Aim: In recent years, adipose-derived stromal cells (ASCs) have been investigated for useas a cellular therapy, due to their immunomodulatory properties and their ability to regu-late the function of immune cells, such as macrophages. Macrophages are plastic cells withboth pro- and anti-inflammatory functions. These features enable them to reduce inflam-mation and prevent fibrosis. Fibrosis can arise as a result of prolonged inflammation andthis leads to decreased tissue functionality. The ASCs can interact with the surroundingscell through both paracrine secretion and cell-cell contact. However, the exact mechanismsof action for the interactions between ASCs and macrophages are still unknown. There-fore, the aim of this study was to investigate the effect of ASCs on the fibrotic effects ofmacrophages.Methods: To develop a macrophage-ASC-coculture, the optimal concentration of activat-ing stimuli, lipopolysaccharide and interferon-γ, was determined by measuring the concen-tration of secreted tumor necrosis factor-α by the macrophages. Hereafter, macrophageswere isolated from the ASCs using Dynabeads coated with CD90 antibody, and then seededonto an extracellular matrix derived from transforming growth factor-β-stimulated fibrob-lasts. After six days, the levels of collagen I and III were determined as a measure ofdeposition of extracellular matrix. Optimisation of fibroblast seeding density allowed themto create a dense extracellular matrix, which was determined through staining with SiriusRed (0.1%) in Picric Acid.Results and Conclusion: A macrophage-ASC-coculture model was established, and theoptimal concentrations of lipopolysaccharide and interferon-γ were found to be 100 ng/mLand 20 ng/mL, respectively. After six days of coculture with fibroblasts, the ASC-treatedmacrophages had resulted in significantly decreased levels of collagen I and III, whichsuggests that macrophages are able to affect the deposition of extracellular matrix. Theoptimal seeding density of the macrophages was 6250 M1/cm2 at which concentration thegreatest significant and numerical difference between the ASC-treated macrophages andthe mature macrophages was found.