However, ectopic expression of β‐catenin did not induce the expression of CD44 (Figure S6P and Q), the receptor of OPN, suggesting that tubular cell derived‐OPN could act on other cells such as fibroblasts, as we have observed the increase in CD44 in interstitial fibroblasts in CKD mice (Figure 2g). This evidence concerns the gene CD44 and chronic kidney disease.