Matthieu Monge

Development of a renal microchip for in vitro distal tubule models

Current developments in tissue engineering and microtechnology fields have allowed the proposal of pertinent tools, microchips, to investigate in vitro toxicity. In the framework of the proposed REACH European directive and the 3R recommendations, the purpose of these microtools is to mimic organs in vitro to refine in vitro culture models and to ultimately reduce animal testing. The microchip consists of functional living cell microchambers interconnected by a microfluidic network that allows continuous cell feeding and waste removal controls by fluid microflow. To validate this approach, Madin Darby Canine Kidney (MDCK) cells were cultivated inside a polydimethylsiloxane microchip. To assess the cell proliferation and feeding, the number of inoculated cells varied from 5 to 10 × 105 cells/microchip (corresponding roughly to 2.5 to 5 × 105 cells/cm2) and from four flow rates 0, 10, 25, and 50 μL/min were tested. Morphological observations have shown successful cell attachment and proliferation inside the microchips. The best flow rate appears to be 10 μL/min with which the cell population was multiplied by about 2.2 ± 0.1 after 4 days of culture, including 3 days of perfusion (in comparison to 1.7 ± 0.2 at 25 μL/min). At 10 μL/min flow rate, maximal cell population reached about 2.1 ± 0.2 × 106 (corresponding to 7 ± 0.7 × 107 cells/cm3). The viability, assessed by trypan blue and lactate deshydrogenase measurements, was found to be above 90% in all experiments. At 10 μL/min, glucose monitoring indicated a cell consumption of 16 ± 2 μg/h/106 cells, whereas the glutamine metabolism was demonstrated with the production of NH3 by the cells about 0.8 ± 0.4 μmol/day/106 cells. Augmentation of the flow rate appeared to increase the glucose consumption and the NH3 production by about 1.5‐ to 2‐fold, in agreement with the tendencies reported in the literature. As a basic chronic toxicity assessment in the microchips, 5 mM and 10 mM ammonium chloride loadings, supplemented in the culture media, at 0, 10, and 25 μL/min flow rates were performed. At 10 μL/min, a reduction of 35% of the growth ratio with 5 mM and of 50% at 10 mM was found, whereas at 25 μL/min, a reduction of 10% with 5 mM and of 30% at 10 mM was obtained. Ammonium chloride contributed to increase the glucose consumption and to reduce the NH3 production. The microchip advantages, high surface/volume ratio, and dynamic loadings, coupled with the concordance between the present and literature results dealing with ammonia/ammonium effects on MDCK illustrate the potential of our microchip for wider in vitro chronic toxicity investigations.

Analysis of transcriptomic and proteomic profiles demonstrates improved Madin–Darby canine kidney cell function in a renal microfluidic biochip

We have evaluated the influence of the microfluidic environment on renal cell functionality. For that purpose, we performed a time lapse transcriptomic and proteomic analysis in which we compared gene and protein expressions of Madin–Darby canine kidney cells after 24 h and 96 h of culture in both microfluidic biochips and plates. The transcriptomic and proteomic integration revealed that the ion transporters involved in calcium, phosphate, and sodium homoeostasis and several genes involved in H+ transporters and pH regulation were up‐regulated in microfluidic biochips. Concerning drug metabolism, we found Phase I (CYP P450), Phase II enzymes (GST), various multidrug resistance genes (MRP), and Phase III transporters (SLC) were also up‐regulated in the biochips. Furthermore, the study shows that those inductions were correlated with the induction of the Ahr and Nrf‐2 dependent pathways, which results in a global cytoprotective response induced by the microenvironment. However, there was no apoptosis situation or cell death in the biochips. Microfluidic biochips may thus provide an important insight into exploring xenobiotic injury and transport modifications in this type of bioartificial microfluidic kidney. Finally, the investigation demonstrated that combining the transcriptomic and proteomic analyses obtained from a cell “on chip” culture would provide a pertinent new tool in the mechanistic interpretation of cellular mechanisms for predicting kidney cell toxicity and renal clearance in vitro.

Transcriptomic analysis of the effect of ifosfamide on MDCK cells cultivated in microfluidic biochips.

