Regressive course of oxalate deposition in primary hyperoxaluria after kidney transplantation

Primary hyperoxaluria (PH) is a rare autosomal recessive disease caused by the functional defect of alanine-glyoxylate aminotransferase (AGT) enzyme in the liver and it is characterized by the deposition of diffuse calcium oxalate crystals. A 38-year-old male patient presented with history of recurrent nephrolithiasis and has received chronic hemodialysis treatment for 2 years. Cadaveric renal transplantation was applied to the case. The patient was reoperated on postoperative day 13 because of the collection surrounding the urethra. During this operation, kidney biopsy was made due to late decrease in creatinine levels. Deposition of diffuse oxalate crystal was detected in allograft kidney biopsy, whereas in the 0-hour biopsy there were no oxalate crystals. Oxalate level was found to be high in a 24-hour urine specimen (118 mg/L, normal level: 7–44 mg/L). The patient was identified with primary hyperoxaluria and followed up in terms of systemic oxalate deposition as well as allograft kidney. In the kidney biopsy taken after 18 months, we detected that oxalate crystals almost entirely disappeared. In our case, bilateral preretinal, intraretinal, and intravascular diffuse oxalate crystals were detected, and argon laser photocoagulation treatments were needed for choroidal and retinal neovascularization. Repeated ophthalmic examinations showed the regressive nature of oxalate depositions. In the 18th month, fundus examination and fluorescein angiography revealed that oxalate crystals were significantly regressed. To increase the quality of life and slow down the systemic effects of oxalosis, kidney-only transplantation is beneficial.     

A porcine model of calcium oxalate kidney stone disease

PURPOSE: The pig has been extensively used in biomedical research because of the similarities in organ structure and function to humans. It is desirable to have an animal model of oxaluria and urolithiasis with physiological, anatomical and nutritional characteristics that more closely resemble those of man. In this study we determined if feeding pigs trans-4-hydroxy-l-proline (HP) increased urine oxalate levels and if it would serve as a model for human hyperoxaluria and stone disease. MATERIALS AND METHODS: Male Yorkshire-Durox cross-bred pigs were fed HP for up to 20 days. Urine was periodically collected and analyzed for oxalate levels and the presence of crystalluria. After 20 days of feeding the kidneys were removed and examined grossly and microscopically for indications of injury, crystal deposition and stone formation. RESULTS: Feeding pigs 10% HP (weight per weight HP/food) produced hyperoxaluria, which reached a maximum and leveled off by day 6. Urine oxalate remained near this level until the study ended at 20 days regardless of the further increase in HP to 20% of the weight of the food. When the kidneys were removed and grossly examined, calcium oxalate encrustations were observed on multiple papillary tips. Histopathological observation of the papillary tissue showed tissue injury and crystal deposition. CONCLUSIONS: Pigs fed HP have hyperoxaluria and calcium oxalate crystalluria, and calcium oxalate papillary deposits form that may be precursors of kidney stones. The use of the pig as a model of human hyperoxaluria and stone formation should prove ideal for studies of these human diseases.     

Mechanism of calcium oxalate renal stone formation and renal tubular cell injury

Abstract:   Formation of calcium oxalate stones tends to increase with age and begins from the attachment of a crystal formed in the cavity of renal tubules to the surface of renal tubular epithelial cells. Though most of the crystals formed in the cavity of renal tubules are discharged as is in the urine, in healthy people, crystals that attach to the surface of renal tubular epithelial cells are thought to be digested by macrophages and/or lysosomes inside of cells. However, in individuals with hyperoxaluria or crystal urine, renal tubular cells are injured and crystals easily become attached to them. Various factors are thought to be involved in renal tubular cell injury. Crystals attached to the surface of renal tubular cells are taken into the cells ( crystal–cell interaction ). And then the crystal and crystal aggregates grow, and finally a stone is formed.     

