SARS-CoV-2 infection of sustentacular cells disrupts olfactory signaling pathways
Abhishek Kumar Verma, Jian Zheng, David K. Meyerholz, Stanley Perlman
Abhishek Kumar Verma, Jian Zheng, David K. Meyerholz, Stanley Perlman
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Research Article COVID-19

SARS-CoV-2 infection of sustentacular cells disrupts olfactory signaling pathways

Abstract

Loss of olfactory function has been commonly reported in SARS-CoV-2 infections. Recovery from anosmia is not well understood. Previous studies showed that sustentacular cells, and occasionally olfactory sensory neurons (OSNs) in the olfactory epithelium (OE), are infected in SARS-CoV-2–infected patients and experimental animals. Here, we show that SARS-CoV-2 infection of sustentacular cells induces inflammation characterized by infiltration of myeloid cells to the olfactory epithelium and variably increased expression of proinflammatory cytokines. We observed widespread damage to, and loss of cilia on, OSNs, accompanied by downregulation of olfactory receptors and signal transduction molecules involved in olfaction. A consequence of OSN dysfunction was a reduction in the number of neurons in the olfactory bulb expressing tyrosine hydroxylase, consistent with reduced synaptic input. Resolution of the infection, inflammation, and olfactory dysfunction occurred over 3–4 weeks following infection in most but not all animals. We also observed similar patterns of OE infection and anosmia/hyposmia in mice infected with other human coronaviruses such as SARS-CoV and MERS-CoV. Together, these results define the downstream effects of sustentacular cell infection and provide insight into olfactory dysfunction in COVID-19–associated anosmia.

Authors

Abhishek Kumar Verma, Jian Zheng, David K. Meyerholz, Stanley Perlman

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Figure 1

Olfactory dysfunction in SARS-CoV-2–infected mice.

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Olfactory dysfunction in SARS-CoV-2–infected mice. (A–E) K18-hACE2 mice ...
(A–E) K18-hACE2 mice were infected with 2000 pfu SARS-CoV-2 intranasally. (A). Weights were monitored. (B and C) BFT and scent-discrimination tests were performed; n = 8 mice. (B) Time taken to find hidden food is shown. Data represent mean ± SEM of results pooled from 2 independent experiments; mock (9 mice), day 2 and 3 (9 mice), day 15–18 (7 mice), day 27 (6 mice). Data were analyzed using 1-way ANOVA. *P < 0.05, **P < 0.01. Scale bar: 40 μm. (C) Time spent exploring novel and familiar scents. Data represent mean ± SEM of results pooled from 2 independent experiments with 5–10 mice per group. Data were analyzed using 2-way ANOVA. *P < 0.05, **P < 0.01. (D) Pathological analysis of OE shows degenerative (green arrow at 4 dpi and 6 dpi) and necrotic changes (inset, 6 dpi). Mitotic cells (black arrow) were observed at 15 dpi in the OE. A few sites of OE disruption and increased cellularity were detected at 20 and 27 dpi (red arrows). (E) Ki-67 staining (red) in OE shows increased proliferation in SARS-CoV-2–infected samples. Summary data represent numbers of Ki-67+ cells in uninfected and 15 dpi OE per 20× field. Four fields from 4 mice were analyzed using Mann-Whitney U tests. *P < 0.05. Scale bar: 50 μm. (F–H) BALB/c mice were infected with SARS2-N501YMA30. (F) Weights were monitored; n = 8 mice. (G and H) BFT and scent-discrimination tests are shown. Data represent the mean ± SEM of results pooled from 2 independent experiments with mock, day 2, and day 3 (10 mice) and days 8, 14, and 21 (8 mice). Data were analyzed using 1-way (B and G) and 2-way (C and H) ANOVA. *P < 0.05, ***P < 0.001.