Control of Matrix Stiffness Using Methacrylate–Gelatin Hydrogels for a Macrophage-Mediated Inflammatory Response

Abstract

The successful tissue integration of a biomedical material is mainly determined by the inflammatory response after implantation. Macrophage behavior toward implanted materials is pivotal to determine the extent of the inflammatory response. Hydrogels with different properties have been developed for various biomedical applications such as wound dressings or cell-loaded scaffolds. However, there is limited investigation available on the effects of hydrogel mechanical properties on macrophage behavior and the further host inflammatory response. To this end, methacrylate–gelatin (GelMA) hydrogels were selected as a model material to study the effect of hydrogel stiffness (2, 10, and 29 kPa) on macrophage phenotype in vitro and the further host inflammatory response in vivo. Our data showed that macrophages seeded on stiffer surfaces tended to induce macrophages toward a proinflammatory (M1) phenotype with increased macrophage spreading, more defined F-actin and focal adhesion staining, and more proinflammatory cytokine secretion and cluster of differentiation (CD) marker expression compared to those on surfaces with a lower stiffness. When these hydrogels were further subcutaneously implanted in mice to assess their inflammatory response, GelMA hydrogels with a lower stiffness showed more macrophage infiltration but thinner fibrotic capsule formation. The more severe inflammatory response can be attributed to the higher percentage of M1 macrophages induced by GelMA hydrogels with a higher stiffness. Collectively, our data demonstrated that macrophage behavior and the further inflammatory response are mechanically regulated by hydrogel stiffness. The macrophage phenotype rather than the macrophage number predominately determined the inflammatory response after the implantation, which can provide new insights into the future design and application of novel hydrogel-based biomaterials.

Cordyceps militaris Immunomodulatory Protein Promotes the Phagocytic Ability of Macrophages through the TLR4-NF-κB Pathway

“…As shown, the content of F-actin rose after CMIMP addition (p < 0.001) (Figure 2E,F). Comparing with the undifferentiated macrophages, the content and microfilament spreading area of F-actin is increased in M1 cells [26]. In line with that, macrophages were induced into M1 phenotype by CMIMP [19].…”

Macrophage–stroma interactions in fibrosis: biochemical, biophysical, and cellular perspectives

“…Several studies have indicated an effect of substrate stiffness on macrophage behaviour. Although the studied stiffnesses and compositions of the substrates varied greatly, stiffening of the substrate is generally associated with more macrophage adhesion and a bigger and more flattened phenotype as compared to a smaller and more rounded shape on soft substrates [71–82]. Nonetheless, these observed morphological changes on two‐dimensional (2D) substrates may not be fully translatable to an in vivo situation.…”

“…The effect of substrate stiffness on pro‐inflammatory or profibrotic responses of macrophages has also not yet been shown conclusively. Most studies indicated more pro‐inflammatory behaviour when substrate stiffness increased, based on the expression of markers such as IL‐1β, IL‐6, and TNF‐α [75,78,80,81,83,88,89], although the opposite has also been described [77,82,87,90]. However, these studies all investigated short‐term responses of macrophages to substrates of various stiffnesses.…”

Silk Biomaterials for Bone Tissue Engineering

“…Therefore, bone biomaterials with favorable immunoregulation properties could create the anticipated immune niches and stimulate the secretion of osteogenic and osteoclast cytokines in bone regeneration process. [ 46–48 ]…”