Abstract Rationale Pulmonary arterial hypertension is a progressive vasculopathy characterized by vascular remodeling, elevated pulmonary arterial pressure and right ventricular hypertrophy (RVH). Regulator of G-protein signaling 5 (Rgs5) is a negative regulator of G protein-coupled receptor (GPCR) signaling enriched in lung pericytes (PCs). Although implicated in pulmonary hypertension (PH) and cardiac fibrosis, its specific role in PC remains undefined. We hypothesize that loss of Rgs5 leads to PC differentiation into smooth muscle-like cells by activating GPCR pathway, thus contributing to vascular remodeling in PH. Methods To study the role of Rgs5 in PCs during PH development, novel Rgs5PC-KO (Higd1b-CreERT2::Rosa26-Rgs5fl/fl) mice were generated and subjected to hypoxia (Hx, FiO2:10%) for 3 weeks to induce PH. PH and RVH were evaluated by measuring right ventricular systolic pressure (RVSP) and Fulton Index (FI). Vascular remodeling in Rgs5PC-KO and wild type was evaluated by immunofluorescence (IF) staining in precision cut lung slices using a high resolution confocal microscope. RGS5 function in human healthy PCs was evaluated by overexpressing RGS5 and contractility of PCs was analyzed by IF staining of smooth muscle cell-specific contractile protein such as SM22 and smooth muscle actin (SMA). Results Overexpression of RGS5 in healthy PCs led to a decrease in the expression of SM22 and SMA, suggesting that RGS5 negatively regulates contractile protein expression in PCs. Consistently, hypoxic Rgs5PC-KO mice developed severe PH, with elevated RVSP (38.4 mmHg, Fig 1B) and RVH (FI: 33.6%, Fig 1C). IF analyses further revealed that PCs integrated into muscularized vessels by expressing Sma and exhibited abnormal Sma+ cell outgrowth along distal pulmonary arterioles in Rgs5PC-KO under normoxic (Nor) and Hx conditions (Fig 1D). Conclusion Rgs5 deficiency in PCs is a key contributor to their differentiation into smooth muscle-like cells, abnormal vascular remodeling, and the PH development (Fig 1A). These findings provide novel insights into the role of RGS5 in PCs which could serve as a new treatment strategy for PAH.Figure 1: Loss of Rgs5 in PCs develop severe vascular remodeling and PH in Rgs5PC-KO mouse after 3wk Hx. (A) Proposed working model. (B) Elevated RVSP after 3wk Hx in Rgs5PC-KO (n = 25) compared to WT (n = 8-18). (C) FI was measured for RVH (n = 7-21). Mean ± S.D. Two-way ANOVA. P-value:**** 0.0001, ***0.001, **0.01, *0.05 (D) Representative IF image of Cd31 (green), Pdgfrβ (red), Sma (white), and DAPI (blue). Yellow boxes highlight magnified area, comparing Sma- PCs in WT and Sma+ PCs covering distal arterioles in Rgs5PC-KO lungs. This abstract is funded by: None
Kim et al. (Fri,) studied this question.