CONCLUSIONS: Using spatial proteomics, we unraveled the heterogeneity of vascular cells in control individuals and patients with SSc. We identified CD34^(+);αSMA^(+);CD31^(+) VECs as a novel endothelial cell population that is increased in patients with SSc, expresses markers for endothelial-to-mesenchymal transition, and is located in close proximity to immune cells and myofibroblasts. CD34^(+);αSMA^(+);CD31^(+) VEC counts were associated with clinical outcomes of progressive …