Epithelial to Mesenchymal Transition (EMT) can be driven by macrophages through multiple signalling pathways

Epithelial to mesenchymal transition (EMT) is a physiological process integral to organogenesis, tissue development, and wound healing. However, it also plays a pathological role in tumour progression, metastasis, and fibrosis (1,2). Macrophages, encompassing both tissue-resident and peripherally recruited populations, are pivotal in modulating the EMT process following injury. These cells secrete various cytokines and signalling molecules that recruit and condition other cell types to promote wound closure and extracellular matrix deposition. Macrophages themselves exhibit remarkable plasticity and readily adapt their phenotypes in response to the local cytokine milieu and pattern recognition molecules present in the cellular microenvironment. Epithelial cells, too, are responsive to the diverse cytokines in this microenvironment. Transforming growth factor-beta (TGF-β) stands out as a critical cytokine linked to EMT, fibrosis, and tumour development. It is believed to be produced not only by tumour-associated macrophages but also by other macrophage subtypes. TGF-β is considered a key player in the regulation of EMT and is a potential target for cancer treatment due to its multifaceted effects and its inverse correlation with cancer progression (2,3). To investigate EMT, researchers traditionally employ methods such as measuring changes in cell migration through a scratch wound assay and assessing alterations in the expression of epithelial and mesenchymal protein markers in response to specific signalling factors. In this study, our focus was on developing a more sophisticated assay to better understand the intricate interactions between different macrophage subtypes and the changes in epithelial cells associated with EMT. The objective of our research was to determine whether macrophages, when introduced into a scratch wound assay, can directly drive EMT. To evaluate the impact of inhibiting the TGFβRI pathway on EMT induction, we employed galunisertib as an inhibitor.

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