Kidney Transplants With Progressing Chronic Diseases Express High Levels of Acute Kidney Injury Transcripts

We previously reported that kidney transplants with early acute injury express transcripts indicating injury repair—the acute kidney injury signal. This study investigated the significance of this signal in transplants with other conditions, including rejection and recurrent disease. The injury signal was elevated in biopsies in many different conditions, including T cell‐mediated rejection and potentially progressive diseases such as antibody‐mediated rejection and glomerulonephritis. A high injury signal correlated with poor function and with inflammation in areas of fibrosis, but not with fibrosis without inflammation. In multivariate survival analysis, the injury signal in late kidney transplant biopsies strongly predicted future graft loss, similar to a published molecular risk score derived in late kidneys. Indeed, the injury signal shared many individual transcripts with the risk score, e.g. ITGB6, VCAN, NNMT. The injury signal was a better predictor of future graft loss than fibrosis, inflammation or expression of collagen genes. Thus the acute injury signal, first defined in early reversible injury, is present in many diseases as a reflection of parenchymal distress, where its significance is dictated by the inducing insult, i.e. treatable/self‐limited versus untreatable and sustained. Progression in troubled transplants is primarily a function of ongoing parenchymal injury by disease, not fibrogenesis. The transcripts typical of acute kidney injury, defined in kidney transplants with early reversible injury, are also expressed in biopsies of late transplants with progressive diseases as a reflection of parenchymal distress, indicating that progression in failing kidneys is not due to fibrosis but to ongoing parenchymal injury. See editorial by Volk et al on page 539.