Th134 - Single Cell Transcriptomics in the Early Childhood Duodenum Reveals Resting and Active Mucosal Mast Cells

Abstract Text: Tissue-resident mast cells (MC) are key sensors and effectors of type 2 immune responses and are important in allergic inflammation. Despite their demonstrated role in inflammatory responses, there has been relatively limited molecular characterization of resident MC in healthy gut tissues. To address this, we analyzed single-cell RNA-seq data of histologically normal duodenal biopsies collected as part of the multi-center Gut-AGE project (n=88 children, aged 7.9 months to 12 years), from Boston, Mississippi, Virginia and Pakistan. Duodenal biopsies were collected and cryopreserved for single-cell RNA sequencing. Biopsies were dissociated using an optimized single-fraction protocol and multiplexed for droplet-based single cell sequencing producing a total of 226,706 individual cells in the whole dataset. A mast cell data object (Seurat) was created and analyzed (n=476 individual mast cells). Seurat analysis and rxtatics packages were utilized to evaluate mast cell populations in participant samples. Cellular pathways were analyzed using GO Enrichment analysis. This analysis revealed two distinct MC clusters: active and resting. The active MC cluster demonstrated upregulation of genes associated with MC degranulation and activation including SIGLEC6, CDK15, ST8SIA6, ENPP3, JAK1 and STAT3. This data demonstrates for the first time that resident MCs exist in both active and resting states in the non-inflamed human pediatric duodenum and the relationship of these cell-states may be important in maintaining mucosal immune homeostasis.