NTN1 and acute kidney injury: Proximal tubule-derived factors identified to polarize Mφ toward an M2 phenotype are Wnt ligands and netrin-1, which are both upregulated during AKI (Reeves et al., 2008; Grenz et al., 2011; Ranganathan et al., 2013; Feng et al., 2018a, 2018b).