Bmp6-Bmpr2 signalling mediates endothelial-matrifibrocyte time-spatial interaction to regulate cardiac fibrosis after myocardial infarction
C H E N G Ni, Y A T I N G RuanAbstract
Background/introduction
Cardiac fibrosis, a key pathological feature of adverse remodelling after myocardial infarction (MI), is driven by activated fibroblasts and contributes to heart failure. Endothelial cells (ECs) are critical modulators of fibrosis through paracrine signalling. Targeting EC-fibroblast crosstalk presents a promising therapeutic strategy.
Purpose
This study aimed to elucidate the role of the Bmp6-Bmpr2 signalling axis between ECs and a specific fibroblast subpopulation (matrifibrocytes) in post-MI cardiac fibrosis, and to investigate its downstream effector, ID1.
Methods
Mice were treated with the soluble guanylate cyclase (sGC) stimulator vericiguat or vehicle after MI. 28 days after, tissues were collected for spatial transcriptome analysis, cardiac ECs (CD31+) and fibroblasts were isolated by fluorescence-activated cell sorting (FACS) from sham, MI, and MI+vericiguat groups for single-cell RNA sequencing (scRNA-seq). Cellular interactions were analysed with CellChat. Spatial transcriptomics assessed cellular co-localisation. Key findings were validated in vitro using mouse aortic endothelial cells (MAECs) and neonatal mouse cardiac fibroblasts via conditioned medium experiments and direct co-culture. Endothelial-specific Bmp6 overexpression and fibroblast-specific Bmpr2 knockdown were achieved using adeno-associated virus and lentivirus, respectively, for in vivo functional validation.
Results
ScRNA-seq identified a COMP-positive fibroblast subpopulation (matrifibrocytes) that expanded significantly post-MI and was reduced by vericiguat. Cell communication analysis revealed enhanced Bmp6 (from ECs)-Bmpr2 (from matrifibrocytes) signalling post-MI, which was attenuated by vericiguat. Spatial transcriptomics confirmed the proximity of Bmp6+ ECs and Bmpr2+ fibroblasts in the infarct border zone. In vitro, conditioned medium from vericiguat-treated MAECs suppressed TGF-β1-induced fibroblast activation and collagen production. Conversely, endothelial-specific Bmp6 overexpression in vivo abrogated the beneficial effects of vericiguat on cardiac function and fibrosis. Similarly, Bmpr2 knockdown in fibroblasts blunted their fibrotic response in vitroand in vivo. Furthermore, ID1 expression was upregulated in matrifibrocytes post-MI and downregulated by vericiguat. This was consistent in vitro, where ID1 expression in fibroblasts was reduced by conditioned medium from vericiguat-treated MAECs or by direct Bmpr2 knockdown.
Conclusion(s)
Our findings demonstrate that post-MI cardiac fibrosis is exacerbated by enhanced Bmp6-Bmpr2 signalling between ECs and matrifibrocytes, leading to increased ID1 expression. Inhibition of this pathway, exemplified by the sGC stimulator vericiguat, ameliorates fibrosis. The endothelial Bmp6-matrifibrocyte Bmpr2-ID1 axis represents a novel mechanistic pathway and a potential therapeutic target for mitigating cardiac fibrosis after MI.