Macrophage anti-inflammatory behaviour in a multiphase model of atherosclerotic plaque development

TL;DR

This paper presents a multiphase model of early atherosclerotic plaques to study how impaired macrophage anti-inflammatory functions influence plaque development and structure, highlighting the roles of cell death, efferocytosis, and emigration.

Contribution

The study introduces a novel free boundary multiphase model to analyze the impact of dysfunctional macrophage behaviour on plaque growth and composition.

Findings

High cell death rates lead to plaques with mostly dead cells.

Efferocytosis and emigration can slow or stop plaque growth.

Impaired macrophage clearance hinders plaque resolution.

Abstract

Atherosclerosis is an inflammatory disease characterised by the formation of plaques, which are deposits of lipids and cholesterol-laden macrophages that form in the artery wall. The inflammation is often non-resolving, due in large part to changes in normal macrophage anti-inflammatory behaviour that are induced by the toxic plaque microenvironment. These changes include higher death rates, defective efferocytic uptake of dead cells, and reduced rates of emigration. We develop a free boundary multiphase model for early atherosclerotic plaques, and we use it to investigate the effects of impaired macrophage anti-inflammatory behaviour on plaque structure and growth. We find that high rates of cell death relative to efferocytic uptake results in a plaque populated mostly by dead cells. We also find that emigration can potentially slow or halt plaque growth by allowing material to exit the plaque, but this is contingent on the availability of live macrophage foam cells in the deep plaque. Finally, we introduce an additional bead species to model macrophage tagging via microspheres, and we use the extended model to explore how high rates of cell death and low rates of efferocytosis and emigration prevent the clearance of macrophages from the plaque.