A review of rodent models of peritoneal dialysis and its complications

Evaluation of peritoneal dialysis prescriptions in uremic rats

BACKGROUND

Patients with end-stage kidney disease (ESKD) require dialysis or transplantation for their survival. There are few experimental animal models mimicking the human situation in which the animals are dependent on dialysis for their survival. We developed a peritoneal dialysis (PD) system for rats to enable long-term treatment under controlled conditions.

METHOD

Rats were chemically nephrectomised using orellanine to render them uremic. Two studies were performed, the first with highly uremic rats on PD for 5 days, and the other with moderately uremic rats on PD for 21 days. Blood and dialysate samples were collected repeatedly from the first study and solute concentrations analysed. Based on these values, dialysis parameters were calculated together with generation rates allowing for kinetic modelling of the effects of PD. In the second study, the general conditions of the rats were evaluated during a longer dialysis period.

RESULTS

For rats with estimated glomerular filtration rate (GFR) 5-10% of normal (moderately uremic rats), five daily PD cycles kept the rats in good condition for 3 weeks. For highly uremic rats (GFR below 3% of normal), more extensive dialysis is needed to maintain homeostasis and our simulations show that a six daily and four nightly PD cycles should be needed to keep the rats in good condition.

CONCLUSION

In conclusion, the PD system described in this study can be used for long-term studies of PD on uremic dialysis-dependent rats mimicking the human setting. To maintain whole body homeostasis of highly uremic rats, intense PD is needed during both day and night.

Transcriptomic analysis identifies novel candidates in cardiorenal pathology mediated by chronic peritoneal dialysis

Peritoneal dialysis (PD) is associated with increased cardiovascular (CV) risk. Studies of PD-related CV pathology in animal models are lacking despite the clinical importance. Here we introduce the phenotypic evaluation of a rat model of cardiorenal syndrome in response to chronic PD, complemented by a rich transcriptomic dataset detailing chronic PD-induced changes in left ventricle (LV) and kidney tissues. This study aims to determine how PD alters CV parameters and risk factors while identifying pathways for potential therapeutic targets. Sprague Dawley rats underwent Sham or 5/6 nephrectomy (5/6Nx) at 10 weeks of age. Six weeks later an abdominal dialysis catheter was placed in all rats before random assignment to Control or PD (3 daily 1-h exchanges) groups for 8 days. Renal and LV pathology and transcriptomic analysis was performed. The PD regimen reduced circulating levels of BUN in 5/6Nx, indicating dialysis efficacy. PD did not alter blood pressure or cardiovascular function in Sham or 5/6Nx rats, though it attenuated cardiac hypertrophy. Importantly PD increased serum triglycerides in 5/6Nx rats. Furthermore, transcriptomic analysis revealed that PD induced numerous changed transcripts involved with inflammatory pathways, including neutrophil activation and atherosclerosis signaling. We have adapted a uremic rat model of chronic PD. Chronic PD induced transcriptomic changes related to inflammatory signaling that occur independent of 5/6Nx and augmented circulating triglycerides and predicted atherosclerosis signaling in 5/6Nx LV tissues. The changes are indicative of increased CV risk due to PD and highlight several pathways for potential therapeutic targets.

Use of paclitaxel carried in solid lipid nanoparticles to prevent peritoneal fibrosis in rats

Background

Progressive fibrous thickening of peritoneal membrane (PM) is a major complication of long-term peritoneal dialysis. TGF-β/SMAD pathway activation, inflammation and neoangiogenesis have an important role in PM changes induced by peritoneal dialysis. Here, we investigated the effects of paclitaxel (PTX) carried in lipid core nanoparticles (LDE) on the development of peritoneal fibrosis (PF) in rats.

