Key genes and pathways of pulmonary hypertension identified by integrating bulk and single-cell RNA sequencing.

Pulmonary hypertension (PH) is a progressive vascular disease, yet the underlying cell-type-specific molecular networks and diagnostic biomarkers remain incompletely defined. Integrating single-cell and bulk transcriptomics, we identified 14 pulmonary cell types in PH, with smooth muscle cells (SMCs) as a central communication hub interacting with monocytes and macrophages. High-dimensional weighted gene co-expression network analysis (hdWGCNA) revealed 4 SMC modules enriched in extracellular matrix organization, TGF-β, and HIF-1 pathways. A five-gene diagnostic signature distinguished PH from controls with an area under the curve of 0.895. Immune infiltration and enrichment analysis showed that activated CD4 memory T cells, activated dendritic cells, and resting mast cells increased in the PH group, while angiogenesis and epithelial-mesenchymal transition pathway were upregulated. In hypoxic human pulmonary artery SMCs, milk fat globule-epidermal growth factor-8 (MFGE8), secreted frizzled-related protein 2 (SFRP2), S100 calcium-binding protein A11 (S100A11), and procollagen C-endopeptidase enhancer 2 (PCOLCE2) were upregulated, and their knockdown suppressed proliferation, highlighting them as potential biomarkers and drivers of vascular remodeling, revealing a new molecular mechanism for PH and providing insights for potential therapeutic targets.