草酸钙结晶-肾小管细胞损伤机制研究进展

草酸钙是肾结石中最常见的化学成分。肾钙盐结晶是草酸钙结石形成的关键步骤之一,而近年来研究发现肾钙盐结晶形成与肾小管上皮细胞损伤密切相关。本文就草酸钙结石形成和肾小管上皮细胞损伤相互作用机制方面进行综述。     

Influence of cranberry juice on the urinary risk factors for calcium oxalate kidney stone formation

Cranberry juice is popular remedy for many ills; apart from the pleasant tasting many people drink it to help in preventing UTIs and stones. Authors from Cape Town (where there is the added benefit of an excellent climate) assessed the influence of cranberry juice on urinary risk factors for calcium oxalate calculi in a randomized crossover trial, showing that it has anti‐lithogenic properties. In the second paper, authors from Jerusalem report on 14 patients with distal ureteric strictures after kidney transplantation, all of whom were treated endourologically. They found transurethral incision of the distal ureteric stricture to be effective.

OBJECTIVE

To investigate the potential influence of cranberry juice on urinary biochemical and physicochemical risk factors associated with the formation of calcium oxalate kidney stones, as this product might affect the chemical composition of urine.

SUBJECTS AND METHODS

Urinary variables were assessed in a randomized cross‐over trial in 20 South African men (students) with no previous history of kidney stones. The first group of 10 subjects drank 500 mL of cranberry juice diluted with 1500 mL tap water for 2 weeks, while the second group drank 2000 mL of tap water for the same period. This was followed by a 2‐week ‘washout’ period before the two groups crossed over. During the experimental phase subjects kept a 3‐day food diary to assess their dietary and fluid intakes; 24‐h urine samples were collected at baseline and on day 14 of the trial periods, and analysed using modern laboratory techniques. Urine analysis data were used to calculate the relative urinary supersaturations of calcium oxalate, uric acid and calcium phosphate. Data were assessed statistically by analysis of variance.

RESULTS

The ingestion of cranberry juice significantly and uniquely altered three key urinary risk factors. Oxalate and phosphate excretion decreased while citrate excretion increased. In addition, there was a decrease in the relative supersaturation of calcium oxalate, which tended to be significantly lower than that induced by water alone.

CONCLUSION

Cranberry juice has antilithogenic properties and, as such, deserves consideration as a conservative therapeutic protocol in managing calcium oxalate urolithiasis.

     

Effects of oxalate on HK-2 cells,a line of proximal tubular epithelial cells from normal human kidney

PURPOSE: Oxalate, a metabolic end product, is a major constituent of majority of renal stones. Previous studies with LLC-PK1 cells, a line of proximal renal epithelial cells of porcine origin, have shown that oxalate produces time and concentration dependent effects on the growth and viability of these cells. We assessed the possibility that oxalate may be toxic to HK-2 cells, a line of human proximal renal epithelial cells. MATERIALS AND METHODS: HK-2 cells were maintained in Dulbecco's modified Eagle's medium supplemented with fetal bovine serum and antibiotics. Cells were exposed to oxalate for various intervals. Trypan blue exclusion criteria were used to assess membrane integrity, cell morphology was assessed by hematoxylin and eosin staining and crystal violet staining was used to measure cell density. DNA synthesis was measured by [3H]-thymidine incorporation and superoxide production was measured by the nitroblue tetrazolium reduction method. RESULTS: Exposure of HK-2 cells to oxalate produced time and concentration dependent increase in the membrane permeability to trypan blue and changes in the light microscopic appearance of the cells. Long-term exposure to oxalate resulted in an increase in DNA synthesis and alterations in cell viability with net cell loss after exposure to high oxalate concentrations. CONCLUSIONS: To our knowledge the results provide the first direct demonstration of the toxic effects of oxalate in HK-2 cells, a line of human renal epithelial cells, and suggest that hyperoxaluria may contribute to renal tubular damage associated with calcium oxalate stone disease.     

Percutaneous nephrolithotomy of a staghorn stone in thoracic ectopic kidney

Congenital thoracic ectopic kidney is a very rare developmental anomaly and the rarest form of all ectopic kidneys. It is usually asymptomatic and discovered incidentally on routine chest radiography. Herein we reported the first case of staghorn stone in a thoracic kidney managed successfully by percutaneous nephrolithotomy.     

