D106-09 Transcriptomic Signatures of Pulmonary Arterial Lesions in Connective Tissue Disease Associated Pulmonary Arterial Hypertension

Abstract Introduction/Rationale Connective tissue disease-associated pulmonary arterial hypertension (CTD-PAH) is a fatal, incurable disease with a short life expectancy. Although the presence of characteristic pulmonary arterial (PA) lesions in CTD-PAH have been established, their transcriptomic signatures and pathobiologic role have not been studied. Methods We applied digital spatial transcriptomics profiling (NanoString) to end-stage CTD-PAH lung tissues (n = 11 subjects) and disease-free lung donors (n = 4). We quantified the entire protein-coding transcriptome across four types of diseased PA lesions (plexiform, obliterative, medial hypertrophy, adventitia) and normal PA compartments (media, adventitia). We performed principal component, differential gene expression, and fast gene set enrichment analyses to elucidate lesion-specific transcriptomic signatures. Results We detected 8,957 transcripts in the CTD-PAH PA lesions and control pulmonary arteries. In the principal component analysis, a significant overlap was observed between CTD-PAH and control PAs. Instead, separation and grouping were observed around individual subjects and vascular compartments. Of the four CTD-PAH lesion types, plexiform lesions and diseased adventitia demonstrated most numbers of differentially expressed genes. Upregulated genes in the two PA lesion types belonged to previously suggested disease drivers, including the complement system (e.g., C3, CFD), innate inflammation (TGF-β signaling, TNFα signaling via NFkB, interleukins, interferons), hypoxia signaling, and angiogenesis. We additionally identified endothelial-mesenchymal transformation as a highly enriched pathway in plexiform, obliterative, and medial hypertrophy lesions of CTD-PAH. MFAP4 was one of the most upregulated transcripts in diseased PAs (n = 178) compared to disease-free control PAs (n = 59). Microfibril-associated protein 4 (MFAP4) is an extracellular matrix glycoprotein implicated in vascular inflammation and remodeling, potentially acting through integrin-dependent activation of TGF-β/SMAD signaling and macrophage recruitment, both key drivers of PAH. Increased MFAP4 expression was confirmed using fluorescence in situ hybridization. Conclusions CTD-PAH PA lesions harbor key, unique transcriptomic signatures to guide mechanistic studies, biomarker development, and therapeutic targeting. The significant enrichment of inflammatory pathways and MFAP4 provide rationale for our ongoing mechanistic study in the transgenic murine model of CTD-PAH. This abstract is funded by: K08HL168310 (NIH), W81XWH2210457/W81XWH2210458 (Department of Defense)