Cardiac mesenchymal stem cells promote fibrosis and remodeling in heart failure: Role of PDGF signaling

Heart failure (HF) is characterized by progressive fibrosis. Both fibroblasts and mesenchymal stem cells (MSCs) can differentiate into pro-fibrotic myofibroblasts. MSCs secrete and express platelet-derived growth factor (PDGF) and its receptors. We hypothesized that PDGF signaling in cardiac MSCs (cMSCs) promotes their myofibroblast differentiation and aggravates post-myocardial infarction left ventricular remodeling and fibrosis. We show that cMSCs from failing hearts post-myocardial infarction exhibit an altered phenotype. Inhibition of PDGF signaling in vitro inhibited cMSC-myofibroblast differentiation, whereas in vivo inhibition during established ischemic HF alleviated left ventricular remodeling and function, and decreased myocardial fibrosis, hypertrophy, and inflammation. Modulating cMSC PDGF receptor expression may thus represent a novel approach to limit pathologic cardiac fibrosis in HF

Mononuclear Phagocytes Are Dispensable for Cardiac Remodeling in Established Pressure-Overload Heart Failure.

Although cardiac and splenic mononuclear phagocytes (MPs), i.e., monocytes, macrophages and dendritic cells (DCs), are key contributors to cardiac remodeling after myocardial infarction, their role in pressure-overload remodeling is unclear. We tested the hypothesis that these immune cells are required for the progression of remodeling in pressure-overload heart failure (HF), and that MP depletion would ameliorate remodeling.C57BL/6 mice were subjected to transverse aortic constriction (TAC) or sham operation, and assessed for alterations in MPs. As compared with sham, TAC mice exhibited expansion of circulating LyC6hi monocytes and pro-inflammatory CD206- cardiac macrophages early (1 w) after pressure-overload, prior to significant hypertrophy and systolic dysfunction, with subsequent resolution during chronic HF. In contrast, classical DCs were expanded in the heart in a biphasic manner, with peaks both early, analogous to macrophages, and late (8 w), during established HF. There was no significant expansion of circulating DCs, or Ly6C+ monocytes and DCs in the spleen. Periodic systemic MP depletion from 2 to 16 w after TAC in macrophage Fas-induced apoptosis (MaFIA) transgenic mice did not alter cardiac remodeling progression, nor did splenectomy in mice with established HF after TAC. Lastly, adoptive transfer of splenocytes from TAC HF mice into naïve recipients did not induce immediate or long-term cardiac dysfunction in recipient mice.Mononuclear phagocytes populations expand in a phasic manner in the heart during pressure-overload. However, they are dispensable for the progression of remodeling and failure once significant hypertrophy is evident and blood monocytosis has normalized

Adoptive transfer of splenocytes from sham-operated and TAC mice.

<p><b><i>A</i>,</b> Schematic of protocol for the adoptive transfer of splenocytes, harvested from CD45.2⁺ MaFIA mice 8 w after TAC or sham operation, into naïve CD45.1⁺ recipient mice. AP20187 or vehicle was administered immediately after transfer. <b><i>B</i>,</b> Representative FACS plots of blood from recipient mice 24 h after adoptive transfer and administration of either vehicle or AP20187, and corresponding group data for CD45.2⁺ cells (n = 10/group). *p<0.05 vs. vehicle. <b><i>C</i>,</b> Heart weight normalized to tibia length in recipient mice 8 w after adoptive transfer of either sham or TAC splenocytes, with or without concomitant AP20187 (n = 5/group). <b><i>D</i>,</b> Echocardiographic parameters in recipient mice, over the 8 w course after adoptive transfer. EF, ejection fraction; EDV and ESV, end-diastolic and end-systolic volume.</p

Cardiac macrophage abundance during pressure-overload remodeling.

<p><b><i>A</i>,</b> Representative gating strategy used to identify cardiac macrophages, as well as CD206⁺ and CD206⁻ macrophage subsets, in mouse hearts. <b><i>B</i></b>, Quantitation of flow cytometry data collected from cardiac mononuclear cell isolates at the indicated time points after TAC or sham operation, including total CD45⁺ leukocytes, total CD45⁺CD11b⁺F480⁺MHCII⁺ macrophages, and <b><i>C</i>,</b> CD206⁻ (M1) and CD206⁺ (M2) macrophages. <b><i>D</i>,</b> Quantitation of flow cytometry data for Lin^–CD11b⁺Ly6C^hi and Lin^–CD11b⁺Ly6C^low peripheral blood monocytes at the indicated time points. n = 6–10 in sham groups; n = 6–12 in TAC groups. *p<0.05 vs. sham.</p

Gravimetric measurements in 8 w TAC and sham mice.

