Heparanase and syndecan-1 interplay orchestrates fibroblast growth factor-2-induced epithelial-mesenchymal transition in renal tubular cells

The epithelial-mesenchymal transition (EMT) of proximal tubular epithelial cells (PTECs) into myofibroblasts contributes to the establishment of fibrosis that leads to end stage renal disease. FGF-2 induces EMT in PTECs. Because the interaction between FGF-2 and its receptor is mediated by heparan sulfate (HS) and syndecans, we speculated that a deranged HS/syndecans regulation impairs FGF-2 activity. Heparanase is crucial for the correct turnover of HS/syndecans. The aim of the present study was to assess the role of heparanase on epithelial-mesenchymal transition induced by FGF-2 in renal tubular cells. In human kidney 2 (HK2) PTEC cultures, although FGF-2 induces EMT in the wild-type clone, it is ineffective in heparanase-silenced cells. The FGF-2 induced EMT is through a stable activation of PI3K/AKT which is only transient in heparanase-silenced cells. In PTECs, FGF-2 induces an autocrine loop which sustains its signal through multiple mechanisms (reduction in syndecan-1, increase in heparanase, and matrix metalloproteinase 9). Thus, heparanase is necessary for FGF-2 to produce EMT in PTECs and to sustain FGF-2 intracellular signaling. Heparanase contributes to a synergistic loop for handling syndecan-1, facilitating FGF-2 induced-EMT. In conclusion, heparanase plays a role in the tubular-interstitial compartment favoring the FGF-2-dependent EMT of tubular cells. Hence, heparanase is an interesting pharmacological target for the prevention of renal fibrosis.