Evaluating the role of cardiac fibroblast p53 in governing the pathologic remodeling response to pressure overload in the heart

ABSTRACT: Cardiomyopathy is characterized by the deposition of extracellular matrix by activated resident cardiac fibroblasts, called myofibroblasts. A current lack of therapeutic approaches to blunt the development of pathological fibrosis and ventricle chamber stiffening that ultimately leads to heart failure necessitates the investigation of the mechanisms that underlie myofibroblast activation. We previously observed that increased degradation of p53 occurs during the cardiac fibroblast expansion phase that acutely follows pressure overload. We created tissue-specific mouse models to delete p53 in quiescent resident cardiac fibroblasts and in activated myofibroblasts, then evaluated consequences to cardiac physiology, cellular biology, and fibrotic remodeling. We then performed RNA sequencing to further elucidate the effects of p53 deletion in cardiac fibroblasts on gene expression at the single cell level. We confirmed these results with a series of in vitro experiments in primary mouse cardiac fibroblasts. Results - Here, we demonstrate that p53 knockout in resident cardiac fibroblasts significantly accelerates proliferation and temporarily insulates the heart from fibrotic remodeling and functional decline in response to pressure overload, but ultimately results in a more deleterious phenotype than in wildtype animals. Conversely, p53 knockout in activated myofibroblasts does not result in a delay in functional loss, and is uniformly deleterious to the heart. Single-cell RNA sequencing revealed that p53 knockout is associated with the development of constitutively mitotic fibroblasts, and increased recruitment of fibroblasts into a main activation trajectory that involves four states: quiescent, early transitional, late transitional, and fully activated. A quiescent, functionally specialized vascular support fibroblast population that is ubiquitous in the wildtype animal is additionally recruited into activation in the p53 knockout condition, resulting in the eventual extreme functional decline seen in these animals. In vitro experimentation using viral deletion of p53 supports these findings - quiescent fibroblasts lacking p53 are resistant to activation, but activated myofibroblasts lacking p53 do not reverse their activation. This was found to be due to parallel hyperactivation of Cdkn2a/Rb1-mediated G1 cell cycle arrest in the p53 knockout condition, which was supported by in vivo studies. Conclusions - These data establish p53 as a major regulator of the myofibroblast activation response to pressure overload. Moreover, the single-cell studies establish an activation trajectory for resident cardiac fibroblasts, and elucidate the fundamental importance of clinical intervention prior to irreversible myofibroblast activation seen in chronic stages of pressure overload.

ORGANISM(S): Mus musculus

PROVIDER: GSE165455 | GEO | 2023/06/23

REPOSITORIES: GEO