Research Article| Volume 235, P129-143, September 2021

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Endoglin deficiency impairs VEGFR2 but not FGFR1 or TIE2 activation and alters VEGF-mediated cellular responses in human primary endothelial cells

  • Author Footnotes
    1 These authors contributed equally to this work.
    Qiuwang Zhang
    1 These authors contributed equally to this work.
    Division of Cardiology, Keenan Research Center for Biomedical Science, St. Michael's Hospital, Unity Health Toronto, University of Toronto, Toronto, Ontario, Canada
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  • Author Footnotes
    1 These authors contributed equally to this work.
    Chenxi Wang
    1 These authors contributed equally to this work.
    Department of Cardiovascular Surgery, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
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  • Anthony Cannavicci
    Division of Cardiology, Keenan Research Center for Biomedical Science, St. Michael's Hospital, Unity Health Toronto, University of Toronto, Toronto, Ontario, Canada

    Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
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  • Marie E. Faughnan
    Toronto HHT Centre, St. Michael's Hospital and Li Ka Shing Knowledge Institute, Toronto, Canada

    Division of Respirology, Department of Medicine, University of Toronto, Toronto, Canada
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  • Michael J.B. Kutryk
    Reprint requests: Michael J. B. Kutryk, Division of Cardiology, Keenan Research Center for Biomedical Science, St. Michael's Hospital, Unity Health Toronto, University of Toronto, 209 Victoria Street, Toronto, Ontario, M5B 1T8, Canada.
    Division of Cardiology, Keenan Research Center for Biomedical Science, St. Michael's Hospital, Unity Health Toronto, University of Toronto, Toronto, Ontario, Canada

    Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
    Search for articles by this author
  • Author Footnotes
    1 These authors contributed equally to this work.
Published:April 21, 2021DOI:
      Hereditary hemorrhagic telangiectasia (HHT) is a genetic disease characterized by vascular dysplasia. Mutations of the endoglin (ENG) gene that encodes a co-receptor of the transforming growth factor β1 signaling pathway cause type I HHT. ENG is primarily expressed in endothelial cells (ECs), but its interaction with other key angiogenic pathways to control angiogenesis has not been well addressed. The aim of this study is to investigate ENG interplay with VEGFR2, FGFR1 and TIE2 in primary human ECs. ENG was knocked-down with siRNA in human umbilical vein ECs (HUVECs) and human lung microvascular ECs (HMVEC-L). Gene expression was measured by RT-qPCR and Western blotting. Cell signaling pathway activation was analyzed by detecting phosphor-ERK and phosphor-AKT levels. Cell migration and apoptosis were assessed using the Boyden chamber assay and the CCK-8 Kit, respectively. Loss of ENG in HUVECs led to significantly reduced expression of VEGFR2 but not TIE2 or FGFR1, which was also confirmed in HMVEC-L. HUVECs lacking ENG had significantly lower levels of active Rac1 and a substantial reduction of the transcription factor Sp1, an activator of VEGFR2 transcription, in nuclei. Furthermore, VEGF- but not bFGF- or angiopoietin-1-induced phosphor-ERK and phosphor-AKT were suppressed in ENG deficient HUVECs. Functional analysis revealed that ENG knockdown inhibited cell migratory but enhanced anti-apoptotic activity induced by VEGF. In contrast, bFGF, angiopoietin-1 and -2 induced HUVEC migration and anti-apoptotic activities were not affected by ENG knockdown. In conclusion, ENG deficiency alters the VEGF/VEGFR2 pathway, which may play a role in HHT pathogenesis.


      HHT (Hereditary hemorrhagic telangiectasia), ENG (Endoglin), EC (Endothelial cell), HUVEC (Human umbilical vein endothelial cell), HMVEC-L (Human lung microvascular endothelial cell), AVM (Arteriovenous malformation), ALK (Activin receptor-like kinase), SMAD (Mothers against decapentaplegic homolog), TGF-β (Transforming growth factor-beta), ANGPT (Angiopoietin), siRNA (Small interfering RNA), RT-qPCR (Reverse transcription-quantitative polymerase chain reaction), ERK (Extracellular signal-regulated kinase), VEGF-A (Vascular endothelial growth factor A), VEGFR2 (Vascular endothelial growth factor receptor 2), TIE2 and TEK (Tyrosine-protein kinase receptor), FGF2 (fibroblast growth factor 2), FGFR (Fibroblast growth factor receptor), NF-kB (Nuclear factor kappa B), Sp1 (Specific protein 1), Rac1 (Ras-related C3 botulinum toxin substrate 1), GAPDH (Glyceraldehyde 3-phosphate dehydrogenase)
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