大鼠肾皮质成肌纤维细胞的体外培养

目的建立肾脏成肌纤维细胞的培养方法，为肾脏纤维化的发病机制和防治措施体外研究提供细胞技术平台。方法采用肾皮质组织块接种培养法，培养的细胞通过相差显微镜观察形态、电镜下观察细胞器，细胞免疫化学染色检测细胞表型标记蛋白等进行鉴定。同时检测细胞对不同细胞因子的生长反应。结果培养的细胞呈梭形，单个核，多突起，表达波形蛋白（vimentin）和平滑肌肌动蛋白（α，SMA），不表达主要存在于血管内皮细胞的抗原上皮氨基肽酶P（EAP），不表达角蛋白（cytokerafin）和结蛋白（desmin）。细胞可以传代至5代，并且保持成肌纤维细胞表型。转化生长因子β1、结缔组织生长因子刺激细胞增殖，而γ-干扰素对细胞无增殖效应。结论原代培养细胞为成肌纤维细胞并且可以传代，具备对细胞因子的生长调节反应，为后续实验提供了基础。     

Inhibitory effects of taraxasterol and aqueous extract of Taraxacum officinale on calcium oxalate crystallization: in vitro study

Objective: We investigated and compared the effects of taraxasterol, aqueous extract of T. officinale (AET) aerial part, and potassium citrate (PC) on calcium oxalate (CaOx) crystallization in vitro.

Materials and methods: CaOx crystallization was induced by adding sodium oxalate to synthetic urine. Taraxasterol (2.5, 5, 7.5 and 12.5?μg/mL), extract (1, 2, 4 and 8?mg/mL), and PC (100, 150, 200 and 350?mg/mL) were subjected to anti-crystallization activities. The absorbance and %inhibition of nucleation of CaOx crystals were evaluated by spectrophotometer at 2, 4, 6, 8, 10, 20, 30, 40, 50 and 60?min and the number and morphology of crystals were studied by light microscopy after 60?min.

Results: Presence of taraxasterol, extract and PC decreased absorbance in experimental samples compared to control, significantly. The nucleation of crystals is inhibited by taraxasterol, extract, and PC (26–64, 55–63 and 60–70%, respectively). The number of CaOx crystals were decreased in presence of taraxasterol (p?p?p?2O₄ monohydrate, while increased CaC₂O₄ dihydrate crystals, significantly. Also, the diameter of CaC₂O₄ dihydrate crystals was decreased in presence of taraxasterol, extract and PC, significantly.

Conclusions: This research indicated that taraxasterol and extract have anti-crystallization activities and effectiveness of the extract is more potent than taraxasterol. It could be because of another constituent in the extract with the synergistic effect.     

4种大鼠肾草酸钙结石模型的比较

目的筛选简便、快捷、成石效果好的SD大鼠肾草酸钙结石的造模方法。方法分别采用目前普遍使用的2种大鼠肾草酸钙结石的模型复制方法和2种改良的造模方法进行造模,并设立空白对照组,造模结束后采集每组大鼠24h尿量及血清,比较大鼠24h尿量、尿Ca2＋、尿Mg2＋、尿pH、尿草酸（0x）及血尿素氮（BUN）、肌酐（cr）、P、Ca2＋、Mg2＋,肾脏病理切片HE染色后光学显微镜下观察和比较各组大鼠肾脏病理改变及草酸钙结晶的沉积情况。结果E组[1％乙二醇＋2％氯化铵＋10％葡萄糖（48d）]在光学显微镜下草酸钙结晶沉积较传统组C组明显增多（P〈0．05）,但有30％大鼠死亡,血肌酐在5组大鼠中最高。D组[1％乙二醇＋2％氯化铵＋10％葡萄糖（28d）]较传统组C组草酸钙结晶沉积明显增多（P〈0．05）,并且造模时间短,大鼠存活率高（80％）,E组与D组相比结晶形成量无统计学意义（P〉0．05）,B组[1％乙二醇（28d）3肾脏中无肾结晶形成,仅有轻微的肾脏病理学改变,大鼠无死亡,肌酐不高。空白对照组无结晶形成,无病理改变。结论用1％乙二醇＋2％氯化铵＋10％葡萄糖诱导28天复制肾草酸钙结石模型的效果好,并且花费时间短,大鼠存活率高,建议选用。     

