Kidney fibrosis is the histological manifestation of functional decline in the kidney. Fibrosis is a reactive process that develops in response to excessive epithelial injury and inflammation. Here, we describe how three key developmental signalling pathways—Notch, Wnt and Hedgehog—are reactivated in response to kidney injury. Although transient activation of these pathways is needed for repair of injured tissue, their sustained activation promotes fibrosis. Excessive Wnt and Notch expression prohibit epithelial differentiation whereas increased Wnt and Hh expression induce fibroblast proliferation and myofibroblastic transdifferentiation. Notch, Wnt and Hedgehog are fundamentally different signalling mechanisms, but their choreographed activation seems to be just as important for fibrosis as it is for embryonic kidney development. Decreasing the activity of Notch, Wnt, or Hh signalling could potentially be a new therapeutic strategy to ameliorate the development of chronic kidney disease.
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