<p>Gravimetric measurements in 8 w TAC and sham mice.</p

TAC-induced cardiac remodeling.

<p><b><i>A</i>,</b><i>Left</i>, Representative 2D images and Doppler traces across the aortic arch in sham-operated and TAC mice at 8 w after surgery demonstrating marked elevated blood flow velocity in TAC mice. <i>Right</i>, corresponding group data for the pressure gradient in the same groups measured serially over time. <b><i>B</i></b>, Representative M-mode echocardiograms performed at various time points after TAC or sham surgery, along with group data for LV posterior wall thickness at end-diastole (LVPWd), relative wall thickness (RWT, 2 * LVPWd/end-diastolic diameter), LV end-diastolic volume (EDV), and LV ejection Fraction (EF). n = 5–6 in sham groups and n = 6–8 in TAC groups. *p<0.05, **p<0.01, ***p<0.001 vs. sham.</p

Dendritic cell populations in the heart during pressure-overload remodeling.

<p><b><i>A</i>,</b> Representative gating strategy used to identify cardiac DCs, including plasmacytoid and classical DCs, in the same mouse hearts as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170781#pone.0170781.g002" target="_blank">Fig 2</a>. <b><i>B</i></b>, Quantitation of flow cytometry data from the heart at the indicated time points after TAC or sham operation, including total CD45⁺CD11c⁺MHCII⁺ DCs, CD11c^lowMHCII⁺B220⁺ plasmacytoid DCs, and CD11c⁺MHCII⁺B220⁻ classical DCs. *p<0.05 vs. sham.</p

Mononuclear phagocyte depletion during pressure-overload in MaFIA mice.

<p><b><i>A</i>,</b> Schematic of the experimental protocol for periodic macrophage and DC ablation in MaFIA mice starting 2 w after TAC or sham operation. <b><i>B</i></b>, Kaplan-Meier survival curves for MaFIA mice treated with either AP20187 or vehicle after TAC or sham operation (n = 5 for sham groups, n = 7 for TAC groups). <b><i>C</i>,</b> Representative FACS plots of EGFP⁺ cells in peripheral blood from MaFIA mice 3 d after AP20187 or vehicle treatment, and corresponding quantitation of EGFP⁺Lin⁻CD11b⁺ monocytes and EGFP⁺Lin⁻CD11c⁺ dendritic cells (n = 5 per group), *p<0.05, **p<0.01 vs. vehicle controls. <b><i>D</i>,</b> Echocardiographic parameters in sham-operated and TAC MaFIA mice treated with either vehicle or AP20187 as per the protocol in panel A. EF, ejection fraction; EDV, end-diastolic volume; ESV, end-systolic volume. <b><i>E</i>,</b> LV gravimetric data for sham and TAC MaFIA mice treated with vehicle or AP20187; TL, tibia length. <b><i>F</i>,</b> Representative Masson trichrome stains of LV sections 16 w after TAC or sham surgery in MaFIA mice treated with either vehicle or AP20187, and quantitation of tissue fibrosis. Scale bar, 100 μm. For panels <b><i>D-F</i></b>, n = 5 in sham groups, n = 7–8 in TAC groups. *p < 0.05, **p<0.01 vs. respective sham group.</p

CCR2+ Monocyte-Derived Infiltrating Macrophages Are Required for Adverse Cardiac Remodeling During Pressure Overload

Summary: Although chronic inflammation is a central feature of heart failure (HF), the immune cell profiles differ with different underlying causes. This suggests that for immunomodulatory therapy in HF to be successful, it needs to be tailored to the specific etiology. Here, the authors demonstrate that monocyte-derived C-C chemokine receptor 2 (CCR2)+ macrophages infiltrate the heart early during pressure overload in mice, and that blocking this response either pharmacologically or with antibody-mediated CCR2+ monocyte depletion alleviates late pathological left ventricular remodeling and dysfunction, T-cell expansion, and cardiac fibrosis. Hence, suppression of CCR2+ monocytes/macrophages may be an important immunomodulatory therapeutic target to ameliorate pressure-overload HF. Key Words: cardiac remodeling, heart failure, inflammation, macrophages, T cell