Early diagnosis of Alzheimer's?

Potential Use of Exfoliated and Cultured Olfactory Neuronal Precursors for In Vivo Alzheimer's Disease Diagnosis: A Pilot Study

Histopathological hallmarks of dementia have been described postmortem in the brain of patients with Alzheimer's disease (AD). Tau, a microtubule associated protein, is abnormally arranged in neurofibrillary tangles. In living AD patients, total tau (t-tau) and hyperphosphorylated tau (p-tau) levels are increased in the cerebrospinal fluid obtained by lumbar puncture. Herein, we studied the t-tau and p-tau levels as well as the subcellular distribution of t-tau in olfactory neuronal precursors obtained by exfoliation of the nasal cavity of AD patients and control participants. Data showed that t-tau and p-tau levels were increased in cell homogenates from AD patients. Also, t-tau immunoreactivity was arranged in a punctate pattern in olfactory neuronal precursors derived from an AD participant with 5 years of evolution and in the oldest participants, either control subjects or those with Alzheimer's disease. Results support that exfoliated neuronal precursors have tau alterations demonstrated in postmortem brain and in the cerebrospinal fluid. This evidence and because the obtainment of olfactory neuronal precursors is a noninvasive procedure, detection of tau alterations shown here might be useful for an early diagnosis of AD-type dementia.

The olfactory system in Alzheimer’s disease: Pathology, pathophysiology and pathway for therapy

Olfaction is frequently mentioned as a “neglected sense”, although the olfactory system has several interesting and unique anatomical and physiological features. Olfactory involvement is present in several degenerative disorders, especially in Alzheimer’s disease (AD). The peripheral and central parts of the olfactory system are damaged even in the early stages of AD, manifesting in profound olfactory deficits. Besides the early pathology, the olfactory system may be involved in the pathogenesis of AD by providing a route of entry for pathological agents still unknown. In contrast to this olfactory vector hypothesis, the olfactory system can be used to deliver therapeutic agents in AD, such as nerve growth factor and insulin, by decreasing the side-effects of the therapy or providing a non-invasive method of delivery.

Histological markers in nasal mucosa of patients with Alzheimer's disease

Neuropathological changes such as dystrophic neurites and the presence of abnormal tau protein in the olfactory system, including primary sensory cells and nerve fibres have previously been demonstrated in nasal mucosa tissue of patients with Alzheimer's disease (AD). These changes were detected in autopsy-derived material from histopathologically confirmed AD cases as well as in biopsy tissue from clinical severely ill AD patients. To investigate the potential usefulness for the early diagnosis of AD, we obtained biopsy tissue from olfactory mucosa from 5 clinically mild to moderate AD patients and stained for the presence of tau or beta-amyloid by immunocytochemistry using a panel of specific antibodies. No positive staining was found in any of the cases. For comparison, post-mortem olfactory tissue from AD patients with severe neuropathological changes (widespread neurofibrillary tangles and amyloid in the brain) was investigated. In these severe cases, tau immunoreactivity was found in fine nerve fibres in the lamina propria and in a few olfactory epithelial cells. These results are consistent with other reports showing that cytoskeletal changes and tau pathology in the olfactory epithelium are not primary (or specific) features of AD and may occur predominantly in late stages of the disease.