Olfactory dysfunction in COVID-19: new insights into the underlying mechanisms

Area of Science:

• Neuroscience
• Infectious Diseases
• Cell Biology

Background:

• Olfactory dysfunction, including anosmia (loss of smell), is a common symptom of COVID-19.
• The precise mechanisms underlying smell loss in COVID-19 remain incompletely understood.
• Current hypotheses require further investigation to explain the observed olfactory alterations.

Purpose of the Study:

• To review and examine potential mechanisms contributing to olfactory dysfunction in COVID-19.
• To evaluate the plausibility of existing hypotheses regarding smell loss and alteration.
• To elucidate the cellular and molecular processes involved in COVID-19-related olfactory impairment.

Main Methods:

• Review of current scientific literature and hypotheses on COVID-19-induced olfactory dysfunction.
• Analysis of proposed cellular mechanisms involving olfactory epithelium support cells.
• Evaluation of the role of mucus composition and cilia function in olfactory signal transduction.

Main Results:

• The most plausible mechanism involves the death of infected support cells in the olfactory epithelium.
• This cell death alters mucus composition and causes retraction of cilia on olfactory receptor neurons.
• Lack of support cell-derived glucose may impair olfactory signal transduction, explaining rapid smell loss and recovery post-regeneration.

Conclusions:

• Support cell damage and subsequent impaired olfactory signal transduction are key mechanisms for COVID-19-related smell loss.
• Host immune responses may influence the duration of olfactory dysfunction but are unlikely to be the primary cause of acute anosmia.
• Understanding these mechanisms facilitates targeted therapeutic strategies for olfactory recovery.