Monobody adapter for functional antibody display on nanoparticles for adaptable targeted delivery applications

Vascular endothelial cells (ECs) play a central role in the pathophysiology of many diseases. The use of targeted nanoparticles (NPs) to deliver therapeutics to ECs could dramatically improve efficacy by providing elevated and sustained intracellular drug levels. However, achieving sufficient levels of NP targeting in human settings remains elusive. Here, we overcome this barrier by engineering a monobody adapter that presents antibodies on the NP surface in a manner that fully preserves their antigen-binding function. This system improves targeting efficacy in cultured ECs under flow by >1000-fold over conventional antibody immobilization using amine coupling and enables robust delivery of NPs to the ECs of human kidneys undergoing ex vivo perfusion, a clinical setting used for organ transplant. Our monobody adapter also enables a simple plug-and-play capacity that facilitates the evaluation of a diverse array of targeted NPs. This technology has the potential to simplify and possibly accelerate both the development and clinical translation of EC-targeted nanomedicines.

O3 Ex vivo normothermic machine perfusion facilitates gymnotic delivery of RNA interference therapeutics in donor kidneys

Introduction

Normothermic machine perfusion (NMP) of donor kidneys prior to transplantation provides a platform for delivery of novel therapeutics to optimize organ quality. This includes RNA interference (RNAi) therapeutics e.g. antisense oligonucleotides (ASO) that block detrimental microRNAs. The intracellular kinetics of RNAi therapeutics are crucial for their pharmacological effect, however, it remains poorly understood. NMP provides an ideal platform to investigate this further.

Method

During NMP, human kidneys (n = 12) were treated for 6 hours with a fluorescently-labelled ASO designed to block microRNA-24-3p activity. Biopsies were taken at 0, 2, 4, and 6 hours. Kidney sections were stained with antibodies against early endosomes (Rab5), late endosomes (Rab7), RNA-induced silencing complexes (GW182) and lysosomes (LAMP2). Confocal microscopy images were obtained and co-localisation quantified using Hugyens™ software following batch deconvolution. The global transcriptomic impact of ASO therapy was also assessed using RNA sequencing.

Result

Following 2 hours of NMP, ASO was primarily found in tubular epithelial cells. Co-localisation studies revealed ASO uptake via endocytosis and endosomal sorting occurring during NMP. This was followed by cytoplasmic escape and co-localisation of ASO with GW182 proteins. This pattern of co-localisation was not seen in scrambled sequence or cold perfusion controls. RNAseq analysis revealed a decrease in inflammatory pathways and upregulation of microRNA-24-3p targets.

Discussion

This is the first study to demonstrate NMP facilitates gymnotic ASO delivery directly into the RISC, whereby, it blocks microRNA-mediated mRNA silencing and increases bioavailability of protective targets. This study highlights the capacity of NMP to re-programme gene expression in donor kidneys using RNAi therapeutics.

Take-home Message

Ex vivo normothermic machine perfusion of donor kidneys provides a unique window of opportunity prior to transplantation when we can deliver therapies to improve the quality of the organ. Novel genetic therapies designed to protect kidneys against ischemia reperfusion injury could potentially increase organ utilisation and improve post-transplant outcomes for the many patients on the kidney transplant waiting list.

Mitochondria-targeted antioxidant MitoQ ameliorates ischaemia-reperfusion injury in kidney transplantation models

BACKGROUND

Ischaemia-reperfusion (IR) injury makes a major contribution to graft damage during kidney transplantation. Oxidative damage to mitochondria is an early event in IR injury. Therefore, the uptake, safety, and efficacy of the mitochondria-targeted antioxidant MitoQ were investigated in models of transplant IR injury.

METHODS

MitoQ uptake by warm and cooled pairs of pig and declined human kidneys was measured when preserved in cold static storage or by hypothermic machine perfusion. Pairs of pigs' kidneys were exposed to defined periods of warm and cold ischaemia, flushed and stored at 4°C with or without MitoQ (50 nmol/l to 250 µmol/l), followed by reperfusion with oxygenated autologous blood in an ex vivo normothermic perfusion (EVNP). Pairs of declined human kidneys were flushed and stored with or without MitoQ (5-100 µmol/l) at 4°C for 6 h and underwent EVNP with ABO group-matched blood.

RESULTS

Stable and concentration-dependent uptake of MitoQ was demonstrated for up to 24 h in pig and human kidneys. Total blood flow and urine output were significantly greater in pig kidneys treated with 50 µmol/l MitoQ compared with controls (P = 0.006 and P = 0.007 respectively). In proof-of-concept experiments, blood flow after 1 h of EVNP was significantly greater in human kidneys treated with 50 µmol/l MitoQ than in controls (P ≤ 0.001). Total urine output was numerically higher in the 50-µmol/l MitoQ group compared with the control, but the difference did not reach statistical significance (P = 0.054).

