Background/Purpose: Systemic sclerosis (SSc) is an autoimmune disease characterized by multiorgan fibrosis. The two main subtypes are diffuse cutaneous SSc (dcSSc) and limited cutaneous SSc (lcSSc). Both conditions present with sclerotic skin and the clinical distinction between the two is based on the extent of skin involvement. Despite these similarities, dcSSc patients more frequently experience severe, multiorgan manifestations. We have previously shown that the transcriptional profile of monocytes is linked to lung dysfunction in dcSSc patients. While myeloid cells have been implicated in multiorgan disease, the contribution of these cells to the variability in SSc comorbidities has not been fully investigated. In this study, we aim to understand these clinical disparities between dcSSc and lcSSc by investigating the transcriptional profiles of myeloid cells in both.

Methods: Blood from SSc patients and skin biopsies from SSc patients and healthy controls were collected as part of this study. Blood was processed to obtain PBMCs.  Skin biopsies were digested and immune (CD45+) and endothelial cells (CD31+) were sorted by FACS for single-cell RNA sequencing (scRNA-seq). Following sequencing, reads were aligned using CellRanger 7.1.0. Cells with high mitochondrial genes expressed and low total genes were removed using miQC and doublets were filtered using DoubletFinder. Analysis including differential gene expression was performed with Seurat.

Results: Two healthy controls and 15 SSc patients were recruited with all patients meeting the ACR classifications of SSc. Nine of these patients had a diagnosis of dcSSc and the other 6, lcSSc. Both controls and all SSc patients had biopsies taken at an initial visit with 4 of those SSc patients also giving blood. At a 12-month follow-up, 7 patients donated skin and one also donated blood.

A total of 76,966 cells were collected with an average of 2,654 cells per sample. Cell types identified in the analysis include endothelial cells, B cells, CD4+ T cells, NK cells, Mast cells, Macrophages (Macs), and dendritic cells (DCs). The ratio of endothelial to immune cells generally remained constant across conditions. Within CD45+ immune clusters, myeloid cells (DCs and Macs) generally constituted a higher proportion in both SSc subtypes as compared to healthy controls. As compared to lcSSc samples, dcSSc samples demonstrated increased expression of genes related to inflammation and cytokine production and decreased expression of genes related to lymphocyte activation.

Conclusion: These findings may suggest that the transcriptional profiles of myeloid cells differentiate lcSSc and dcSSc sclerotic skin, potentially aiding in understanding why dcSSc has more severe disease manifestations. Future analysis will investigate the relationship between PBMCs and skin immune cells within the same patients and how the overall transcriptional profiles relate to each patient’s clinical presentation.

« Back to ACR Convergence 2024

ACR Meeting Abstracts - https://acrabstracts.org/abstract/characterizing-the-contribution-of-myeloid-cells-to-limited-and-diffuse-cutaneous-systemic-sclerosis/