Combined Liver-Kidney Transplantation for Primary Hyperoxaluria Type 2: A Case Report.

Combined liver/kidney transplant is the preferred transplant option for most patients with primary hyperoxaluria type 1 (PH1) since orthotopic liver transplantation replaces the deficient liver-specific AGT enzyme, thus restoring normal metabolic oxalate production. However, primary hyperoxaluria type 2 (PH2) is caused by deficient glyoxylate reductase/hydroxypyruvate reductase (GRHPR), and this enzyme is widely distributed throughout the body. Though the relative abundance and activity of GRHPR in various tissues is not clear, some evidence suggests that the majority of enzyme activity may indeed reside within the liver. Thus the effectiveness of liver transplantation in correcting this metabolic disorder has not been demonstrated. Here we report a case of 44-year-old man with PH2, frequent stone events, and end-stage renal disease; he received a combined liver/kidney transplant. Although requiring confirmation in additional cases, the normalization of plasma oxalate, urine oxalate, and urine glycerate levels observed in this patient within a month of the transplant that remain reduced at the most recent follow-up at 13 months suggests that correction of the GRHPR deficiency in PH2 can be achieved by liver transplantation.

Sustained pyridoxine response in primary hyperoxaluria type 1 recipients of kidney alone transplant.

Combined liver kidney transplant is the preferred transplant option for most patients with primary hyperoxaluria type 1 (PH1) given that it removes the hepatic source of oxalate production and improves renal allograft survival. However, PH1 patients homozygous for the G170R mutation can develop normal urine oxalate levels with pyridoxine therapy and may be candidates for kidney alone transplant (KTx). We examined the efficacy of pyridoxine therapy following KTx in five patients homozygous for G170R transplanted between September 1999 and July 2013. All patients were maintained on pyridoxine posttransplant. Median age at transplant was 39 years (range 33-67 years). Median follow-up posttransplant was 8.5 years (range 0.2-13.9 years). At the end of follow-up, four grafts were functioning. One graft failed 13.9 years posttransplant due to recurrent oxalate nephropathy following an acute medical illness. After tissue oxalate stores had cleared, posttransplant urine oxalate levels were <0.5 mmol/24 h the majority of times checked. Calcium oxalate crystals were noted in only 3/13 allograft biopsies. This series suggests that a subgroup of PH1 patients demonstrate sustained response to pyridoxine therapy following KTx. Therefore, pyridoxine combined with KTx should be considered for PH1 patients with a homozygous G170R mutation.

Urine high and low molecular weight proteins one-year post-kidney transplant: relationship to histology and graft survival.

Increased urinary protein excretion is common after renal transplantation and portends worse outcome. In this study we assessed the prognostic contribution of several urinary proteins. Urinary total protein, albumin, retinol binding protein (RBP), α-1-microglobulin, IgG and IgM were measured in banked urine samples from 221 individuals 1 year after renal transplantation (age 52 ± 13 years, 55% male, 93% Caucasian and 82% living donor). Levels of all proteins measured were higher than in normal nontransplant populations. Patients with glomerular lesions had higher urinary albumin than those with normal histology, while those with interstitial fibrosis and tubular atrophy plus inflammation (ci>0, cg = 0, i>0) had higher levels of IgG, IgM, α-1-microglobulin and RBP. Concomitant normal levels of urinary albumin, IgM and RBP identified normal histology (specificity 91%, sensitivity 15%,). Urinary levels of the specific proteins were highly correlated, could not differentiate among the histologic groups, and appeared to result from tubulointerstitial damage. Increased urinary excretion of the low molecular weight protein RBP was a sensitive marker of allografts at risk, predicting long-term graft loss independent of histology and urinary albumin. This study highlights the prognostic importance of tubulointerstitial disease for long-term graft loss.

Effect of Cystone® on urinary composition and stone formation over a one year period.

