Monroe, K. | Search bioRxiv

bioRxiv2022

COVID-19 Causes Ciliary Dysfunction as Demonstrated by Human Intranasal Micro-Optical Coherence Tomography Imaging

Severe acute respiratory syndrome coronavirus (SARS-CoV-2), causative agent of coronavirus disease 2019 (COVID-19), binds via ACE2 receptors, highly expressed in ciliated cells of the nasal epithelium. Micro-optical coherence tomography (OCT) is a minimally invasive intranasal imaging technique that can determine cellular and functional dynamics of respiratory epithelia at 1-m resolution, enabling real time visualization and quantification of epithelial anatomy, ciliary motion, and mucus transport. We hypothesized that respiratory epithelial cell dysfunction in COVID-19 will manifest as reduced ciliated cell function and mucociliary abnormalities, features readily visualized by OCT. Symptomatic outpatients with SARS-CoV-2 aged [≥] 18 years were recruited within 14 days of symptom onset. Data was interpreted for subjects with COVID-19 (n=13) in comparison to healthy controls (n=8). Significant reduction in functional cilia, diminished ciliary beat frequency, and abnormal ciliary activity were evident. Other abnormalities included denuded epithelium, presence of mucus rafts, and increased inflammatory cells. Our results indicate that subjects with mild but symptomatic COVID-19 exhibit functional abnormalities of the respiratory mucosa underscoring the importance of mucociliary health in viral illness and disease transmission. Ciliary imaging enables investigation of early pathogenic mechanisms of COVID-19 and may be useful for evaluating disease progression and therapeutic response. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=94 SRC="FIGDIR/small/499336v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@1f4bb17org.highwire.dtl.DTLVardef@271438org.highwire.dtl.DTLVardef@1a08762org.highwire.dtl.DTLVardef@184847_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2021

Loss of TREM2 reduces hyperactivation of progranulin deficient microglia but not lysosomal pathology

GRN haploinsufficiency causes frontotemporal lobar degeneration and results in microglial hyperactivation, lysosomal dysfunction and TDP-43 deposition. To understand the contribution of microglial hyperactivation to pathology we evaluated genetic and pharmacological approaches suppressing TREM2 dependent transition of microglia from a homeostatic to a disease associated state. Trem2 deficiency in Grn KO mice led to a reduction of microglia activation. To explore antibody-mediated pharmacological modulation of TREM2-dependent microglial states, we identified antagonistic TREM2 antibodies. Treatment of macrophages from GRN-FTLD patients with these antibodies allowed a complete rescue of elevated levels of TREM2 together with increased shedding and reduction of TREM2 signaling. Furthermore, antibody-treated PGRN deficient hiMGL showed dampened microglial hyperactivation, reduced TREM2 signaling and phagocytic activity, however, lack of rescue of lysosomal dysfunction. Similarly, lysosomal dysfunction, lipid dysregulation and glucose hypometabolism of Grn KO mice were not rescued by TREM2 ablation. Furthermore, NfL, a biomarker for neurodegeneration, was elevated in the Grn/Trem2 KO. These findings suggest that microglia hyperactivation is not necessarily contributing to neurotoxicity, and instead demonstrates that TREM2 exhibits neuroprotective potential in this model.

neuroscience↗