A Multipotent Fibroblast Population Drives a PDGFR-beta-Dependent Immuno-Fibrotic Response in Heart Failure
openNHLBI - National Heart Lung and Blood Institute
Project Summary/Abstract
Cardiac fibrosis compromises left ventricular (LV) function and worsens clinical outcomes in heart failure (HF).
Currently, there are no clinical therapies that target fibrosis in the failing heart. Platelet-derived growth factor
(PDGF), a central mediator of fibrotic responses, acts via two receptors - PDGFRα and PDGFRβ. Our pilot
studies using explant cultures, flow sorting, single cell RNA sequencing (scRNAseq), and in vivo mouse models
have uncovered a novel stem cell antigen(Sca)-1-expressing PDGFRα+ multipotent cardiac fibroblast population
that sources myofibroblasts, interacts with tissue macrophages, and drives fibrotic and inflammatory responses
during adverse LV remodeling. During HF, these cells decrease PDGFRα expression and instead upregulate
PDGFRβ. The role of PDGFRβ in cardiac fibroblast biology in HF is unknown. We propose the novel hypothesis
that a heretofore unrecognized Sca-1+PDGFRβ expressing cardiac fibroblast with mesenchymal stem cell
features (termed cFMSCs) are key drivers of a PDGFRβ-dependent immunofibrotic axis in HF. Three Aims will
test this hypothesis. In Aim 1, using a murine coronary ligation model, in vitro studies of cell function, scRNAseq,
and inducible cardiac fibroblast-specific and Sca1+ cell-specific PDGFRβ-deletion mouse models, we will
comprehensively define the importance of PDGFRβ in cFMSC cell function in ischemic HF. We will isolate
Sca1+PDGFRα+ cFMSCs and assess PDGFR β-dependent myofibroblast differentiation, multipotency,
downstream signaling and immuno-fibrotic secretome, and cFMSC-macrophage interactions. scRNAseq of
sorted cells will assess cFMSC subpopulations and changes in transcriptomic profiles. In Aim 2, we will establish
the pathogenetic role of cFMSC-localized PDGFRβ in chronic HF, by using inducible cardiac fibroblast-specific
PDGFRβ knockout mice, deleting cFMSC PDGFRβ during chronic HF, and assessing late effects on LV
remodeling, fibrosis, tissue macrophages, and inflammatory profiles. To establish necessity of cFMSC PDGFRβ
signaling, cardiac fibroblast PDGFRβ loss will be induced by tamoxifen in PDGFRβf/f-Tcf21MerCreMer mice 4 w post-
MI and LV remodeling, fibrosis, and tissue macrophage and inflammatory profiles will be assessed 6 w Iater.
The effects of sustained cardiac fibroblast PDGFRβ activation on LV remodeling will be assessed using
PDGFRβ[S]D849V-Tcf21MerCreMer mice. To establish sufficiency of cFMSC PDGFRβ signaling, we will perform
intramyocardial adoptive transfer of sorted PDGFRβ-deficient and -competent Sca1+PDGFRα+ cFMSCs from
HF mice into naïve mice and assess late LV remodeling and fibrosis. In Aim 3, we will test potentially translatable
therapies to antagonize cFMSC PDGFRβ signaling in chronic HF, including CP-67345, a specific small molecule
PDGFRβ inhibitor, fibroblast-targeted nanoparticle delivery of PDGFRβ siRNA, and anti-PDGFRβ neutralizing
antibody. We will measure the effects of these therapies on LV remodeling, fibrosis, cFMSC abundance, cardiac
macrophages, and tissue inflammation. By conclusively defining the role of cFMSCs and fibroblast PDGFRβ in
pathological LV remodeling, these studies will provide novel perspectives on the immunofibrotic response in HF.
Up to $765K
health research