Quantifying the proteolytic release of extracellular matrix-sequestered VEGF with a computational model

Area of Science:

• Biochemistry
• Cell Biology
• Biophysics

Background:

• Vascular Endothelial Growth Factor (VEGF) proteolysis by plasmin or matrix metalloproteinases (MMPs) is critical for regulating vascular patterning by releasing VEGF from the extracellular matrix (ECM).
• Quantitative understanding of VEGF cleavage kinetics and cell-mediated release efficiency is limited.
• A molecular-detailed quantitative model of VEGF proteolysis in endothelial sprouts was developed to address these gaps.

Purpose of the Study:

• To quantitatively model VEGF proteolysis, including MMP secretion, VEGF-ECM binding, VEGF cleavage, and receptor-mediated recapture.
• To determine the kinetics of VEGF cleavage by plasmin.
• To assess the capacity of single cells and tissue components in mediating VEGF release and processing.

Main Methods:

• Developed a molecular-detailed quantitative model of VEGF proteolysis.
• Incorporated MMP secretion, VEGF-ECM binding, VEGF cleavage (VEGF165 to VEGF114), and receptor-mediated recapture into the model.
• Estimated the effective bimolecular rate constant for VEGF165 cleavage by plasmin using experimental data.

Main Results:

• The effective bimolecular rate constant for VEGF165 cleavage by plasmin was estimated at 328 M(-1) s(-1) at 25°C, indicating relatively slow kinetics.
• Single cells demonstrated minimal capacity for VEGF cleavage (<0.1% conversion).
• Tip cells showed inefficient recapture of cleaved VEGF due to impaired association with Neuropilin-1.

Conclusions:

• VEGF cleavage in vivo is likely a collective cellular process, not an autocrine single-cell function.
• Heparan sulfate proteoglycans (HSPGs) enhance VEGF cleavage by increasing tissue clearance time.
• The VEGF-HSPG complex is more protease-sensitive than soluble VEGF, suggesting relevance in signaling. Pathological VEGF cleavage levels require protease concentrations far exceeding experimentally measured soluble levels.