IL13RA2 downregulation in fibroblast promotes keloid fibrosis via JAK/STAT6 activation.

Abstract

Keloid is considered as a fibro-proliferative disease characterized by chronic inflammation that is induced following skin injury. Deciphering the underlying mechanism of keloid formation is essential for improving treatment outcomes. Here, we found that more macrophages were activated towards M2 subtype in keloid dermis when compared to normal dermis. Western Blot revealed that the level of phosphorylated STAT6, a known inducer of M2 polarization, was higher in keloid fibroblasts as opposed to fibroblasts from normal dermis. Moreover, keloid fibrosis was shown to be positively correlated with the level of phosphorylated STAT6. Further, we identified downregulation of IL13RA2, a 'decoy' receptor of IL13, in keloid fibroblasts compared to fibroblasts from normal dermis. Ectopic expression of IL13RA2 in keloid fibroblasts resulted in inhibition of STAT6 phosphorylation, cell proliferation, migration, invasion, extracellular matrix secretion and myofibroblast marker expression, as well as an increase in apoptosis. Consistently, knockdown of IL13RA2 in normal fibroblasts induced a 'keloidal' status. Furthermore, both in vitro application and intra-tumoral injection of pSTAT6 inhibitor AS1517499 in a PDX keloid-implantation mouse model, resulted in proliferation inhibition, tissue necrosis, apoptosis and myofibroblast marker reduction. Collectively, this study elucidates the key role of IL13RA2 in keloid pathology and inspire further translational research of keloid treatment concerning JAK/STAT6 inhibition.