Methods

To induce PF, 21 male Wistar rats (300-350g) were injected with chlorhexidine gluconate for 15 consecutive days and randomly assigned to three groups: 1)PF, n = 5: no treatment; 2)LDE, n = 8: treated with LDE only, 3/3 days during 15 days; 3)LDE-PTX, n = 8: treated with PTX (4mg/kg) associated with LDE, 3/3 days during 15 days. A Control group without PF induction (n = 5) was designed, received saline solution, 3/3 days. Peritoneum function tests were performed, and anterior abdominal wall samples of the PM were collected for analyses of peritoneal thickness, immunohistochemitry, and gene expression.

Results

LDE-PTX treatment preserved the membrane function, maintaining the ultrafiltration rate and mass transfer of glucose at normal levels. LDE-PTX also prevented PM thickening induced by chlorhexidine gluconate injections. LDE-PTX treatment reduced the number of myofibroblasts infiltrating PM and inhibited the cell proliferation. Gene expression of fibronectin, FSP-1, VEGF, TGF-β, and SMAD3 were reduced by LDE-PTX.

Conclusions

LDE-PTX was effective to prevent development of PF and preserve the PM filtration capacity in this rat model, with clear-cut actions on pro-fibrotic mechanisms. Thus, LDE-PTX can be candidate for future clinical trials as adjuvant to peritoneal dialysis to prevent PF development, since this preparation is devoid of toxicity as shown previously.

Establishment of a novel mouse peritoneal dialysis-associated peritoneal injury model

BACKGROUND

Peritoneal fibrosis induced by various factors during peritoneal dialysis (PD) can eventually lead to ultrafiltration failure and termination of PD treatment. The existing animal models are caused by a single stimulus, and cannot accurately simulate complex pathogenesis of peritoneal injury and fibrosis. We aim to develop an efficient and realistic mouse model of PD-associated peritoneal injury using daily intraperitoneal injection (I.P.) of human peritonitis PD effluent.

METHODS

Eight-week-old male C57BL/6 mice were classified into six groups: saline control; 2.5% PD fluid; 2.5% PD fluid + lipopolysaccharide (LPS); 4.25% PD fluid; 4.25% PD fluid + LPS; and peritonitis effluent. Mice received daily I.P. for 6 weeks, and were sacrificed to determine peritoneal structural and functional damage, inflammation, and fibrosis.

RESULTS

Mice in the peritonitis effluent group had low mortality. The submesothelial thickness in the peritonitis effluent group was significantly greater than that in the 2.5% PD fluid group. The peritonitis effluent group had increased expression of fibrosis markers (α-SMA, Collagen I, etc.), neutrophil granulocytes (MPO), and macrophages (CD68, F4/80) in the peritoneum based on immunohistochemical staining; and significantly higher expression of inflammation markers (IL-1β, IL-6, etc.) and fibrosis markers (TGF-β1, α-SMA, etc.) based on real-time qPCR. Modified peritoneal equilibration tests (PET) demonstrated that I.P. of peritonitis effluent reduced peritoneal ultrafiltration.

CONCLUSION

Our novel animal model of PD-associated peritoneal injury faithfully simulates the clinical pathophysiological process. This animal model may be useful for study of the pathogenesis of PD-associated peritoneal injury and identification of novel treatments.

Experimental models in peritoneal dialysis (Review)

Peritoneal dialysis (PD) is one of the most commonly used dialysis methods and plays an important role in maintaining the quality of life of patients with end-stage renal disease. However, long-term PD treatment is associated with adverse effects on the structure and function of peritoneal tissue, which may lead to peritoneal ultrafiltration failure, resulting in dialysis failure and eventually PD withdrawal. In order to prevent the occurrence of these effects, the important issues that need to be tackled are improvement of ultrafiltration, protection of peritoneal function and extension of dialysis time. In basic PD research, a reasonable experimental model is key to the smooth progress of experiments. A good PD model should not only simulate the process of human PD as accurately as possible, but also help researchers to understand the evolution process and pathogenesis of various complications related to PD treatment. To better promote the clinical application of PD technology, the present review will summarize and evaluate the in vivo PD experimental models available, thus providing a reference for relevant PD research.

