Modeling Microglia Activation and Inflammation-Based Neuroprotectant Strategies During Ischemic Stroke

TL;DR

This paper develops a nonlinear differential equation model of microglia activation during ischemic stroke, analyzing how neuroprotectants can shift microglia from harmful to beneficial phenotypes to improve recovery.

Contribution

It introduces a novel mathematical model capturing bidirectional microglia phenotype switching and evaluates neuroprotectant strategies to promote beneficial microglia activation.

Findings

Bidirectional switching significantly affects M1/M2 ratio.

Early M1 inhibition and M2 support reduce harmful microglia.

Model highlights importance of timing in neuroprotectant application.

Abstract

Neural inflammation immediately follows the onset of ischemic stroke. During this process, microglial cells can be activated into two different phenotypes: the M1 phenotype, which can worsen brain injury by producing pro-inflammatory cytokines; or the M2 phenotype, which can aid in long term recovery by producing anti-inflammatory cytokines. In this study, we formulate a nonlinear system of differential equations to model the activation of microglia post-ischemic stroke, which includes bidirectional switching between the microglia phenotypes, as well as the interactions between these cells and the cytokines that they produce. Further, we explore neuroprotectant-based modeling strategies to suppress the activation of the detrimental M1 phenotype, while promoting activation of the beneficial M2 phenotype. Through use of global sensitivity techniques, we analyze the effects of the model parameters on the ratio of M1 to M2 microglia and the total number of activated microglial cells in the system over time. Results demonstrate the significance of bidirectional microglia phenotype switching on the ratio of M1 to M2 microglia, in both the absence and presence of neuroprotectant terms. Simulations further suggest that early inhibition of M1 activation and support of M2 activation leads to a decreased minimum ratio of M1 to M2 microglia and allows for a larger number of M2 than M1 cells for a longer time period.