Transcriptional analysis of kidneys during repair from AKI reveals possible roles for NGAL and KIM-1 as biomarkers of AKI-to-CKD transition

Abstract

Acute kidney injury (AKI) is being increasingly shown to be a risk factor for chronic kidney disease (CKD), but little is known about the possible mechanistic links. We hypothesized that analysis of the genomic signature in the repair stage after AKI would reveal pathways that could link AKI and CKD. Unilateral renal pedicle clamping for 45 min was performed in male C57BL/6J mice. Mice were euthanized at 3, 10, and 28 days after ischemia-reperfusion injury (IRI). Total RNA was isolated from kidney and analyzed using an Illumina mouse array. Among 24,600 tested genes, 242, 146, and 46 genes were upregulated at days 3, 10, and 28 after IRI, and 85, 35, and 0 genes were downregulated, respectively. Gene ontology analysis showed that gene expression changes were primarily related to immune and inflammatory pathways both early and late after AKI. The most highly upregulated genes late after AKI were hepatitis A virus cellular receptor 1 (Havcr1) and lipocalin 2 (Lcn2), which code for kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL), respectively. This was unexpected since they are both primarily potential biomarkers of the early stage of AKI. Furthermore, increases observed in gene expression in amiloride binding protein 1, vascular cell adhesion molecule-1, and endothelin 1 could explain the salt-sensitive hypertension that can follow AKI. These data suggested that 1) persistent inflammation and immune responses late after AKI could contribute to the pathogenesis of CKD, 2) late upregulation of KIM-1 and NGAL could be a useful marker for sustained renal injury after AKI, and 3) hypertension-related gene changes could underlie mechanisms for persistent renal and vascular injury after AKI.

AKI Transition of Care

“…These clinical findings are supported by preclinical data that mirror those risk factors identified in large observational studies (17,(32)(33)(34).…”

“…The main mechanisms incriminated in CKD progression include inappropriate vascular, interstitial, and tubular regeneration after AKI (17). These maladaptive processes appear to be linked to impaired angiogenesis and reduced endothelial proliferation (35,36), cell cycle arrest (37), persistent fibrosis (38), epigenetic changes (33), increased expression in kidney tissue microRNAs associated with renal fibrosis (39), and ongoing inflammation (34). Further research to identify potential therapeutic targets to mitigate CKD progression after AKI in humans is urgently needed.…”

Follow-Up Renal Assessment of Injury Long-Term After Acute Kidney Injury (FRAIL-AKI)

“…Preliminary studies have reported on the potential utility of KIM-1 as a CKD biomarker (23,24). Animal models of AKI-to-CKD transition have identified NGAL and KIM-1 as two of the most upregulated genes and proteins in the kidney, revealing a possible role for these proteins as potential biomarkers to predict risk of CKD after AKI (25). The persistent elevation in KIM-1 and IL-18 in AKIpositive patients suggests ongoing kidney injury.…”

Cell-specific translational profiling in acute kidney injury

“…Several promising biomarkers have emerged from these studies (16,17). Analysis of temporal and spatial differences in their expression highlights the cellular complexity of the AKI response (ref.…”