Adipose tissue-derived stromal cells' conditioned medium modulates endothelial-mesenchymal transition induced by IL-1β/TGF-β2 but does not restore endothelial function

Objectives Endothelial cells undergo TGF-beta-driven endothelial-mesenchymal transition (EndMT), representing up to 25% of cardiac myofibroblasts in ischaemic hearts. Previous research showed that conditioned medium of adipose tissue-derived stromal cells (ASC-CMed) blocks the activation of fibroblasts into fibrotic myofibroblasts. We tested the hypothesis that ASC-CMed abrogates EndMT and prevents the formation of adverse myofibroblasts. Materials and methods Human umbilical vein endothelial cells (HUVEC) were treated with IL-1 beta and TGF-beta 2 to induce EndMT, and the influence of ASC-CMed was assessed. As controls, non-treated HUVEC or HUVEC treated only with IL-1 beta in the absence or presence of ASC-CMed were used. Gene expression of inflammatory, endothelial, mesenchymal and extracellular matrix markers, transcription factors and cell receptors was analysed by RT-qPCR. The protein expression of endothelial and mesenchymal markers was evaluated by immunofluorescence microscopy and immunoblotting. Endothelial cell function was measured by sprouting assay. Results IL-1 beta/TGF-beta 2 treatment induced EndMT, as evidenced by the change in HUVEC morphology and an increase in mesenchymal markers. ASC-CMed blocked the EndMT-related fibrotic processes, as observed by reduced expression of mesenchymal markers TAGLN (P = 0.0008) and CNN1 (P = 0.0573), as well as SM22 alpha (P = 0.0501). The angiogenesis potential was impaired in HUVEC undergoing EndMT and could not be restored by ASC-CMed. Conclusions We demonstrated that ASC-CMed reduces IL-1 beta/TGF-beta 2-induced EndMT as observed by the loss of mesenchymal markers. The present study supports the anti-fibrotic effects of ASC-CMed through the modulation of the EndMT process.