Targeted Ablation of Periostin-Expressing Activated Fibroblasts Prevents Adverse Cardiac Remodeling in Mice

Abstract

Rationale: Activated cardiac fibroblasts (CF) are crucial players in the cardiac damage response; excess fibrosis, however, may result in myocardial stiffening and heart failure development. Inhibition of activated CF has been suggested as a therapeutic strategy in cardiac disease, but whether this truly improves cardiac function is unclear. Objective: To study the effect of CF ablation on cardiac remodeling. Methods and Results: We characterized subgroups of murine CF by single-cell expression analysis and identified periostin as the marker showing the highest correlation to an activated CF phenotype. We generated bacterial artificial chromosome–transgenic mice allowing tamoxifen-inducible Cre expression in periostin-positive cells as well as their diphtheria toxin-mediated ablation. In the healthy heart, periostin expression was restricted to valvular fibroblasts; ablation of this population did not affect cardiac function. After chronic angiotensin II exposure, ablation of activated CF resulted in significantly reduced cardiac fibrosis and improved cardiac function. After myocardial infarction, ablation of periostin-expressing CF resulted in reduced fibrosis without compromising scar stability, and cardiac function was significantly improved. Single-cell transcriptional analysis revealed reduced CF activation but increased expression of prohypertrophic factors in cardiac macrophages and cardiomyocytes, resulting in localized cardiomyocyte hypertrophy. Conclusions: Modulation of the activated CF population is a promising approach to prevent adverse cardiac remodeling in response to angiotensin II and after myocardial infarction.

Fibroblast-specific TGF-β–Smad2/3 signaling underlies cardiac fibrosis

“…We also introduced a single Rosa26-loxP-Stop-loxP-EGFP (R26 EGFP ) reporter allele to allow irreversible tracking of all activated fibroblasts, as previously described (29). Importantly, periostin expression is specifically induced in essentially all activated fibroblasts (myofibroblasts) of the heart with injury (30)(31)(32). Young adult mice were subjected to cardiac pressure overload stimulation by transverse aortic constriction (TAC) surgery over 4 to 12 weeks in the presence of tamoxifen food so that the MCM protein could mediate recombination in activated fibroblasts ( Figure 2B).…”

Preexisting endothelial cells mediate cardiac neovascularization after injury

“…Immunostaining for GFP and PECAM showed that there was no GFP + endothelial cell in hearts before and after injury (Supplemental Figure 5A). It has been reported that periostin is highly expressed in the activated cardiac fibroblasts or myofibroblasts of the injured heart, which are derived from tissue-resident fibroblasts of the TCF21 lineage, but not endothelial cells (6,11). We also used Postn-MerCreMer R26R-GFP for lineage tracing of myofibroblasts in injured heart and did not detect any GFP + endothelial cells (Supplemental Figure 5B).…”

“…During the process of cardiac repair, cardiac fibroblasts are key players and their proliferation is often accompanied by recruitment of blood vascular endothelial cells (6,(11)(12)(13). Ubil et al showed that a substantial number of cardiac fibroblasts contribute to coronary vessels through mesenchymal-to-endothelial transition (MEndoT) in the injured heart (9).…”

Fibroblast deletion of ROCK2 attenuates cardiac hypertrophy, fibrosis, and diastolic dysfunction

“…Fibroblast-specific periostin promoter-driven Cre (Postn-Cre) transgenic mice (mixed background) were provided by Simon J. Conway (Indiana University School of Medicine, Indianapolis, Indiana, USA). Cre recombinase was driven by a 3.9-kb mouse Postn promoter (44)(45)(46). To obtain a fibroblast-specific deletion of the Rock2 gene, (A and B) Representative fluorescent images and quantification of cellular hypertrophy of H9C2 cells stained with sarcomeric α-actinin (green) and DAPI (nuclei, blue).…”