Ischemia/reperfusion-induced renal failure in rats as a model for evaluating cell therapies

Role of Iberin as an anti-apoptotic agent on renal ischemia-reperfusion injury in rats

Ischemia-reperfusion injury (IRI) is a major contributor to acute and chronic kidney failure, heart failure, and ischemic stroke. This study aimed to investigate the therapeutic potential of Iberin, known for its anti-inflammatory, antioxidant, and antiapoptotic properties, in a rat model of renal IRI. Twenty-four adult male rats were randomly divided into four groups: Group I (Sham group) underwent laparotomy without IRI induction; Group II (Control group) underwent laparotomy followed by renal artery clamping for 30 minutes to induce ischemia, followed by 2 hours of reperfusion; Group III (Iberin treatment group) received a pre-injection of Iberin (15 mg/kg) and underwent 30 minutes of ischemia followed by 2 hours of reperfusion; and Group IV (Vehicle-treated group) received the vehicle (ethanol) 1 hour prior to ischemia and reperfusion induction. Iberin was diluted with ethanol. Biomarkers associated with inflammation, oxidative stress, and apoptosis were measured using enzyme-linked immunosorbent assay. Iberin treatment significantly reduced levels of inflammatory cytokines interleukin-1β (IL-1β) and IL-6, Bcl-2-associated X protein (BAX), tumor necrosis factor α (TNF-α), nuclear factor kappa p56, high mobility group B1, and neutrophil gelatinase-associated lipocalin. Moreover, Iberin increased levels of heat shock protein and Bcl2 compared to the control and vehicle groups. Iberin treatment prolonged the ischemic tolerance of renal tissue, potentially preventing or delaying irreversible injuries. These findings highlight the potential of Iberin as a promising candidate for mitigating renal injury caused by ischemia-reperfusion, due to its ability to modulate inflammatory markers.

Estradiol Ameliorates Acute Kidney Ischemia-Reperfusion Injury by Inhibiting the TGF-βRI-SMAD Pathway

Renal ischemia–reperfusion injury (IRI) is less extensive in females than males in both animals and humans; however, this protection diminishes after menopause, suggesting that estrogen plays a pivotal role in IRI, but the underlying mechanism remains largely unknown. Our study found that 45 min of warm ischemia was sufficient to induce significant pathological changes without causing death in model animals. Compared with male rats, female rats exhibited less extensive apoptosis, kidney injury, and fibrosis; these effects were worsened in ovariectomized (OVX) rats and ameliorated upon estradiol (E₂) supplementation. Furthermore, the levels of TGF-βRI, but not TGF-βRII or TGF-β1, were significantly increased in OVX rats, accompanied by phosphorylated SMAD2/3 activation. Interestingly, the alteration trend of the nuclear ERα level was opposite that of TGF-βRI. Furthermore, dual luciferase reporter and chromatin immunoprecipitation assays showed that ERα could bind to the promoter region of TGF-βRI and negatively regulate its mRNA expression. Moreover, an in vitro study using NRK-52E cells showed that ERα knockdown blocked E₂-mediated protection, while TGF-βRI knockdown protected cells against hypoxic insult. The findings of this study suggest that renal IRI is closely related to the TGF-βRI-SMAD pathway in females and that E₂ exert its protective effect via the ERα-mediated transcriptional inhibition of TGF-βRI expression.

Dynamic regulation of anti-oxidation following donation repairing after circulatory determined death renal transplantation with prolonged non-heart-beating time

Donation after circulatory-determined death (DCD) is an important part of renal transplantation. Therefore, DCD renal transplantation animal model should be established to study the mechanism of organ injury. Here, we established a stable DCD rat renal transplantation model and investigated the dynamic regulation of graft self-repairing and antioxidant capacities with different non-heart-beating times (NHBTs). Male Sprague-Dawley rats were randomly divided into four groups with the NHBT of the donors from 0 to 15, 30, and 45 minutes. Recipients in long NHBT groups had a significantly lower survival rate and poorer graft function than those in short NHBT groups. Grafts from the 15-minute and 30-minute NHBT groups showed light and severe injury respectively at an early stage after transplantation and recovered within 7 days after transplantation, whereas the self-repairing of the grafts in the 45-minute NHBT group was delayed. The expressions of proliferating cell nuclear antigen (PCNA) and von Willebrand factor (vWF) were dependent on NHBT. The expression of antioxidant proteins paralleled graft recovery. In conclusion, the recipients can up-regulate antioxidant capacity to enhance graft self-repairing in DCD renal transplantation. Prolonged NHBT can delay the self-repairing and antioxidation of grafts.

