# The Influence of Sulfation Degree of Glycosaminoglycan-Functionalized 3D Collagen I Networks on Cytokine Profiles of In Vitro Macrophage–Fibroblast Cocultures

## TL;DR

This study explores how modifying collagen networks with sulfated glycosaminoglycans affects cytokine profiles in macrophage-fibroblast cocultures during wound healing.

## Contribution

A novel in vitro hydrogel model using sulfated glycosaminoglycan-functionalized collagen I networks was developed to study extracellular matrix effects on cytokine communication.

## Key findings

- Cytokine secretion (IL-6, FGF-2) was significantly influenced by glycosaminoglycan functionalization of collagen networks.
- The coculture model successfully simulated progressed wound healing processes with stable collagen network structures.
- Functionalized collagen networks modulate paracrine and autocrine communication between fibroblasts and macrophages.

## Abstract

Cell–cell interactions between fibroblasts and immune cells, like macrophages, are influenced by interaction with the surrounding extracellular matrix during wound healing. In vitro hydrogel models that mimic and modulate these interactions, especially of soluble mediators like cytokines, may allow for a more detailed investigation of immunomodulatory processes. In the present study, a biomimetic extracellular matrix model based on fibrillar 3D collagen I networks with a functionalization with heparin or 6-ON-desulfated heparin, as mimics of naturally occurring heparan sulfate, was developed to modulate cytokine binding effects with the hydrogel matrix. The constitution and microstructure of the collagen I network were found to be stable throughout the 7-day culture period. A coculture study of primary human fibroblasts/myofibroblasts and M-CSF-stimulated macrophages was used to show its applicability to simulate processes of progressed wound healing. The quantification of secreted cytokines (IL-8, IL-10, IL-6, FGF-2) in the cell culture supernatant demonstrated the differential impact of glycosaminoglycan functionalization of the collagen I network. Most prominently, IL-6 and FGF-2 were shown to be regulated by the cell culture condition and network constitution, indicating changes in paracrine and autocrine cell–cell communication of the fibroblast–macrophage coculture. From this perspective, we consider our newly established in vitro hydrogel model suitable for mechanistic coculture analyses of primary human cells to unravel the role of extracellular matrix factors in key events of tissue regeneration and beyond.