SARS-CoV-2 mainly affects non-neuronal gene expression resulting in altering olfactory function

Title: Non-neuronal expression of SARS-CoV-2 entry genes in the olfactory system suggests mechanisms underlying COVID-19–associated anosmia

Journal: Science Advances (2020) 31(6) Link: science.org/doi/full/10.1126/sciadv.abc5801

Comments: To this day, the COVID-19 pandemic remains a major global public health challenge. However, different from the initial confusion in COVID-19 outbreak, researchers have found the mechanisms of many common symptoms in COVID-19 through their unremitting efforts.

A common clinical symptom in COVID-19 is anosmia or odor perception disorder. The nasal cavity is covered by olfactory epithelium (OE) to feel sense of smell. OE consists of not only olfactory sensory neuron (OSN) but also non-neuronal cells such as globose basal cell (GBC), horizontal basal cell (HBC) and sustentacular cell (SUS). Despite such heterogeneity of the cell types in OE, it remains unclear what type of cells are affected directly by SARS-CoV-2. Analysis by single-cell RNA sequencing showed that the virus affected primarily non-neuronal cells such as SUS, which in turn induced inflammatory response and impair neuronal functions. In line with this, Through ACE2 immunostaining of a human olfactory mucosal biopsy, the resulting shows that ACE2 protein is detected in SUS cells and HBCs but not in OSNs. This once again confirms the previous conclusion that non-neuronal cell type infection, rather than olfactory sensory neuron, leads to anosmia and odor perception disorder in COVID-19 patients.