CONCLUSION

Mitochondria-targeted antioxidant MitoQ can be administered to ischaemic kidneys simply and effectively during cold storage, and may improve outcomes after transplantation.

Ex vivo normothermic perfusion of isolated segmental porcine bowel: a novel functional model of the small intestine

BACKGROUND

There is an unmet need for suitable ex vivo large animal models in experimental gastroenterology and intestinal transplantation. This study details a reliable and effective technique for ex vivo normothermic perfusion (EVNP) of segmental porcine small intestine.

METHODS

Segments of small intestine, 1.5-3.0 m in length, were retrieved from terminally anaesthetized pigs. After a period of cold ischaemia, EVNP was performed for 2 h at 37°C with a mean pressure of 80 mmHg using oxygenated autologous blood diluted with Ringer's solution. The duration of EVNP was extended to 4 h for a second set of experiments in which two segments of proximal to mid-ileum (1.5-3.0 m) were retrieved from each animal and reperfused with whole blood (control) or leucocyte-depleted blood to examine the impact of leucocyte depletion on reperfusion injury.

RESULTS

After a mean cold ischaemia time of 5 h and 20 min, EVNP was performed in an initial group of four pigs. In the second set of experiments, five pigs were used in each group. In all experiments bowel segments were well perfused and exhibited peristalsis during EVNP. Venous glucose levels significantly increased following luminal glucose stimulation (mean(s.e.m.) basal level 1.8(0.6) mmol/l versus peak 15.5(5.8) mmol/l; P < 0.001) and glucagon-like peptide 1 (GLP-1) levels increased in all experiments, demonstrating intact absorptive and secretory intestinal functions. There were no significant differences between control and leucocyte-depleted animals regarding blood flow, venous glucose, GLP-1 levels or histopathology at the end of 4 h of EVNP.

CONCLUSIONS

This novel model is suitable for the investigation of gastrointestinal physiology, pathology and ischaemia reperfusion injury, along with evaluation of potential therapeutic interventions.

Risk factors for transplant renal artery stenosis after live donor transplantation

Background

Renal transplant surgeons are making increasing use of live donor kidneys with multiple renal arteries. This study aimed to identify independent risk factors for the development of transplant renal artery stenosis (TRAS) in the modern era of complex arterial reconstruction for multiple vessels.

Methods

Multivariable logistic regression analysis with a stepwise variable deletion model was used to identify risk factors for the development of TRAS in a consecutive series of live donor kidney transplants.

Results

Of 506 kidney transplants, 19 (3·8 per cent) had evidence of significant TRAS on CT angiography. Functional TRAS, defined by improvement in BP control or renal function after correction of a stenosis by angioplasty, occurred in 13 of 506 patients (2·6 per cent). Independent risk factors for TRAS were: use of an explanted internal iliac artery graft from the recipient (odds ratio (OR) 4·95; P = 0·020) and total ischaemia time (OR 1·82; P = 0·010). TRAS was associated with a lower 5-year allograft survival rate (79 versus 88·7 per cent; P = 0·020) but only one graft loss was attributed directly to TRAS. The 5-year allograft survival rate after internal iliac artery grafting was 86 per cent.

Conclusion

Although use of an internal iliac artery graft is an independent risk factor for TRAS after live donor kidney transplantation, this technique is still a useful option for complex arterial reconstruction.

Normothermic machine perfusion for the assessment and transplantation of declined human kidneys from donation after circulatory death donors

BACKGROUND

A significant proportion of donation after circulatory death (DCD) kidneys are declined for transplantation because of concerns over their quality. Ex vivo normothermic machine perfusion (NMP) provides a unique opportunity to assess the quality of a kidney and determine its suitability for transplantation.

METHODS

In phase 1 of this study, declined human DCD kidneys underwent NMP assessment for 60 min. Kidneys were graded 1-5 using a quality assessment score (QAS) based on macroscopic perfusion, renal blood flow and urine output during NMP. In phase 2 of the study, declined DCD kidneys were assessed by NMP with an intention to transplant them.

RESULTS

In phase 1, 18 of 42 DCD kidneys were declined owing to poor in situ perfusion. After NMP, 28 kidneys had a QAS of 1-3, and were considered suitable for transplantation. In phase 2, ten of 55 declined DCD kidneys underwent assessment by NMP. Eight kidneys had been declined because of poor in situ flushing in the donor and five of these were transplanted successfully. Four of the five kidneys had initial graft function.

CONCLUSION

NMP technology can be used to increase the number of DCD kidney transplants by assessing their quality before transplantation.

