Standardized Colon Ascendens Stent Peritonitis in Rats - a Simple, Feasible Animal Model to Induce Septic Acute Kidney Injury
Summary
Acute kidney injury (AKI) is a severe complication in critically ill patients and is related with an increased mortality. Here, we present a reliable and reproducible in vivo model to mimic AKI under inflammatory conditions that might contribute towards understanding the pathogenesis of septic AKI.
Abstract
AKI in septic patients is associated with increased mortality and poor outcome despite major efforts to refine the understanding of its pathophysiology. Here, an in vivo model is presented that combines a standardized septic focus to induce AKI and an intensive care (ICU) setup to provide an advanced hemodynamic monitoring and therapy comparable in human sepsis. Sepsis is induced by standardized colon ascendens stent peritonitis (sCASP). AKI is investigated functionally by measurement of blood and urine samples as well as histologically by evaluation of histopathological scores. Furthermore, the advanced hemodynamic monitoring and the possibility of repetitive blood gas sampling enable a differentiated analysis of severity of induced sepsis.
The sCASP method is a standardized, reliable and reproducible method to induce septic AKI. The intensive care setup, continuous hemodynamic and gas exchange monitoring, low mortality rate as well as the opportunity of detailed analyses of kidney function and impairments are advantages of this setup. Therefore, the described method may serve as a new standard for experimental investigations of septic AKI.
Introduction
Sepsis still remains the leading cause of death on non-cardiac intensive care units (ICU) with mortality rates of ≈ 30 – 50%1,2,3. A hallmark of severe sepsis and septic shock is the acute kidney injury that causes a further increase of mortality rate when it is associated with distant organ dysfunction such as cardiac and respiratory failure4,5,6. The overall incidence of AKI in ICU patients varies from 20 to 50%7. Despite the pivotal role of AKI regarding outcome and mortality in sepsis the underlying pathomechanism is still poorly understood.
Overall there are the 3 major components: inflammation, toxic injury, and hemodynamic changes that contribute to AKI development7. Hemodynamic changes encompass reduced renal blood flow (RBF) and global or regional renal ischemia. Here, it has to be considered that sepsis can also cause an impairment of renal microcirculation due to systemic hypotension and/or endothelial barrier disruption8. Therefore, the study of septic AKI should always include hemodynamic monitoring. Recent in vivo studies about AKI used mostly animal models such as renal ischemia-reperfusion injury or bilateral nephrectomy. These studies usually showed a lack of hemodynamic monitoring and intensive care.
The investigation of potential new pathomechanisms and therapies of septic AKI requires an in vivo model with a defined septic focus, an intensive care setup, a predictable outcome and an organ injury9,10,11,12. Here, we describe an innovative rodent model for septic AKI that meets the requirements mentioned before. Septic AKI is induced by standardized colon ascendens stent peritonitis (sCASP). The used sCASP model causes an abdominal sepsis by an intestinal fecal leakage leading to bacterial invasion and multi organ failure13. It has been shown that pathophysiological changes after CASP are similar to those in human sepsis and thus CASP represents a clinically relevant model in sepsis research11,14.
Furthermore, an intensive care (ICU) setup that comprises an advanced hemodynamic monitoring and ICU therapy is established in the experimental protocol. The ICU setup enables fluid resuscitation, analgesia application intravenously and repetitive blood gas analysis. The kidney function is evaluated by measurement of standard values such as creatinine and by inulin- and p-aminohippuric-acid-(PAH) clearance. Additional information is delivered by pathohistological scores of harvested tissue and organs at the end of the experiment. The sCASP model to induce septic AKI is already evaluated and revealed new insights in renal pathology15. Further application of this protocol presented below might help to refine the understanding of septic AKI.
Protocol
Representative Results
Discussion
The pathophysiology of septic AKI still remains unknown in its complexity. Clinical research and trials in patients will not enable gains of new insights with respect to histopathology changes, microcirculation disturbances or drug interactions on cellular levels15. It has been postulated previously that there is a need for improved and new animal models to investigate acute kidney injury associated with sepsis19. Therefore, we established a new animal model for septic AKI …
Disclosures
The authors have nothing to disclose.
Acknowledgements
M.A. Schick and N. Schlegel received funding from the Deutsche Forschungsgemeinschaft (DFG) SCHL 1962/2-1 and SCHL 1962/4-1.
Materials
| Sprague-Dawley rats | Janvier Labs, France | ||
| Isoflurane CP | cp-pharma, Burgdorf, Germany | ||
| polyethylen catheter PE 10; 30m | A. Hartenstein, Wuerzburg, Germany | 0.58×0.96 mm | |
| Swivel (375/D/20) | Instech, Plymouth Meeting, PA, USA | (375/D/20) | |
| plastic button tethers | Instech, Plymouth Meeting, PA, USA | LW105S | |
| Perfusor | B. Braun; Melsungen, Germany | Perfusor fm | |
| suction catheter ch. 10 | B.Braun Melsungen AG, Germany | suction catheter typy „Ideal“; ch. 10 | |
| suture | Syneture; USA | Surgipro; Monofilament Polypropylen 4-0 | |
| suture | Ethicon; Scotland | Prolene; Polypropylen 5-0 | |
| 14G-i.v. catheter | BD Insynte; BD Vialon; Madrid; Spain | 14GA i.v. catheter | |
| cotton buds | NOBA Verbandmittel Danz GmbH u Co KG; Wetter; Germany | ||
| rodent respirator | Hugo Sachs Elektronik KG, Germany | rodent respirator, Type:7025 | |
| Midazolam | Ratiopharm, Germany | Midazolam | |
| Thermodilutioncatheter | ADInstruments, Spechbach, Germany | ||
| p-Aminohippuric acid | Sigma-Aldrich; St. Louis; USA | p-Aminohippuric acid sodium salt; A3759-25G | |
| Inulin | Sigma-Aldrich; St. Louis; USA | Inulin-FITC; F3272-1G | |
| Formaldehyde | Otto Fischar GmbH & CoKG; Saarbrücken, Germany | Formaldehyde 3.5% | |
| Cyclopentan | Merck; Darmstadt; Germany | Uvasol: 2-Methylbutan | |
| alcohol based scrub | Schülke & Mayr GmbH, Norderstedt; Germany | kodan Tinktur forte; 45g 2-Propanol, 10g 1-Propanol per 100g | |
| povidone iodine solution | B.Braun Melsungen AG, Germany | Braunol, 7.5g Povidone Iodine per 100g |
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