Pathogenic Roles of Cardiac Fibroblasts in Pediatric Dilated Cardiomyopathy

Abstract

Background Dilated cardiomyopathy (DCM) is a major cause of heart failure in children. Despite intensive genetic analyses, pathogenic gene variants have not been identified in most patients with DCM, which suggests that cardiomyocytes are not solely responsible for DCM. Cardiac fibroblasts (CFs) are the most abundant cell type in the heart. They have several roles in maintaining cardiac function; however, the pathological role of CFs in DCM remains unknown. Methods and Results Four primary cultured CF cell lines were established from pediatric patients with DCM and compared with 3 CF lines from healthy controls. There were no significant differences in cellular proliferation, adhesion, migration, apoptosis, or myofibroblast activation between DCM CFs compared with healthy CFs. Atomic force microscopy revealed that cellular stiffness, fluidity, and viscosity were not significantly changed in DCM CFs. However, when DCM CFs were cocultured with healthy cardiomyocytes, they deteriorated the contractile and diastolic functions of cardiomyocytes. RNA sequencing revealed markedly different comprehensive gene expression profiles in DCM CFs compared with healthy CFs. Several humoral factors and the extracellular matrix were significantly upregulated or downregulated in DCM CFs. The pathway analysis revealed that extracellular matrix receptor interactions, focal adhesion signaling, Hippo signaling, and transforming growth factor‐β signaling pathways were significantly affected in DCM CFs. In contrast, single‐cell RNA sequencing revealed that there was no specific subpopulation in the DCM CFs that contributed to the alterations in gene expression. Conclusions Although cellular physiological behavior was not altered in DCM CFs, they deteriorated the contractile and diastolic functions of healthy cardiomyocytes through humoral factors and direct cell–cell contact.

Differential expression and co-expression reveal cell types relevant to rare disease phenotypes

“…For instance, dilated cardiomyopathy is significantly associated with both cardiomyocytes and fibroblasts in the literature (e.g. Tsuru et al, 2023) and both cell types were significantly associated based on both differential expression and co-expression analyses. However, in other cases, partial involvement of a subset of genes in each cell type might not yield significant results for each cell type independently.…”

Atomic force microscopy for investigating cell and tissue mechanics as heterogeneous and hierarchical materials

“…The improvement of AFM may require at least two technical advancements. The first is to sophisticate the force curve method, in which the force curves can be directly analyzed by applying Boltzmann's superposition principle within a preselected relaxation modulus model (Efremov et al, 2020) or the multi-frequency force modulation method (Takahashi and Okajima, 2015;Tanaka et al, 2020;Matsumoto et al, © The Japan Society of Mechanical Engineers 2022; Tsuru et al, 2023), in which the cantilever is vibrated at multiple frequencies, and each frequency component is detected using a multi-frequency lock-in amplifier. The second is to use the high-speed AFM technique, which has been widely used to observe the topographical features of samples (Ando et al, 2013).…”