Successful Transplantation of Human Kidneys Deemed Untransplantable but Resuscitated by Ex Vivo Normothermic Machine Perfusion

We report the successful transplantation of a pair of human kidneys that were declined for transplantation due to inadequate in situ perfusion but subsequently transplanted after perfusion and assessment using ex vivo normothermic perfusion (EVNP). The kidneys were from a 35-year-old man, a donation after circulatory death donor. Both kidneys were declined by all UK transplant centers. On arrival, the kidneys had significant areas of incomplete clearance of blood from the microcirculation that did not clear after a further attempt to flush them. Kidneys underwent 60 min of EVNP with an oxygenated packed red blood cell-based solution warmed to 35.2°C. During EVNP, the patchy areas cleared in both kidneys. The mean renal blood flow and total urine output were 68.0 mL/min/100 g and 560 mL in the left kidney and 59.9 mL/min/100 g, 430 mL in the right, respectively. Based on the EVNP perfusion parameters, both kidneys were deemed suitable for transplantation. They were transplanted without any complications, and both recipients had initial graft function. The serum creatinine levels at 3 months were 1.2 mg/dl in the recipient of the left kidney and 1.62 mg/dl in the recipient of the right kidney. EVNP technology can be used to assess and rescue kidneys previously deemed unsuitable for transplantation.

The use of ex-vivo normothermic perfusion for the resuscitation and assessment of human kidneys discarded because of inadequate in situ perfusion

Background

Many kidneys are rejected for transplantation due to inadequate in situ perfusion during organ retrieval because of the risk of additional ischaemic injury and microvasculature thrombosis. This study describes the use of ex vivo normothermic perfusion (EVNP) for the resuscitation and assessment of human kidneys that were discarded after inadequate in situ perfusion.

Methods

Twenty-two human kidneys were retrieved but then deemed unsuitable for transplantation, primarily due to inadequate in situ perfusion. After a period of static cold storage, kidneys were perfused for 60 min with an oxygenated red cell based solution at 36 °C.

Results

Nineteen out of 22 kidneys (86 %) were from DCD donors. During EVNP, kidneys were assessed and scored based on their macroscopic appearance, measures of renal blood flow and urine production. Kidneys were scored from 1 indicating the least injury to 5, indicating the worst. Twelve kidneys had an EVNP score of 1–2, 7 scored 3–4 and 3 kidneys scored 5. The EVNP score 5 kidneys had a low level of tubular function compared to the score 1–4 kidneys. Their perfusion parameters did not improve during EVNP and they were considered non-transplantable. There was no association between the histological evaluation and EVNP parameters.

Conclusion

EVNP restores function ex vivo and enables an assessment of kidneys that have been declined for transplantation due to inadequate in situ perfusion.

Use of Ex Vivo Normothermic Perfusion for Quality Assessment of Discarded Human Donor Pancreases

A significant number of pancreases procured for transplantation are deemed unsuitable due to concerns about graft quality and the associated risk of complications. However, this decision is subjective and some declined grafts may be suitable for transplantation. Ex vivo normothermic perfusion (EVNP) prior to transplantation may allow a more objective assessment of graft quality and reduce discard rates. We report ex vivo normothermic perfusion of human pancreases procured but declined for transplantation, with ABO-compatible warm oxygenated packed red blood cells for 1-2 h. Five declined human pancreases were assessed using this technique after a median cold ischemia time of 13 h 19 min. One pancreas, with cold ischemia over 30 h, did not appear viable and was excluded. In the remaining pancreases, blood flow and pH were maintained throughout perfusion. Insulin secretion was observed in all four pancreases, but was lowest in an older donation after cardiac death pancreas. Amylase levels were highest in a gland with significant fat infiltration. This is the first study to assess the perfusion, injury, as measured by amylase, and exocrine function of human pancreases using EVNP and demonstrates the feasibility of the approach, although further refinements are required.

Ex vivo normothermic perfusion for quality assessment of marginal donor kidney transplants

BACKGROUND

A significant proportion of kidneys procured for transplantation are discarded because of concerns about their suitability. In this study ex vivo normothermic perfusion (EVNP) was used as a quality assessment device before renal transplantation.

METHODS

Seventy-four human kidneys deemed unsuitable for transplantation following retrieval underwent 60 min of EVNP with an oxygenated red cell-based solution at 36°C. Receiver operating characteristic (ROC) curves were used to identify thresholds of renal blood flow and urine output. These thresholds and a grading of macroscopic appearance were incorporated into an EVNP assessment score (highest quality, 1; lowest, 5). This was applied to a series of 36 kidneys transplanted after EVNP.

