RARA and acute kidney injury: If so, how renal RA/RAR activity pathologically re-distributes in different AKI and CKD, whether such pathologically activated signalling in other renal cells, such as proximal tubular cells and infiltrating cells in ischaemia–reperfusion AKI39 and renal progenitor cell in Adriamycin-induced nephropathy40, has the same roles as the RA/RAR in the CD, and how all these RA/RAR signalling interacts are important questions to answer.