Altered Intercellular Communication and Extracellular Matrix Signaling as a Potential Disease Mechanism in Human Hypertrophic Cardiomyopathy

Abstract

Objectives: To understand Hypertrophic Cardiomyopathy-associated alterations in gene expression and intercellular communication at the single cell level in left ventricular outflow tract lesions. Background: Human hypertrophic cardiomyopathy (HCM) is considered a disorder of the sarcomere (i.e., cardiomyocytes) but the paradoxical association of nonmyocyte phenotypes such as fibrosis, mitral valve anomalies and microvascular occlusion is unexplained. Methods: To understand the interplay between cardiomyocyte and nonmyocyte cell types in human HCM, single nuclei RNA-sequencing (snRNA-seq) was performed on myectomy specimens from HCM patients with left ventricular outflow tract obstruction and control samples from donor hearts free of cardiovascular disease. Results: Clustering analysis identified a total of 34 distinct cell populations, which were classified into 10 different cell types based on marker gene expression. Differential gene expression analysis comparing HCM to Normal datasets revealed differences in sarcomere and extracellular matrix gene expression. Analysis of expressed ligand-receptor pairs across multiple cell types indicated profound disruption in HCM intercellular communication, particularly between cardiomyocytes and fibroblasts, fibroblasts and lymphocytes and involving integrin β1 and its multiple extracellular matrix (ECM) cognate ligands. Conclusions: These findings provide evidence for intercellular interactions in HCM that link sarcomere dysfunction with altered cardiomyocyte secretion of ECM ligands, altered fibroblast ligand-receptor interactions with a variety of cell types and increased fibroblast to lymphocyte signaling, which can further alter the ECM composition, disrupt cellular function and promote nonmyocyte phenotypes.

Common and Distinctive Intercellular Communication Patterns in Human Obstructive and Nonobstructive Hypertrophic Cardiomyopathy

“…Of the 26 clusters, 14 were assigned as cardiomyocytes, 5 were assigned as fibroblasts, 2 were assigned as endotheliial cells with single clusters of neurons, smooth muscle cells, pericytes, dendritic cells and leukocytes, for a total of 8 unique cell types. Cardiomyocyte and fibroblast diversity in the human heart likely reflects cell subtypes in different physiological states and has been previously reported in multiple studies [10][11][12][13][14]. No clusters specific to a single condition were observed (Fig.…”

“…The 22 datasets for control (6), obstructive HCM (10) and nonobstructive HCM (6) samples have been previously described [12][13][14]. The datasets are available from the Gene Expression Omnibus (GEO) database under accession numbers GSE161921, GSE174691 and GSE181764.…”

“…The final dataset thus consisted of 26 clusters. Cell type assignment for each cluster was performed as described previously [12][13][14]. Briefly, clusters were assessed for expression of cell type-specific gene markers, differentially expressed genes queried against panglaoDB [16], gene ontology (GO) using GOStats [17] and Ingenuity Pathway Analysis [18].…”

“…To determine the relationships between cell types represented by nuclei in different clusters and between cells represented by nuclei within a cluster, we performed trajectory analysis using Monocle3 [19]. Previous analysis of relationships between cellular subtypes in obstructive HCM normal tissue and between cellular subtypes in nonobstructive HCM and normal tissue by trajectory analysis did not reveal any significant differences between each type of HCM and normal tissue trajectories, although many genes were differentially expressed between conditions along the trajectories [13,14]. Similarly, in this work no differences were seen in trajectories between obstructive and nonobstructive HCM (data not shown), although differences were seen in gene expression along the trajectory paths.…”

“…Single cell RNA-sequencing and single nuclei RNA-sequencing (snRNA-seq) have facilitated the analysis of cellular diversity and intercellular communication in the human heart [10][11][12][13]. We have previously defined the cellular diversity of the human heart IVS [12] and have delineated important changes in communication between the cells of the IVS in obstructive HCM, through mechanisms involving integrin-1 (ITGB1) and the extracellular matrix (ECM) [13]. We have also performed a separate study comparing the snRNA-seq profiles of nonobstructive HCM IVS tissue with normal IVS tissue and have found an increase in dendritic cell communication [14].…”