Extracellular matrix rigidity controls podosome induction in microvascular endothelial cells

Area of Science:

• Cell Biology
• Endothelial Cell Biology
• Cytoskeletal Dynamics

Background:

• Podosomes are actin-based structures crucial for endothelial cell functions like adhesion and matrix degradation.
• While known in large vessel cells, podosome formation in microvascular endothelial cells, particularly liver sinusoidal endothelial cells (LSECs), remained uncharacterized.
• Liver fibrosis impacts LSECs, causing dedifferentiation and loss of fenestrae, potentially influenced by matrix stiffness.

Purpose of the Study:

• To investigate the presence and regulation of podosomes in microvascular endothelial cells, specifically LSECs.
• To determine the impact of substrate rigidity on podosome formation in LSECs.
• To explore factors influencing podosome stability and formation in LSECs.

Main Methods:

• Primary LSECs were cultured and analyzed for podosome formation.
• Matrix stiffness was manipulated to assess its effect on podosome structures.
• Cell treatments included cytokines (TGF-β, VEGF), detachment/reseeding, and actin-destabilizing drugs.

Main Results:

• Primary LSECs constitutively form podosomes, independent of cytokines like TGF-β or VEGF.
• Podosome presence in LSECs is modulated by matrix stiffness.
• LSECs lose podosomes upon dedifferentiation in culture but can reform them after stress or drug treatment.
• Constitutive podosomes were observed in primary microvascular endothelial cells from other organs.

Conclusions:

• Microvascular endothelial cells possess the intrinsic ability to form podosomes without external stimulation.
• Substrate rigidity emerges as the key determinant for inducing podosome formation in these cells.
• These findings highlight the role of the cellular microenvironment in regulating microvascular endothelial cell behavior.