RESULTS

In the discarded kidney series, 60 (81 per cent) scored 1-4 and 14 (19 per cent) scored 5. Although none of these kidneys was transplanted, those with a score from 1 to 4 were considered suitable for transplantation. In the 36 transplanted kidneys, the score ranged between 1 and 3 (score 1, 17; score 2, 11; score 3, 8). All of these kidneys were transplanted without any complications or primary non-function. The delayed graft function rate was 6 per cent (1 of 17) in kidneys scoring 1, 0 per cent (0 of 11) in those scoring 2 and 38 per cent (3 of 8) in those scoring 3 (P = 0·024). The mean(s.d.) estimated glomerular filtration rate at 12 months was 51(16), 63(15) and 38(21) ml in kidneys scoring 1, 2 and 3 respectively (P = 0·015).

CONCLUSION

EVNP combined with a simple scoring system is an innovative technology for pretransplant assessment of kidney quality and acceptability for transplantation. This study suggests that a high percentage of retrieved kidneys are being discarded unnecessarily.

Ischaemic conditioning reduces kidney injury in an experimental large-animal model of warm renal ischaemia

BACKGROUND

Ischaemic conditioning, using short repeated sequences of intermittent ischaemia, is a strategy that may ameliorate ischaemia-reperfusion injury. The aim of the study was to assess the effects of direct and remote ischaemic conditioning in a porcine model of renal warm ischaemia-reperfusion injury.

METHODS

Pigs (50 kg) underwent laparotomy and 60-min occlusion of the left renal pedicle followed by right nephrectomy. Animals were divided into three groups: untreated controls (n = 8); direct postconditioning involving six 15-s cycles of clamping then releasing of the left renal artery (n = 7); or remote periconditioning involving four 5-min cycles of clamping then releasing of the left common iliac artery (n = 8). After 7 days kidney tissue was harvested, and blood and urine samples were collected on postoperative days 1, 3 and 7.

RESULTS

The direct postconditioning group had a lower area under the serum creatinine curve (mean(s.d.) 1378(157) versus 2001(1022) µmol/l · day respectively; P = 0.036) and peak creatinine level (316(46) versus 501(253) µmol/l respectively; P = 0.033) compared with values in control animals. There was a significant increase in serum levels of tumour necrosis factor α on day 1 in control animals but not in the conditioning groups (P = 0.013). Urinary levels of neutrophil gelatinase-associated lipocalin increased over the study period in both the control and remote groups (P = 0.001 for both), but not in the direct group (P = 0.176). There was no mortality and no complications related to either conditioning technique.

CONCLUSION

In this in vivo large-animal model, direct renal artery ischaemic postconditioning protected kidneys against warm ischaemia injury. This straightforward technique could readily be translated into clinical practice. Surgical relevance Ischaemic conditioning has been shown to improve outcomes in both experimental studies and clinical trials in cardiac surgery. Evidence from small-animal and human studies assessing ischaemic conditioning techniques in renal transplantation have not yet established the optimal technique and timing of conditioning. In this study, a large-animal model of renal warm ischaemia was used to compare different conditioning techniques. Postconditioning applied directly to the renal artery was shown to reduce renal injury. Furthermore, new evidence is provided that shorter cycles of ischaemic postconditioning than previously described can protect against renal injury. Evidence from a large-animal model is provided for different conditioning techniques. The beneficial postconditioning technique described is straightforward to perform and provides an alternative method of conditioning following renal transplantation, with potential for application in clinical practice.

The first clinical case of intermediate ex vivo normothermic perfusion in renal transplantation

A short period of ex vivo normothermic perfusion (EVNP) immediately before transplantation can revive the kidney and reduce the effects of cold ischemic (CI) injury. Herein, we report a clinical case of EVNP carried out at an intermediate period of the preservation interval. The kidney was retrieved from a 63-year-old extended criteria donor. After 10 h 29 min of CI the kidney underwent EVNP with 1 unit of compatible packed red blood cells mixed with a priming solution at 35.0°C while the recipient was being prepared for surgery. The mean renal blood flow was 93.6 mL/min/100 g and the kidney produced 60 mL of urine. Shortly after the start of surgery the first intended recipient became unfit for transplantation. After 60 min EVNP the kidney was flushed with cold preservation solution and re-packed in ice. The second period of CI was 5 h and 21 min. The kidney was transplanted without any complications into a 54-year-old predialysis patient. The recipient had immediate graft function with serum creatinine levels falling from 315 to 105 µmol/L by day 7. This is the first report of an intermediate period of EVNP in clinical renal transplantation. This case demonstrates the feasibility and safety of the technique.

