole hippocampi were carefully excised and preserved in 10% formalin. Tissues were processes using the formalin-fixed-paraffin-embedded technique, then sectioned at 5μm using a microtome. Sections were mounted on histological slides for staining and histochemical demonstrations. Tissues were demonstrated and observed using the hematoxylin and eosin [H&E] for brain tissue architcture; Beta amyloid for amyloid plaques; glial fibrillary acidic proteins [Gfap] antibody for Astrocytes; Cresyl fast violet stain for Nissl bodies in neurons; NeuN as a neuronal marker; and the Iba1 antibody for microglia. Images of tissues were scanned using the Motic scanner and observed at various magnifications for attributes of interest.

Results and Discussions: The H&E method could demonstrate pathological hallmarks in each of the conditions studied. For senile degeneration of the brain, the H&E shows neuritic plaques with dystrophic and dilated neurons. For dementia without behavioral disturbance, H&E stains shows homogenous pink bodies with surrounding halo. In the case of intracerebral hemorrhage, H&E shows tissue edema with mononuclear cell infiltrations. For the cerebrovascular disease, H&E shows multiple foci of perivascular and perineuronal edema with eosinophilic neurons (red neurons). Also, vascular thrombus and mononuclear cell infiltration are present. In the case of glioblastoma, H&E shows the accumulation of atypical neoplastic cells with marked hypercellularity, pleomorphism, and hyperchromasia. There is also prominent vascularity. Whereas, for the Picks’ disease, H&E shows dilated swollen neurons with basophilic inclusions within some neuronal cells.

Collectively, these H&E specific brain-changes in the studied diseases could help in defining histological changes to the hippocampus in these conditions. Furthermore, molecular or antibody-specific changes were also observed in certain conditions. Senile degeneration of the brain was positive for the beta-amyloid, showing numerous neuritic plaques with long pink filaments within the neuronal cytoplasm. In the same condition, GFAP shows evidence of degenerative astrocytes while the Cresyl fast violet stain shows evidence of degenerative neurons. Also, in dementia without behavioral disturbance, the anti-beta amyloid immunostain shows numerous neuritic plaques with neurofibrillary tangles while GFAP shows evidence of reactive astrocytes. In cerebrovascular disease, GFAP shows necrotic and reactive astrocytes. It is interesting to note that brain changes in other conditions including intracerebral hemorrhage, glioblastoma and Picks’ disease were only mainly demonstrated with the H&E technique.

Conclusion: Condition specific histopathological and immunohistochemical changes could help to define specific neurological diseases in the human brain hippocampus using H&E and complemented by immunohistochemical methods. Further quantitative analyses would enrich these findings.