Kidney stones are a common problem for which inadequate prevention exists. We recruited ten recurrent kidney stone formers with documented calcium oxalate stones into a two phased study to assess safety and effectiveness of Cystone(®), an herbal treatment for prevention of kidney stones. The first phase was a randomized double-blinded 12 week cross over study assessing the effect of Cystone(®) vs. placebo on urinary supersaturation. The second phase was an open label one year study of Cystone(®) to determine if renal stone burden decreased, as assessed by quantitative and subjective assessment of CT. Results revealed no statistically significant effect of Cystone(®) on urinary composition short (6 weeks) or long (52 weeks) term. Average renal stone burden increased rather than decreased on Cystone(®). Therefore, this study does not support the efficacy of Cystone(®) to treat calcium oxalate stone formers. Future studies will be needed to assess effects on stone passage, or on other stone types.

Transplantation outcomes in primary hyperoxaluria.

Optimal transplantation strategies are uncertain in primary hyperoxaluria (PH) due to potential for recurrent oxalosis. Outcomes of different transplantation approaches were compared using life-table methods to determine kidney graft survival among 203 patients in the International Primary Hyperoxaluria Registry. From 1976-2009, 84 kidney alone (K) and combined kidney and liver (K + L) transplants were performed in 58 patients. Among 58 first kidney transplants (32 K, 26 K + L), 1-, 3- and 5-year kidney graft survival was 82%, 68% and 49%. Renal graft loss occurred in 26 first transplants due to oxalosis in ten, chronic allograft nephropathy in six, rejection in five and other causes in five. Delay in PH diagnosis until after transplant favored early graft loss (p = 0.07). K + L had better kidney graft outcomes than K with death-censored graft survival 95% versus 56% at 3 years (p = 0.011). Among 29 year 2000-09 first transplants (24 K + L), 84% were functioning at 3 years compared to 55% of earlier transplants (p = 0.05). At 6.8 years after transplantation, 46 of 58 patients are living (43 with functioning grafts). Outcomes of transplantation in PH have improved over time, with recent K + L transplantation highly successful. Recurrent oxalosis accounted for a minority of kidney graft losses.

[Current issues in measurement and reporting of urinary albumin excretion]. / Données actuelles sur le dosage de l'excrétion urinaire de l'albumine.

Urinary excretion of albumin indicates kidney damage and is recognized as a risk factor for progression of kidney disease and cardiovascular disease. The role of urinary albumin measurements has focused attention on the clinical need for accurate and clearly reported results. The National Kidney Disease Education Program and the IFCC convened a conference to assess the current state of preanalytical, analytical, and postanalytical issues affecting urine albumin measurements and to identify areas needing improvement. The chemistry of albumin in urine is incompletely understood. Current guidelines recommend the use of the albumin/creatinine ratio (ACR) as a surrogate for the erro-prone collection of timed urine samples. Although ACR results are affected by patient preparation and time of day of sample collection, neither is standardized. Considerable intermethod differences has been reported for both albumin and creatinine measurement, but trueness is unknown because there are no reference measurement procedures for albumin and no referance materials for either analyte in urine. The recommanded reference intervals for the ACR do not take into account the large intergroup differences in creatinine excretion (e.g., related to differences in age, sex, and ethicity) nor the continuous increase in risk related to albumin excretion. Clinical needs have been identified for standardization of (a) urine collection methodes, (b) urine albumin and creatinine measurements based on a complete reference system, (c) reporting of test results, and (d) reference intervals for the ACR.

Do calcifying nanoparticles promote nephrolithiasis? A review of the evidence.

Although much has been learned regarding the pathogenesis of kidney stones, the reason(s) why some individuals form stones while others do not remains incompletely understood. Nanoparticles, which have been observed in geologic samples, have also been isolated from biologic specimens, including kidney stones. These nanoparticles have certain properties that are consistent with a novel life form, including in vitro self-replication, and contain lipids, DNA and proteins. Therefore, it has been hypothesized that nanoparticles may represent a type of infective agent that initiates stone formation in some individuals. Despite a large body of intriguing and suggestive evidence, the true biologic nature of these entities has been elusive, and controversy remains as to whether these nano-sized particles are analogous to other recently described unusual and novel microorganisms, or a transmissible, yet inert nanoparticle. Although unique DNA or RNA has yet to be identified, a proteomic biosignature is beginning to emerge that may allow more definitive clinical investigation. This review evaluates the current evidence regarding nanoparticles as causal to disease and emphasizes the need for additional research to further elucidate their role in human stone formation.