Super-Resolution Imaging with Ultrasound for Visualization of the Renal Microvasculature in Rats Before and After Renal Ischemia: A Pilot Study

In vivo monitoring of the microvasculature is relevant since diseases such as diabetes, ischemia, or cancer cause microvascular impairment. Super-resolution ultrasound imaging allows in vivo examination of the microvasculature by detecting and tracking sparsely distributed intravascular microbubbles over a minute-long period. The ability to create detailed images of the renal vasculature of Sprague-Dawley rats using a modified clinical ultrasound platform was investigated in this study. Additionally, we hypothesized that early ischemic damage to the renal microcirculation could be visualized. After a baseline scan of the exposed kidney, 10 rats underwent clamping of the renal vein (n = 5) or artery (n = 5) for 45 min. The kidneys were rescanned at the onset of clamp release and after 60 min of reperfusion. Using a processing pipeline for tissue motion compensation and microbubble tracking, super-resolution images with a very high level of detail were constructed. Image filtration allowed further characterization of the vasculature by isolating specific vessels such as the ascending vasa recta with a 15–20 μm diameter. Using the super-resolution images alone, it was only possible for six assessors to consistently distinguish the healthy renal microvasculature from the microvasculature at the onset of vein clamp release. Future studies will aim at attaining quantitative estimations of alterations in the renal microvascular blood flow using super-resolution ultrasound imaging.

Metabolic reprogramming associated with progression of renal ischemia reperfusion injury assessed with hyperpolarized [1-13C]pyruvate

Acute kidney injury is a major clinical challenge affecting as many as 1 percent of all hospitalized patients. Currently it is not possible to accurately stratify and predict the outcome of the individual patient. Increasing evidence supports metabolic reprogramming as a potential target for new biomarkers. Hyperpolarized [1-¹³C]pyruvate imaging is a promising new tool for evaluating the metabolic status directly in the kidneys. We here investigate the prognostic potential of hyperpolarized [1-¹³C]pyruvate in the setting of acute kidney injury in a rodent model of ischemia reperfusion. A significant correlation was found between the intra-renal metabolic profile 24 hours after reperfusion and 7 days after injury induction, as well as a correlation with the conventional plasma creatinine biomarker of renal function and markers of renal injury. This leads to a possible outcome prediction of renal function and injury development from a metabolic profile measured in vivo. The results support human translation of this new technology to renal patients as all experiements have been performed using clinical MRI equipment.

Reno-protection of Urine-derived Stem Cells in A Chronic Kidney Disease Rat Model Induced by Renal Ischemia and Nephrotoxicity

Purpose: Drug-induced nephrotoxicity can occur in patients with pre-existing renal dysfunction or renal ischemia, potentially leading to chronic kidney disease (CKD) and end-stage renal disease (ESRD). Prompt treatment of CKD and the related side effects is critical in preventing progression to ESRD. The goal of this study was to demonstrate the therapeutic potential of urine-derived stem cells (USC) to treat chronic kidney disease-induced by nephrotoxic drugs and renal ischemia.

Materials and methods: Human USC were collected, expanded and characterized by flow cytometry. A CKD model was induced by creating an ischemia-reperfusion injury and gentamicin administration. Twenty-eight adult immunodeficient rats were divided into three groups: PBS-treated group (n=9), USC-treated group (n=9), and sham group with age-matched control animals (n=10). Cell suspension of USC (5 x 10⁶ / 100µl / kidney) or PBS was injected bilaterally into the renal parenchyma 9 weeks after CKD model creation. Renal function was evaluated by collection blood and urine samples to measure serum creatinine and glomerulus filtration rate. The kidneys were harvested 12 weeks after cell injection. Histologically, the extent of glomerulosclerosis and tubular atrophy, the amount of collagen deposition, interstitial fibrosis, inflammatory monocyte infiltration, and expression of transforming growth factor beta 1 (TGF-ß1), and superoxide dismutase 1 (SOD-1) were examined.

