Artificial shear stress effects on leukocytes at a biomaterial interface

Area of Science:

• Biomaterials Science
• Immunology
• Medical Device Engineering

Background:

• Ventricular assist devices (VADs) involve foreign materials and artificial shear stress.
• The combined effects on leukocytes and immune response are not fully understood.
• This knowledge gap hinders understanding of VAD-related infections and pump thrombosis.

Purpose of the Study:

• To investigate the impact of common VAD biomaterials (DLC, sapphire, titanium) on leukocyte function.
• To determine how shear stress influences these biomaterial-leukocyte interactions.
• To elucidate mechanisms underlying VAD-associated complications like infection and thrombosis.

Main Methods:

• Exposed whole human blood to diamond-like carbon (DLC), sapphire (Sap), and titanium (Ti) surfaces under static and sheared (1000 s⁻¹) conditions.
• Analyzed blood for complete cell counts, leukocyte activation (L-selectin expression), cell death, microparticle generation, phagocytosis, reactive oxygen species (ROS) production, and pro-inflammatory cytokine release.
• Assessed LPS-stimulated macrophage migration inhibitory factor (MIF) production.

Main Results:

• Biomaterials alone and with shear stress decreased L-selectin expression on monocytes.
• Shear stress on Sap and Ti surfaces activated neutrophils, indicated by decreased L-selectin.
• Sap and Ti blunted LPS-stimulated MIF production, particularly Ti under shear stress.
• Biomaterials activated leukocytes statically, with shear stress exacerbating this activation.

Conclusions:

• Biomaterials used in VADs can activate leukocytes, with shear stress potentially worsening this effect.
• Titanium, a common biocompatible material, can induce immune cell activation and inhibit MIF secretion under shear stress.
• Findings offer insights into VAD-related infections, sepsis susceptibility, and pump thrombosis.