Integrated age-related immunohistological changes occur in human olfactory epithelium and olfactory bulb

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • Mira Fitzek - , University Hospital Carl Gustav Carus Dresden (Author)
  • Parthkumar K Patel - , Tufts University (Author)
  • Peter D Solomon - , Tufts University (Author)
  • Brian Lin - , Tufts University (Author)
  • Thomas Hummel - , Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Carl Gustav Carus Dresden (Author)
  • James E Schwob - , Tufts University (Author)
  • Eric H Holbrook - , Tufts University (Author)

Abstract

Olfactory epithelium (OE) is capable of lifelong regeneration due to presence of basal progenitor cells that respond to injury or neuronal loss with increased activity. However, this capability diminishes with advancing age and a decrease in odor perception in older individuals is well established. To characterize changes associated with age in the peripheral olfactory system, an in-depth analysis of the OE and its neuronal projections onto the olfactory bulb (OB) as a function of age was performed. Human olfactory tissue autopsy samples from 36 subjects with an average age of 74.1 years were analyzed. Established cell type-specific antibodies were used to identify OE component cells in whole mucosal sheets and epithelial sections as well as glomeruli and periglomerular structures in OB sections. With age, a reduction in OE area occurs across the mucosa progressing in a posterior-dorsal direction. Deterioration of the olfactory system is accompanied with diminution of neuron-containing OE, mature olfactory sensory neurons (OSNs) and OB innervation. On an individual level, the neuronal density within the epithelium appears to predict synapse density within the OB. The innervation of the OB is uneven with higher density at the ventral half that decreases with age as opposed to stable innervation at the dorsal half. Respiratory metaplasia, submucosal cysts, and neuromata, were commonly identified in aged OE. The finding of respiratory metaplasia and aneuronal epithelium with reduction in global basal cells suggests a progression of stem cell quiescence as an underlying pathophysiology of age-related smell loss in humans. KEY POINTS: A gradual loss of olfactory sensory neurons with age in human olfactory epithelium is also reflected in a reduction in glomeruli within the olfactory bulb. This gradual loss of neurons and synaptic connections with age occurs in a specific, spatially inhomogeneous manner. Decreasing mitotically active olfactory epithelium basal cells may contribute to age-related neuronal decline and smell loss in humans.

Details

Original languageEnglish
Pages (from-to)2154-2175
Number of pages22
JournalThe Journal of comparative neurology
Volume530
Issue number12
Publication statusPublished - Aug 2022
Peer-reviewedYes

External IDs

PubMedCentral PMC9232960
Scopus 85127687919
unpaywall 10.1002/cne.25325
WOS 000779675700001
Mendeley 5d49d963-2847-396d-a9ed-bd9cddf973f0
ORCID /0000-0001-9713-0183/work/146645232

Keywords

ASJC Scopus subject areas

Keywords

  • Aged, Anosmia, Humans, Metaplasia, Olfactory Bulb/chemistry, Olfactory Mucosa/injuries, Olfactory Receptor Neurons/physiology, horizontal basal cells, neuronal aging, globose basal cells, OMP, whole mount staining, autopsy, immunofluorescence