DKK1 and renal fibrosis: Wnt signaling has been implicated in the pathogenesis of renal fibrosis based on the findings that expression of Wnt ligands is upregulated in fibrotic kidneys, and inhibition of Wnt signaling using DKK-1, sFRP4 or paricalcitol can reduce renal fibrosis in mice (DiRocco et al., 2013; Hao et al., 2011; He et al., 2009; Ren et al., 2013; Surendran et al., 2005).