ABSTRACT Pulmonary arterial hypertension (PAH) is a life‐threatening condition with no cure, making research into its underlying mechanisms critical. The platelet‐derived growth factor (PDGF) signaling pathway plays a crucial role in vascular remodeling, a key factor in PAH progression. Anti‐PDGF receptor therapies, such as imatinib, show promise but are associated with significant side effects. Recent research identified PDGF‐D as a new risk gene in idiopathic PAH, highlighting the need for further investigation into the PDGF pathway in the disease. In this study, we investigated PDGF‐D, a specific PDGFRβ ligand, as a potential therapeutic target. RNA‐Seq data from healthy lungs indicated that PDGF‐D is predominantly expressed in inflammatory cells, whereas in vascular lesions of idiopathic PAH patients, PDGF‐D was produced by various cell types. In vitro, PDGF‐D induced mitogenic effects on pulmonary arterial smooth muscle cells. However, genetic deletion of PDGF‐D in the chronic hypoxia mouse model of pulmonary hypertension showed no significant impact on vascular muscularization, hemodynamic parameters, or right ventricular hypertrophy. But, the absence of hypoxia‐induced Pdgfrb upregulation and the lack of increased expression of PAH‐regulated genes, Fgf2 and Notch3, in PDGF‐D‐deficient mice, suggests activation of alternative mechanisms. MicroRNA analyses revealed PDGF‐d‐related alterations in the expression of miR‐21 and miR‐451, both important regulators in PAH, further supporting the notion that PDGF‐D plays a unique role in PAH development. Taken together, our data suggest that PDGF‐D may target a distinct population of PDGFRβ‐expressing cells, separate from those stimulated by PDGF‐B, positioning PDGF‐D as a potentially unique and compelling therapeutic target for PAH.

Vascular smooth muscle cell plasticity plays a pivotal role in the pathophysiology of vascular diseases. Despite compelling evidence demonstrating the importance of transcription factor GATA6 in vascular smooth muscle, the functional role of GATA6 remains poorly understood. The aim of this study was to elucidate the role of GATA6 on cell migration and to gain insight into GATA6-sensitive genes in smooth muscle. We found that overexpression of GATA6 promotes migration of human coronary artery smooth muscle cells in vitro, and that silencing of GATA6 in smooth muscle cells resulted in reduced cellular motility. Furthermore, a complete microarray screen of GATA6-sensitive gene transcription resulted in 739 upregulated and 248 downregulated genes. Pathways enrichment analysis showed involvement of transforming growth factor beta (TGF-β) signaling which was validated by measuring mRNA expression level of several members. Furthermore, master regulators prediction based on microarray data revealed several members of (mitogen activated protein kinase) MAPK pathway as a master regulators, reflecting involvement of MAPK pathway also. Our findings provide further insights into the functional role of GATA6 in vascular smooth muscle and suggest that targeting GATA6 may constitute as a new approach to inhibit vascular smooth muscle migration.

Background: Hypertension remains a major risk factor for cardiovascular diseases, but the underlying mechanisms are not well understood. We hypothesize that appropriate mechanotransduction and contractile function in vascular smooth muscle cells are crucial to maintain vascular wall integrity. The Hippo pathway effectors YAP (yes-associated protein 1) and TAZ (WW domain containing transcription regulator 1) have been identified as mechanosensitive transcriptional coactivators. However, their role in vascular smooth muscle cell mechanotransduction has not been investigated in vivo. Methods: We performed physiological and molecular analyses utilizing an inducible smooth muscle–specific YAP/TAZ knockout mouse model. Results: Arteries lacking YAP/TAZ have reduced agonist-mediated contraction, decreased myogenic response, and attenuated stretch-induced transcriptional regulation of smooth muscle markers. Moreover, in established hypertension, YAP/TAZ knockout results in severe vascular lesions in small mesenteric arteries characterized by neointimal hyperplasia, elastin degradation, and adventitial thickening. Conclusions: This study demonstrates a protective role of YAP/TAZ against hypertensive vasculopathy.

OBJECTIVE Smooth muscle cells contribute significantly to lipid-laden foam cells in atherosclerotic plaques. However, the underlying mechanisms transforming smooth muscle cells into foam cells are poorly understood. The purpose of this study was to gain insight into the molecular mechanisms regulating smooth muscle foam cell formation. APPROACH AND RESULTS Using human coronary artery smooth muscle cells we found that the transcriptional co-activator MRTFA promotes lipid accumulation via several mechanisms, including direct transcriptional control of LDL receptor, enhanced fluid-phase pinocytosis and reduced lipid efflux. Inhibition of MRTF activity with CCG1423 and CCG203971 significantly reduced lipid accumulation. Furthermore, we demonstrate enhanced MRTFA expression in vascular remodeling of human vessels. CONCLUSIONS This study demonstrates a novel role for MRTFA as an important regulator of lipid homeostasis in vascular smooth muscle cells. Thus, MRTFA could potentially be a new therapeutic target for inhibition of vascular lipid accumulation.

Background & Aims YAP (Yap1) and TAZ (Wwtr1) are transcriptional co-activators and downstream effectors of the Hippo pathway, which play crucial roles in organ size control and cancer pathogenesis. Genetic deletion of YAP/TAZ has shown their critical importance for embryonic development of the heart, vasculature, and gastrointestinal mesenchyme. The aim of this study was to determine the functional role of YAP/TAZ in adult smooth muscle cells in vivo. Methods Because YAP and TAZ are mutually redundant, we used YAP/TAZ double-floxed mice crossed with mice that express tamoxifen-inducible CreERT2 recombinase driven by the smooth muscle–specific myosin heavy chain promoter. Results Double-knockout of YAP/TAZ in adult smooth muscle causes lethality within 2 weeks, mainly owing to colonic pseudo-obstruction, characterized by severe distension and fecal impaction. RNA sequencing in colon and urinary bladder showed that smooth muscle markers and muscarinic receptors were down-regulated in the YAP/TAZ knockout. The same transcripts also correlated with YAP/TAZ in the human colon. Myograph experiments showed reduced contractility to depolarization by potassium chloride and a nearly abolished muscarinic contraction and spontaneous activity in colon rings of YAP/TAZ knockout. Conclusions YAP and TAZ in smooth muscle are guardians of colonic contractility and control expression of contractile proteins and muscarinic receptors. The knockout model has features of human chronic intestinal pseudo-obstruction and may be useful for studying this disease.