Tenascin-C protects against acute kidney injury by recruiting Wnt ligands.

The development of acute kidney injury (AKI) is a complex process involving tubular, inflammatory, and vascular components, but less is known about the role of the interstitial microenvironment. We have previously shown that the extracellular matrix glycoprotein tenascin-C (TNC) is induced in fibrotic kidneys. In mouse models of AKI induced by ischemia-reperfusion injury (IRI) or cisplatin, TNC was induced de novo in the injured sites and localized to the renal interstitium. The circulating level of TNC protein was also elevated in AKI patients after cardiac surgery. Knockdown of TNC by shRNA in vivo aggravated AKI after ischemic or toxic injury. This effect was associated with reduced renal ß-catenin expression, suggesting an impact on Wnt signaling. In vitro, TNC protected tubular epithelial cells against apoptosis and augmented Wnt1-mediated ß-catenin activation. Co-immunoprecipitation revealed that TNC physically interacts with Wnt ligands. Furthermore, a TNC-enriched kidney tissue scaffold prepared from IRI mice was able to recruit and concentrate Wnt ligands from the surrounding milieu ex vivo. The ability to recruit Wnt ligands in this ex vivo model diminished after TNC depletion. These studies indicate that TNC is specifically induced at sites of injury and recruits Wnt ligands, thereby creating a favorable microenvironment for tubular repair and regeneration after AKI.