Renal transplantation after ex vivo normothermic perfusion: the first clinical study

Ex vivo normothermic perfusion (EVNP) is a novel method of preservation that restores circulation and allows an organ to regain function prior to transplantation. The aim of this study was to assess the effects of EVNP in kidneys from marginal donors. Eighteen kidneys from extended criteria donors (ECD) underwent a period of EVNP immediately before transplantation. Kidneys were perfused with a plasma free red-cell based solution at a mean temperature of 34.6°C. The outcome of these kidneys was compared to a control group of 47 ECD kidneys that underwent static cold storage (CS). The mean donor age was 61 ± 1 years in the EVNP and 62 ± 6 years in the CS group (p = 0.520). EVNP kidneys were perfused for an average of 63 ± 16 min and all were transplanted successfully. The delayed graft function rate (DGF), defined as the requirement for dialysis within the first 7 days was 1/18 patients (5.6%) in the EVNP group versus 17/47 (36.2%) in the CS group (p = 0.014). There was no difference in graft or patient survival at 12 months (p = 0.510, 1.000). This first series of EVNP in renal transplantation demonstrates that this technique is both feasible and safe. Our preliminary data suggests that EVNP offers promise as a new technique of kidney preservation.

Effects of hydrogen sulphide in an experimental model of renal ischaemia-reperfusion injury

BACKGROUND

Renal ischaemia-reperfusion injury (IRI) is a major cause of acute renal failure and renal transplant dysfunction. The aim of this study was to investigate the efficacy of the endogenous gaseous signalling molecule hydrogen sulphide in protecting against renal IRI.

METHODS

Large White female pigs underwent laparotomy and cross-clamping of the left renal pedicle for 60 min. Animals were allocated randomly to treatment with either intravenous hydrogen sulphide (n = 6) or saline control (n = 6) 10 min before clamp release, and then underwent a right nephrectomy. Staff were blinded to treatment allocation and animals were recovered for 7 days.

RESULTS

Hydrogen sulphide therapy resulted in a marked reduction in kidney injury with reduced serum creatinine levels on days 1-5, in a reduced area under the creatinine-time curve, and a halving of the time to achieve a creatinine level of less than 250 µmol/l, compared with the control. Hydrogen sulphide also preserved glomerular function, as shown by the urinary protein/creatinine ratio, which, compared with baseline, increased on days 1 and 3 in the control group (mean(s.e.m.) 3·22(1·43), P = 0·016 and 2·59(1·27), P = 0·031), but not in the treatment group (0·99(0·23), P = 0·190 and 1·06(0·44), P = 0·110, respectively). Mean(s.e.m.) tumour necrosis factor α levels at 6 h postreperfusion increased in the control animals (56(6) versus 115(21) pg/ml; P = 0·026), but not in the hydrogen sulphide-treated animals (61(7) versus 74(11) pg/ml; P = 0·460). Renal neutrophil infiltration at 30 min (myeloperoxidase staining) was also significantly reduced by treatment with hydrogen sulphide (P = 0·016).

CONCLUSION

Hydrogen sulphide offers a promising new approach to ameliorating renal IRI with potential translation into a number of clinical settings, including renal transplantation.

Use of internal iliac artery as a side-to-end anastomosis in renal transplantation

The internal iliac artery is less commonly used in renal transplantation in comparison to the external iliac artery due to its size and the risk of compromising distal vascular supply to the pelvis. We report a cadaveric renal transplant in which we performed a side-to-end anastomosis using the internal iliac artery. This technique can provide adequate perfusion to the transplant kidney without the associated risks and complications in the patient whose internal iliac artery is of a good diameter and quality.

Rapamycin toxicity in MIN6 cells and rat and human islets is mediated by the inhibition of mTOR complex 2 (mTORC2)

AIMS/HYPOTHESIS

Rapamycin (sirolimus) is one of the primary immunosuppressants for islet transplantation. Yet there is evidence that the long-term treatment of islet-transplant patients with rapamycin may be responsible for subsequent loss of islet graft function and viability. Therefore, the primary objective of this study was to elucidate the molecular mechanism of rapamycin toxicity in beta cells.

METHODS

Experiments were performed on isolated rat and human islets of Langerhans and MIN6 cells. The effects of rapamycin and the roles of mammalian target of rapamycin complex 2 (mTORC2)/protein kinase B (PKB) on beta cell signalling, function and viability were investigated using cell viability assays, insulin ELISA assays, kinase assays, western blotting, pharmacological inhibitors, small interfering (si)RNA and through the overproduction of a constitutively active mutant of PKB.

RESULTS

Rapamycin treatment of MIN6 cells and islets of Langerhans resulted in a loss of cell function and viability. Although rapamycin acutely inhibited mTOR complex 1 (mTORC1), the toxic effects of rapamycin were more closely correlated to the dissociation and inactivation of mTORC2 and the inhibition of PKB. Indeed, the overproduction of constitutively active PKB protected islets from rapamycin toxicity whereas the inhibition of PKB led to a loss of cell viability. Moreover, the selective inactivation of mTORC2 using siRNA directed towards rapamycin-insensitive companion of target of rapamycin (RICTOR), mimicked the toxic effects of chronic rapamycin treatment.

