Journal Article
Post-COVID-19 Hyposmia Does Not Exhibit Main Neurodegeneration Markers in the Olfactory Pathway
Tommaso Schirinzi; Daniela Maftei; Riccardo Maurizi; Maria Albanese; Clara Simonetta; Roberta Bovenzi; Jacopo Bissacco; Davide Mascioli; Laura Boffa; Maria Grazia Di Certo; Francesca Gabanella; Beatrice Francavilla; Stefano Di Girolamo; Nicola Biagio Mercuri; Francesco Maria Passali; Roberta Lattanzi; Cinzia Severini
Molecular Neurobiology · Vol. 61, Issue 11 · pp. 8921-8927 · 2024
Abstract
The biological substrate of persistent post-COVID-19 hyposmia is still unclear. However, as many neurodegenerative diseases present with smell impairment at onset, it may theoretically reflect degeneration within the central olfactory circuits. However, no data still exist regarding the post-COVID-19 patients. As the olfactory neurons (ONs) mirror pathological changes in the brain, allowing for tracking the underlying molecular events, here, we performed a broad analysis of ONs from patients with persistent post-COVID-19 OD to identify traces of potential neurodegeneration. ONs were collected through the non-invasive brushing of the olfactory mucosa from ten patients with persistent post-COVID-19 hyposmia (lasting > 6 months after infection) and ten age/sex-matched controls. Immunofluorescence staining for protein quantification and RT-PCR for gene expression levels were combined to measure ONs markers of α-synuclein, amyloid-β, and tau pathology, axonal injury, and mitochondrial network. Patients and controls had similar ONs levels of oligomeric α-synuclein, amyloid-β peptide, tau protein, neurofilament light chain (NfL), cytochrome C oxidase subunit 3 (COX3), and the heat shock protein 60 (HSP60). Our findings thus did not provide evidence for synucleinopathy and amyloid-β mismetabolism or gross traces of neuronal injury and mitochondrial dysfunction within the olfactory system in the early phase of persistent post-COVID-19 hyposmia.