Severe histomorphological alterations in post-mortem olfactory glomeruli in Alzheimer's disease

Novel, standardized sample collection from the brain-nose interface

BACKGROUND

Diagnostics for neurodegenerative diseases lack non-invasive approaches suitable for early-stage biochemical screening and routine examination of neuropathology. Biomarkers of neurodegenerative diseases pass through the brain-nose interface (BNI) and accumulate in nasal secretion. Sample collection from the brain-nose interface presents a compelling prospect as basis for a non-invasive molecular diagnosis of neuropathologies. Here, we evaluated a novel medical device (nosecollect) that is tailored for the standardized collection of nasal secretion samples from BNI, focusing on its sample collection safety and efficiency.

METHOD

A class I medical device (nosecollect) was developed, to enable the standardized collection of nasal secretion exclusively from BNI in a user-friendly, safe, and comfortable manner. We performed a clinical study to test the collection device on a heterogenous cohort (n = 923) at 8 study centers and evaluated its performance to collect sufficient sample volume from the targeted BNI area, its safety and tolerability. Samples were collected by trained medical personnel (medical doctors and nurses).

RESULTS

Nosecollect gathered a mean volume of 452 ± 317 μl from the BNI. Successful positioning of the absorption material (AM) in the BNI was observed in 95 % of the cases. Pain level/level of discomfort and occurrences of adverse events remained minimal (visual analogue scale (VAS) = 1.97 ± 1.99 (range 0-10), adverse events: 1 %, no serious adverse events). Analysis of the nasal secretion sample identified detectable levels of CNS biomarkers in it.

CONCLUSIONS

The precision and ergonomic design of nosecollect ensures a standardized, targeted and safe collection of non-diluted nasal secretion samples from BNI, thus outperforming traditional methods such as swabs, lavage etc which are not customized for accessing undiluted samples from BNI. In addition, the device offers a non-invasive and accessible approach for the acquisition of nasal secretion samples from BNI, signifying a crucial step in the future development of a BNI-based non-invasive diagnostic platform for neurodegenerative diseases.

Progressive Spread of Beta-amyloid Pathology in an Olfactory-driven Amyloid Precursor Protein Mouse Model

Years before Alzheimer's disease (AD) is diagnosed, patients experience an impaired sense of smell, and β-amyloid plaques accumulate within the olfactory mucosa and olfactory bulb (OB). The olfactory vector hypothesis proposes that external agents cause β-amyloid to aggregate and spread from the OB to connected downstream brain regions. To reproduce the slow accumulation of β-amyloid that occurs in human AD, we investigated the progressive accumulation of β-amyloid across the brain using a conditional mouse model that overexpresses a humanized mutant form of the amyloid precursor protein (hAPP) in olfactory sensory neurons. Using design-based stereology, we show the progressive accumulation of β-amyloid plaques within the OB and cortical olfactory regions with age. We also observe reduced OB volumes in these mice when hAPP expression begins prior-to but not post-weaning which we tracked using manganese-enhanced MRI. We therefore conclude that the reduced OB volume does not represent progressive degeneration but rather disrupted OB development. Overall, our data demonstrate that hAPP expression in the olfactory epithelium can lead to the accumulation and spread of β-amyloid through the olfactory system into the hippocampus, consistent with an olfactory system role in the early stages of β-amyloid-related AD progression.

Non-Invasive Nasal Discharge Fluid and Other Body Fluid Biomarkers in Alzheimer’s Disease

The key to current Alzheimer’s disease (AD) therapy is the early diagnosis for prompt intervention, since available treatments only slow the disease progression. Therefore, this lack of promising therapies has called for diagnostic screening tests to identify those likely to develop full-blown AD. Recent AD diagnosis guidelines incorporated core biomarker analyses into criteria, including amyloid-β (Aβ), total-tau (T-tau), and phosphorylated tau (P-tau). Though effective, the accessibility of screening tests involving conventional cerebrospinal fluid (CSF)- and blood-based analyses is often hindered by the invasiveness and high cost. In an attempt to overcome these shortcomings, biomarker profiling research using non-invasive body fluid has shown the potential to capture the pathological changes in the patients’ bodies. These novel non-invasive body fluid biomarkers for AD have emerged as diagnostic and pathological targets. Here, we review the potential peripheral biomarkers, including non-invasive peripheral body fluids of nasal discharge, tear, saliva, and urine for AD.

Seed-induced Aβ deposition alters neuronal function and impairs olfaction in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is characterized by the accumulation of amyloid-β (Aβ) which ultimately forms plaques. These Aβ deposits can be induced in APP transgenic mouse models by prion-like seeding. It has been widely accepted that anosmia and hyposmia occur during the early stages of AD, even before cognitive deficits are present. In order to determine the impact of seed-induced Aβ deposits on olfaction, we performed intracerebral injections of seed-competent brain homogenate into the olfactory bulb of young pre-depositing APP transgenic mice. Remarkably, we observed a dramatic olfactory impairment in those mice. Furthermore, the number of newborn neurons as well as the activity of cells in the mitral cell layer was decreased. Notably, exposure to an enriched environment reduced Aβ seeding, vivified neurogenesis and most importantly reversed olfactory deficits. Based on our findings, we conclude that altered neuronal function as a result of induced Aβ pathology might contribute to olfactory dysfunction in AD.