We investigated the behavior of renal cells cultivated in microfluidic biochips when exposed to 50 μM of ifosfamide, an antineoplastic drug treatment. The microarray analysis revealed that ifosfamide had any effect in Petri conditions. The microfluidic biochips induced an early inflammatory response in the MDCK in the untreated cells. This was attributed to cells adapting to the dynamics and micro environment created by the biochips. This led to modulations in the mitochondria dysfunction pathway, the Nrf-2 and oxidative stress pathways and some related cancer genes. When exposed to 50 μM of ifosfamide, we detected a modulation of the pathways related to the cancer and inflammation in the MDCK cultivated in the biochips via modulation of the ATM, p53, MAP Kinase, Nrf-2 and NFKB signaling. In addition, the genes identified and related proteins affected by the ifosfamide treatment in the biochips such as TXNRD1, HSP40 (DNAJB4 and DNAJB9), HSP70 (HSPA9), p21 (CDKN1A), TP53, IKBalpha (NFKBIA) are reported to be the molecular targets in cancer therapy. We also found that the integrin pathway was perturbed with the ifosfamide treatment. Finally, the MYC proto-oncogene appeared to be a potential bridge between the integrin signaling and the anti-inflammatory response.

Localized Amyloidosis of the Genitourinary Tract: Report of 5 New Cases and Review of the Literature

Primary localized amyloidosis of the genitourinary tract is a rare entity characterized by small pseudotumors localized in the renal pelvis, ureters, or bladder. Amyloid fibrils are derived from immunoglobulin light chains, but no systemic plasma cell proliferation is detected. The clinical and radiologic features mimic urinary tract cancer, and local treatment is indicated. The prognosis is excellent in most cases, although disease recurrence is possible.We report 5 new cases of localized amyloidosis of the urinary tract, with lambda (4/5), or kappa (1/5) chain amyloid protein, involving the bladder (5/5), and the ureter and renal pelvis (1/5), with multiple, bilateral lesions in 1 case. The presenting complaint was painless hematuria in 4 cases. All cases were of primary (AL)-type amyloidosis. All patients underwent extensive investigation, and none presented any signs of generalized amyloidosis. A favorable outcome was observed in every case. We performed a comprehensive review of the literature, and summarize the data.Abbreviations: AA = secondary amyloidosis, AL = primary amyloidosis, CT = computed tomography, KMnO4 = potassium permanganate, MGUS = monoclonal gammopathy of unknown significance, MRI = magnetic resonance imaging, SAA = serum amyloid A, TTR = transthyretin.

Investigation into modification of mass transfer kinetics by acrolein in a renal biochip

In this study we present a method for investigating the effect of acrolein, a nephrotoxic and urotoxic metabolite of the anticancerous prodrugs ifosfamide and cyclophosphamide, in a blood-renal barrier biochip. The real time monitoring of mass transfers of caffeine, vitamin B12 and albumin in the biochip was performed thanks to an in vitro dialysis method. The diffusion coefficients of the solutes and their dialysance from the apical to the basolateral compartments were found to be molecular weight and cell-membrane dependent, thus demonstrating the cell-barrier functionality. The toxicity induced by the acrolein led to modifications to mass transfer properties which appeared to be acrolein dose, time and solute molecular weight dependent. Solute mass transfer across the cell layer increased with acrolein concentrations. The sensitivity of this analysis method contributes to identify the mass transfer properties and to monitor the modification to the renal parameter when submitted to toxic cell compounds. The results provide the foundation for exploring kidney behavior in response to drugs thanks to a blood-tissue barrier model using a technique based on in vitro dialysis and real time analysis.

Reappraisal of 2003 NKF-K/DOQI guidelines for management of hyperparathyroidism in chronic kidney disease patients

The 2003 guidelines for the management of hyperparathyroidism in chronic kidney disease compiled by the Kidney Disease Outcomes Quality Initiative of the National Kidney Foundation (NKF-K/DOQI) were formulated on the basis of work published up until 2001. Since then, new drugs (e.g. calcimimetics and lanthanum carbonate) have become available, and others (e.g. sevelamer, nicotinamide and paricalcitol) have been more stringently clinically evaluated. Because of these advancements, a reappraisal of the 2003 guidelines is justified. In this article we critically review the following recommendations of the NKF-K/DOQI: (i) routine use of 1.25 mmol/l (5.0 mg/dl) dialysate calcium and 1αOH-vitamin D derivatives; (ii) limitation of the maximal daily dose of calcium-based oral phosphate binders to 1.5 g of elemental calcium; and (iii) not correcting vitamin D insufficiency in dialysis patients.