香豆素对实验性大鼠草酸钙结石形成的影响

应用偏光显微镜和解剖镜观察ＶｉｔａｍｉｎＫ（Ｖｉｔ－Ｋ）拮抗剂香豆素对大鼠草酸钙结石形成影响，观察到香豆素显著地增加大鼠肾内草酸钙结晶数目，肾组织匀浆中草酸含量（１．１４±０．７３ｍｇ／ｇ）也显著高于对照组（０．０３６±０．１５ｍｇ／ｇ，Ｐ＜０．０５）。当停用香豆素后，肾内草酸钙结晶数又可减少。推测香豆素可拮抗Ｖｉｔ－Ｋ使得肾内依赖Ｖｉｔ－Ｋ的羧化作用减弱，肾内草酸钙抑制物Ｎｅｐｈｒｏｃａｌｃｉｎ（Ｎｃ）中谷氨酸转化成γ－羧基谷氨酸（Ｇｌａ）减少，Ｎｃ与钙结合减少，对草酸钙结晶抑制活性降低，易发生草酸钙结石。提示Ｖｉｔ－Ｋ缺乏可促进肾结石形成。     

Potential nephrotoxicity of intravenous infusions of naftidrofuryl oxalate

We report two cases of acute renal failure in patients witharteriosclerosis obliterans treated by intravenous infusionof naftidrofuryl oxalate. At renal biopsy the histological lesionswere identical with those found in ARF due to hyperoxaluriaof other causes, revealing tubular epithelial necrosis and massiveintra-tubular precipitation of calcium oxalate monohydrate (Cl)crystals. A second study was then conducted in four other patientswith arteriosclerosis obliterans to evaluate serum and urinarylevels of oxalate, and crystalluria during the intravenous administrationof 800 mg of naftidrofuryl oxalate per day for 10 days. Duringthe course of treatment, the serum and urinary oxalate levelswere found to increase substantially, with the gradual onsetof massive Cl crystalluria. These results indicate that naftidrofuryloxalate was responsible for the acute renal failure in the firsttwo patients. High intravenous doses of naftidrofuryl oxalatemust be used cautiously, with close surveillance of renal function.     

Assessment of oxalate absorption from almonds and black beans with and without the use of an extrinsic label

PURPOSE: Oxalate bioavailability is an important determinant of whether the consumption of a particular food is a high risk in individuals predisposed to kidney stones. We estimated and compared oxalate absorption from a high oxalate containing legume (black beans) and a high oxalate containing nut (almonds). We also compared an isotope method using extrinsically labeled oxalate and an oxalate load method to assess oxalate absorption. MATERIALS AND METHODS: Six male and 5 female subjects participated in the 4 oxalate load tests, namely almonds, almonds with 20 mg C2-oxalic acid, black beans and black beans with 20 mg C2-oxalic acid. Each treatment provided a total of 120 mg oxalate, after which timed urine samples were collected for the analysis of oxalate, calcium and creatinine. RESULTS: Average oxalate absorption from the 2 almond treatments (5.9%) using the oxalate load method was significantly higher than that from the 2 black bean treatments (1.8%) during the 24-hour post-oxalate load collection period. In contrast, C2-oxalic acid absorption from the almond (7.9%) and black bean (8.6%) treatments did not significantly differ. CONCLUSIONS: The higher oxalate absorption from almonds than from black beans suggests that the relative amount of soluble and insoluble oxalate in food has an important role in the determination of oxalate absorption. Since extrinsically provided C2-oxalate and oxalate naturally occurring in the high oxalate test foods appeared to be differentially absorbed, the data do not support the use of extrinsically labeled oxalate to assess food oxalate absorption.     

