A review of the pathology and pathogenesis of acute renal failure due to acute tubular necrosis

Potentiating Renal Regeneration Using Mesenchymal Stem Cells

BACKGROUND

The potential of a mesenchymal stem cell (MSC) therapy to accelerate the repair of ischemically damaged human kidneys during 24 hours of warm perfusion was evaluated. The hypothesis was that by administering MSC directly to the renal tissue, there would be an improved opportunity for cellular repair mediated by intrarenal paracrine effects.

METHODS

Studies were performed using the exsanguinous metabolic support (EMS) tissue-engineering platform. Five pairs of human kidney allografts from donation after circulatory death donors were studied. One human kidney was EMS perfused for 24 hours (control), whereas its paired kidney was EMS perfused with MSC (1 × 10). The kidneys were evaluated for DNA synthesis, cytokine/chemokine synthesis, cytoskeletal regeneration, and mitosis.

RESULTS

Treatment with MSC resulted in reduced inflammatory cytokines synthesized by the kidneys. Mesenchymal stem cell treatment led to a significant increase in the synthesis of adenosine triphosphate and growth factors resulting in normalization of metabolism and the cytoskeleton. Toluidine Blue staining of MSC-treated kidneys demonstrated a significant increase in the number of renal cells undergoing mitosis (26%) compared with EMS perfusion alone.

CONCLUSIONS

To our knowledge, our work is the first to have demonstrated actual renal regeneration while ischemically damaged human kidneys are perfused ex vivo for 24 hours. The observed regeneration entails: increased synthesis of adenosine triphosphate, a reduced inflammatory response, increased synthesis of growth factors, normalization of the cytoskeleton and mitosis. The ability to regenerate renal tissue ex vivo sufficiently to result in immediate function could revolutionize transplantation by solving the chronic organ shortage.

Expression of cleaved caspase-3 in renal tubular cells in Plasmodium falciparum malaria patients

AIM

In Plasmodium falciparum malaria, the clinical manifestation of acute kidney injury (AKI) is commonly associated with acute tubular necrosis (ATN) in the kidney tissues. Renal tubular cells often exhibit various degrees of cloudy swelling, cell degeneration, and frank necrosis. To study individual cell death, this study evaluates the degree of renal tubular necrosis in association with apoptosis in malarial kidneys.

METHODS

Kidney tissues from P. falciparum malaria with AKI (10 cases), and without AKI (10 cases) were evaluated for tubular pathology. Normal kidney tissues from 10 cases served as controls. Tubular necrosis was assessed quantitatively in kidney tissues infected with P. falciparum malaria, based on histopathological evaluation. In addition, the occurrence of apoptosis was investigated using cleaved caspase-3 marker. Correlation between tubular necrosis and apoptosis was analyzed.

RESULTS

Tubular necrosis was found to be highest in P. falciparum malaria patients with AKI (36.44% ± 3.21), compared to non-AKI (15.88% ± 1.63) and control groups (2.58% ± 0.39) (all p < 0.001). In the AKI group, the distal tubules showed a significantly higher degree of tubular necrosis than the proximal tubules (p = 0.021) and collecting tubules (p = 0.033). Tubular necrosis was significantly correlated with the level of serum creatinine (r = 0.596, p = 0.006), and the occurrence of apoptosis (r = 0.681, p = 0.001).

CONCLUSION

In malarial AKI, the process of apoptosis occurs in ATN.

Renal tubular disease in the era of combination antiretroviral therapy

OBJECTIVES

To describe the spectrum of renal tubular disease (RTD) in HIV-positive patients and its association with exposure to antiretroviral therapy (ART).

DESIGN

Review of 265 consecutive renal biopsies from HIV-positive patients attending eight clinics in the United Kingdom between 2000 and 2012.

METHODS

We described the clinical characteristics of patients with RTD and compared current/recent exposure (at the time of, or up to 3 months prior to the date of biopsy) to potentially nephrotoxic ART [tenofovir (TDF), atazanavir (ATV), indinavir (IDV) and lopinavir/ritonavir (LPV/r)]. We also analysed the incidence of RTD in the UK CHIC cohort. Kruskall-Wallis, analysis of variance and Fisher's exact tests were used to evaluate between-group differences.

