A New Mouse Model of Hemorrhagic Shock-Induced Acute Kidney Injury

Current animal models of hemorrhagic shock-induced acute kidney injury (HS-induced AKI) require extensive surgical procedures and constant monitoring of hemodynamic parameters. Application of these HS-induced AKI models in mice to produce consistent kidney injury is challenging. In the present study, we developed a simple and highly reproducible mouse model of HS-induced AKI by combining moderate bleeding and renal pedicle clamping, which was abbreviated as HS-AKI. HS was induced by retroorbital bleeding of 0.4 ml blood in C57BL/6 mice. Mice were left in HS stage for 30 min, followed by renal pedicle clamping for 18 min at 36.8–37.0°C. Mean arterial pressure (MAP) and heart rate were monitored with preimplanted radio transmitters throughout the experiment. The acute response in renal blood flow (RBF) triggered by HS was measured with transonic flow probe. Mice received sham operation; bleeding alone and renal pedicle clamping alone served as respective controls. MAP was reduced from 77 ± 4 to 35 ± 3 mmHg after bleeding. RBF was reduced by 65% in the HS period. Plasma creatinine and kidney injury molecule-1 levels were increased by more than 22-fold 24 h after reperfusion. GFR was declined by 78% of baseline 3 days after reperfusion. Histological examination revealed a moderate-to-severe acute tubular damage, mostly at the cortex-medulla junction area, followed by the medullar and cortex regions. HS alone did not induce significant kidney injury, but synergistically enhanced pedicle clamping-induced AKI. This is a well-controlled, simple, and reliable mouse model of HS-AKI. Acute kidney injury (AKI) is characterized by a rapid loss of renal function, including a sudden and sustained fall in glomerular filtration rate (GFR) with retention of nitrogenous waste products (13, 16, 18, 30). AKI is responsible for ~2 million annual deaths worldwide and costs ~10 billion dollars each year in the United States (7–9, 12, 32). Recent epidemiology studies demonstrated that patients who survive an episode of AKI have a significant increase in risk for progression to chronic kidney disease and long-term mortality (5, 22, 29, 36, 37). Despite the fact that AKI is a major health problem, there is currently no specific guideline to prevent AKI or effective therapeutic remedy for AKI. Therefore, further understanding the pathophysiological mechanism of AKI is crucial to find a potential target of treatment and prevention for AKI. Hemorrhagic shock (HS) and ischemia-reperfusion injury (IRI) are common causes of AKI. HS leads to reduced tissue perfusion and inadequate delivery of oxygen and nutrient, which subsequently leads to multiple systemic organ ischemia. On therapeutic treatment to reestablish tissue perfusion, further injuries are induced and result in IRI (5, 28, 45). Kidneys are highly susceptible to IRI (14, 29). Various animal models of AKI have been generated by either applying toxic, hypoxic, or septic insult to the kidneys (11, 22, 33, 36, 37). Among them, IRI induced by obstruction of renal blood flow (RBF) is the most commonly used method. A graded injury response can be achieved using IRI (1–3, 37). While these widely used IRI-induced AKI models mimic the clinical situations of kidney transplantation, abdominal and cardiac surgeries, and cardiac arrest in clinical situations (22, 37), these AKI models do not simulate HS-induced AKI, because there is no significant blood volume reduction (6, 19). Current animal models of HS-induced AKI are induced by either fixed pressure or fixed blood volume reduction (41). Although some recent reported HS-induced AKI models have been associated with moderate kidney injury in rats (20, 35, 46) and mice (24, 25), these models required extensive surgeries and continuous monitoring of hemodynamic parameters. In addition, the long duration of experimental process is accompanied with high mortality rate and variability in kidney injury. In the present study, we described a simple and a highly reproducible HS-AKI mouse model induced by moderate bleeding plus bilateral clamping of renal pedicles. The AKI in these mice were associated with consistent kidney injury, reduction in GFR, and systemic responses to hemorrhage