Abstract Rationale Vascular remodeling is a significant feature of pulmonary arterial hypertension (PAH). The thickening and fibrosis of vascular walls have been observed. Macrophages are known to modulate fibroblast activity in fibrotic lung diseases. However, the spatial interactions between endothelial cells, fibroblasts and macrophages within the lung tissue context of PAH remain largely unexplored. Methods High-resolution spatial transcriptomics was used to characterize cell-cell interactions in pulmonary arterial hypertension (PAH). Mice with endothelial-specific deletion of Egln1 (Egln1Tie2Cre, or CKO) were studied, as these animals develop spontaneous and severe pulmonary hypertension with marked vascular remodeling. Lung tissues from wild-type (WT) and CKO mice were profiled using the 10x Genomics Visium HD platform. Whole-transcriptome data were acquired at 2μm resolution, and adjacent pixels were aggregated into 8μm regions to approximate single-cell dimensions. Cell identities were inferred using the RCTD algorithm (v1.2.0), integrating matched single-cell RNA-seq datasets from WT and CKO lungs. Machine-learning-based approaches were then applied to assign transcriptomic profiles to individual cells and to quantify spatial distances between endothelial cells, fibroblasts and macrophages. Results Seventeen cell types were identified in WT and CKO lungs (Figure A), consistent with histological findings. CKO mice displayed prominent regions enriched with fibroblasts and inflammatory cells. Specifically, the inflammatory cells, fibroblasts (AF) and smooth muscle cells near vascular regions increase in CKO compared to WT. The capillary endothelial cells reduced in CKO compared to WT. Notably, we also observed that interstitial macrophages (IMs) and fibroblasts enriched in the peri-arterial regions in CKO mouse lung. This is not observed in WT mouse (Figure B). Additionally, we also observed the spatial distance between fibroblasts and macrophages significantly reduced in CKO lungs (Figure C). Conclusion High-resolution spatial transcriptomics (Visium HD) effectively delineates changes of cell populations in PH lungs. The colocalization of IMs and fibroblasts in peri-arterial regions in PH mice suggests increased spatial interactions between arterial endothelial cells, fibroblasts and IMs, which may drive pulmonary vascular remodeling and contribute to PAH pathogenesis. This abstract is funded by: NHLBI
Liu et al. (Fri,) studied this question.