Neutrophil gelatinase-associated lipocalin (NGAL) levels in response to unilateral renal ischaemia in a novel pilot two-kidney porcine model

Mesenchymal Stem Cells-Derived Exosomes Ameliorate Ischemia/Reperfusion Induced Acute Kidney Injury in a Porcine Model

Exosomes are membrane-enclosed vesicles secreted by cells, containing a variety of biologically active ingredients including proteins, nucleic acids and lipids. In this study, we investigated the therapeutic effects of the exosomes and underlying mechanisms in a miniature pig model of ischemia/reperfusion-induced acute kidney injury (I/R-AKI). The exosomes were extracted from cultured human umbilical cord derived mesenchymal stem cells (hUC-MSCs) and infused into a miniature pig model of I/R AKI. Our results showed that 120 min of unilateral ischemia followed by reperfusion and contralateral nephrectomy resulted in renal dysfunction, severe kidney damage, apoptosis and necroptosis. Intravenous infusion of one dose of exosomes collected from about 4 × 108 hUC-MSCs significantly improved renal function and reduced apoptosis and necroptosis. Administration of hUC-MSC exosomes also reduced the expression of some pro-inflammatory cytokines/chemokines, decreased infiltration of macrophages to the injured kidneys and suppressed the phosphorylation of nuclear factor-κB and signal transducer and activator of transcription 3, two transcriptional factors related to inflammatory regulation. Moreover, hUC-MSC exosomes could promote proliferation of renal tubular cells, angiogenesis and upregulation of Klotho and Bone Morphogenetic Protein 7, two renoprotective molecules and vascular endothelial growth factor A and its receptor. Collectively, our results suggest that injection of hUC-MSC exosomes could ameliorate I/R-AKI and accelerate renal tubular cell repair and regeneration, and that hUC-MSC exosomes may be used as a potential biological therapy for Acute kidney injury patients.

Porcine models of acute kidney injury

Pigs represent a potentially attractive model for medical research. Similar body size and physiological patterns of kidney injury that more closely mimic those described in humans make larger animals attractive for experimentation. Using larger animals, including pigs, to investigate the pathogenesis of acute kidney injury (AKI) also serves as an experimental bridge, narrowing the gap between clinical disease and preclinical discoveries. This article compares the advantages and disadvantages of large versus small AKI animal models and provides a comprehensive overview of the development and application of porcine models of AKI induced by clinically relevant insults, including ischemia-reperfusion, sepsis, and nephrotoxin exposure. The primary focus of this review is to evaluate the use of pigs for AKI studies by current investigators, including areas where more information is needed.

Effects of pneumoperitoneum with carbon dioxide on renal and hepatic functions in rats

Introduction

Laparoscopic surgery is a preferred method based on its many benefits. However, increasing abdominal pressure by CO₂ insufflation during the implementation of this technique poses challenges.

Aim

To determine the degree of renal and liver injury that occurs in a pneumoperitoneum (PP) model of prolonged CO₂ insufflation.

Material and methods

Twenty-one female Sprague Dawley rats were separated randomly into three groups. Group 1 was the control group and given anesthesia for 3 h. In group 2, PP was administered under anesthesia for 1 h. In the last group, PP was administered under anesthesia to animals for 3 h. We measured renal and liver injury biomarkers and made a histopathological evaluation to estimate the degree of injury and assessed the correlation of biomarkers including kidney injury molecule-1 (KIM-1) with histopathological findings.

Results

Histopathological analysis according to the kidney ischemia tubular damage score showed a statistically significant difference between the 3 groups (p < 0.001). There was an increase in KIM-1 levels in the groups, although it was not statistically significant (p = 0.062, p = 0.156, p = 0.350 respectively). According to the correlation test in this research, KIM-1 results had a statistically significant association with creatinine, urea, aspartate aminotransferase and alanine aminotransferase levels in all control and study groups.