CONCLUSIONS/INTERPRETATION

This report provides evidence that rapamycin toxicity is mediated by the inactivation of mTORC2 and the inhibition of PKB and thus reveals the molecular basis of rapamycin toxicity and the essential role of mTORC2 in maintaining beta cell function and survival.

Post-biopsy renal allograft compartment syndrome: Addressing the problem, illustrated with a case report

INTRODUCTION

Renal allograft compartment syndrome (RACS) has recently been coined to describe early allograft dysfunction secondary to raised pressure in the retroperitoneal space. This may be caused by direct compression of the renal vessels or by a diffuse renal parenchymal compression. Herein, we report a renal allograft compartment syndrome secondary to a needle core transplant biopsy and discuss the management strategies in line with an updated literature review.

PRESENTATION OF CASE

A retrospective case-note review was carried out where a 45-year-old male had a transplant renal biopsy at 4-weeks after transplant for raising creatinine. Following biopsy patient developed abdominal discomfort and had haematuria.

DISCUSSION

Doppler ultrasound scanning of graft demonstrated good perfusion but a small haematoma (2 × 2 × 2 cm) in the upper pole of the kidney at the site of the biopsy. Patient was thereafter assessed conservatively with serial ultrasound monitoring. After 24 h, significant deterioration of graft function was observed. The third scan, demonstrated reversed flow in diastole in the upper pole of the kidney with a resistive index of 1.0 in the main renal vessel. With the above findings the kidney transplant was explored immediately and the transplant released from a 300 ml of liquefied haematoma, which was under considerable pressure. In the next 24-h, the patient showed an immediate return of graft function.

CONCLUSION

We recommend sequential ultrasound Doppler scanning as an invaluable tool to help identify early RACS. The surgical exploration and adequate heamostasis with surgical glue should be sought out in all RACS.

Hypothermic machine perfusion after static cold storage does not improve the preservation condition in an experimental porcine kidney model

Background

Combining hypothermic techniques, as a more practical approach to preservation, may enhance the condition of kidneys donated after cardiac death.

Methods

Porcine kidneys were retrieved after 10 min in situ warm ischaemia, then preserved by either 18 h static cold storage (CS), hypothermic machine perfusion for 18 h (HMP) or 14 h static CS followed by 4 h HMP (4HMP). Kidneys were reperfused for 3 h with oxygenated autologous blood on an isolated organ perfusion system to assess renal function and injury.

Results

Intrarenal resistance was significantly higher in the 4HMP group than in the CS and HMP groups: mean(s.d.) area under the curve (AUC) 8·48(2·97), 3·41(1·80) and 3·78(1·68) mmHg/min.h respectively (P = 0·011). Creatinine clearance was lower after 4HMP and CS: AUC 2·3(0·6) and 2·2(1·7) ml per min per 100g.h respectively versus 9·8(7·3) ml per min per 100g.h in the HMP group (P = 0·022). Levels of endothelin 1 were higher in the 4HMP and CS groups: mean(s.d.) 21·6(4·0) and 24·2(2·3) pg/ml respectively versus 11·4(4·6) pg/ml in the HMP group (P = 0·002). Morphological damage was increased in the 4HMP group.

Conclusion

This porcine kidney study demonstrated no advantage to the addition of 4 h of HMP after CS.

Complete resolution of oral Kaposi's sarcoma achieved by changing immunosuppression: a case report

A 38-year-old Afro-Caribbean woman, who was pre-dialysis with polycystic kidney disease, received a live-donor kidney transplant from her 55-year-old mother. This study documents her imunosuppression therapy including resolution of an oral Kaposi's sarcoma and explores the many underlying problems with converting to an mTOR inhibitor.

Hydrogen sulphide ameliorates ischaemia-reperfusion injury in an experimental model of non-heart-beating donor kidney transplantation

BACKGROUND

: Therapies to alleviate ischaemia-reperfusion (IR) injury have an important role in kidney transplantation. This study used a porcine model of non-heart-beating (NHB) donor kidneys to investigate the effects of hydrogen sulphide on IR injury.

METHODS

: Porcine kidneys were subjected to 25 min of warm ischaemia and 18 h of cold storage. They were reperfused ex vivo with autologous oxygenated blood to assess renal function. A group treated with hydrogen sulphide (0.5 mmol/l) infused 10 min before and after reperfusion (n = 6) was compared with an untreated control group (n = 7).