Decreased renal expression of the putative calcium oxalate inhibitor Tamm-Horsfall protein in the ethylene glycol rat model of calcium oxalate urolithiasis

PURPOSE: Tamm-Horsfall protein is believed to inhibit calcium oxalate crystallization, aggregation or adhesion to the renal epithelium. We determined whether ethylene glycol induced urolithiasis changes the expression of renal and urinary Tamm-Horsfall protein. For comparison the expression of another calcium oxalate inhibitor, osteopontin, was also analyzed. MATERIALS AND METHODS: Male rats were treated with 0.75% ethylene glycol plus an AIN-76 diet (Dyets, Bethlehem Pennsylvania) (ethylene glycol group) or standard rat chow and water (control group) for up to 8 weeks (6 per group for 8 weeks and 3 per group for 3 days to 6 weeks). Kidneys and urine (8 weeks only) were harvested and analyzed by Northern and Western blot analysis, and immunohistochemistry. RESULTS: Tamm-Horsfall protein message and protein (membrane bound form) were decreased, while those of osteopontin were increased in the kidneys of rats treated with ethylene glycol for 8 weeks. As judged by immunochemistry Tamm-Horsfall protein and osteopontin were consistently present in a few tubules in rats in the ethylene glycol and control groups, respectively. In urine expression of the free form of Tamm-Horsfall protein (approximately 75 kDa.) was decreased but detectable in ethylene glycol treated rats. Although readily detected in tissue, osteopontin was not detected in the urine of control or ethylene glycol treated rats. In the time course experiment Tamm-Horsfall protein did not decrease until 4 weeks, when calcium oxalate crystals were detectable in the kidneys of treated rats. In contrast, osteopontin was increased, although inconsistently, beginning at 3 days. CONCLUSIONS: Unlike other calcium oxalate inhibitors, such as osteopontin, renal message and protein for Tamm-Horsfall protein was decreased in ethylene glycol treated rats. Tamm-Horsfall protein expression did not decrease until aggregates of crystals had been deposited in the kidneys, while osteopontin expression began to increase almost immediately. Comparisons of the data on kidneys and urine obtained by RNA or protein blot analysis and immunochemistry underscore the need to examine tissue and urine by multiple techniques to obtain the most accurate assessment of how protein expression is changed by a given treatment.     

Klotho基因多态性与新疆地区维吾尔族特发性草酸钙肾结石的相关性研究

目的:探讨Klotho基因rs1207568与新疆地区维吾尔族特发性草酸钙肾结石的相关性。方法:选择400例维吾尔族草酸钙肾结石患者(病例组)和410例维吾尔族健康体检者(对照组),应用SNaPshot方法对Klotho基因rs1207568进行基因检测,并分析其与特发性草酸钙肾结石发病的相关性以及对血脂、血生化的影响。结果:对照组的基因型分布均符合Hardy-Weinberg平衡。病例组和对照组rs1207568基因型比较差异有统计学意义(P<0.01),且病例组携带等位基因C的风险高于对照组(OR=1.295,95%CI:1.019～1.645,P<0.05)。CC基因型患者的血钙、血磷、血氯、尿素氮、尿酸均高于CT+TT基因型,差异有统计学意义(P<0.05),而二者血镁、血钾、血钠水平比较差异无统计学意义。在血脂方面,二者甘油三酯(TG)、总胆固醇(TC)比较差异有统计学意义(P<0.05)。结论:Klotho基因rs1207568在维吾尔族人群中与特发性草酸钙肾结石发病风险显示有相关性,rs1207568C等位基因是其危险因素。     

尿液成分对草酸钙结石的影响

目的 探讨尿液成分对草酸钙尿结石形成的影响。方珐 应用红外光谱仪对50份尿结石标本进行成分检测；对16例一水草酸钙（COM）与10例二水草酸钙（COD）尿结石患者的24h尿液进行生化检测，并比较两组生化指标。结果 87．5％的c0M结石患者和90％的c0D结石患者24h尿量减少；COM结石患者尿钙（4．94±2．11）mmol／24h，COD结石患者尿钙（9．43±3．78）mmol／24h；差异有统计学意义（P〈0．01）；COM结石患者尿磷（20．50±8．76）mmol／24h，COD结石患者尿磷（28．38±10．21）mmol／24h，差异有统计学意义（P〈0．05）；87．5％的COM结石患者尿枸橼酸低于正常水平。结论 COD结石患者尿钙、尿磷高于COM结石患者，表明COD结石的形成与高钙尿和高磷尿有关；COM结石的形成可能与低尿枸橼酸有关。