Hyperoxaluric nephrolithiasis is a complication of Roux-en-Y gastric bypass surgery.

Roux-en-Y bypass surgery is the most common bariatric procedure currently performed in the United States for medically complicated obesity. Although this leads to a marked and sustained weight loss, we have identified an increasing number of patients with episodes of nephrolithiasis afterwards. We describe a case series of 60 patients seen at Mayo Clinic-Rochester that developed nephrolithiasis after Roux-en-Y gastric bypass (RYGB), including a subset of 31 patients who had undergone metabolic evaluation in the Mayo Stone Clinic. The mean body mass index of the patients before procedure was 57 kg/m(2) with a mean decrease of 20 kg/m(2) at the time of the stone event, which averaged 2.2 years post-procedure. When analyzed, calcium oxalate stones were found in 19 and mixed calcium oxalate/uric acid stones in two patients. Hyperoxaluria was a prevalent factor even in patients without a prior history of nephrolithiasis, and usually presented more than 6 months after the procedure. Calcium oxalate supersaturation, however, was equally high in patients less than 6 months post-procedure due to lower urine volumes. In a small random sampling of patients undergoing this bypass procedure, hyperoxaluria was rare preoperatively but common 12 months after surgery. We conclude that hyperoxaluria is a potential complicating factor of RYGB surgery manifested as a risk for calcium oxalate stones.

Renal stone epidemiology in Rochester, Minnesota: an update.

Studies in Western countries have suggested an increasing incidence of nephrolithiasis (NL) in the latter part of the 20th century. Therefore, we updated NL epidemiology data for the Rochester population over the years 1970-2000. All Rochester residents with any diagnostic code that could be linked to NL in the years of 1970, 1980, 1990, and 2000 were identified, and the records reviewed to determine if they met the criteria for a symptomatic kidney stone as defined in a previous Rochester, MN study. Age-adjusted incidence (+/-s.e.) of new onset symptomatic stone disease for men was 155.1 (+/-28.5) and 105.0 (+/-16.8) per 100,000 per year in 1970 and 2000, respectively. For women, the corresponding rates were 43.2 (+/-14.0) and 68.4 (+/-12.3) per 100,000 per year, respectively. On average, rates for women increased by about 1.9% per year (P=0.064), whereas rates for men declined by 1.7% per year (P=0.019). The overall man to woman ratio decreased from 3.1 to 1.3 during the 30 years (P=0.006). Incident stone rates were highest for men aged 60-69 years, whereas for women, they plateaued after age 30. Therefore, since 1970 overall NL incidence rates in Rochester have remained relatively flat. However, NL rates for men have declined, whereas rates for women appear to be increasing. The reasons remain to be determined.

Sialic acid-containing glycoproteins on renal cells determine nucleation of calcium oxalate dihydrate crystals.

BACKGROUND: The interaction between the surfaces of renal epithelial cells and calcium oxalate dihydrate (COD), the most common crystal in human urine, was studied to identify critical determinants of kidney stone formation. METHODS: A novel technique utilizing vapor diffusion of oxalic acid was employed to nucleate COD crystals onto the apical surface of living cells. Confluent monolayers were grown in the inner 4 wells of 24-well culture plates. To identify cell surface molecules that regulate crystal nucleation, cells were pretreated with a protease (trypsin or proteinase K) to alter cell surface proteins, neuraminidase to alter cell surface sialoglycoconjugates, or buffer alone. COD crystals were nucleated on the surface of cells by diffusion of oxalic acid vapor into a calcium-containing buffer overlying the cells. Crystal face-specific nucleation was evaluated by scanning electron microscopy. RESULTS: Nucleation and growth of a COD crystal onto an untreated control cell occurred almost exclusively via its (001) face, an event rarely observed during COD crystallization. In contrast, when COD crystals were nucleated onto protease- or neuraminidase-treated cells, they did so via the (100) face of the crystal. CONCLUSIONS: Specific sialic acid-containing glycoproteins, and possibly glycolipids (sialoglycoconjugates), appear to be critical determinants of face-specific nucleation of COD crystals on the apical renal cell surface. We hypothesize that crystal retention within the nephron, and the subsequent development of a kidney stone, may result when the number or composition of these cell surface molecules is modified by genetic alterations, cell injury, or drugs in tubular fluid.

