Substrate stiffness modulates bone marrow-derived macrophage polarization through NF-κB signaling pathway

Mimi Chen; Yu Zhang; Pinghui Zhou; Xingzhi Liu; Huan Zhao; Xichao Zhou; Qiaoli Gu; Bin Li; Xuesong Zhu; Qin Shi

doi:10.1016/j.bioactmat.2020.05.004

Substrate stiffness modulates bone marrow-derived macrophage polarization through NF-κB signaling pathway

Bioact Mater. 2020 Jun 30;5(4):880-890. doi: 10.1016/j.bioactmat.2020.05.004. eCollection 2020 Dec.

Authors

Mimi Chen¹, Yu Zhang¹, Pinghui Zhou¹, Xingzhi Liu¹, Huan Zhao¹, Xichao Zhou¹, Qiaoli Gu¹, Bin Li¹, Xuesong Zhu¹, Qin Shi^{1

2}

Affiliations

¹ Department of Orthopedics, The First Affiliated Hospital of Soochow University, Orthopedic Institute, Medical College, Soochow University, 188 Shizi Road, Suzhou, Jiangsu, 215006, PR China.
² Key Laboratory of Stem Cells and Biomedical Materials of Jiangsu Province and Chinese Ministry of Science and Technology, 199 Renai Road, Suzhou, 215123, PR China.

Abstract

The stiffness of the extracellular matrix (ECM) plays an important role in regulating the cellular programming. However, the mechanical characteristics of ECM affecting cell differentiation are still under investigated. Herein, we aimed to study the effect of ECM substrate stiffness on macrophage polarization. We prepared polyacrylamide hydrogels with different substrate stiffness, respectively. After the hydrogels were confirmed to have a good biocompatibility, the bone marrow-derived macrophages (BMMs) from mice were incubated on the hydrogels. With simulated by the low substrate stiffness, BMMs displayed an enhanced expression of CD86 on the cell surface and production of reactive oxygen species (ROS) in cells, and secreted more IL-1β and TNF-α in the supernatant. On the contrary, stressed by the medium stiffness, BMMs expressed more CD206, produced less ROS, and secreted more IL-4 and TGF-β. In vivo study by delivered the hydrogels subcutaneously in mice, more CD68⁺CD86⁺ cells around the hydrogels with the low substrate stiffness were observed while more CD68⁺CD206⁺ cells near by the middle stiffness hydrogels. In addition, the expressions of NIK, phosphorylated p65 (pi-p65) and phosphorylated IκB (pi-IκB) were significantly increased after stimulation with low stiffness in BMMs. Taken together, these findings demonstrated that substrate stiffness could affect macrophages polarization. Low substrate stiffness promoted BMMs to shift to classically activated macrophages (M1) and the middle one to alternatively activated macrophages (M2), through modulating ROS-initiated NF-κB pathway. Therefore, we anticipated ECM-based substrate stiffness with immune modulation would be under consideration in the clinical applications if necessary.

Keywords: Macrophage polarization; NF-κB signaling pathway; Substrate stiffness.