Distinct metabolic profiles of circulating plasmacytoid dendritic cells in systemic sclerosis patients stratified by clinical phenotypes

Background: Plasmacytoid dendritic cells (pDCs) play a key role in systemic sclerosis (SSc) pathophysiology. However, despite the recognised importance of metabolic reprogramming for pDC function, their metabolic profile in SSc remains to be elucidated. Thus, our study aimed to explore the metabolic profile of pDCs in SSc and their potential contribution to the disease. Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from the blood of healthy donors and SSc patients. SCENITH™, a single-cell flow cytometry-based method, was applied to infer the metabolic profile of circulating pDCs from patients with SSc. pDCs (CD304⁺ Lin⁻) at steady-state or stimulated with CpG A were analysed. Toll-like receptor (TLR)9 activation was confirmed by ribosomal protein S6 phosphorylation. Results: Circulating pDCs from ten healthy donors and fourteen SSc patients were analysed. pDCs from anti-centromere antibody-positive (ACA⁺) patients displayed higher mitochondrial dependence and lower glycolytic capacity than those from anti-topoisomerase I antibody-positive (ATA⁺) patients. Furthermore, cells from both ACA⁺ patients and limited cutaneous SSc (lcSSc) patients showed a stronger response towards TLR9 activation than cells from ATA⁺, anti-RNA polymerase III antibody-positive (ARA⁺) or diffuse cutaneous SSc (dcSSc) patients. Conclusions: An innovative single cell flow cytometry-based methodology was applied to analyse the metabolic profile of pDCs from SSc patients. Our results suggest that pDCs from ACA⁺ patients rely more on oxidative phosphorylation (OXPHOS) and are more responsive to external stimuli, whereas pDCs from ATA⁺ patients may exhibit a more activated or exhausted profile.