Renal cell-urinary crystal interactions.

Crystals of calcium oxalate and calcium phosphate bind to anionic molecules on the apical surface of renal collecting duct cells. Atomic arrays on crystal faces interact stereospecifically with cell-surface anions to bind crystals that nucleate in tubular fluid, or those that nucleate directly on the plasma membrane. The internalization of adherent crystals, changes in gene expression, and secretion of specific proteins ensue, and appear to be important processes in crystal retention and kidney stone pathogenesis.

Adhesion of uric acid crystals to the surface of renal epithelial cells.

Adhesion of microcrystals that nucleate in tubular fluid to the apical surface of renal tubular cells could be a critical step in the formation of kidney stones, 12% of which contain uric acid (UA) either alone or admixed with calcium oxalates or calcium phosphates. UA crystals bind rapidly to monolayer cultures of monkey kidney epithelial cells (BSC-1 line), used to model the surface of the nephron, in a concentration-dependent manner. The urinary glycoproteins osteopontin, nephrocalcin, and Tamm-Horsfall glycoprotein had no effect on binding of UA crystals to the cell surface, whereas other polyanions including specific glycosaminoglycans blocked UA crystal adhesion. Specific polycations also inhibited adhesion of UA crystals and appeared to exert their inhibitory effect by coating cells. However, removal of anionic cell surface molecules with neuraminidase, heparitinase I, or chondroitinase ABC each increased UA crystal binding, and sialic acid-binding lectins had no effect. These observations suggest that hydrogen bonding and hydrophobic interactions play a major role in adhesion of electrostatically neutral UA crystals to renal cells, unlike the interaction of calcium-containing crystals with negatively charged molecules on the apical cell surface via ionic forces. After adhesion to the plasma membrane, subsequent cellular events could contribute to UA crystal retention in the kidney and the development of UA or mixed calcium and UA calculi.

Regulation of renal epithelial cell affinity for calcium oxalate monohydrate crystals.

The binding and internalization of calcium oxalate monohydrate (COM) crystals by tubular epithelial cells may be a critical step leading to kidney stone formation. Exposure of MDCK cells to arachidonic acid (AA) for 3 days, but not oleic or linoleic acid, decreased COM crystal adhesion by 55%. Exogenous prostaglandin PGE(1) or PGE(2) decreased crystal binding 96% within 8 h, as did other agents that raise intracellular cAMP. Actinomycin D, cycloheximide, or tunicamycin each blocked the action of PGE(2), suggesting that gene transcription, protein synthesis, and N-glycosylation were required. Blockade of crystal binding by AA was not prevented by the cyclooxygenase inhibitor flurbiprofen, and was mimicked by the nonmetabolizable AA analog eicosatetryanoic acid (ETYA), suggesting that generation of PGE from AA is not the pathway by which AA exerts its effect. These studies provide new evidence that binding of COM crystals to renal cells is regulated by physiological signals that could modify exposure of cell surface molecules to which the crystals bind. Intrarenal AA, PGs, and/or other agents that raise the intracellular concentration of cAMP may serve a protective function by preventing crystal adhesion along the nephron, thereby defending the kidney against crystal retention and stone formation.

Nucleation, adhesion, and internalization of calcium-containing urinary crystals by renal cells.