Conclusions

According to our results, the increase in KIM-1 was correlated with Cr levels and compatible with histopathological analysis. Moreover, intra-abdominal pressure statistically significantly increased the degree of kidney injury and there was not a significant increase in the levels of KIM-1. There was no difference in liver damage between groups.

The effects of prolonged CO2 insufflation on kidney function in a rat pneumoperitoneum model

INTRODUCTION

Pneumoperitoneum (PP) is known to cause ischemia in kidneys and other intra-abdominal organs because of decreased splanchnic blood flow.

AIM

We aimed to determine the degree of renal injury that occurs due to a PP and prolonged PP. We measured renal injury biomarkers and made a histopathological evaluation to estimate the degree of injury and assessed the correlation of biomarkers with histopathological findings.

MATERIAL AND METHODS

Twenty-one female Sprague Dawley rats were separated randomly into three groups. Group 1 was the control group and was given anesthesia for 3 h. In group 2, a PP was administered under anesthesia for 1 h. A pneumoperitoneum was administered under anesthesia to animals in group 3 for 3 h.

RESULTS

Pathological analysis showed a significant statistical difference between the 3 groups. In particular, neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C (Cys C) levels at the 24^th h and preoperative mean urea levels showed a significant difference between the groups. The 24^th-hour NGAL level in group 3 was significantly higher than that of group 1. The preoperative Cys C level was higher in group 1 than in either group 2 or 3. Cys C was decreased significantly in group 1 and increased significantly in both groups 2 and 3.

CONCLUSIONS

The increase in NGAL and Cys C levels directly correlated with the duration of PP and intra-abdominal pressure, and they are therefore good biomarkers in diagnosing acute renal injury in the early phase. Serum creatinine level is not a good biomarker in the early phase of renal injury.

Pyruvate Kinase M2: A Novel Biomarker for the Early Detection of Acute Kidney Injury

The identification of biomarkers for the early detection of acute kidney injury (AKI) is clinically important. Acute kidney injury (AKI) in critically ill patients is closely associated with increased morbidity and mortality. Conventional biomarkers, such as serum creatinine (SCr) and blood urea nitrogen (BUN), are frequently used to diagnose AKI. However, these biomarkers increase only after significant structural damage has occurred. Recent efforts have focused on identification and validation of new noninvasive biomarkers for the early detection of AKI, prior to extensive structural damage. Furthermore, AKI biomarkers can provide valuable insight into the molecular mechanisms of this complex and heterogeneous disease. Our previous study suggested that pyruvate kinase M2 (PKM2), which is excreted in the urine, is a sensitive biomarker for nephrotoxicity. To appropriately and optimally utilize PKM2 as a biomarker for AKI requires its complete characterization. This review highlights the major studies that have addressed the diagnostic and prognostic predictive power of biomarkers for AKI and assesses the potential usage of PKM2 as an early biomarker for AKI. We summarize the current state of knowledge regarding the role of biomarkers and the molecular and cellular mechanisms of AKI. This review will elucidate the biological basis of specific biomarkers that will contribute to improving the early detection and diagnosis of AKI.

