Abstract Background The pathogenesis of psoriasis, an inflammatory skin disease, is incompletely understood. Growing evidence substantiates the involvement of stromal cells in the inflammatory process. Objectives To investigate the roles of stromal cells, including fibroblasts, vascular endothelial cells (VECs) and smooth muscle cells (VSMCs), in the psoriatic inflammatory microenvironment and the possible underlying mechanisms involved. Methods This study employed combination of single-cell, spatial transcriptome and bulk RNA sequencing using lesional and nonlesional skin samples from patients with psoriasis vulgaris (PV) and healthy skin samples from unaffected individuals. Results Through the analysis of transcriptome from 364,098 single cells, we uncovered WNT5A+ fibroblasts, ITIH5+ VECs and VCAN+ VSMCs with the significantly increased cell proportions in the papillary dermis of lesional skin. We defined eight unique subclusters of fibroblasts in the skin and observed a shift of WIF1+ fibroblasts towards WNT5A+ fibroblasts, with abnormal activation of the non-canonical Wnt signaling pathway and increased capabilities of angiogenesis and pro-inflammatory. For the microvascular cells, VSMCs could undergo phenotypic transformation from a contractile phenotype to a synthetic phenotype in the development of psoriatic inflammation. ITIH5+ VECs and VCAN+ VSMCs were identified with an essential role in regulating angiogenesis and vascular remodeling involved in the mechanism of psoriatic pathological changes. Ligand receptor analyses demonstrated WNT5A+ fibroblasts were extensively implicated in interactions with various cell types in skin, especially with ITIH5+ VECs and VCAN+ VSMCs within the papillary dermis. Conclusions Interactions of stromal cells in the papillary dermis were identified as possible pathogenic elements in psoriasis vulgaris. Improving the inflammatory microenvironment by targeting stromal cells might be a potential treatment strategy for psoriasis.

Multitranscriptome analysis revealed that stromal cells in the papillary dermis promote angiogenesis in psoriasis vulgaris