RESULTS

Of the 60 RTD cases, 54 (90%) were included in the analyses. RTD comprised of three distinct patterns: acute tubular injury (ATI, n = 22), tubulo-interstitial nephritis (TIN, n = 20) and interstitial fibrosis and tubular atrophy (IFTA, n = 12). Compared with TIN and IFTA, ATI cases were less likely to be of black ethnicity (10 vs. 42-55%; P = 0.006), more likely to be on ART (100 vs. 55-68%; P = 0.001), with HIV-RNA below 200 copies/ml (100 vs. 54-58%; P < 0.001), and more likely to have current/recent exposure to TDF (P < 0.001). We did not find evidence for an association between exposure to TDF, ATV/r or LPV/r and either TIN or IFTA.

CONCLUSION

RTD was present in approximately 20% of renal biopsies and comprised three distinct injury patterns with considerable clinical overlap. ATI was associated with TDF exposure, although the overall incidence of biopsy-defined ATI was low.

Pathophysiology of acute kidney injury

Acute kidney injury (AKI) is the leading cause of nephrology consultation and is associated with high mortality rates. The primary causes of AKI include ischemia, hypoxia, or nephrotoxicity. An underlying feature is a rapid decline in glomerular filtration rate (GFR) usually associated with decreases in renal blood flow. Inflammation represents an important additional component of AKI leading to the extension phase of injury, which may be associated with insensitivity to vasodilator therapy. It is suggested that targeting the extension phase represents an area potential of treatment with the greatest possible impact. The underlying basis of renal injury appears to be impaired energetics of the highly metabolically active nephron segments (i.e., proximal tubules and thick ascending limb) in the renal outer medulla, which can trigger conversion from transient hypoxia to intrinsic renal failure. Injury to kidney cells can be lethal or sublethal. Sublethal injury represents an important component in AKI, as it may profoundly influence GFR and renal blood flow. The nature of the recovery response is mediated by the degree to which sublethal cells can restore normal function and promote regeneration. The successful recovery from AKI depends on the degree to which these repair processes ensue and these may be compromised in elderly or chronic kidney disease (CKD) patients. Recent data suggest that AKI represents a potential link to CKD in surviving patients. Finally, earlier diagnosis of AKI represents an important area in treating patients with AKI that has spawned increased awareness of the potential that biomarkers of AKI may play in the future.

Renal tubular dysfunction caused by dietary hexachlorocyclohexane (HCH) isomers

Dietary administration of beta- and gamma-hexachlorocyclohexane (HCH) to albino rats caused an abnormal excessive excretion of glucose in the urine, blood glucose level being nearly normal. Occurrence of glucosuria was also accompanied by increased excretions of the two low-threshold compounds - creatinine and urea, their levels in blood being normal. The interference of HCH isomers with renal function as evidenced by biochemical data was also indicated by histopathological lesions observed in the kidney sections, viz., hypertrophy and degeneration of the renal tubular epithelia.

The acute toxicity and teratogenicity of cadmium in the pregnant rat

Until the 16th day of gestation the intravenous LD50 of Cd2+ in the pregnant Wistar-Porton rat is higher, but not significantly different from that (1.8 mg Cd2+ per kg body weight) in nulliparous females. At 20 days it is 1.1 mg Cd2+ kg per body weight. This decrease is related to the rapid increase in weight of the conceptuses in late gestation and to the retention of most of the dose in the maternal compartment. If the dose is based on body weight at conception, the LD50 for the 20-day pregnant rat (1.6 mg Cd2+ per kg body weight) and non-gravid female do not differ significantly. Nevertheless, after the same Cd2+ dose, hepatic and renal Cd2+ concentrations are less in the pregnant than in the non-pregnant animal. The Cd2+ concentrations, therefore, do not determine the liver and kidney damage, which is restricted to the pregnant rat. Placentae also accumulate Cd2+ and placental haemorrhage follows the injection of the appropriate Cd2+ LD50 on day 12-20 of gestation. In those animals that die between 16 and 30 h after dosing, haemorrhage and death appear to be correlated. Renal damage, therefore, probably results from haemorrhagic shock. It is not dependent on the transfer of protein-bound Cd2+ from the necrotic placentae to the kidney. Between the 8th and 15th day of gestation, Cd2+ (1.25 mg per kg body weight) is highly teratogenic. Hydrocephalus is the most frequent abnormality when the dose is given between the 8th and 12th day. Other malformations include eye defects, gastroschiasis and umbilical hernia.