Results: USC expressed renal parietal epithelial cells (CD24, CD29 and CD44). Renal function, measured by GFR and serum Cr in USC-treated group were significantly improved compared to PBS-treated animals (p<0.05). The degree of glomerular sclerosis and atrophic renal tubules, the amount of fibrosis, and monocyte infiltration significantly decreased in USC-treated group compared to the PBS group (p<0.05). The level of TGF-ß1 expression in renal tissues was also significantly lower in the PBS group, while the level of SOD-1 expression was significantly elevated in the USC group, compared to PBS group (p<0.05).

Conclusions: The present study demonstrates the nephron-protective effect of USC on renal function via anti-inflammatory, anti-oxidative stress, and anti-fibrotic activity in a dual-injury CKD rat model. This provides an alternative treatment for CKD in certain clinical situations, such as instances where CKD is due to drug-induced nephrotoxicity and renal ischemia.

Volume incompliance and transfusion are essential for transfusion-associated circulatory overload: a novel animal model

BACKGROUND

Transfusion‐associated circulatory overload (TACO) is the predominant complication of transfusion resulting in death. The pathophysiology is poorly understood, but inability to manage volume is associated with TACO, and observational data suggest it is different from simple cardiac overload due to fluids. We developed a two‐hit TACO animal model to assess the role of volume incompliance (“first‐hit”) and studied whether volume overload (“second‐hit”) by red blood cell (RBC) transfusion is different compared to fluids (Ringer's lactate [RL]).

MATERIALS AND METHODS

Male adult Lewis rats were stratified into a control group (no intervention) or a first hit: either myocardial infarction (MI) or acute kidney injury (AKI). Animals were randomized to a second hit of either RBC transfusion or an equal volume of RL. A clinically relevant difference was defined as an increase in left ventricular end‐diastolic pressure (ΔLVEDP) of +4.0 mm Hg between the RBC and RL groups.

RESULTS

In control animals (without first hit) LVEDP was not different between infusion groups (Δ + 1.6 mm Hg). LVEDP increased significantly more after RBCs compared to RL in animals with MI (Δ7.4 mm Hg) and AKI (Δ + 5.4 mm Hg), respectively. Volume‐incompliant rats matched clinical TACO criteria in 92% of transfused versus 25% of RL‐infused animals, with a greater increase in heart rate and significantly higher blood pressure.

CONCLUSION

To our knowledge, this is the first animal model for TACO, showing that a combination of volume incompliance and transfusion is essential for development of circulatory overload. This model allows for further testing of mechanistic factors as well as therapeutic approaches.

Preconditioning against renal ischaemia reperfusion injury: the failure to translate to the clinic

Acute kidney injury (AKI) as a result of ischaemia-reperfusion represents a major healthcare burden worldwide. Mortality rates from AKI in hospitalized patients are extremely high and have changed little despite decades of research and medical advances. In 1986, Murry et al. demonstrated for the first time the phenomenon of ischaemic preconditioning to protect against ischaemia-reperfusion injury (IRI). This seminal finding paved the way for a broad body of research, which attempted to understand and ultimately harness this phenomenon for human application. The ability of preconditioning to limit renal IRI has now been demonstrated in multiple different animal models. However, more than 30 years later, a safe and consistent method of protecting human organs, including the kidneys, against IRI is still not available. This review highlights agents which, despite strong preclinical data, have recently failed to reduce AKI in human trials. The multiple reasons which may have contributed to the failure to translate some of the promising findings to clinical therapies are discussed. Agents which hold promise in the clinic because of their recent efficacy in preclinical large animal models are also reviewed.

Protective effect of zinc preconditioning against renal ischemia reperfusion injury is dose dependent

Objectives

Ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury and chronic kidney disease. Two promising preconditioning methods for the kidney, intermittent arterial clamping (IC) and treatment with the hypoxia mimetic cobalt chloride, have never been directly compared. Furthermore, the protective efficacy of the chemically related transition metal Zn²⁺ against renal IRI is unclear. Although Co²⁺ ions have been shown to protect the kidney via hypoxia inducible factor (HIF), the effect of Zn²⁺ ions on the induction of HIF1α, HIF2α and HIF3α has not been investigated previously.

