Multimodal analysis of vascular remodeling in human obliterative bronchiolitis after lung transplantation

Chronic lung allograft dysfunction (CLAD) is the leading cause of late morbidity and mortality after lung transplantation. Bronchiolitis obliterans syndrome (BOS), a major CLAD phenotype, is characterized by obliterative bronchiolitis (OB). Although microvascular perturbations are described in BOS, their cellular and molecular characteristics remain unclear. Intact human CLAD lungs (n = 3) underwent hierarchical phase-contrast tomography for 3-dimensional vascular mapping. In OB-affected airways vs controls (n = 4 each), endothelial subtypes were characterized by multiplex immunofluorescence imaging, and interactome changes were quantified with CellChat and GeoMx spatial transcriptomics performed on CD31⁺ regions. Hierarchical phase-contrast tomography revealed hypertrophic vessels infiltrating obliterated airways and forming web-like microvascular networks, absent in controls. Immunofluorescent imaging showed increased plasmalemma vesicle-associated protein⁺/Von Willebrand factor A domain containing 1⁺ systemic venous and podoplanin+ lymphatic cells in OB lesions. Cell-cell interaction analysis showed that plasmalemma vesicle-associated protein+/Von Willebrand factor A domain containing 1+ systemic venous cells exhibited increased incoming and outgoing interaction strength, primarily directed toward other endothelial cells and fibroblasts, characterized by inflammatory and fibrotic signaling. Spatial transcriptomics demonstrated upregulation of inflammatory/matrix-remodeling genes and downregulation of homeostatic regulators in BOS endothelial cells. BOS lungs display altered vascular architecture and endothelial composition, with gene expression shifts consistent with proinflammatory and fibrogenic processes in CD31⁺ regions. These findings suggest a potential involvement of vascular remodeling in CLAD pathophysiology.