RESULTS

: Hydrogen sulphide significantly improved renal blood flow compared with control values (mean(s.d.) area under the curve (AUC) 614.9(165.5) versus 270.3(86.7) ml per min per 100 g.h; P = 0.001) and renal function (AUC creatinine: 1640(248) versus 2328(154) micromol/l.h; P = 0.001; AUC creatinine clearance: 6.94(5.03) versus 0.96(0.32) ml per min per 100 g.h; P = 0.004). Oxidative damage was also reduced by hydrogen sulphide (urinary 8-isoprostane at 1 h of reperfusion: 478.9(237.1) versus 1605.6(632.7) pg/ml per mmol/l creatinine; P = 0.032).

CONCLUSION

: Hydrogen sulphide ameliorated the renal dysfunction associated with ischaemic damage, and has potential as a therapy against IR injury in NHB donor kidney transplantation.

Randomized clinical trial of laparoscopic versus open donor nephrectomy

Background

This randomized controlled trial was designed to determine the safety and efficacy of laparoscopic donor nephrectomy (LDN) in comparison with short-incision open donor nephrectomy (ODN).

Methods

Eighty-four live kidney donors were randomized in a 2 : 1 ratio to LDN (56 patients) or short-incision ODN without rib resection (28). Primary endpoints were pain relief and duration of inpatient stay.

Results

There was no donor death or allograft thrombosis in either group. The first warm ischaemic time median (range) 4 (2–7) versus 2 (1–5) min; P = 0·001) and the duration of operation (160 (110–250) versus 150 (90–200); P = 0·004) were longer for LDN. LDN led to a reduction in parenteral morphine requirement 59 (6–136) versus 90 (35–312) mg; P = 0·001) and hospital stay (4 (2–6) versus 6 (2–9) days; P = 0·001), and earlier return to employment (42 (14–84) versus 66·5 (14–112) days; P = 0·004). Postoperative respiratory function was improved after LDN. There were more postoperative complications per donor in the ODN group (0·6(0·7) versus 0·3(0·5); P = 0·033). At a median follow-up of 74 months, there were no differences in renal function or allograft survival between the groups.

Conclusion

LDN removes some of the disincentives to live donation without compromising the outcome of the recipient transplant.

Comparison of preservation solutions in an experimental model of organ cooling in kidney transplantation

Background

Viscous preservation solutions such as University of Wisconsin solution (UW) may be less effective at rapid removal of blood from an organ so that cooling takes longer. This study assessed the temperature changes of kidneys flushed with UW and hyperosmolar citrate (HOC).

Methods

Porcine kidneys were retrieved and flushed with 500 ml UW or HOC at 4 °C while monitoring kidney temperature at depths of 5 and 20 mm. Renal function was measured on an isolated organ preservation system.

Results

The mean(s.d.) rate of temperature fall was slower with UW (at 20 mm: 0·64(0·11) versus 1·01(0·56) °C per min per 100 g; P = 0·016). The perfusion flow rate required to reduce the temperature to less than 10 °C at a depth of 20 mm was lower in the UW group (P = 0·002). Kidneys flushed with HOC gained more weight than those flushed with UW (mean(s.d.) 50(8) versus 7(13) per cent; P = 0·002). Flushing with UW was associated with less histological injury but there were no significant differences in renal function parameters between the groups.

Conclusion

UW cooled kidneys more slowly than HOC, but with no adverse effect on renal function. UW resulted in less oedema and histological injury than HOC.

Case-matched comparison of long-term results of non-heart beating and heart-beating donor renal transplants

BACKGROUND

Function and survival of non-heart-beating donor (NHBD) renal transplants have been shown to be comparable to those from heart-beating donors (HBDs) up to 10 years after transplantation. However, there are few data on outcome after 10 years, particularly from uncontrolled NHBD donors.

METHODS

All NHBD renal transplants (predominantly uncontrolled) performed between April 1992 and January 2002 were retrospectively matched with HBD renal transplants performed over the same period.

RESULTS

Some 112 NHBD renal transplants were compared with 164 HBD renal transplants. Delayed graft function was significantly higher in the NHBD group (83.9 versus 22.0 per cent respectively; P < 0.001). Primary non-function rates were similar (5.4 versus 1.8 per cent respectively; P = 0.164). Overall serum creatinine was significantly higher in NHBDs (P < 0.001). Median graft and patient survival was 126 months for NHBD and 159 months for HBD kidneys. Death-censored graft survival at 1, 5, 10 and 15 years was respectively 91.8, 77.5, 61.0 and 44.2 per cent for NHBD, and 91.1, 86.3, 71.7 and 58.5 per cent for HBD kidneys (P = 0.108).

CONCLUSION

Despite increased delayed graft function rates and serum creatinine levels, the long-term survival of NHBD renal transplants was similar to those from HBDs. However, there was a trend to poorer function and survival from 10 years after transplant.

