S-endoglin expression is induced in hyperoxia and contributes to altered pulmonary angiogenesis in bronchopulmonary dysplasia development

Abstract

Altered pulmonary angiogenesis contributes to disrupted alveolarization, which is the main characteristic of bronchopulmonary dysplasia (BPD). Transforming growth factor β (tGfβ) plays an important role during lung vascular development, and recent studies have demonstrated that endoglin is engaged in the modulation of tGfβ downstream signalling. Although there are two different isoforms of endoglin, L-and S-endoglin, little is known about the effect of S-endoglin in developing lungs. We analysed the expression of both L-and S-endoglin in the lung vasculature and its contribution to tGfβ-activin-like kinase (ALK)-Smad signalling with respect to BPD development. Hyperoxia impaired pulmonary angiogenesis accompanied by alveolar simplification in neonatal mouse lungs. S-endoglin, phosphorylated Smad2/3 and connective tissue growth factor levels were significantly increased in hyperoxia-exposed mice, while L-endoglin, phosphor-Smad1/5 and platelet-endothelial cell adhesion molecule-1 levels were significantly decreased. Hyperoxia suppressed the tubular growth of human pulmonary microvascular endothelial cells (ECs), and the selective inhibition of ALK5 signalling restored tubular growth. These results indicate that hyperoxia alters the balance in two isoforms of endoglin towards increased S-endoglin and that S-endoglin attenuates TGFβ-ALK1-Smad1/5 signalling but stimulates tGfβ-ALK5-Smad2/3 signalling in pulmonary ECs, which may lead to impaired pulmonary angiogenesis in developing lungs. open Scientific RepoRtS | (2020) 10:3043 | https://doi.org/10.1038/s41598-020-59928-x www.nature.com/scientificreports www.nature.com/scientificreports/ through enhancement of the TGFβ-ALK1-Smad1/5 pathway, while connective tissue growth factor (CTGF) expression increases through enhancement of the TGFβ-ALK5-Smad2/3 pathway [27][28][29][30][31] .Several independent findings have demonstrated that endoglin is engaged in TGFβ receptor complex formation and the modulation of downstream signalling [32][33][34][35] . The expression of two alternatively spliced isoforms, long (L-) endoglin and short (S-) endoglin, has been demonstrated in human and mouse lung tissues in vivo 33,34,36,37 . L-endoglin is the predominant isoform, and its pre-mRNA can be alternatively spliced by intron retention, producing the less abundant form, S-endoglin 36,37 . Evidence indicates that L-endoglin, the predominant isoform in ECs, promotes EC proliferation via TGFβ-ALK1 signalling, whereas S-endoglin acts as an antagonist of L-endoglin via activation of the TGFβ-ALK5 pathway 32,33,36,37 .To date, most studies published on endoglin have focused on L-endoglin. It has been found that L-endoglin enhances ALK1-Smad1/5 signalling in ECs, leading to proliferation and migration, which are the main characteristics of the activation phase of angiogenesis 15,18,20,22,[38][39][40][41][42][43] . However, a role of S-endoglin during endothelial senescence was recently described 36,37 . The S-endoglin:L-endoglin ratio increases during the senescence of ECs in vitro as well ...

Endothelial to mesenchymal transition during neonatal hyperoxia‐induced pulmonary hypertension

“…To counter this, Smad7 antagonizes TGF‐β signaling by binding to ALK5 and inhibiting the recruitment and phosphorylation of Smad2 and Smad3 [48]. Previous studies have shown that neonatal hyperoxic exposure spatiotemporally affects TGF‐β signaling in mouse lungs [49–52]. We found that hyperoxic exposure increased the phosphorylation of both Smad2 and Samd3, and reduced Smad7 protein levels in cultured lung ECs.…”

BMP Receptor Inhibition Enhances Tissue Repair in Endoglin Heterozygous Mice

“…Both isoforms are able to bind TGFβ but differ in phosphorylation status and their ability to interact with ALK1 and ALK5 [ 43 , 44 ]. A recent study showed that hypoxia-induced expression of S-endoglin stimulates signaling via TGFβ/ALK5/Smad2, causing impaired angiogenesis in the pulmonary vasculature of the developing lung [ 45 ]. Although we analyzed the impact of endoglin heterozygosity, determining which isoform of endoglin is involved in the pathology of HHT is an interesting topic for future research.…”

Alternative splicing in endothelial cells: novel therapeutic opportunities in cancer angiogenesis

“… S-endoglin Expression/function Interacts with TGFβ type I receptors ALK5, stimulating ALK5 pathway. Associated with altered pulmonary angiogenesis [ 98 ]. It is induced by senescence and able to contribute to NO-dependent vascular homeostasis.…”

“…In senescent ECs, SRSF1 leads to an increased expression of S-endoglin mRNA [ 161 ]. More recently, S-endoglin-mediated ALK5 signaling has been related to altered pulmonary angiogenesis induced by hyperoxia [ 98 ].…”