Epithelial to mesenchymal transition (EMT) is a normal process involved in organogenesis, tissue development and wound healing. This occurs as part of normal physiological processes, but also pathologically in tumour progression, metastasis and fibrosis(1,2). Macrophages, both tissue-resident and those recruited from the periphery, have been implicated in regulating the EMT process following injury; by recruiting inflammatory cells, myofibroblasts and influencing cell organisation during the wound healing process. They do this by secreting various cytokines and other signalling molecules to enable other cell types to change processes toward wound closure and extracellular matrix (ECM) deposition. Macrophages themselves are highly plastic and respond to the local milieu of cytokines and pattern recognition molecules, thus adapting their phenotype dependent on the local cellular environment. TGF-β is one cytokine associated with EMT, fibrosis, and tumour development and is believed to be produced by tumour associated macrophages (TAMs), but also by other macrophage subtypes. TGF-β is thought to be one of the key cytokines that regulates EMT and is seen as a potential target in treatment of cancer due to it pleiotropic effects, and its associated negative correlation with cancer progression(2,3).
EMT is routinely investigated by measuring changes in migration through a scratch wound assay and by assessing changes in expression of epithelial and mesenchymal protein markers in response to specific signalling factors. We were interested to look at developing a more complex assay to interrogate the interplay between different macrophage subtypes and epithelial cells changes associated with EMT. The aim of this work was to investigate if macrophage-conditioned medium could drive EMT. Galunisertib was used as an inhibitor of the TGFβRI to assess the effect of inhibiting this pathway, for the induction of EMT.