Effect of flow on polymorphonuclear leukocyte/endothelial cell adhesion

Area of Science:

• Biomedical Engineering
• Cellular Biology
• Immunology

Background:

• Polymorphonuclear leukocytes (PMNL) play a crucial role in inflammatory responses.
• Endothelial cells form the inner lining of blood vessels and are involved in regulating leukocyte interactions.
• Understanding the dynamics of PMNL-endothelial cell adhesion under flow is vital for comprehending inflammatory processes.

Purpose of the Study:

• To investigate the effect of fluid flow on the adhesion of PMNL to vascular endothelium.
• To quantify PMNL adhesion to stimulated and unstimulated human umbilical vein endothelial cells (HUVEC) under varying shear stresses.
• To compare PMNL adhesion to endothelial cells with adhesion to a non-biological surface.

Main Methods:

• Utilized a parallel plate chamber with a controlled flow field to simulate physiological conditions.
• Washed PMNL were perfused over HUVEC monolayers pretreated with formyl-methionyl-leucyl-phenylalanine (FMLP) or interleukin-1 (IL-1).
• Measured PMNL adhesion to HUVEC and a nylon-coated surface across a range of wall shear stresses (0.98 to 3.92 dynes/cm²).

Main Results:

• PMNL adhesion to FMLP-treated HUVEC was significantly higher than to control HUVEC at lower shear stresses (0.98 and 1.96 dynes/cm²).
• At higher shear stress (3.92 dynes/cm²), PMNL adherence decreased substantially on both control and FMLP-treated HUVEC.
• IL-1 treated HUVEC showed markedly increased PMNL adhesion compared to controls at 1.96 dynes/cm², with adhesion dropping at 3.01 dynes/cm².

Conclusions:

• Fluid flow is a critical determinant of PMNL adhesion to vascular endothelium.
• The level of shear stress directly influences the extent of PMNL-endothelial cell interactions.
• These findings highlight the importance of flow dynamics in the context of inflammatory cell recruitment.