PECAM1 and systemic sclerosis: Using spatial proteomics, Rigau et al. unraveled the heterogeneity of vascular cells in control individuals and patients with SSc [21], identifying CD34+ αSMA+ CD31+ ECs 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.