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Neff LS, Biggs RM, Zhang Y, Van Laer AO, Baicu CF, Subramanian S, Berto S, DeLeon-Pennell K, Zile MR, Bradshaw AD. Role of macrophages in regression of myocardial fibrosis following alleviation of left ventricular pressure overload. Am J Physiol Heart Circ Physiol 2024; 326:H1204-H1218. [PMID: 38363214 DOI: 10.1152/ajpheart.00240.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 01/30/2024] [Accepted: 02/12/2024] [Indexed: 02/17/2024]
Abstract
Sustained hemodynamic pressure overload (PO) produced by murine transverse aortic constriction (TAC) causes myocardial fibrosis; removal of TAC (unTAC) returns left ventricle (LV) hemodynamic load to normal and results in significant, but incomplete regression of myocardial fibrosis. However, the cellular mechanisms that result in these outcomes have not been defined. The objective was to determine temporal changes in myocardial macrophage phenotype in TAC and unTAC and determine whether macrophage depletion alters collagen degradation after unTAC. Myocardial macrophage abundance and phenotype were assessed by immunohistochemistry, flow cytometry, and gene expression by RT-PCR in control (non-TAC), 2 wk, 4 wk TAC, and 2 wk, 4 wk, and 6 wk unTAC. Myocardial cytokine profiles and collagen-degrading enzymes were determined by immunoassay and immunoblots. Initial collagen degradation was detected with collagen-hybridizing peptide (CHP). At unTAC, macrophages were depleted with clodronate liposomes, and endpoints were measured at 2 wk unTAC. Macrophage number had a defined temporal pattern: increased in 2 wk and 4 wk TAC, followed by increases at 2 wk unTAC (over 4 wk TAC) that then decreased at 4 wk and 6 wk unTAC. At 2 wk unTAC, macrophage area was significantly increased and was regionally associated with CHP reactivity. Cytokine profiles in unTAC reflected a proinflammatory milieu versus the TAC-induced profibrotic milieu. Single-cell sequencing analysis of 2 wk TAC versus 2 and 6 wk unTAC revealed distinct macrophage gene expression profiles at each time point demonstrating unique macrophage populations in unTAC versus TAC myocardium. Clodronate liposome depletion at unTAC reduced CHP reactivity and decreased cathepsin K and proMMP2. We conclude that temporal changes in number and phenotype of macrophages play a critical role in both TAC-induced development and unTAC-mediated partial, but incomplete, regression of myocardial fibrosis.NEW & NOTEWORTHY Our novel findings highlight the dynamic changes in myocardial macrophage populations that occur in response to PO and after alleviation of PO. Our data demonstrated, for the first time, a potential benefit of macrophages in contributing to collagen degradation and the partial regression of interstitial fibrosis following normalization of hemodynamic load.
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Affiliation(s)
- Lily S Neff
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Rachel M Biggs
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Yuhua Zhang
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
| | - An O Van Laer
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Catalin F Baicu
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Suganya Subramanian
- Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Stefano Berto
- Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina, United States
| | - Kristine DeLeon-Pennell
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
- The Ralph H. Johnson Department of Veteran's Affairs Medical Center, Charleston, South Carolina, United States
| | - Michael R Zile
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
- The Ralph H. Johnson Department of Veteran's Affairs Medical Center, Charleston, South Carolina, United States
| | - Amy D Bradshaw
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States
- The Ralph H. Johnson Department of Veteran's Affairs Medical Center, Charleston, South Carolina, United States
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Neff LS, Zhang Y, Van Laer AO, Baicu CF, Karavan M, Zile MR, Bradshaw AD. Mechanisms that limit regression of myocardial fibrosis following removal of left ventricular pressure overload. Am J Physiol Heart Circ Physiol 2022; 323:H165-H175. [PMID: 35657618 PMCID: PMC9236876 DOI: 10.1152/ajpheart.00148.2022] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 05/09/2022] [Accepted: 05/26/2022] [Indexed: 11/22/2022]
Abstract
Left ventricular pressure overload (LVPO) can develop from antecedent diseases such as aortic valve stenosis and systemic hypertension and is characterized by accumulation of myocardial extracellular matrix (ECM). Evidence from patient and animal models supports limited reductions in ECM following alleviation of PO, however, mechanisms that control the extent and timing of ECM regression are undefined. LVPO, induced by 4 wk of transverse aortic constriction (TAC) in mice, was alleviated by removal of the band (unTAC). Cardiomyocyte cross-sectional area, collagen volume fraction (CVF), myocardial stiffness, and collagen degradation were assessed for: control, 2-wk TAC, 4-wk TAC, 4-wk TAC + 2-wk unTAC, 4-wk TAC + 4-wk unTAC, and 4-wk TAC + 6-wk unTAC. When compared with 4-wk TAC, 2-wk unTAC resulted in increased reactivity of collagen hybridizing peptide (CHP) (representing initiation of collagen degradation), increased levels of collagenases and gelatinases, decreased levels of collagen cross-linking enzymes, but no change in CVF. When compared with 2-wk unTAC, 4-wk unTAC demonstrated decreased CVF, which did not decline to control values. At 4-wk and 6-wk unTAC, CHP reactivity and mediators of ECM degradation were reduced versus 2-wk unTAC, whereas levels of tissue inhibitor of metalloproteinase (TIMP)-1 increased. ECM homeostasis changed in a time-dependent manner after removal of LVPO and is characterized by early increases in collagen degradation, followed by a later dampening of this process. Tempered ECM degradation with time is predicted to contribute to the finding that normalization of hemodynamic overload alone does not completely regress myocardial fibrosis.NEW & NOTEWORTHY In this study, a murine model demonstrated persistent interstitial fibrosis and myocardial stiffness following alleviation of pressure overload.
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Affiliation(s)
- Lily S Neff
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Yuhua Zhang
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - An O Van Laer
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Catalin F Baicu
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Mark Karavan
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Michael R Zile
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
- The Ralph H. Johnson Department of Veterans Affairs Medical Center, Charleston, South Carolina
| | - Amy D Bradshaw
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
- The Ralph H. Johnson Department of Veterans Affairs Medical Center, Charleston, South Carolina
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