Materials and methods

The efficacy of different preconditioning techniques was assessed using a Sprague-Dawley rat model of renal IRI. Induction of HIF proteins following Zn²⁺ treatment of the human kidney cell lines HK-2 (immortalized normal tubular cells) and ACHN (renal cancer) was measured using Western Blot.

Results

Following 40 minutes of renal ischemia in rats, cobalt preconditioning offered greater protection against renal IRI than IC as evidenced by lower peak serum creatinine and urea concentrations. ZnCl₂ (10 mg/kg) significantly lowered the creatinine and urea concentrations compared to saline-treated control rats following a clinically relevant 60 minutes of ischemia. Zn²⁺ induced expression of HIF1α and HIF2α but not HIF3α in HK-2 and ACHN cells.

Conclusion

ZnCl₂ preconditioning protects against renal IRI in a dose-dependent manner. Further studies are warranted to determine the possible mechanisms involved, and to assess the benefit of ZnCl₂ preconditioning for clinical applications.

Imaging technologies for monitoring the safety, efficacy and mechanisms of action of cell-based regenerative medicine therapies in models of kidney disease

The incidence of end stage kidney disease is rising annually and it is now a global public health problem. Current treatment options are dialysis or renal transplantation, which apart from their significant drawbacks in terms of increased morbidity and mortality, are placing an increasing economic burden on society. Cell-based Regenerative Medicine Therapies (RMTs) have shown great promise in rodent models of kidney disease, but clinical translation is hampered due to the lack of adequate safety and efficacy data. Furthermore, the mechanisms whereby the cell-based RMTs ameliorate injury are ill-defined. For instance, it is not always clear if the cells directly replace damaged renal tissue, or whether paracrine effects are more important. Knowledge of the mechanisms responsible for the beneficial effects of cell therapies is crucial because it could lead to the development of safer and more effective RMTs in the future. To address these questions, novel in vivo imaging strategies are needed to monitor the biodistribution of cell-based RMTs and evaluate their beneficial effects on host tissues and organs, as well as any potential adverse effects. In this review we will discuss how state-of-the-art imaging modalities, including bioluminescence, magnetic resonance, nuclear imaging, ultrasound and an emerging imaging technology called multispectral optoacoustic tomography, can be used in combination with various imaging probes to track the fate and biodistribution of cell-based RMTs in rodent models of kidney disease, and evaluate their effect on renal function.

The Effect of the Antioxidant Drug "U-74389G" on Creatinine Levels during Ischemia Reperfusion Injury in Rats

OBJECTIVE

The aim of this experimental study was to examine the effect of the antioxidant drug "U-74389G" on a rat model using an ischemia reperfusion protocol. The effect of U-74389G was studied biochemically by measuring mean blood creatinine levels.

MATERIALS AND METHODS

Forty rats were used in the study. Creatinine levels were measured at 60 min of reperfusion (groups A and C) or at 120 min of reperfusion (groups B and D), where groups A and B were controls and groups C and D received U-74389G administration.

RESULTS

U-74389G administration significantly decreased the predicted creatinine levels by 21.02 ± 5.06% (p = 0.0001). Reperfusion time non-significantly increased the predicted creatinine levels by 4.20 ± 6.12% (p = 0.4103). However, U-74389G administration and reperfusion time together produced a significant combined effect in decreasing the predicted creatinine levels by 11.69 ± 3.16% (p = 0.0005).

CONCLUSION

Independent of reperfusion time, U-74389G administration significantly decreased the creatinine levels in an ischemic rat model. This study demonstrates that short-term U-74389G administration improves renal function by increasing creatinine excretion.

