Project description:Purpose: Acute kidney injury (AKI) is defined as a sudden event of kidney failure or kidney damage occurring within a short period. Ischemia-reperfusion injury (IRI) is a critical factor to induce severe AKI and end-stage kidney disease in the kidney. However, biological mechanisms of ischemia and reperfusion are not well elucidated due to its complex pathophysiological processes. We aim to investigate key biological pathways affected by ischemia and by reperfusion separately at the transcriptome level. Method: We analyzed steady-state gene expressions using RNA-seq transcriptome data for normal (pre-ischemia), ischemia and reperfusion conditions obtained from the human kidney tissue. A conventional differential expression analysis and self-organizing map (SOM) clustering analysis followed by pathway analysis were performed to identify the underlying biological mechanisms of ischemia and reperfusion. Results: Differential expression analysis showed that metabolism and gap junction-related pathways were dysregulated in ischemia, whereas hypertrophy and immune response-related pathways were dysregulated in reperfusion. In addition, SOM clustering analysis revealed that metabolism, apoptosis, and fibrosis-related pathways were significantly dysregulated by ischemia compared to pre-ischemia. On the other hand, cell growth, migration, and immune response-related pathways were highly dysregulated by reperfusion after ischemia. Pro-apoptotic genes and death receptors were down-regulated during ischemia, indicating a protective process against ischemic injury. Reperfusion induced alteration of genes associated with immune components such as B-cell, neutrophil, and interleukin-15. Additionally, genes related to cell growth and migration such as AKT, KRAS, and Rho signaling were down-regulated, which might imply injury responses during reperfusion. Semaphorin 4D and plexin B1 were also down-regulated. However, further investigations are needed to identify their roles. Conclusion: We showed that specific biological pathways were distinctively involved in ischemia and reperfusion during IRI, suggesting that condition-specific therapeutic strategies may be required to prevent severe kidney damage after IRI in clinical research.

Project description:Introduction: Renal ischemia-reperfusion (IR) causes acute kidney injury (AKI) with high mortality and morbidity. The objective of this study was to ameliorate kidney IR injury and identify novel biomarkers for kidney injury and repair. Methods: Left renal ischemia was induced in rats by clamping renal artery for 45 minutes, followed by reperfusion and right nephrectomy. Thirty minutes prior to ischemia, rats (n=8/group) received Valproic Acid (150 mg/kg; VPA), Dexamethasone (3 mg/kg; Dex) or Vehicle (Saline) intraperitoneally. Animals were sacrificed at 3h, 24h or 120h post- IR and blood, urine and kidney were collected. Results: Serum creatinine (mg/dL) at 24 h IR in VPA (2.7±1.8) and Dex (2.3±1.2) was reduced (P<0.05) compared to Vehicle (3.8±0.5). At 3h post-IR, urine albumin (mg/ml) was higher in Vehicle (1.47±0.10), VPA (0.84±0.62) and Dex (1.04±0.73) compared to uninjured/untreated control (0.14±0.26) group. At 24h post-IR urine Lipocalin-2 (µg/ml) was significantly higher (P<0.05) in VPA, Dex and Vehicle groups (9.61-11.36) compared to uninjured/untreated control (0.67±o.29); also, Kidney Injury Molecule-1 (KIM-1; ng/ml) was significantly higher in VPA, Dex and Vehicle groups (13.7-18.7) compared uninjured/untreated control (1.7±1.9). KIM-1 levels were significantly (P<0.05) higher in all groups compared to uninjured/untreated control levels. Histopathology at 3h post IR demonstrated (P<0.05) reduction in ischemic injury in the renal cortex in VPA (Grade 1.6± 1.5) compared to Vehicle (Grade 2.9±1.1) group. Inflammatory cytokines IL1β and IL6 were down-regulated in VPA and Dex groups. BCL2 was higher in VPA group. DNA microarray analysis demonstrated reduced stress response and injury, and improved recovery related gene expression in the kidneys of VPA treated animals. Conclusions: VPA administration reduced kidney IR injury and improved regeneration. KIM-1 and Lipocalin-2 appear to be promising early urine biomarkers of acute ischemic kidney injury. We had three experimental groups. Group A, VPA treatment; Group B, Dexamethasone treatment; and Group C, No treatment (vehicle saline control). Treatments were administered prior to the induction of left renal ischemia. Animals underwent 45 minutes of left renal ischemia, followed by reperfusion, and right nephrectomy as described above. Following reperfusion, animals were sacrificed at 3, 24 or 120 hours (n=8/group). In the 3 hour group, rats were maintained under anesthesia after surgery until sacrifice. In the 24 and 120 hour groups, the rats were recovered and returned to the cages for normal housing. Analgesic buprenorphine (0.05mg/kg) was administered every 12 h for three days post-operatively. After animal sacrifice, urine, blood, and kidney were collected for kidney functional biomarker assays, histology and / or molecular analyses. Urine was obtained via cystocentesis and blood was obtained via the left renal vein. Tissue and urine samples collected from normal (naïve) animals (n=5) were used for baseline measurements. A subset of 46 animals (n = 4-5 per group) were selected for microarray analysis.

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Mouse kidney ischemia-reperfusion injury time course

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