Treatment of cardiac fibrosis: from neuro-hormonal inhibitors to CAR-T cell therapy

Abstract

Cardiac fibrosis is characterized by the deposition of extracellular matrix proteins in the spaces between cardiomyocytes following both acute and chronic tissue damage events, resulting in the remodeling and stiffening of heart tissue. Fibrosis plays an important role in the pathogenesis of many cardiovascular disorders, including heart failure and myocardial infarction. Several studies have identified fibroblasts, which are induced to differentiate into myofibroblasts in response to various types of damage, as the most important cell types involved in the fibrotic process. Some drugs, such as inhibitors of the renin-angiotensin-aldosterone system, have been shown to be effective in reducing cardiac fibrosis. There are currently no drugs with primarily anti-fibrotic action approved for clinical use, as well as the evidence of a clinical efficacy of these drugs is extremely limited, despite the numerous encouraging results from experimental studies. A new approach is represented by the use of CAR-T cells engineered in vivo using lipid nanoparticles containing mRNA coding for a receptor directed against the FAP protein, expressed by cardiac myofibroblasts. This strategy has proved to be safe and effective in reducing myocardial fibrosis and improving cardiac function in mouse models of cardiac fibrosis. Clinical studies are required to test this novel approach in humans.

Keywords: Anti-fibrotic therapies; CAR-T cells; Fibrosis; Heart failure; Myocardium.

Fig. 1

Types of cardiac fibrosis. The extracellular matrix in the healthy heart (left) is a three-dimensional network of collagen fibrils that incorporates cardiomyocytes, capillaries, and fibroblasts. The “reparative” fibrosis (center) is visible as a collagen-based scar that replaces necrotic cardiomyocytes after acute and extensive damage. “Reactive” fibrosis (right) accompanies heart failure and pressure overload, and manifests as diffuse collagen deposition in interstitial and perivascular areas. Modified with permission from Schimmel et al. [115]

Fig. 2

Schematic representation of heterogeneity in fibrotic progression. (Illustration: Maartje Kunen, Medical Visuals.) AngII, angiotensin II; CTGF, connective tissue growth factor; DAMPS, danger-associated molecular patterns; ET-1, endothelin-1; IL, interleukin; L, lymphocyte; Ma, macrophage; MC, mast cell; MCP-1, monocyte chemoattractant protein-1; MF/MyoF, myofibroblast; MMP, matrix metalloproteinase; MV, microvessel; N, neutrophil; PAI, plasminogen activator inhibitor; PDGF, platelet-derived growth factor; TGF, transforming growth factor; TIMP, tissue inhibitor of metalloproteinase; TNF, tumor necrosis factor. Reprinted with permission by de Boer et al. [14]

Fig. 3

Regulation of TGF-β signaling in cardiac fibrosis. Active TGF-β binds to type II and type I receptors, activating downstream Smad-dependent signaling cascades and Smad-independent pathways. TGF-β binding to the ALK5 type 1 receptor and downstream activation of Smad3 signaling induces a matrix-preserving program in cardiac fibroblasts and plays an important role in their activation following cardiac injury. In contrast, the role of ALK1/Smad1/5 signaling in regulation of fibroblast phenotype is poorly understood. Activation of Smad-independent pathways, including RhoA and MAPK signaling, mediates some of the effects of TGF-b in cardiac fibroblasts. Endogenous pathways for negative regulation of TGF-b cascades may protect from excessive or unrestrained fibrotic responses. The inhibitory Smads (Smad6/7), pseudoreceptors such as BAMBI, and soluble endoglin may serve as endogenous inhibitors of TGF-b signaling, limiting pro-fibrotic responses. Reprinted with permission from Frangogiannis [6]

Fig. 4

Ex vivo production of CAR-T cells. Autologous T cells are extracted from the patient, then they are engineered in the laboratory to obtain CAR expression and the differentiation of T lymphocytes into CAR-T cells, which will then be amplified and re-infused into the patient with prior lymphodepletion. Reprinted with permission from https://www.cancer.gov/about-cancer/treatment/research/car-t-cells

Fig. 5

In vivo production of CAR-T cells using CD5/LNP-FAPCAR. Administration of LNP coated with anti-CD5 antibodies and containing mRNA coding for the FAPCAR membrane receptor, which selectively recognizes the FAP protein expressed by cardiac myofibroblasts, allows to obtain transients CAR-T cells in vivo that specifically eliminate the pro-fibrotic cells from the injured myocardium. CAR, chimeric antigen receptor; FAP, fibroblast activation protein; LNP, lipid nanoparticle. Reprinted with permission from Rurik et al. [24]

Fig. 6

In vivo engineered CAR-T cells against FAP improve cardiac function after myocardial damage. Adult wild-type mice C57BL/6 received a continuous infusion with saline or Ang II + PE via mini-osmotic pump implanted for 28 days. After a week of heart damage due to pressure overload, mice received a single dose of 10 mg of CD5/LNP-FAPCAR. Mice were analyzed 2 weeks after treatment. Telediastolic (A) and telesystolic (B) volume measurement of LV. Left Ventricular Mass Index (LVMI) (C), diastolic function (E/e ratio) (D), EF (E), and global longitudinal strain (F) estimation. Picrosirius red staining (G) highlights collagen (pink) in coronal section of uninjured mice (n = 8, 3 weeks after saline infusion pump implantation + 1-week saline injection), damaged control mice (n = 11, Ang II + PE + saline), and damaged treated mice (n = 12, Ang II + PE + CD5/LNP-FAPCAR). The quantification of fibrosis is expressed as a percentage of the observed ventricle. The data are expressed as average ± standard error. The p values shown derive from Tukey’s post hoc test after one-way ANOVA (p < 0.05). Ang II, angiotensin II; EF, ejection fraction; PE, phenylephrine. Modified with permission from Rurik et al. [24]