Fibroblasts under pressure: Cardiac fibroblast responses to hypertension and antihypertensive therapies.

Approximately 50% of Americans have hypertension which significantly increases the risk of heart failure. In response to increased peripheral resistance in hypertension, intensified mechanical stretch in the myocardium induces cardiomyocyte hypertrophy and fibroblast activation to withstand increased pressure overload. This changes the structure and function of the heart leading to pathological cardiac remodeling and eventual progression to heart failure. In the presence of hypertensive stimuli, cardiac fibroblasts activate and differentiate to myofibroblast phenotype capable of enhanced extracellular matrix secretion in coordination with other cell types, mainly cardiomyocytes. Both systemic and local renin angiotensin/aldosterone system activation leads to increased angiotensin II stimulation of fibroblasts. Angiotensin II directly activates fibrotic signaling such as transforming growth factor /SMAD and mitogen activated protein kinase (MAPK) signaling to produce extracellular matrix comprised of collagens and matricellular proteins. With the advent of single cell RNA sequencing techniques, heterogeneity in fibroblast populations has been identified in the left ventricle in models of hypertension and pressure overload. The various clusters of fibroblasts reveal a range of phenotypes and activation states. Select antihypertensive therapies have been shown to be effective in limiting fibrosis with some having direct actions on cardiac fibroblasts. The present review will focus on the fibroblast-specific changes that occur in response to hypertension and pressure overload, the knowledge gained from single cell analyses, and the effect of antihypertensive therapies. Understanding the dynamics of hypertensive fibroblast population and their similarities and differences by sex is crucial for the advent of new targets and personalized medicine.