Basement Membrane Remodeling Controls Endothelial Function in Idiopathic Pulmonary Arterial Hypertension

Abstract

The extracellular matrix (ECM) increasingly emerges as an active driver in several diseases, including idiopathic pulmonary arterial hypertension (IPAH). The basement membrane (BM) is a specialized class of ECM proteins. In pulmonary arteries, the BM is in close contact and direct proximity to vascular cells, including endothelial cells. So far, the role of the BM has remained underinvestigated in IPAH. Here, we aimed to shed light on the involvement of the BM in IPAH, by addressing its structure, composition, and function. On an ultrastructural level, we observed a marked increase in BM thickness in IPAH pulmonary vessels. BM composition was distinct in small and large vessels and altered in IPAH. Proteoglycans were mostly responsible for distinction between smaller and larger vessels, whereas BM collagens and laminins were more abundantly expressed in IPAH. Type IV collagen and laminin both strengthened endothelial barrier integrity. However, only type IV collagen concentration dependently increased cell adhesion of both donor and IPAH-derived pulmonary arterial endothelial cells (PAECs) and induced nuclear translocation of mechanosensitive transcriptional coactivator of the hippo pathway YAP (Yes-activated protein). On the other hand, laminin caused cytoplasmic retention of YAP in IPAH PAECs. Accordingly, silencing of COL4A5 and LAMC1, respectively, differentially affected tight junction formation and barrier integrity in both donor and IPAH PAECs. Collectively, our results highlight the importance of a well-maintained BM homeostasis. By linking changes in BM structure and composition to altered endothelial cell function, we here suggest an active involvement of the BM in IPAH pathogenesis.

Endothelial Basement Membrane Components and Their Products, Matrikines: Active Drivers of Pulmonary Hypertension?

“…Other BM collagens, COL4A1/COL4A2, were decreased in isolated and cultured ECs from IPAH [173]. In larger PAs, BM glycoproteins such as laminins were mostly affected [4]. Similarly, other BM components, such as the proteoglycan versican, have been elevated in remodeled PAs [174], and protein levels of BM HSPGs agrin and perlecan were higher in lung tissue of PAH patients [175].…”

“…Similarly, other BM components, such as the proteoglycan versican, have been elevated in remodeled PAs [174], and protein levels of BM HSPGs agrin and perlecan were higher in lung tissue of PAH patients [175]. Ultimately, those changes are reflected on the ultrastructure level where the BM appeared thickened, repeatedly underlined by areas with partially degraded BM-like material, and occasionally multiple-layered in remodeled arteries [4].…”

“…The main feature of PH is the remodeling of distal and proximal PAs accompanied by increased ECM deposition and turnover [167]. This takes place in all three layers of the vessel wall, with the neointima being most affected [4,5,168]. Increasingly, research identified that ECM deposition is not merely a consequence, but an active driver of the disease [169].…”

“…Several alterations in the expression of BM components have been identified in PH (see Figure 2). A comparative transcriptomic analysis of healthy and remodeled small, distal PAs obtained via laser-capture microdissection identified the BM as one of the most affected cellular components [4,5], and COL4A5, COL14A1, and COL18A1 were upregulated in small remodeled PAs, in the intima and media layer [5]. Other BM collagens, COL4A1/COL4A2, were decreased in isolated and cultured ECs from IPAH [173].…”

“…The culture of PAEC on type IV collagen and laminin strengthen barrier and integrity. While adhesion to type IV collagen triggers nuclear translocation of YAP/TAZ, adhesion to laminin α5β2γ1 retains YAP/TAZ in the cytoplasm [4]. Endostatin blocks ID-1 gene expression and decreases THBS1-transcription and production [177].…”