Renal tubular fluid in the distal nephron is supersaturated favoring nucleation of the most common crystals in renal stones, which are composed of calcium oxalate and calcium phosphate. The mechanisms whereby these newly formed crystals can be retained in the nephron and develop into calculi are not known. Calcium oxalate monohydrate and hydroxyapatite (calcium phosphate) crystals rapidly adhere to anionic sites on the surface of cultured renal epithelial cells, but this process is inhibited by specific urinary anions such as citrate, glycosaminoglycans, uropontin, or nephrocalcin, each of which can coat the crystals. Therefore, competition for the crystal surface between soluble anions in tubular fluid and anions anchored on the apical cell surface could determine whether a crystal binds to a tubular cell. Crystals of calcium oxalate dihydrate can also nucleate directly on the surface of cultured BSC-1 cells in a face-specific manner, suggesting another potential pathway for crystal deposition in the nephron. Once present on the cell surface, calcium oxalate monohydrate, calcium oxalate dihydrate, and hydroxyapatite crystals are quickly internalized by renal cells; alterations in gene expression and initiation of proliferation may then ensue. Calcium oxalate crystals can also dissolve after renal cells internalize them, but this process may require up to several weeks. Increased knowledge about cell-crystal interactions, including identification of molecules in tubular fluid and on the cell surface that modulate the process, appear critical for understanding the pathogenesis of nephrolithiasis.

Reduced crystallization inhibition by urine from men with nephrolithiasis.

BACKGROUND: Human urine is known to inhibit growth, aggregation, nucleation, and cell adhesion of calcium oxalate monohydrate (COM) crystals, the main solid phase of human kidney stones. This study tests the hypothesis that low levels of inhibition are present in men with calcium oxalate stones and could therefore promote stone production. METHODS: In 17 stone-forming men and 17 normal men that were matched in age to within five years, we studied the inhibition by dialyzed urine proteins of COM growth, aggregation, and binding to cultured BSC-1 renal cells, as well as whole urine upper limits of metastability (ULM) for COM and calcium phosphate (CaP) in relationship to the corresponding supersaturation (SS). RESULTS: Compared with normals, patient urine showed reduced COM growth inhibition and reduced ULM in relationship to SS. When individual defects were considered, 15 of the 17 patients were abnormal in one or more inhibition measurements. ULM and growth inhibition defects frequently coexisted. CONCLUSIONS: Reduced COM growth and CaP and CaOx ULM values in relationship to SS are a characteristic of male stone formers. Both defects could promote stones by facilitating crystal nucleation and growth. Abnormal inhibition may be a very important cause of human nephrolithiasis.

Cell-crystal interactions and kidney stone formation.

BACKGROUND: Renal tubular fluid in the distal nephron is supersaturated with calcium and oxalate ions that nucleate to form crystals of calcium oxalate monohydrate (COM), the most common crystal in renal stones. How these nascent crystals are retained in the nephron to form calculi in certain individuals is not known. METHODS: The results of experiments conducted in this and other laboratories that employ cell culture model systems to explore renal epithelial cell-urinary crystal interactions are described. RESULTS: COM crystals rapidly adhere to anionic sites on the surface of cultured renal epithelial cells, but this process can be inhibited, if specific urinary anions such as glycosaminoglycans, uropontin, nephrocalcin, or citrate are available to coat the crystalline surface. Therefore, competition for the crystal surface between soluble anions in tubular fluid and anions on the apical cell surface could determine whether or not a crystal binds to the cell. A similar paradigm describes adhesion of calcium phosphate (hydroxyapatite) crystals, also a common constituent of human stones. Once bound, COM and hydroxyapatite crystals are quickly internalized by renal cells; reorganization of the cytoskeleton, alterations in gene expression, and initiation of proliferation may then ensue. Each of these cellular events appears to be regulated by a different set of extracellular factors. Over several weeks in culture, renal cells (BSC-1 line) dissolve internalized crystals, although once a cell binds a crystal, additional crystals are more likely to bind, possibly forming a positive feedback loop that results in kidney stone formation. CONCLUSIONS: Increased knowledge about the cell-crystal interaction, including identification of molecules in tubular fluid and on the cell surface that modulate the process, and understanding its mechanism of action appear critical for explaining the pathogenesis of nephrolithiasis.

Direct nucleation of calcium oxalate dihydrate crystals onto the surface of living renal epithelial cells in culture.

