A SINGLE-CELL SURVEY OF GASTRIC MUSCULARIS MACROPHAGES IN DIABETIC GASTROPARESIS

Background: Gastric muscularis propria immune cells play an instrumental role in homeostasis and disease. A subset of these cells, muscularis macrophages (MMs) are involved in the pathobiology of diabetic gastroparesis (DG) but are poorly understood. This study aims to survey transcriptional and functional profiling of gastric MMs in DG and diabetes. Methods: Full-thickness gastric body biopsies were obtained from patients with DG and diabetic controls. CD45+ cells were isolated from dissociated muscle tissue using magnetic beads. 10xGenomics was used for scRNA-seq library prep and cells sequenced by Illumina HiSeq4000. Bioinformatic analyses was performed using Suite and Seurat. Myeloid cells were annotated through a pseudogating strategy that identifies cells by differential expression levels of HLA-DR, CD14, CD11b, and CD11c based on flow cytometry-based gating utilized in a recent analysis of human small intestinal MMs. Canonical signaling pathways were determined using Ingenuity Pathway Analysis (IPA). Results: A total of 21,740 high-quality single-cell transcriptomes were generated from 16 subjects (DG=6, age 32±8 yr, BMI 23.7±3.9, 48.2±40.1% 4 hr gastric retention, average GCSI score 3.7±0.5;Diabetic controls= 10, age 53±13 yr, BMI 42.2±5.7). Through annotating 8,693 myeloid cells (DG 1509, Controls 7184), we characterized 1,788 as MMs (CD45+HLA-DR+) and 448 as dendritic cells (CD14-CD11c+). Utilizing a priori markers for pseudogating, the MMs were divided into four populations (Figure 1): subset 1 (CD14+CD11c+HLA-DRint, 5.6%), subset 2 (CD14+CD11c+HLA-DRhi, 36.0%), subset 3 (CD14+CD11c-CD11b-, 41.8%), and subset 4 (CD14+CD11c-CD11b+, 16.6%). The overall proportions of cells in the 4 subsets were similar to a prior approach in small bowel using gating. The expected ratio of cells from DG/diabetic control was 21% based on imputed cells. Subsets 1 and 4 were significantly decreased in DG compared to controls with ratios 15% and 14% respectively while subsets 2 and 3 were unchanged (21% and 20%). On IPA, phagosome formation and immune cell trafficking represented canonical signaling pathways of subset 1 and coronavirus phagocytosis pathway and phagosome formation of subset 4. Canonical genes of subset 1 included S100A12, A8, A9, and CSTA and subset 4 as LYVE1, MAF, MRC1 (CD206), MS4A4, and A2M. Subset 4 also had the highest expression of neuron-related genes (NPTX2, BMP2) similar to that observed in the small intestine. Conclusions: Pseudogating based on the transcriptomic expression of gastric immune cells reveal MM clusters similar in gene expression and proportions to previously characterized MMs in human small bowel using gating. The reduction of MM clusters associated with anti-inflammatory, phagocytosis, and neuronal signaling in specialized MMs subsets may suggest candidate targets in the pathophysiology of DG. Supported by NIHDK074008. (Figure Presented) Figure 1. Single-Cell RNA-Seq Profiling of Human Gastric Muscularis Macrophages in DG and Diabetes. T-distributed Stochastic Neighbor Embedding (tSNE) plot of muscularis macrophages in DG and diabetic control subjects by their differential genes from MAST (FDR < 0.05), color-coded by Status. *Mf1 and Mf2 not visualized as distinct clusters due to inadequate separation of overall gene expression in cells distinguished by HLA-DRint (Mf1) and HLA-DRhi (Mf2)

Altered platelet proteome and platelet-leukocyte interactions in patients with COVID-19

Background: Patients with severe coronavirus disease 19 (COVID-19) are at increased risk of thrombosis, which is associated with enhanced coagulopathy and increased mortality. Previous studies showed enhanced platelet aggregation in patients with COVID-19, however the underlying mechanism and how this contributes to thrombosis is still unclear. Aims: To evaluate the platelet proteome, platelet functional responses and platelet/leukocyte aggregate formation in patients with COVID-19. Methods: This study was approved by the local ethics committee. Platelets were isolated from patients with COVID-19 and healthy controls after providing informed consent. Platelet lysates were subjected to tandem mass tag mass spectrometry (TMT-MS) proteomic analysis. Platelet functional responses such as integrin a IIb b 3 activation, P-selectin expression, platelet/leukocyte aggregates and PS exposure were analysed by FACS analysis. Results: The platelet proteome was altered in COVID-19, with enrichment of ribosomal and mitochondrial proteins, and reduced levels of thrombopoietin (TPO) receptor and signalling proteins. Circulating platelets from COVID-19 patients furthermore showed enhanced basal PS exposure, whereas basal integrin a IIb b 3 activation and P-selectin expression were unaltered. In contrast, agonist stimulated integrin a IIb b 3 activation and PS exposure were significantly decreased in COVID-19 patients. Furthermore, we found high levels of platelet/leukocyte aggregate formation in COVID-19 patients, which was reduced by a blocking anti-P-selectin antibody, suggesting immunothrombosis is part of the COVID-19 phenotype. Interestingly, however platelets in these platelet/leukocyte aggregates did not show enhanced integrin a IIb b 3 activation, suggesting they are generally in a low activation state, or having undergone activation followed by desensitisation. Conclusions: High levels of platelet/leukocyte aggregates are present and given the increased thrombotic tendency in severely ill patients, these findings point to an immunothrombotic pathogenesis. It will be important now to determine whether these changes are the result of direct activation of platelets or leukocytes by viral contact or cellular infection.