Drug Insight: renal indications of calcimimetics

Calcimimetics suppress the secretion of parathyroid hormone by sensitizing the parathyroid calcium receptor to serum calcium. Cinacalcet (Sensipar®/Mimpara®, Amgen Inc., Thousand Oaks, CA), the first-in-class calcimimetic agent approved for treatment of secondary hyperparathyroidism in dialysis patients, is, in association with higher dose of a calcium-based oral phosphate binder, a well-tolerated and effective alternative to standard treatments such as vitamin D derivatives in association with a non-calcium-based oral phosphate binder. Here, we present an overview of evidence in support of this assertion. We extend our discussion to encompass other indications for calcimimetics—secondary hyperparathyroidism in predialysis chronic kidney disease patients, hypercalcemic hyperparathyroidism in renal transplant recipients, primary hyperparathyroidism, and hypercalcemia associated with parathyroid carcinoma—as well as providing guidance on optimal usage of this drug.

Thrombotic thrombocytopenic purpura due to anti-ADAMTS13 antibodies in multiple myeloma.

CONTEXTnThrombotic thrombocytopenic purpura (TTP) is a particularly serious form of thrombotic microangiopathy (TMA) due to the risk of multiple organ dysfunction. Several etiological factors such as infection, auto-immune disease, certain medications and cancers have been associated with TTP.nnnCLINICAL CASESnA 74-year-old hypertensive woman with a history of thromboembolic disease was hospitalized for acute kidney injury (AKI) associated with pneumonia. Initial investigations were suggestive of Pneumocystis jirovecii infection and myeloma cast nephropathy. Several days later, the patient presented features of TTP. Von Willebrand factor-cleaving protease activity was less than 5% with a high level of IgG antibody directed against ADAMTS13. Treatment consisted of monthly 4-day cycles of dexamethasone and melphalan in combination with plasmapheresis and resulted in a favorable outcome. Three years after ceasing treatment, the patient presented no signs of hemolysis, but required chronic hemodialysis.nnnCONCLUSIONnThe association of TMA, especially TTP, and multiple myeloma is exceptional. The authors report such a case that induced irreversible renal damage, but with stable clinical and laboratory parameters with a follow-up of 4 years.

Sarcoidosis and the kidney: not only the granulomatous interstitial nephritis.

Renal involvement in sarcoidosis displays a wide range of manifestations, and kidney dysfunction may involve all three mechanisms of renal failure. We report a new case of systemic sarcoidosis presenting as a severe renal failure due to hypercalcemia, sarcoidosis-related bilateral nephrolithiasis and granulomatous interstitial nephritis. A prostate adenocarcinoma was also diagnosed, but has to be regarded as an unrelated disease.

Retroperitoneal hematoma compressing a single functioning kidney : an unusual cause of obstructive renal failure

We report a case of a retroperitoneal hematoma occurring in a patient under anticoagulation therapy for deep-venous thrombosis and presenting as an anuric acute renal failure. A coexisting polycythemia vera led to misdiagnosis that could have been life-threatening. A woman, known for polycythemia vera and a single functioning right kidney, was admitted with mild abdominal pain in a context of recent deep venous thrombosis under low-molecular weight heparin. Clinical examination revealed hepatomegaly associated with polycythemia vera. Biochemical evaluation disclosed an acute renal failure, and renal ultrasonography showed no dilation of the renal pelvis. Retroperitoneal hematoma resulted in shock, progressive anemia and obstructive renal failure, related to renal pelvic compression. A right renal indwelling catheter was introduced to restore urine flow after one hemodialysis session, and an inferior vena cava filter was placed because of anti-coagulation contra-indication. However, pulmonary embolism occurred, so that oral anticoagulants were introduced. The hematoma resorbed spontaneously, and a year after this episode, the patient is still alive and well. Retroperitoneal hematoma is a rare cause of obstructive acute renal failure and a life-threatening complication of anti-coagulation therapy.