BACKGROUND: The interaction of the most common crystal in human urine, calcium oxalate dihydrate (COD), with the surface of monkey renal epithelial cells (BSC-1 line) was studied to identify initiating events in kidney stone formation. METHODS: To determine if COD crystals could nucleate directly onto the apical cell surface, a novel technique utilizing vapor diffusion of oxalic acid was employed. Cells were grown to confluence in the inner four wells of 24-well plates. At the start of each experiment, diethyloxalate in water was placed into eight adjacent wells, and the plates were sealed tightly with tape so that oxalic acid vapor diffused into a calcium-containing buffer overlying the cells. RESULTS: Small crystals were visualized on the cell surface after two hours, and by six hours the unambiguous habitus of COD was confirmed. Nucleation onto cells occurred almost exclusively via the (001) face, one that is only rarely observed when COD crystals nucleate onto inanimate surfaces. Similar results were obtained when canine renal epithelial cells (MDCK line) were used as a substrate for nucleation. Initially, COD crystals were internalized almost as quickly as they formed on the apical cell surface. CONCLUSIONS: Face-specific COD crystal nucleation onto the apical surface of living renal epithelial cells followed by internalization is a heretofore unrecognized physiological event, suggesting a new mechanism to explain crystal retention within the nephron, and perhaps kidney stone formation when this process is dysregulated or overwhelmed.

Adhesion, internalization and metabolism of calcium oxalate monohydrate crystals by renal epithelial cells.

The interaction between crystals that nucleate in the nephron lumen and tubular cells could be an important determinant of renal calcification. Kidney epithelial cells in monolayer culture (BSC-1 line), used to model the tubule, rapidly bound and internalized crystals of calcium oxalate monohydrate (COM), the most common constituent of renal stones. Transmission and scanning electron microscopy, enzyme histochemistry, and kinetic analysis of [14C]-labeled crystals were used to study the interaction between renal cells and COM crystals. Electron microscopy revealed that adherent crystals on the apical cell surface can serve as sites for aggregation of additional crystals. Enhanced binding of exogenous crystals to plasma membrane domains overlying internalized crystals was observed for at least 24 hours after the initial cell-crystal interaction. Following internalization, crystals appeared to dissolve within lysosomal inclusion bodies during the ensuing five to seven weeks. Over this time, many cells still containing crystals clustered together in the monolayer. These observations suggest that adhesion and internalization can promote crystal retention in the nephron, whereas intracellular dissolution of crystals may serve as an important, hitherto unrecognized defense against pathologic renal calcification.

Adhesion of hydroxyapatite crystals to anionic sites on the surface of renal epithelial cells.

Adhesion of microcrystals that nucleate in tubular fluid to the apical surface of renal tubular cells could be a critical step in the formation of kidney stones, 20% of which contain hydroxyapatite (HA). HA crystals bound rapidly to monolayer cultures of monkey kidney epithelial cells (BSC-1 line), used to model the surface of the nephron, in a concentration-dependent manner. Adhesion was blocked by diverse polyanions including heparin, pentosan polysulfate, polyaspartate, and polyglutamate, as well as many found in tubular fluid such as chondroitin sulfates A and B, heparan sulfate, citrate, nephrocalcin, and osteopontin. The polycations cetylpyridinium chloride and cationized ferritin, as well as the cationic dyes alcian blue, polyethylenimine, and brilliant blue R, also inhibited adhesion of HA crystals, as did specific lectins including Triticum vulgaris (wheat germ agglutinin). Anions that inhibited adhesion of crystals appeared to act on the crystal surface, whereas cations and lectins exerted their effect on the cell. Treatment of cells with neuraminidase inhibited binding of crystals, suggesting that anionic cell surface sialic acid residues function as HA crystal receptor sites that can be blocked by specific cations or lectins. Adherence of HA crystals to cells of another renal line (MDCK) and, to 3T3 fibroblasts was also inhibited by heparin, polyaspartate, alcian blue, and T vulgaris lectin, suggesting that these crystals bind to analogous molecules on the surface of different types of cells. These results suggests that the structure, quantity, and/or function of soluble anions in tubular fluid, as well as those anchored to the cell surface, could be critical determinants of HA crystal retention in the nephron and the subsequent formation of a renal stone.