Limited overlap between plasma, renal, and urinary microRNAs altered by ischemia reperfusion-induced Acute Kidney Injury (AKI)

Over 13 million people worldwide are affected by acute kidney injury (AKI), or the rapid reduction of renal function over a short period of time. Causes of AKI include genetics, nephrotoxic drugs, and medical interventions, when combined with lack of prevention and treatment interventions results in a death rate of 300,000/year. MicroRNAs (miRs) are thought to regulate apoptotic and inflammatory processes involved with AKI primarily through suppressing gene expression. Thus, miR expression profiles could serve as viable AKI biomarkers. Our goal was to identify miRs that are altered in kidney cortex tissue, urine, and plasma samples following renal ischemia-reperfusion injury (IRI). We hypothesized that in the 24 hours following IRI, alterations in miR abundance in the kidney would be reflected by similar or inverse changes in clinically accessible measured bio-fluids (urine and plasma), and that miRs altered in those bio-fluid samples would overlap. AKI was induced in 10-wk-old male Sprague Dawley rats by bilaterally clamping both the renal artery and vein for 30 mins, followed by 24 hrs of reperfusion (n=7). Sham surgeries were performed without vessel occlusion (n=5). Upon surgical recovery, rats were placed in metabolic cages for 24-hour urine collection. Blood, urine, and kidneys were collected and processed for blood assays, small RNA library preparation and sequencing following the 24-hour period. Small RNA sequencing results were analyzed using EdgeR2 to evaluate differential expression (DE) based on Benjamini-Hochberg adjusted p-value (p.adj) ≤ 0.05. An extensive literary search was performed to identify DE miRs involvement in AKI based on renal IRI models.Blood panel results show SCr (IR: 3.8 vs sham: 0.32mg/dL) and BUN (IR: 96.57 vs sham: 17.60mg/dL) were elevated in renal IRI male rats (p< 0.05). The miRNA seq data assayed 528 miRs, 174 were differentially altered in the cortical, urinary, and plasma samples (p.adj ≤ 0.05) following renal IRI. DE miRs in only 1 sample: 53 cortex-specific (10↑, 43↓); 50 plasma-specific (20↑, 30↓) and 27 urine-specific (16↑, 11↓). In total, 19 DE miRs were common to 2 sample types: 5 in plasma and urine samples, 8 in cortex and plasma samples; 6 in cortex and urine samples; 2 miRs in all three. Of the 21 overlapped DE miRs, 9 are associated with AKI pathology in published literature.AKI presents economic and clinical burdens that call for novel biomarkers of disease pathology that facilitate earlier treatment interventions. Using a clinically relevant AKI IR rat model, we observed that 11% of total DE miRs identified were common to 2 sample types and only 1% were common to all three. Future directions call for understanding miR abundance levels in circulation while also determining miR origin. This project highlights the need for more comprehensive analysis of miRs that are proposed as clinically relevant biomarkers of disease pathology that are representative of both the primary insult and circulation. The project described was supported by Award Number 2T32HL007852. The content is solely the responsibilities of the authors and does not necessarily represent the official views of the NIH. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.