Work

M2 macrophage co-culture overrides viscoelastic hydrogel mechanics to promote IL-6-dependent fibroblast activation

Year: 2025

Type: article

Abstract: Fibroblast activation drives fibrotic disease; however, the complex interplay of how tissue mechanics and macrophage signaling combine to influence fibroblast activation remains unclear. Using hyaluronic acid hydrogels to mimic lung stiffness and viscoelasticity, we investigated macrophage influence on fibroblast activation. Fibroblasts cultured on stiff (50 kPa) hydrogels mimicking fibrotic tissue exhibit increased activation, as measured by cell spreading and type I collagen and cadherin-11 expression, compared with fibroblasts cultured on soft (1 kPa) viscoelastic hydrogels mimicking normal lung. Macrophage-conditioned media did not alter these trends, however co-culture with M2 macrophages increased fibroblast activation independent of direct macrophage contact, even on soft viscoelastic hydrogels. Blocking interleukin-6 (IL-6) signaling mitigated this pro-fibrotic effect but did not affect fibroblast-only cultures. These findings demonstrate that M2 macrophages override hydrogel viscoelasticity to promote fibroblast activation independent of direct contact in an IL-6-dependent manner and highlight the utility of hydrogels in deconstructing complex tissue microenvironments. • M2 macrophages override mechanical cues to activate fibroblasts on soft matrices • Macrophage-conditioned media alone is insufficient to activate fibroblasts • IL-6 is a critical factor in M2 macrophage-induced fibroblast activation Given the limited treatment options and poor prognosis of fibrotic lung diseases, a deeper understanding of the factors that trigger and drive disease progression is critical. Fibrotic diseases develop when fibroblasts become overactive, producing excess amounts of protein that stiffen tissue and impair function. However, the combined influence of changes in tissue stiffness and immune signaling on this process is not well understood. To explore this, we used tunable hydrogels that mimic the mechanical properties of normal and fibrotic lung tissue. We found fibroblasts on stiffer hydrogels, resembling scarred lung tissue, showed increased activation. Surprisingly, while macrophage-secreted factors alone had little effect, co-culturing fibroblasts with M2 macrophages significantly enhanced activation, even on soft, healthy tissue-like hydrogels. This effect was dependent on IL-6 signaling, suggesting that M2 macrophages can override the mechanical environment to drive fibrosis. These findings emphasize the role of immune cells in fibrosis progression and demonstrate how engineered hydrogels can help unravel complex cell-matrix interactions. Macrophages and fibroblasts are central to fibrosis progression, driving the extracellular matrix remodeling that leads to tissue stiffening. Using a hyaluronic acid-based hydrogel system to mimic normal and fibrotic tissue, M2 macrophage co-culture activated fibroblasts independent of direct contact, even on soft viscoelastic hydrogels. However, inhibiting interleukin-6 signaling reduced this activation and restored fibroblast quiescence in co-cultures with M2 macrophages.

Source: Cell Biomaterials

DOI: 10.1016/j.celbio.2025.100052

Authors: Leilani R. Astrab, Mackenzie L. Skelton, Steven R. Caliari

Institution: University of Virginia

Language: English

Topic: Interstitial Lung Diseases and Idiopathic Pulmonary Fibrosis

Subfield: Pulmonary and Respiratory Medicine

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: hybrid

Estimated APC paid: $9,350