Abstract Body (Do not enter title and authors here): Background: Pulmonary arterial hypertension (PAH) is a fatal disease characterized by progressive vascular remodeling, leading to increased pulmonary arterial pressure and right ventricular failure. Our previous studies identified regulator of G-protein signaling 5 (Rgs5) as a key negative regulator of G protein-coupled receptor (GPCR) signaling, uniquely expressed in pulmonary pericytes (PCs). Rgs5 has been implicated in the development of pulmonary hypertension (PH), and its deficiency has been linked to cardiac fibrosis. However, the specific role of Rgs5 in PC function is underinvestigated. Therefore, we hypothesize that Rgs5 deficiency promotes PC differentiation into contractile protein-enriched cells by activating the GPCR pathway, contributing to vascular remodeling during PH development.
Methods: To directly examine the role of Rgs5 in PCs during PH development, novel Rgs5^PC-KO (Higd1b-CreERT2::Rosa26-Rgs5^fl/fl) transgenic mice were generated and subjected to hypoxia (FiO₂:10%) for 3 weeks. PH and right ventricle hypertrophy were evaluated by measuring right ventricle systolic pressure (RVSP) and Fulton index (FI). Vascular remodeling in Rgs5^PC-KO and WT were 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 using the pcDNA3-RGS5 plasmid.
Results: Overexpression of RGS5 in healthy PCs resulted in the downgulation of smooth muscle cell-specific contractile protein expression such as SMA, Vimentin, and SM22, indicating RGS5 negatively regulates contractile protein expression in PCs. Additionally, hypoxic Rgs5^PC-KO mice developed severe PH with RVSP reaching up to 38.4 mmHg (Fig 1B) and RVH (FI: 34.1%, Fig 1C). IF analyses revealed that PCs integrated into muscularized vessels with coexpression of SMA, and exhibited abnormal stromal cell outgrowth along distal pulmonary arterioles in Rgs5^PC-KO under normoxic and hypoxic conditions (Fig 1D).
Conclusions: Loss of Rgs5 in PCs is a key contributor to PC differentiation into contractile protein-enriched cells, abnormal vascular remodeling, and the PH development (Fig 1A). These findings provide novel insights into the role of RGS5 in PCs and could serve as a new treatment strategy for PAH.