Matrix stiffness-dependent microglia activation in response to inflammatory cues: in situ investigation by scanning
Yulin Liu1,2, Junjie Zhang1,2, Yabei Li2,3
1The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University Xi'an 710049 P. R. China fengxu@mail.xjtu.edu.cn feili@mail.xjtu.edu.cn.
Abstract:
Microglia play a crucial role in maintaining the homeostasis of the central nervous system (CNS) by sensing and responding to mechanical and inflammatory cues in their microenvironment. However, the interplay between mechanical and inflammatory cues in regulating microglia activation remains elusive. In this work, we constructed in vitro mechanical-inflammatory coupled microenvironment models of microglia by culturing BV2 cells (a murine microglial cell line) on polyacrylamide gels with tunable stiffness and incorporating a lipopolysaccharide (LPS) to mimic the physiological and pathological microenvironment of microglia in the hippocampus. Through characterization of activation-related proteins, cytokines, and reactive oxygen species (ROS) levels, we observed that the LPS treatment induced microglia on a stiff matrix to exhibit overexpression of NOX2, higher levels of ROS and inflammatory factors compared to those on a soft matrix. Additionally, using scanning electrochemical microscopy (SECM), we performed in situ characterization and discovered that microglia on a stiff matrix promoted extracellular ROS production, leading to a disruption in their redox balance and increased susceptibility to LPS-induced ROS production. Furthermore, the respiratory activity and migration behavior of microglia were closely associated with their activation process, with the stiff matrix-LPS-induced microglia demonstrating the most pronounced changes in respiratory activity and migration ability. This work represents the first in situ and dynamic monitoring of microglia activation state alterations under a mechanical-inflammatory coupled microenvironment using SECM. Our findings shed light on matrix stiffness-dependent activation of microglia in response to an inflammatory microenvironment, providing valuable insights into the mechanisms underlying neuroinflammatory processes in the CNS.
Insights
Matrix stiffness influences microglia activation. Stiff environments amplify inflammatory responses, increasing reactive oxygen species (ROS) and altering cell behavior, crucial for understanding neuroinflammation.
Area of Science:
- Neuroscience
- Cell Biology
- Biomaterials Science
Background:
- Microglia are key immune cells in the central nervous system (CNS), maintaining homeostasis by responding to environmental cues.
- The interaction between mechanical forces and inflammation in regulating microglia activation is not fully understood.
- Understanding these interactions is vital for neuroinflammatory disease research.
Purpose of the Study:
- To investigate how mechanical cues (matrix stiffness) and inflammatory signals (lipopolysaccharide - LPS) synergistically regulate microglia activation.
- To develop and utilize advanced in vitro models for dynamic monitoring of microglia responses.
- To elucidate the role of mechanical-inflammatory coupling in CNS neuroinflammation.
Main Methods:
- Construction of in vitro mechanical-inflammatory coupled microenvironment models using polyacrylamide gels of tunable stiffness and LPS stimulation.
- Culturing of BV2 murine microglial cells on these models to mimic CNS microenvironments.
- Characterization of activation markers, including proteins, cytokines, and reactive oxygen species (ROS).
- In situ monitoring using scanning electrochemical microscopy (SECM) to assess real-time cellular activity and ROS production.
Main Results:
- Microglia cultured on stiff matrices exhibited enhanced overexpression of NOX2, increased ROS levels, and elevated inflammatory factors upon LPS treatment compared to those on soft matrices.
- Stiff matrices promoted extracellular ROS production, disrupting redox balance and increasing susceptibility to LPS-induced ROS.
- Microglia activation on stiff matrices with LPS significantly altered respiratory activity and migration behavior.
- SECM enabled the first in situ, dynamic monitoring of microglia activation under coupled mechanical-inflammatory conditions.
Conclusions:
- Matrix stiffness plays a critical role in modulating microglia activation in response to inflammatory stimuli.
- Stiff microenvironments exacerbate LPS-induced inflammatory responses in microglia, impacting ROS production and cellular functions.
- These findings provide novel insights into the mechanisms of neuroinflammation and offer potential targets for therapeutic interventions in CNS disorders.
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