The acute toxic effects of hexachloro-1 : 3-butadiene on the rat kidney

A single intraperitoneal injection of hexochloro-1 : 3-butadiene (HCBD) at 100 mg/kg or above produced renal tubular necrosis in the rat by 24 h. Histological examination of the kidneys indicated damage to the straight portion of the proximal tubules. Urinary analysis showed diuresis, increased proteinuria and an increase in the excretion of N-acetyl-beta-D-glucosaminidase, and alkaline phosphatase at doses above 100 mg/kg. At doses below 100 mg/kg only a mild increase in protein excretion was observed. Twenty-four hours after 200 mg/kg HCBD, i.p., there was a marked decrease in the glomerular filtration rate (inulin clearance) and in the clearance of the organic anion (p-aminohippuric acid, PAH) and the organic cation (tetraethylammonium bromide, TEA) by the kidney. HCBD did not affect the accumulation of PAH or TEA by renal cortical slices when added in vitro at a concentration up to 0.1 mM. However, a decrease in PAH, but not TEA accumulation, was seen in renal cortical slices from rats treated with HCBD 24 h previously. Mercuric chloride (HgCl2), a known nephrotoxin, was used as a positive control for these studies. HCBD appears to specifically damage the straight portion of the proximal renal tubule and thereby selectively damage the organic anion transport system.

Glomerular mesangial and endothelial cell swelling following temporary renal ischemia and its role in the no-reflow phenomenon

The purpose of these experiments was to define changes in glomeruli of rats kidneys which could account for a marked reduction of blood flow immediately following temporary ischemia. After the renal artery had been clamped for 60 minutes, mesangial and endothelial cellular swelling was sufficiently severe to compress and trap intracapillary erythrocytes, obstruct capillary lumens, and prevent reflow of an isotonic carbon suspension. Perfusion of saline solution before the renal arteries were clamped washed blood from the kidney, and the resulting cellular swelling alone was not sufficient to block capillary lumens. Erythrocyte trapping did not occur after 15 minutes of ischemia. Swelling of glomerular and tubular epithelial cells produced some extrinsic capillary compression that could contribute to erythrocyte trapping, but this appeared to be of minor importance in producing the no-reflow phenomenon.

Studies on the modification of renal lesions due to aspirin and oxyphenbutazone in the rat and the effects on the kidney of 2:4 dinitrophenol

Cortical tubular necrosis induced by either aspirin (300 mg/kg) or oxyphenbutazone (444 mg/kg) was reduced if probenecid (300 mg/kg) was administered at the same time. The prior administration of aspirin (600 mg/kg) reduced the tubular necrosis that follows administration of oxyphenbutazone (444 mg/kg) alone, thus demonstrating that some degree of cross-tolerance between the two drugs occurs. Phenacetin pretreatment (597 mg/kg) was less effective, while paracetamol (503 mg/kg) was without effect in this regard. Those substances that reduced the oxyphenbutazone-induced cortical lesion also ameliorated the focal degenerative change in the lower nephron attributed to this drug. Oral administration of 2:4 dinitrophenol (20 mg/kg) led to only minor cortical tubular necrosis in a few animals.

Renal tubular necrosis due to shock: light and electron-microscope observations

The renal biopsy findings in a 76 yr-old woman suffering grom anuria due to acute tubular necrosis are described. The glomeruli were normal on light- and electron microscopy. Immunofluorescent studies failed to reveal any fibrin or immunoglobulins in the glomerular capillaries. Extensive focal areas of necrosis were seen in the tubular epithelium often exposing the lumen of the tubule directly to the tubular basement-membrane. In some areas necrotic cells lay adjacent to normal or near normal cells. The proximity of the necrotic tubular epithelium to the oedematous interstitial tissue and the peritubular capillaries, together with the finding of normal glomeruli is compatible with the theory of back diffusion as a mechanism for the oliguria.