AKT/FOXO1 axis links cross-talking of endothelial cell and pericyte in TIE2-mutated venous malformations

Abstract

Background: Venous malformations (VMs), most of which associated with activating mutations in the endothelial cells (ECs) tyrosine kinase receptor TIE2, are characterized by dilated and immature veins with scarce smooth muscle cells (SMCs) coverage. However, the underlying mechanism of interaction between ECs and SMCs responsible for VMs has not been fully understood. Methods: Here, we screened 5 patients with TIE2-L914F mutation who were diagnosed with VMs by SNP sequencing, and we compared the expression of platelet-derived growth factor beta (PDGFB) and α-SMA in TIE2 mutant veins and normal veins by immunohistochemistry. In vitro, we generated TIE2-L914F-expressing human umbilical vein endothelial cells (HUVECs) and performed BrdU, CCK-8, transwell and tube formation experiments on none-transfected and transfected ECs. Then we investigated the effects of rapamycin (RAPA) on cellular characteristics. Next we established a co-culture system and investigated the role of AKT/FOXO1/PDGFB in regulating cross-talking of mutant ECs and SMCs. Results: VMs with TIE2-L914F mutation showed lower expression of PDGFB and α-SMA than normal veins. TIE2 mutant ECs revealed enhanced cell viability and motility, and decreased tube formation, whereas these phenotypes could be reversed by rapamycin. Mechanically, RAPA ameliorated the physiological function of mutant ECs by inhibiting AKT-mTOR pathway, but also facilitated the nuclear location of FOXO1 and the expression of PDGFB in mutant ECs, and then improved paracrine interactions between ECs and SMCs. Moreover, TIE2 mutant ECs strongly accelerated the transition of SMCs from contractile phenotype to synthetic phenotype, whereas RAPA could prevent the phenotype transition of SMCs. Conclusions: Our data demonstrate a previously unknown mechanistic linkage of AKT-mTOR/FOXO1 pathway between mutant ECs and SMCs in modulating venous dysmorphogenesis, and AKT/FOXO1 axis might be a potential therapeutic target for the recovery of TIE2-mutation causing VMs.

Phenotypic Transition of Vascular Smooth Muscle Cells Induced by Endothelial TIE2 Mutations in Venous Malformations

“…3A). Although Tie2 mutation is commonly recognized as an abnormally activated mutation [13,20], the sequencing results showed that the Tie2 mutation background induced the downregulation of 126 genes in pulmonary vascular malformations, and more than 62 genes were upregulated (Fig. 3B).…”

“…Under the in uence of TIE2 mutation in ECs, most studies have focused on the recruitment de ciency of VSMCs [7,12]. However, few investigations have been carried out to emphasize the alteration of the contractile function and strength of VSMCs, which may also play an important role in the VM formation process [13].…”

The Genetic Architecture of Vascular Anomalies: Current Data and Future Therapeutic Perspectives Correlated with Molecular Mechanisms

“…In vitro, it has been shown that all TEK ( TIE2 ) mutations lead to ligand-independent hyperphosphorylation of the receptor and a permanent activation of the PI3K/AKT/mTOR signaling pathway, the effect being stronger in the presence of a double mutation, compared to the presence of a single mutation of the TEK gene [ 39 , 40 ].…”

“…Mutations in the TEK/ TIE2 gene significantly impede the ability of ECs to produce PDGFB. Downregulation of PDGFB depends on AKT phosphorylation (FOXO1-Mediated Activation of AKT) [ 40 ]. Si et al [ 40 ] showed that the TEK L9144F mutation acts through the AKT/FOXO1/PDGFB pathway to produce VMs.…”

“…Downregulation of PDGFB depends on AKT phosphorylation (FOXO1-Mediated Activation of AKT) [ 40 ]. Si et al [ 40 ] showed that the TEK L9144F mutation acts through the AKT/FOXO1/PDGFB pathway to produce VMs. Based on this proven fact, AKT pathway inhibitory therapy could represent an effective therapeutic strategy in the case of VMs caused by the TEK L9144F mutation [ 40 ].…”