Single-cell and spatial transcriptome profiling reveals innate-adaptive crosstalk in alopecia areata

Summary: Abstract Body: Alopecia areata (AA) is an autoimmune disorder characterized by immune attack on hair follicles, resulting in non-scarring hair loss. The pathogenesis of this condition is multifaceted and involves T cells, myeloid cells, and innate immune cells. However, the transcriptional profiles of these immune cell types remain inadequately defined, and delineation of aberrant or dysregulated pathways has the potential to identify therapeutic targets. In this study, we created a comprehensive atlas of various immune cells within AA skin lesions in a murine model, achieving single-cell resolution through integrative single-cell analysis, spatial transcriptomics, flow cytometry, and immunofluorescence. We found that macrophage infiltration occurred around the AA hair follicles and correlated with flow cytometry-based data. Significant expansion and transcriptional changes were observed in CD8+ T cells and macrophages within AA skin lesions. We identified two distinct macrophage subpopulations (Folr2+ and Folr2-Arg1+), each exhibiting unique transcriptional profiles. These subpopulations showed upregulation of genes related to T cell activation as well as pathways involved in leukocyte and myeloid cell differentiation. Additionally, four different subsets of CD8+ T cells revealed heterogeneity in their interactions with macrophages, as demonstrated by ligand-receptor mapping. Spatial transcriptome and flow cytometry imaging data revealed Folr2+ tissue resident macrophages (TRMs) interacted with CD8+ T cells and positively correlated with T cell infiltration. This study examines the roles of macrophages and CD8+ T cells in the recruitment of pathogenic immune cells, as well as the underlying mechanisms involved in AA lesions. Consequently, the findings highlight crucial immunopathogenic characteristics of AA lesions, thereby providing significant insights into the potential immunological alterations associated with this condition. Otgonzaya Ayush¹, Ryan Reis¹, Samuel J. Connell¹, Maddison Lensing¹, Zhaowen Zhu¹, Nicholas Henderson¹, Ali Jabbari¹ 1. Dermatology, University of Iowa Hospitals and Clinics, Iowa City, IA, United States. Cell Communication Networks and Stromal Biology