Quantitative evaluation of aerosol generation during manual facemask ventilation.

Manual facemask ventilation, a core component of elective and emergency airway management, is classified as an aerosol-generating procedure. This designation is based on one epidemiological study suggesting an association between facemask ventilation and transmission during the SARS-CoV-1 outbreak in 2003. There is no direct evidence to indicate whether facemask ventilation is a high-risk procedure for aerosol generation. We conducted aerosol monitoring during routine facemask ventilation and facemask ventilation with an intentionally generated leak in anaesthetised patients. Recordings were made in ultraclean operating theatres and compared against the aerosol generated by tidal breathing and cough manoeuvres. Respiratory aerosol from tidal breathing in 11 patients was reliably detected above the very low background particle concentrations with median [IQR (range)] particle counts of 191 (77-486 [4-1313]) and 2 (1-5 [0-13]) particles.l-1 , respectively, p = 0.002. The median (IQR [range]) aerosol concentration detected during facemask ventilation without a leak (3 (0-9 [0-43]) particles.l-1 ) and with an intentional leak (11 (7-26 [1-62]) particles.l-1 ) was 64-fold (p = 0.001) and 17-fold (p = 0.002) lower than that of tidal breathing, respectively. Median (IQR [range]) peak particle concentration during facemask ventilation both without a leak (60 (0-60 [0-120]) particles.l-1 ) and with a leak (120 (60-180 [60-480]) particles.l-1 ) were 20-fold (p = 0.002) and 10-fold (0.001) lower than a cough (1260 (800-3242 [100-3682]) particles.l-1 ), respectively. This study demonstrates that facemask ventilation, even when performed with an intentional leak, does not generate high levels of bioaerosol. On the basis of this evidence, we argue facemask ventilation should not be considered an aerosol-generating procedure.

Is convalescent plasma futile in COVID-19? A Bayesian re-analysis of the RECOVERY randomized controlled trial.

BACKGROUND: Randomized trials are generally performed from a frequentist perspective, which can conflate absence of evidence with evidence of absence. The RECOVERY trial evaluated convalescent plasma for patients hospitalized with coronavirus disease 2019 (COVID-19) and concluded that there was no evidence of an effect. Re-analysis from a Bayesian perspective is warranted. METHODS: Outcome data were extracted from the RECOVERY trial by serostatus and time of presentation. A Bayesian re-analysis with a wide variety of priors (vague, optimistic, sceptical, and pessimistic) was performed, calculating the posterior probability for: any benefit, an absolute risk difference of 0.5% (small benefit, number needed to treat 200), and an absolute risk difference of one percentage point (modest benefit, number needed to treat 100). RESULTS: Across all patients, when analysed with a vague prior, the likelihood of any benefit or a modest benefit with convalescent plasma was estimated to be 64% and 18%, respectively. The estimated chance of any benefit was 95% if presenting within 7 days of symptoms, or 17% if presenting after this. In patients without a detectable antibody response at presentation, the chance of any benefit was 85%. However, it was only 20% in patients with a detectable antibody response at presentation. CONCLUSIONS: Bayesian re-analysis suggests that convalescent plasma reduces mortality by at least one percentage point among the 39% of patients who present within 7 days of symptoms, and that there is a 67% chance of the same mortality reduction in the 38% who are seronegative at the time of presentation. This is in contrast to the results in people who already have antibodies when they present. This biologically plausible finding bears witness to the advantage of Bayesian analyses over misuse of hypothesis tests to inform decisions.

A quantitative evaluation of aerosol generation during supraglottic airway insertion and removal.

Many guidelines consider supraglottic airway use to be an aerosol-generating procedure. This status requires increased levels of personal protective equipment, fallow time between cases and results in reduced operating theatre efficiency. Aerosol generation has never been quantitated during supraglottic airway use. To address this evidence gap, we conducted real-time aerosol monitoring (0.3-10-µm diameter) in ultraclean operating theatres during supraglottic airway insertion and removal. This showed very low background particle concentrations (median (IQR [range]) 1.6 (0-3.1 [0-4.0]) particles.l-1 ) against which the patient's tidal breathing produced a higher concentration of aerosol (4.0 (1.3-11.0 [0-44]) particles.l-1 , p = 0.048). The average aerosol concentration detected during supraglottic airway insertion (1.3 (1.0-4.2 [0-6.2]) particles.l-1 , n = 11), and removal (2.1 (0-17.5 [0-26.2]) particles.l-1 , n = 12) was no different to tidal breathing (p = 0.31 and p = 0.84, respectively). Comparison of supraglottic airway insertion and removal with a volitional cough (104 (66-169 [33-326]), n = 27), demonstrated that supraglottic airway insertion/removal sequences produced <4% of the aerosol compared with a single cough (p < 0.001). A transient aerosol increase was recorded during one complicated supraglottic airway insertion (which initially failed to provide a patent airway). Detailed analysis of this event showed an atypical particle size distribution and we subsequently identified multiple sources of non-respiratory aerosols that may be produced during airway management and can be considered as artefacts. These findings demonstrate supraglottic airway insertion/removal generates no more bio-aerosol than breathing and far less than a cough. This should inform the design of infection prevention strategies for anaesthetists and operating theatre staff caring for patients managed with supraglottic airways.

Sensitivity of RT-PCR testing of upper respiratory tract samples for SARS-CoV-2 in hospitalised patients: a retrospective cohort study

Background: This study aimed to determine the sensitivity and specificity of reverse transcription PCR (RT-PCR) testing of upper respiratory tract (URT) samples from hospitalised patients with coronavirus disease 2019 (COVID-19), compared to the gold standard of a clinical diagnosis.