Extracellular Matrix Stiffness Controls VEGF Signaling and Processing in Endothelial Cells

Area of Science:

• Cell Biology
• Biomaterials Science
• Mechanobiology

Background:

• Vascular endothelial growth factor A (VEGF) is crucial for endothelial cell function, maintenance, and angiogenesis.
• Endothelial cell behavior and signaling are known to be influenced by the mechanical properties of their surrounding extracellular matrix (ECM).
• The interplay between VEGF activity and the mechanical cellular environment, specifically ECM stiffness, requires further investigation.

Purpose of the Study:

• To investigate how extracellular matrix (ECM) stiffness modulates VEGF binding, internalization, and signaling in endothelial cells.
• To elucidate the role of VEGF-cell-matrix tethering and β1 integrin activation in stiffness-dependent VEGF processing.
• To understand the microenvironmental influence on tissue regeneration and disease response.

Main Methods:

• Endothelial cells were cultured on fibronectin (Fn)-linked polyacrylamide gels of varying stiffness.
• VEGF binding, internalization, and signaling were analyzed as a function of substrate stiffness.
• Inhibitors (sucrose octasulfate) and enhancers (heparin) of VEGF-matrix binding, along with β1 integrin inhibition, were employed.

Main Results:

• Softer substrates showed reduced VEGF binding but enhanced VEGF internalization and signaling.
• VEGF internalization was dependent on ECM binding, with heparin enhancing and sucrose octasulfate inhibiting this process.
• β1 integrin activation was stiffness-dependent, modulating VEGF uptake, with harder surfaces showing decreased activation and greater sensitivity to β1 inhibition.

Conclusions:

• ECM stiffness significantly influences VEGF processing and signaling by altering VEGF-cell-matrix and β1 integrin interactions.
• Coordinated binding and activation of VEGF-matrix and β1 integrins are critical for VEGF internalization, with stiffness playing a modulatory role.
• These findings provide insights into how the mechanical microenvironment impacts tissue regeneration and pathological processes.