Animal Models of Peritoneal Dialysis: Thirty Years of Our Own Experience

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.

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.

Therapeutic effect of 1,25(OH)2-VitaminD3 on fibrosis and angiogenesis of peritoneum induced by chlorhexidine

The biological activity of vitamin D, which mediated by the vitamin D receptor, is widespread throughout the body. The present study aimed to define whether 1,25-dihydroxy vitamin D3 (1,25-(OH)2D3) can protect against the progression of peritoneum fibrosis (PF) through its impact on the expression of connective tissue growth factor (CTGF) and heat shock protein 47 (HSP47) in vivo and in vitro. The male Sprague-Dawley (SD) rats of PF were induced by daily intraperitoneally injection of chlorhexidine gluconate (CG) for 4 wks. PF Rats were also treated with calcitriol (i.p. 6 ng/100g*d) from initiation of the CG. In calcitriol rats, the ultrafiltration and the ratio of dialysate urea nitrogen to blood urea nitrogen were improved (P < 0.05), pathological changes and peritoneal thickness were milder than that of the PF group. Calcitriol ameliorated high glucose-induced HSP47 expression in peritoneal mesothelial cells via CTGF down-regulation both at the mRNA level and protein level. Furthermore, calcitriol prevented angiogenic mediators of fibrosis by reduced the expression of CD34 and vascular endothelial growth factor (VEGF). The present study demonstrated that 1,25-(OH)2D3 intervention had a partially protective effect on peritoneum fibrosis, which might inhibit CTGF/HSP47 and CD34/VEGF in the peritoneum tissues.

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.

Peripheral Interventions Enhancing Brain Glutamate Homeostasis Relieve Amyloid β- and TNFα- Mediated Synaptic Plasticity Disruption in the Rat Hippocampus

Dysregulation of glutamate homeostasis in the interstitial fluid of the brain is strongly implicated in causing synaptic dysfunction in many neurological and psychiatric illnesses. In the case of Alzheimer's disease (AD), amyloid β (Aβ)-mediated disruption of synaptic plasticity and memory can be alleviated by interventions that directly remove glutamate or block certain glutamate receptors. An alternative strategy is to facilitate the removal of excess glutamate from the nervous system by activating peripheral glutamate clearance systems. One such blood-based system, glutamate oxaloacetate transaminase (GOT), is activated by oxaloacetate, which acts as a co-substrate. We report here that synthetic and AD brain-derived Aβ-mediated inhibition of synaptic long-term potentiation in the hippocampus is alleviated by oxaloacetate. Moreover the effect of oxaloacetate was GOT-dependent. The disruptive effects of a general inhibitor of excitatory amino acid transport or TNFα, a pro-inflammatory mediator of Aβ action, were also reversed by oxaloacetate. Furthermore, another intervention that increases peripheral glutamate clearance, peritoneal dialysis, mimicked the beneficial effect of oxaloacetate. These findings lend support to the promotion of the peripheral clearance of glutamate as a means to alleviate synaptic dysfunction that is caused by impaired glutamate homeostasis in the brain.

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.

Rapamycin inhibits epithelial-to-mesenchymal transition of peritoneal mesothelium cells through regulation of Rho GTPases

Epithelial-mesenchymal transition (EMT) of peritoneal mesothelial cells (PMCs) is a key process of peritoneal fibrosis. Rapamycin has been previously shown to inhibit EMT of PMCs and prevent peritoneal fibrosis. In this study, we investigated the undefined molecular mechanisms by which rapamycin inhibits EMT of PMCs. To define the protective effect of rapamycin, we initially used a rat PD model which was daily infused with 20 mL of 4.25% high glucose (HG) dialysis solution for 6 weeks to induce fibrosis. The HG rats showed decreased ultrafiltration volume and obvious fibroproliferative response, with markedly increased peritoneal thickness and higher expression of α-smooth muscle actin (α-SMA) and transforming growth factor-β1. Rapamycin significantly ameliorated those pathological changes. Next, we treated rat PMCs with HG to induce EMT and/or rapamycin for indicated time. Rapamycin significantly inhibited HG-induced EMT, which manifests as increased expression of α-SMA, fibronectin, and collagen I, decreased expression of E-cadherin, and increased mobility. HG increased the phosphorylation of PI3K, Akt, and mTOR. Importantly, rapamycin inhibits the RhoA, Rac1, and Cdc42 activated by HG. Moreover, rapamycin repaired the pattern of F-actin distribution induced by HG, reducing the formation of stress fiber, focal adhesion, lamellipodia, and filopodia. Thus, rapamycin shows an obvious protective effect on HG-induced EMT, by inhibiting the activation of Rho GTPases (RhoA, Rac1, and Cdc42).

Animal models in peritoneal dialysis

Peritoneal dialysis (PD) has been extensively used over the past years as a method of kidney replacement therapy for patients with end stage renal disease (ESRD). In an attempt to better understand the properties of the peritoneal membrane and the mechanisms involved in major complications associated with PD, such as inflammation, peritonitis and peritoneal injury, both in vivo and ex vivo animal models have been used. The aim of the present review is to briefly describe the animal models that have been used, and comment on the main problems encountered while working with these models. Moreover, the differences characterizing these animal models, as well as, the differences with humans are highlighted. Finally, it is suggested that the use of standardized protocols is a necessity in order to take full advantage of animal models, extrapolate their results in humans, overcome the problems related to PD and help promote its use.