Soluble α-Klotho protects dermal microvascular endothelial cells against endothelial-to-mesenchymal transition

Endothelial-to-mesenchymal transition (EndMT) is a key contributor to dermal fibrosis. The soluble form of the α-Klotho (sKL) hormone has been shown to counteract fibrotic processes in multiple organs, but its role in dermal fibrosis and EndMT remains unexplored. To investigate whether sKL may inhibit transforming growth factor β1 (TGFβ1)-induced EndMT in human dermal microvascular endothelial cells (H-dMVECs), cells pretreated with recombinant human sKL and subsequently stimulated with recombinant human TGFβ1 were assessed for morphological changes, gene and protein expression of both endothelial and mesenchymal/myofibroblast markers, and functional contractility through qPCR, Western blotting, immunofluorescence, and collagen gel contraction assays, respectively. TGFβ1-treated H-dMVECs underwent significant changes in cell morphology, with loss of endothelial markers (i.e., CD31 and VE-cadherin) and a concomitant increase in the expression of mesenchymal/myofibroblast markers (i.e., α-smooth muscle actin, type I collagen, and S100A4/fibroblast-specific protein 1) and of EndMT-associated transcription factors (Snail1, Twist1, and Zeb1). Moreover, TGFβ1-treated H-dMVECs acquired the ability to contract collagen gel matrices. Pretreatment with sKL significantly attenuated all the aforementioned morphological, molecular, and functional changes, preserving the endothelial phenotype and mitigating myofibroblast-like contractile activity. In conclusion, sKL effectively prevented TGFβ1-induced EndMT in H-dMVECs, highlighting its potential as a novel therapeutic agent against dermal fibrosis.