Quality of design and reporting of animal research in peritoneal dialysis: A scoping review

The concerns about reproducibility and validity of animal studies are partly related to poor experimental design and reporting. Here, we undertook a scoping review of the literature to determine the extent and quality of reporting of animal studies on peritoneal dialysis (PD). Online databases were searched to identify 567 relevant original articles published between 1979 and 2018. These were analyzed with respect to bibliographic parameters and general aspects of animal experimentation. A subgroup of 120 studies was analyzed in detail in terms of the impact on the reporting quality of the Animal Research: Reporting of In Vivo Experiments (ARRIVE) guidelines for animal studies. The number of animal studies on PD increased continuously over the years with a thematic shift toward long-term preservation of the peritoneum as a dialyzing organ. There were significant deficiencies in research design with the lack of sample size estimation, randomization, and blinding being the commonest shortcomings. The description of animal numbers, housing conditions, use of medication, and statistical analysis was incomplete. The introduction in 2010 of the ARRIVE guidelines produced very little improvement in the completeness of reporting regardless of journal impact factor. The animal studies on PD suffer from deficits in experimental protocols and transparent reporting. These drawbacks need to be corrected to ensure high-quality and much-needed animal research in PD.

Evaluation of Candida peritonitis with underlying peritoneal fibrosis and efficacy of micafungin in murine models of intra-abdominal candidiasis

Candida peritonitis is a crucial disease, however the optimal antifungal therapy regimen has not been clearly defined. Peritoneal fibrosis (PF) can be caused by abdominal surgery, intra-abdominal infection, and malignant diseases, and is also widely recognized as a crucial complication of long-term peritoneal dialysis. However, the influence of PF on Candida peritonitis prognosis remains unknown. Here, we evaluated the severity of Candida peritonitis within the context of PF and the efficacy of micafungin using mice. A PF mouse model was generated by intraperitoneally administering chlorhexidine gluconate. Candida peritonitis, induced by intraperitoneal inoculation of Candida albicans, was treated with a 7-day consecutive subcutaneous administration of micafungin. Candida infection caused a higher mortality rate in the PF mice compared with the control mice on day 7. Proliferative Candida invasion into the peritoneum and intra-abdominal organs was confirmed pathologically only in the PF mice. However, all mice in both groups treated with micafungin survived until day 20. Micafungin treatment tends to suppress inflammatory cytokines in the plasma 12 h after infection in both groups. Our results suggest that PF enhances early mortality in Candida peritonitis. Prompt initiation and sufficient doses of micafungin had good efficacy for Candida peritonitis, irrespective of the underlying PF.

Early peritoneal dialysis reduces lung inflammation in mice with ischemic acute kidney injury

Although dialysis has been used in the care of patients with acute kidney injury (AKI) for over 50 years, very little is known about the potential benefits of uremic control on systemic complications of AKI. Since the mortality of AKI requiring renal replacement therapy (RRT) is greater than half in the intensive care unit, a better understanding of the potential of RRT to improve outcomes is urgently needed. Therefore, we sought to develop a technically feasible and reproducible model of RRT in a mouse model of AKI. Models of low- and high-dose peritoneal dialysis (PD) were developed and their effect on AKI, systemic inflammation, and lung injury after ischemic AKI was examined. High-dose PD had no effect on AKI, but effectively cleared serum IL-6, and dramatically reduced lung inflammation, while low-dose PD had no effect on any of these three outcomes. Both models of RRT using PD in AKI in mice reliably lowered urea in a dose-dependent fashion. Thus, use of these models of PD in mice with AKI has great potential to unravel the mechanisms by which RRT may improve the systemic complications that have led to increased mortality in AKI. In light of recent data demonstrating reduced serum IL-6 and improved outcomes with prophylactic PD in children, we believe that our results are highly clinically relevant.