Background/Purpose: Systemic sclerosis (SSc) is characterized by an initial inflammatory phase followed by fibrosis. Esophageal dysfunction in SSc is associated with gastroesophageal reflux, leading to severe complications and contributing to fibrosis. Studies have shown that SSc patients exhibit increased numbers of specific immune cells, such as fibroblasts, and tissue macrophages, which correlate with disease severity and reduced survival. The role of immune cell populations in the different regions of the affected esophagus remains poorly understood. This study aims to investigate the transcriptional heterogeneity of immune cells in the esophagus of SSc patients, focusing on regional differences between the proximal and distal esophagus.

Methods: Esophageal biopsies were obtained from nine SSc patients, with cells divided into proximal and distal esophageal regions (a total of 15 samples). Single-cell RNA sequencing (scRNA-Seq) and cellular indexing of transcriptomes and epitopes by sequencing (CITE-Seq) were performed on CD45+ immune cells isolated from dissociated tissue using fluorescence-activated cell sorting (FACS). Data were processed and analyzed using the 10x Genomics Cell Ranger 6.0.0 pipeline and the Seurat package. CITE-Seq was utilized to confirm the expression of specific cell-identifying markers.

Results: Analysis of the integrated immune cell data identified 19 individual clusters from about 30,000 cells, including T cells, B cells, and various myeloid cell subsets. Within the myeloid subsets (18% of CD45+), eight distinct clusters were identified, including multiple dendritic cell subsets (LAMP3+ ~5%) and macrophages. Notably, dendritic cells were more prevalent in the distal region compared to the proximal region. In contrast, T cells and B cells showed a higher ratio in the proximal region, with regulatory T (Treg) cells having the highest number of cells in the distal region. Cluster-specific analysis revealed differences in gene expression between the distal and proximal regions, characterized by differential expression of specific markers such as FABP4, CD11b, CD11c, CCR2, and APOE, as well as varying expression of HLA-antigens, indicating differences in antigen presentation capabilities.

Conclusion: This study is the first to evaluate immune cells in the esophagus of SSc patients with a focus on regional differences. We demonstrate the presence of diverse macrophage and other immune cell subsets within the esophagus of SSc patients, each potentially contributing to distinct functions and mechanisms in the pathogenesis of SSc. These findings underscore the importance of precisely identifying immune cell populations within affected organs and targeting specific subsets to effectively intervene in the inflammatory process of SSc. Future research will investigate the differential characteristics of these immune cell subsets between the proximal and distal esophagus.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/transcriptional-heterogeneity-of-immune-cells-in-the-esophagus-of-systemic-sclerosis-patients-a-comparison-of-upper-and-lower-esophageal-regions/