Bioartificial kidney in the treatment of acute renal failure associated with sepsis

A bioartificial renal tubule device embedding human renal stem/progenitor cells

We present a bio-inspired renal microdevice that resembles the in vivo structure of a kidney proximal tubule. For the first time, a population of tubular adult renal stem/progenitor cells (ARPCs) was embedded into a microsystem to create a bioengineered renal tubule. These cells have both multipotent differentiation abilities and an extraordinary capacity for injured renal cell regeneration. Therefore, ARPCs may be considered a promising tool for promoting regenerative processes in the kidney to treat acute and chronic renal injury. Here ARPCs were grown to confluence and exposed to a laminar fluid shear stress into the chip, in order to induce a functional cell polarization. Exposing ARPCs to fluid shear stress in the chip led the aquaporin-2 transporter to localize at their apical region and the Na⁺K⁺ATPase pump at their basolateral portion, in contrast to statically cultured ARPCs. A recovery of urea and creatinine of (20±5)% and (13±5)%, respectively, was obtained by the device. The microengineered biochip here-proposed might be an innovative “lab-on-a-chip” platform to investigate in vitro ARPCs behaviour or to test drugs for therapeutic and toxicological responses.

Improvement of cytokine response and survival time by bioartificial kidney therapy in acute uremic pigs with multi-organ dysfunction

OBJECTIVE

To explore whether bioartificial kidney (BAK) ameliorates cytokine response and biochemical indices, and prolongs the survival time in acute uremic pigs with multiple organ dysfunction syndrome (MODS).

METHODS

Hybridized pigs suffering from MODS and acute renal failure (ARF) were treated with BAK (Group A, n=6) or sham-BAK containing no cells (Group B, n=6), or received no treatment (Group C, n=5). Data on blood pressure, hepatic and renal function, IL-10, TNF-α, arterial blood gas, and survival time of all the pigs was recorded.

RESULTS

Mean arterial pressure (MAP, mmHg) responded more rapidly and reached higher values in Group A (91.82 ± 5.73) compared with Groups B and C at 24 hours (p<0.01). The peak level of serum IL-10 (pg/mL) in Group A (249.57 ± 43.51) was significantly higher than in Groups B and C (132.06 ± 17.53, 104.25 ± 13.42, p<0.01). Serum TNF-α level (pg/mL) in Group A dropped gradually to 402.91 ± 32.47 at 24 hours, and showed a significant discrepancy compared with those before treatment (537.16 ± 38.45) and Group B (512.94 ± 19.5, p<0.05). There was no difference in plasma endotoxin and serum IL-6 between pre-treatment and post-treatment in Groups A and B. BAK treatment, however, resulted in a significant decline in IL-6/IL-10 ratios. The average survival time (hours) in Group A (113.01 ± 14.32) was significantly longer, prolonged by 35.93% and 63.90% compared to Groups B and C (p<0.01), respectively.

CONCLUSIONS

The addition of renal tubule cell therapy to hemofiltration in an acutely uremic animal model with MODS altered systemic cytokine balance, ameliorated MAP, and prolonged survival time.

Membranes for dialysis: can we do without them?

Over the past five decades, membranes used for the treatment of chronic kidney disease have continuously evolved. In the course of this evolution, the use of classical non-modified cellulose membranes has declined in favor of cellulose-based membranes in which the basic structure has been modified to improve the biocompatibility profile of the material as well as membranes based on synthetic polymers. In addition to providing improved biocompatibility, manufacturing methods have been innovatively adapted to produce membranes with optimized pore size and pore size distribution. This has led to the more effective removal of molecules involved in the development of complications associated with dialysis treatment. More recently, the approach has been move membranes beyond being just selective barriers with a high performance and to incorporate biological function. Despite these advances, membranes in current clinical use represent a compromise: while efficient in their removal of water soluble compounds, they are non selective, retain some bioreactivity and differ in their ability to adsorb endotoxins or bacterial fragments that may be present in the dialysis fluid. In this paper, an overview of the membranes used in current clinical practice and their limitations are discussed, together with approaches to solute transport in which no membranes are used.

The kidney in the critically ill

Acute kidney injury (AKI) is a common and serious complication in the intensive care setting. It seldom occurs in isolation, but is mostly part of a multiple organ dysfunction syndrome. The pathogenesis is frequently multifactorial, with sepsis contributing to 50% of the cases.The development of AKI in critically-ill patients is "bad news": patients with AKI have a high morbidity and mortality. In addition, AKI, even in its mildest from, is not only a marker of illness severity but appears to be independently associated with mortality. Prevention of AKI is therefore a major goal to improve outcome of critically-ill patients. Treatment of established AKI is largely supportive. The optimal modality for renal replacement therapy in critically-ill patients still remains a matter of debate). The majority of survivors recover renal function.

2-aminoadipic acid is a marker of protein carbonyl oxidation in the aging human skin: effects of diabetes, renal failure and sepsis

We hypothesized that the epsilon-amino group of lysine residues in longlived proteins oxidatively deaminates with age forming the carbonyl compound, allysine (alpha-aminoadipic acid-delta-semialdehyde), which can further oxidize into 2-aminoadipic acid. In the present study, we measured both products in insoluble human skin collagen from n=117 individuals of age range 10-90 years, of which n=61 and n=56 were non-diabetic and diabetic respectively, and a total of n=61 individuals had either acute or chronic renal failure. Allysine was reduced by borohydride into 6-hydroxynorleucine and both products were measured in acid hydrolysates by selective ion monitoring gas chromatography (GC)-MS. The results showed that 2-aminoadipic acid (P<0.0001), but not 6-hydroxynorleucine (P=0.14), significantly increased with age reaching levels of 1 and 0.3 mmol/mol lysine at late age respectively. Diabetes in the absence of renal failure significantly (P<0.0001) increased 2-aminoadipic acid up to <3 mmol/mol, but not 6-hydroxynorleucine (levels<0.4 mmol/mol, P=0.18). Renal failure even in the absence of diabetes markedly increased levels reaching up to <0.5 and 8 mmol/mol for 6-hydroxynorleucine and 2-aminoadipic acid respectively. Septicaemia significantly (P<0.0001) elevated 2-aminoadipic acid in non-diabetic, but not diabetic individuals, and mildly correlated with other glycoxidation markers, carboxymethyl-lysine and the methylglyoxal-derived products, carboxyethyl-lysine, argpyrimidine and MODIC (methylglyoxal-derived imidazolium cross-link). These results provide support for the presence of metal-catalysed oxidation (the Suyama pathway) in diabetes and the possible activation of myeloperoxidase during sepsis. We conclude that 2-aminoadipic acid is a more reliable marker for protein oxidation than its precursor, allysine. Its mechanism of formation in each of these conditions needs to be elucidated.