Defining an Upstream VEGF (Vascular Endothelial Growth Factor) Priming Signature for Downstream Factor-Induced...

Area of Science:

• Cell Biology
• Molecular Biology
• Vascular Biology

Background:

• Human vascular morphogenesis and maturation involve complex growth factor signaling.
• Endothelial cell (EC) tube formation and pericyte interactions are critical for blood vessel development.

Purpose of the Study:

• To define growth factor requirements for human vascular morphogenesis.
• To elucidate the signaling basis for EC tube formation and maturation.
• To investigate the role of vascular endothelial growth factor (VEGF) priming in EC responses.

Main Methods:

• Utilized a serum-free model of EC tube morphogenesis in 3D collagen matrices.
• Employed VEGF pretreatment (priming) of ECs.
• Investigated the roles of RhoA, Rho-kinase (Rock1), protein kinase C alpha (PKCα), and protein kinase D2 (PKD2) using siRNA and pharmacological blockade.
• Analyzed EC factor receptor and growth factor expression.

Main Results:

• VEGF priming for 8 hours significantly increased EC response to growth factors, including tip cell formation, tubulogenesis, pericyte recruitment, and basement membrane deposition.
• VEGF priming necessitates VEGFR2, selectively enhancing the priming response without affecting basal tubulogenesis.
• Key signaling molecules for VEGF priming include RhoA, Rock1, PKCα, and PKD2.
• VEGF priming upregulated EC factor receptors and EC-derived growth factors like PDGF-BB, PDGF-DD, and HB-EGF, promoting pericyte activity.

Conclusions:

• VEGF priming represents a distinct upstream step that activates ECs.
• This activation enables ECs to respond to downstream factors essential for forming branching vascular networks with mural cells.