A novel rodent model of severe renal ischemia reperfusion injury

Renal ischemia reperfusion injury (IRI) is a major problem, currently without treatments in clinical use. This reflects the failure of animal models to mimic the severity of IRI observed in clinical practice. Most described models lack both the ability to inflict a permanent reduction in renal function and the sensitivity to demonstrate the protective efficacy of different therapies in vivo. To test novel cell-based therapies, we have developed a model of renal IRI in Fisher 344 rats. Animals were subjected to 120 min of unilateral warm ischemia, during which they underwent an intra-renal artery infusion of therapeutic agents or vehicle. At either 2 or 6 weeks post-surgery, animals underwent terminal glomerular filtration rate (GFR) studies by inulin clearance to most accurately quantify renal function. Harvested kidneys underwent histological analysis. Compared to sham operations, saline treated animals suffered a long-term reduction in GFR of ≈50%. Histology revealed short- and long-term disruption of renal architecture. Despite the injury severity, post-operative animal losses are <5%. This model produces a severe, consistent renal injury that closely replicates the pathological processes encountered in clinical medicine. Renal artery infusion mimics the route likely employed in clinical transplantation, where the renal artery is accessible. Inulin clearance characterizes GFR, allowing full assessment of therapeutic intervention. This model is useful for screening therapeutic agents prior to testing in a transplant model. This reduces animal numbers needed to test drugs for clinical transplantation and allows for refinement of dosing schedules.

Kidney diseases and tissue engineering

Kidney disease is a worldwide public health problem. Renal failure follows several disease stages including acute and chronic kidney symptoms. Acute kidney injury (AKI) may lead to chronic kidney disease (CKD), which can progress to end-stage renal disease (ESRD) with a mortality rate. Current treatment options are limited to dialysis and kidney transplantation; however, problems such as donor organ shortage, graft failure and numerous complications remain a concern. To address this issue, cell-based approaches using tissue engineering (TE) and regenerative medicine (RM) may provide attractive approaches to replace the damaged kidney cells with functional renal specific cells, leading to restoration of normal kidney functions. While development of renal tissue engineering is in a steady state due to the complex composition and highly regulated functionality of the kidney, cell therapy using stem cells and primary kidney cells has demonstrated promising therapeutic outcomes in terms of restoration of renal functions in AKI and CKD. In this review, basic components needed for successful renal kidney engineering are discussed, and recent TE and RM approaches to treatment of specific kidney diseases will be presented.

Cell-based therapy for kidney disease

The prevalence of renal disease continues to increase worldwide. When normal kidney is injured, the damaged renal tissue undergoes pathological and physiological events that lead to acute and chronic kidney diseases, which frequently progress to end stage renal failure. Current treatment of these renal pathologies includes dialysis, which is incapable of restoring full renal function. To address this issue, cell-based therapy has become a potential therapeutic option to treat renal pathologies. Recent development in cell therapy has demonstrated promising therapeutic outcomes, in terms of restoration of renal structure and function impaired by renal disease. This review focuses on the cell therapy approaches for the treatment of kidney diseases, including various cell sources used, as well recent advances made in preclinical and clinical studies.

Aged kidneys are refractory to ischemic postconditioning in a rat model

BACKGROUND

Ischemic postconditioning (IPoC) is defined as a series of intermittent interruptions of blood flow in the early phase of reperfusion that mechanically alters the hydrodynamics of reperfusion and it attenuates renal damage after ischemia/reperfusion (I/R) injury in vivo. But all of these data had been obtained in adult populations and whether this protection was maintained in aging kidneys was unknown. The objective of this study was to establish whether the efficacy of IPoC is maintained in aging kidneys.

MATERIALS AND METHODS

The aged (24-month-old) and young (3-month-old) Wistar rats were used. Rats were subjected to 45 min of renal ischemia, both with and without treatment with IPoC. Serum urea nitrogen and creatinine levels, histological examination and apoptosis were assessed at 24 h. Oxidative stress was evaluated and apoptosis-related molecules were studied by Western blotting.

RESULTS

In young rat kidneys, IPoC significantly attenuated the renal dysfunction and cell apoptosis induced by I/R. In contrast, IPoC failed to limit renal dysfunction, possibly a consequence of increased apoptosis in aged rat kidneys.

CONCLUSIONS

Our data indicated that IPoC was ineffective in aged rat kidneys. These findings may have major implications in that severe apoptosis in aged kidneys might be refractory to anti-apoptotic effect by IPoC.