# Dual inhibition of TGFβ and PDGF improves RV remodeling and function in response to RV pressure or volume‐loading

## TL;DR

Blocking TGFβ and PDGF together improves heart function in conditions causing right ventricular stress.

## Contribution

The study shows that dual inhibition of TGFβ and PDGF with Tranilast improves RV remodeling in pressure and volume overload.

## Key findings

- TRN reduced TGFβ signaling and improved RV fibrosis, hypertrophy, and function in pressure-loaded rats.
- TRN normalized ERK1/2 activity and reduced hypertrophy and diastolic dysfunction in volume-loaded rats.
- PDGF drives fibroblast activation via SMAD2/3, JNK, and β-catenin pathways in RV remodeling.

## Abstract

Right ventricular (RV) pressure and volume loading induce RV fibrosis in association with RV dysfunction, morbidity, and mortality in repaired tetralogy of Fallot. Transforming‐growth factor‐β1 (TGFβ1) and platelet‐derived growth factor (PDGF) activate common downstream signaling pathways via TGFβ canonical and non‐canonical signaling to promote increased fibroblast activation, proliferation, and fibrosis in other organs. However, the role of PDGF and TGFβ canonical and non‐canonical signaling in RV fibrosis is incompletely characterized. Here, we investigate whether dual inhibition of TGFβ and PDGF, using Tranilast (TRN), improves RV remodeling in response to pulmonary artery banding (PAB) or pulmonary regurgitation (PR). TRN reduced TGFβ canonical signaling in PAB rats associated with improved RV fibrosis, hypertrophy, and RV function. In response to PR, TRN reduced PDGFRβ expression and normalized ERK1/2 activity, which were associated with reduced RV hypertrophy and improved diastolic relaxation. We identify that PDGF drives RV fibroblast proliferation and activation via SMAD2/3, JNK, and β‐catenin signaling. Our studies suggest that TGFβ and PDGF are interconnected drivers of RV fibrosis and hence synergistic targets to improve RV remodeling in RV pressure and volume loading.