Dynamics of Urinary Calprotectin after Renal Ischaemia

Background: Urinary calprotectin has been identified as a promising biomarker for acute kidney injury. To date, however, the time-dependent changes of this parameter during acute kidney injury remain elusive. The aim of the present work was to define the time-course of urinary calprotectin secretion after ischaemia/reperfusion-induced kidney injury in comparison to neutrophil gelatinase—associated lipocalin, thereby monitoring the extent of tubular damage in nephron sparing surgery for kidney tumours. Methods: The study population consisted of 42 patients. Thirty-two patients underwent either open or endoscopic nephron sparing surgery for kidney tumours. During the surgery, the renal arterial pedicle was clamped with a median ischaemic time of 13 minutes (interquartile range, 4.5–20.3 minutes) in 26 patients. Ten retro-peritoneoscopic living donor nephrectomy patients and 6 nephron sparing surgery patients in whom the renal artery was not clamped served as controls. Urinary calprotectin and neutrophil gelatinase—associated lipocalin concentrations were repeatedly measured by enzyme-linked immunosorbent assay and assessed according to renal function parameters. Results: Urinary concentrations of calprotectin and neutrophil gelatinase—associated lipocalin increased significantly after ischaemia/reperfusion injury, whereas concentrations remained unchanged after nephron sparing surgery without ischaemia/reperfusion injury and after kidney donation. Calprotectin and neutrophil gelatinase—associated lipocalin levels were significantly increased 2 and 8 hours, respectively, post-ischaemia. Both proteins reached maximal concentrations after 48 hours, followed by a subsequent persistent decrease. Maximal neutrophil gelatinase—associated lipocalin and calprotectin concentrations were 9-fold and 69-fold higher than their respective baseline values. The glomerular filtration rate was only transiently impaired at the first post-operative day after ischaemia/reperfusion injury (p = 0.049). Conclusion: Calprotectin and neutrophil gelatinase—associated lipocalin can be used to monitor clinical and sub-clinical tubular damage after nephron sparing surgery for kidney tumours. Urinary calprotectin concentrations start rising within 2 hours after ischaemia/reperfusion-induced kidney injury.

Novel biomarkers of acute kidney injury: Evaluation and evidence in urologic surgery

Patients undergoing urologic surgery are at risk of acute kidney injury (AKI) and consequently long-term deterioration in renal function. AKI is further associated with significantly higher odds of perioperative complications, prolonged hospital stay, higher mortality and costs. Therefore, better awareness and detection of AKI, as well as identification of AKI determinants in the urological surgery setting is warranted to pre-empt and mitigate further deterioration of renal function in patients at special risk. New consensus criteria provide precise definitions of diagnosis and description of the severity of AKI. However, they rely on serum creatinine (SCr), which is known to be an inaccurate marker of early changes in renal function. Therefore, several new urinary and serum biomarkers promise to address the gap associated with the use of SCr. Novel biomarkers may complement SCr measurement or most likely improve the diagnostic accuracy of AKI when used in combinations. However, novel biomarkers have to prove their clinical applicability, accuracy, and cost effectiveness prior to implementation into clinical practice. Most preferably, novel biomarkers should help to positively improve a patient’s long-term renal functional outcomes. The purpose of this review is to discuss currently available biomarkers and to review their clinical evidence within urologic surgery settings.

Catheter-based induction of renal ischemia/reperfusion in swine: description of an experimental model

Several techniques to induce renal ischemia have been proposed: clamp, PVA particles, and catheter-balloon. We report the development of a controlled, single-insult model of unilateral renal ischemia/reperfusion (I/R) without contralateral nephrectomy, using a suitable model, the pig. This is a balloon-catheter-based model using a percutaneous, interventional radiology procedure. One angioplasty balloon-catheter was placed into the right renal artery and inflated for 120 min and reperfusion over 24 h. Serial serums were sampled from the inferior vena cava and urine was directly sampled from the bladder throughout the experiment, and both kidneys were excised after 24 h of reperfusion. Analyses of renal structure and function were performed by hematoxylin-eosin/periodic Acid-Schiff, serum creatinine (SCr), blood urea nitrogen (BUN), fractional excretion of ions, and glucose, SDS-PAGE analysis of urinary proteins, and serum neutrophil gelatinase-associated lipocalin (NGAL). Total nitrated protein was quantified to characterize oxidative stress. Acute tubular necrosis (ATN) was identified in every animal, but only two animals showed levels of SCr above 150% of baseline values. As expected, I/R increased SCr and BUN. Fractional sodium, potassium, chloride, and bicarbonate excretion were modulated during ischemia. Serum-nitrated proteins and NGAL had two profiles: decreased with ischemia and increased after reperfusion. This decline was associated with increased protein excretion during ischemia and early reperfusion. Altogether, these data show that the renal I/R model can be performed by percutaneous approach in the swine model. This is a suitable translational model to study new early renal ischemic biomarkers and pathophysiological mechanisms in renal ischemia.

