Lymphatic endothelial cells adapt their barrier function in response to changes in shear stress

Area of Science:

• Biomedical Engineering
• Cell Biology
• Physiology

Background:

• Lymphatic endothelial cells (LECs) form a critical barrier for lymph formation and propulsion.
• The impact of physical forces, specifically fluid shear stress, on LEC barrier function remains largely unexplored.

Purpose of the Study:

• To investigate how laminar flow affects the barrier function of human dermal microlymphatic endothelial cells (HMLEC-d).
• To determine if LECs activate their intracellular actin cytoskeleton in response to altered shear stress to improve barrier function.

Main Methods:

• HMLEC-d were cultured on electrodes within a flow channel to measure transendothelial electrical resistance (TER) as an index of barrier function.
• Cells were subjected to varying levels of laminar shear stress (0.5 to 9.0 dynes/cm(2)).
• Pharmacological agents were used to block actin dynamics (phalloidin) and Rac1 activity (NSC23766), and protein kinase A (H-89).

Main Results:

• Increased shear stress led to a dose-dependent enhancement of barrier function (TER), which was reversible upon return to baseline flow.
• The flow-induced increase in barrier function was abolished by phalloidin and significantly inhibited by NSC23766.
• Blockade of protein kinase A did not affect the response, and mathematical modeling indicated altered paracellular current flow.

Conclusions:

• Lymphatic endothelial cells exhibit dynamic alterations in morphology and barrier function in response to shear stress.
• This response is mediated by Rac1-dependent actin cytoskeleton dynamics.
• These findings highlight a novel mechanism for maintaining lymphatic endothelial barrier integrity under physiological flow conditions.