Aim: Here, we explored the role of NCAM/FGFR1 signaling and pro-fibrotic gene expression signatures as initiating or driving forces of EMT program in cultured human proximal tubular epithelial cells. Introduction: Epithelial-to-mesenchymal transition (EMT) contributes to maladaptive repair and parenchymal damage during renal fibrosis. Based on previous reports, neural cell adhesion molecule (NCAM) and fibroblast growth factor receptor 1 (FGFR1) are both considered to be mechanistically involved in the EMT process. Material and Methods: By using an established in vitro model of EMT of the human proximal tubular epithelial cells (HK-2 cells) in response to TGF-β1 (10ng/mL) exposure, NCAM/FGFR1 signaling responses were analyzed by light microscopy, immune-labelling, qRT-PCR and scratch assays. Modulation of FGFR1 was induced using PD173074 (100nM). Distribution of TGF-β1 downstream effectors was assessed in HK-2 cells of the EMT program as well as in 50 biopsies of different human kidney diseases to explore their in vivo correlation. Results: EMT associated with morphological changes started 48h after TGF-ß1 treatment of the HK-2 cells and was clearly apparent after 72 hours, associated with loss of CDH1 (encoding E-Cadherin) and transcriptional induction of SNAI1 (encoding SNAIL), SNAI2 (encoding SLUG), TWIST1, MMP2, MMP9, CDH2 (encoding N-Cadherin), ITGA5 (encoding integrin-α5), ITGB1 (encoding integrin-β1), ACTA2 (encoding α-SMA) and S100A4 (encoding FSP1). After 24 hours of TGF-β1 exposure at the early stage of SPECIJALNA SESIJA: SESIJA SPECIJALIZANATA 7 MATERIA MEDICA • Vol. 34 • Issue 1, suplement 1 • april 2018. EMT program, transcriptional induction of several NCAM isoforms along with FGFR1 was observed, implicating a mechanistic link between NCAM/FGFR1 signaling and induction of EMT. These assumptions were further supported by the inhibition of the EMT program after specific blocking of FGFR1 signaling responses by PD173074. Moreover, there was evidence for an in vivo TGF-β1 pathway activation with EMT response signal signatures in diseased human kidneys in correlation to impaired renal excretory functions. Conclusion: Modulation of NCAM/FGFR1 signaling blocks the EMT program in cultured human proximal tubular epithelial cells. NCAM/FGFR1 signaling appears to be involved in initial phases of TGF-ß1 initiated EMT of tubular cells and thus could contribute to maladaptive repair and parenchymal damage during renal fibrosis.

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