Single-cell Transcriptomics Reveal Cellular Heterogeneities Of Vascular Remodeling In Circulatory And Respiratory Diseases

Vascular remodeling is the key pathological changes in multiple cardiovascular diseases and respiratory diseases.There are two types of vascular remodeling(i.e.,aortic and peripheral microvascular remodeling)based on the diameters of vessels whereas remodeling occurred.However,cellular and molecular mechanism of different types of vascular remodeling were poorly understood,thus systemically deciphering the mechanisms was needed.To investigate the heterogeneities of remodeling mechanism,abdominal aortic aneurysm(AAA)as a classical outward aortic remodeling and pulmonary hypertension as a typical inward microvascular remodeling were involved.Single cell RNA sequencing(scRNA-seq)was performed to demonstrate the cellular heterogeneities.ScRNA-seq was performed on an angiotensin II-induced mouse model of AAA.Macrophages,B cells,T cells,fibroblasts,smooth muscle cells and endothelial cells were identified through bioinformatic analyses.Intriguingly,we defined CD45+COL1+fibrocytes in AAA and extended our findings to the single cell dataset of ATAA patients,of which the existence was further validated by immunostaining in mouse and human AAA tissues.More importantly,the fibrocytes were proposed to attenuate AAA formation through modulating extracellular matrix(ECM)production and thus enhancing aortic stability.ScRNA-seq was performed on lung tissues from mice exposed to chronic hypoxia or Sugen5416 combined with hypoxia,rats exposed to monocrotaline and control animals.Cell populations perturbed in rats and mice were similar to those found in human disease,with macrophages and endothelial cells being the most affected.A novel DHCR24high macrophage population harboring both tissue remodeling and pro-inflammatory features were consistently increased across PH models.Phenotypic modulation of DHCR24high macrophages corresponded with PH progression.Several functionally diverse endothelial subtypes were found,including novel ETB+and NOX2+subpopulations,reflecting enhanced apoptosis,dysregulated angiogenesis and proliferation,and reactive oxygen species mediated stress.These macrophage and endothelial subtypes expressed numerous PH drug target genes,and exhibited several potential intercellular interactions involving the ANGPTL4,CXCL12,and SEMA3 signaling axes.In addition,computational cell type deconvolution on bulk transcriptomics data can be utilized to systemically demonstrate the cell proportions of remodeling tissues.A novel Bayesian framework,tranSig,was developed to improve signature matrix inference from scRNA-seq by leveraging shared cell type-specific expression patterns across different tissues and studies.Our simulations show that tranSig is robust to the number of signature genes and tissues specified in the model.Applications of tranSig to bulk RNA sequencing data from peripheral blood,bronchoalveolar lavage,and aorta demonstrate its accuracy and power to characterize biological heterogeneity across groups.In summary,tranSig offers an accurate and robust approach to defining gene expression signatures of different cell types,facilitating improved in silico cell type deconvolutions.In conclusion,we leveraged scRNA-seq data of AAA uncovering a novel cell type fibrocyte involved in AAA pathogenesis.Notably,a comprehensive single-cell atlas of mainstream rodent PH models was established,highlighting several novel macrophage and endothelial subtypes and signaling motifs potentially contributing to human disease.Moreover,an add-on tool for cell type signature matrix was developed to accurately infer the cell proportions in remodeling tissues and enable researchers to comprehensively understand cellular alterations in diseases.