Impact of 6% hydroxyethyl starch 130/0.42 and 4% gelatin on renal function in a pediatric animal model

OBJECTIVES

Artificial colloids, frequently used to prevent hemorrhagic shock in children, may induce serious renal side effects in critically ill adult patients. The impact of perioperative colloid infusion on the renal function in adults and children remains unclear.

AIM

To determine the impact of single doses of artificial colloids on renal function tests, we conducted an experimental animal study. We hypothesized that neither the infusion of moderate doses of 6% hydroxyethyl starch (HES) nor of 4% gelatin (GEL) would have a serious impact on the renal function of healthy piglets.

METHODS

Fifteen sedated piglets were randomly assigned to receive an infusion of either 20 ml·kg(-1) HES or GEL or a balanced electrolyte solution (BS, control group) over 30 min. Before and 7 days after infusion, serum and urine renal function tests were recorded and renal biopsies were taken.

RESULTS

Serum and urine renal function tests (e.g., creatinine, urea, cystatin C, and neutrophil gelatinase-associated lipocalin) were within normal ranges, and a microscopic examination of the renal tissue in all groups revealed no major alterations such as tubular necrosis, interstitial bleeding, interstitial inflammation, or vacuoles.

CONCLUSIONS

In this pediatric animal model, the infusion of moderate doses of artificial colloids was not found to have any relevant impact on renal function. Further clinical investigations are necessary to provide a conclusive assessment of the risk for renal impairment after HES and GEL administration during major pediatric surgery.

Urine neutrophil gelatinase-associated lipocalin as a marker of acute kidney injury after kidney surgery

PURPOSE

We evaluated urine NGAL as a marker of acute kidney injury in patients undergoing partial nephrectomy. We sought to identify the preoperative clinical features and surgical factors during partial nephrectomy that are associated with renal injury, as measured by increased urine NGAL vs controls.

MATERIALS AND METHODS

Using patients treated with radical nephrectomy or thoracic surgery as controls, we prospectively collected and analyzed urine and serum samples from patients treated with partial or radical nephrectomy, or thoracic surgery between April 2010 and April 2012. Urine was collected preoperatively and at multiple time points postoperatively. Differences in urine NGAL levels were analyzed among the 3 surgical groups using a generalized estimating equation model. The partial nephrectomy group was subdivided based on a preoperative estimated glomerular filtration rate of less than 60, or 60 ml/minute/1.73 m(2) or greater.

RESULTS

Of 162 patients included in final analysis more than 65% had cardiovascular disease. The median estimated glomerular filtration rate was greater than 60 ml/minute/1.73 m(2) in the radical and partial nephrectomy, and thoracic surgery groups (61, 78 and 84.5 ml/minute/1.73 m(2), respectively). Preoperatively, a 10 unit increase in the estimated glomerular filtration rate was associated with a 4 unit decrease in urine NGAL in the partial nephrectomy group. Postoperatively, urine NGAL in the partial nephrectomy group was not higher than in controls and did not correlate with ischemia time. Patients with partial nephrectomy with a preoperative estimated glomerular filtration rate of less than 60 ml/minute/1.73 m(2) had higher urine NGAL postoperatively than those with a higher preoperative estimated rate.

CONCLUSIONS

Urine NGAL does not appear to be a useful marker for detecting renal injury in healthy patients treated with partial nephrectomy. However, patients with poorer preoperative renal function have higher baseline urine levels and appear more susceptible to acute kidney injury, as detected by urine levels and Acute Kidney Injury Network criteria, than those with a normal estimated glomerular filtration rate.