VEGFR3 is required for button junction formation in lymphatic vessels

Area of Science:

• Molecular Biology
• Cell Biology
• Physiology

Background:

• Lymphatic capillaries absorb large molecules and fluid via discontinuous cell-cell junctions.
• Vascular endothelial growth factor receptor 2 (VEGFR2) signaling can seal these junctions.
• The role of vascular endothelial growth factor receptor 3 (VEGFR3) in lymphatic junction regulation is not fully understood.

Purpose of the Study:

• To investigate the function of VEGFR3 signaling in lymphatic endothelial cell junctions.
• To determine the role of VEGFR3 in the formation of specialized lymphatic junctions and absorption.

Main Methods:

• Utilized lymphatic-specific Flt4 knockout mice to study VEGFR3 signaling.
• Performed knockdown of FLT4 in human lymphatic endothelial cells.
• Assessed NOTCH1 expression and activation.
• Overexpressed the NOTCH1 intracellular domain in Flt4 knockout vessels.

Main Results:

• Loss of Flt4 (VEGFR3) prevented specialized button junction formation in lymphatic vessels across multiple tissues.
• Impaired interstitial absorption was observed in Flt4 knockout mice.
• FLT4 knockdown in human lymphatic endothelial cells led to reduced NOTCH1 expression and activation.
• NOTCH1 intracellular domain overexpression rescued button junction formation and molecular absorption in Flt4 knockout vessels.

Conclusions:

• VEGFR3 and NOTCH1 signaling are essential for the development of button junctions in lymphatic vessels during postnatal development.
• This pathway is critical for proper lymphatic absorption.
• Findings may have clinical implications for lymphatic diseases involving impaired VEGFR3 signaling.