Case-control comparison of laparoscopic and open washout for peritoneal dialysis-associated peritonitis

BACKGROUND

Peritonitis is the major complication of peritoneal dialysis (PD). Some 25-40 per cent of patients require surgical intervention, traditionally laparotomy, washout and removal of the PD catheter. The aim was to compare this open procedure with laparoscopic washout and catheter removal.

METHODS

In a case-control comparison, 20 patients who had laparoscopic washout for PD-associated peritonitis were matched by age and causative organism with 20 patients who had open washout.

RESULTS

The groups were well matched for age, sex, causative organism, preoperative C-reactive protein level, white cell count and presence of bowel wall sclerosis. Laparoscopic surgery was quicker than open operation (mean(s.d.) 49(13) versus 73(30) min; P = 0.006) and postoperative morphine requirements were significantly lower (median 0 versus 27 mg; P < 0.001). Bowel function recovered more quickly in the laparoscopic group, as measured by time to first passage of flatus (mean(s.d.) 2(1) versus 5(4) days; P = 0.004) and resumption of free fluids (median 2 versus 4 days; P = 0.044). Reoperation rates and 30-day mortality were identical in the two groups.

CONCLUSION

This study suggests that laparoscopic washout for PD peritonitis is as effective as open washout, but is quicker and less painful with earlier return of bowel function.

Application of nitric oxide and carbon monoxide in a model of renal preservation

Background

Nitric oxide and carbon monoxide exert vasodilatory effects that minimize ischaemia–reperfusion injury. An isolated porcine kidney model was used to assess the effects of administering the nitric oxide donor sodium nitroprusside (SNP) and carbon monoxide-releasing molecule (CORM) 3 during a period of warm preservation followed by reperfusion.

Methods

Kidneys were perfused under warm preservation conditions after 10 min of warm ischaemia and 16 h of cold storage in four groups: SNP, control, CORM-3 and inactive CORM-3 (inactive control). Renal function and viability were assessed.

Results

SNP and CORM-3 increased renal blood flow (RBF) during warm preservation (P = 0·014). After reperfusion, RBF was significantly improved in the CORM-3 group compared with the control group (P = 0·019). The reduction in creatinine clearance was significantly less in the CORM-3 group than in the inactive CORM-3 group (P = 0·021), and serum creatinine levels were significantly lower (P = 0·029). There was a negative correlation between RBF during warm preservation and functional parameters during reperfusion (creatinine concentration: rs = − 0·722, P &lt; 0·001; sodium excretion: rs = − 0·912, P &lt; 0·001).

Conclusion

The beneficial vasodilatory effects of CORM-3 during warm preservation improved renal function during reperfusion; SNP exerted similar, although less pronounced, effects.

A successful scheme for reducing waiting times for arteriovenous fistula formation

PURPOSE

In a bid to reduce waiting times for arteriovenous fistula (AVF) formation we introduced a scheme whereby nephrologists were able to place patients directly on the waiting list for surgery. This study evaluated the quality of these direct referrals and assessed the reduction in waiting times.

METHODS

Fifty consecutive patients referred directly to the waiting list were compared with 50 patients placed on the waiting list after being assessed in our vascular access clinic.

RESULTS

Forty-nine patients from the direct group and 47 patients from the clinic group underwent surgery. In the direct group 39 patients (80%) underwent the same procedure as they had been originally listed for, compared with 39 patients (83%) in the clinic group (p=0.80). A fistula suitable for needling was created in 37 patients (76%) of the direct group and 38 patients (81%) of the clinic group (p=0.62). The median wait from referral to surgery in the direct group was significantly lower than in the clinic group (62 vs.141 days; p<0.0001).

CONCLUSION

This study demonstrates that nephrologists are able to effectively assess select patients for AVF formation. This significantly reduces waiting times for surgery, without an increase in cancelled operations, or a reduction in technical success.

Experimental renal preservation by normothermic resuscitation perfusion with autologous blood

BACKGROUND

Normothermic perfusion (NP) has the potential to improve metabolic support and maintain the viability of ischaemically damaged organs. This study investigated the effects of NP compared with current methods of organ preservation in a model of controlled non-heart-beating donor (NHBD) kidneys.

METHODS

Porcine kidneys (n = 6 in each group) were subjected to 10 min warm ischaemia and then preserved as follows: 2 h cold storage (CS) in ice (CS2 group), 18 h CS (CS18 group), 18 h cold machine perfusion (CP group) or 16 h CS + 2 h NP (NP group). Renal haemodynamics and function were measured during 3 h reperfusion with autologous blood using an isolated organ perfusion system.

RESULTS

Increasing CS from 2 to 18 h reduced renal blood flow (mean(s.d.) area under the curve (AUC) 444(57) versus 325(70) ml per 100 g; P = 0.004), but this was restored by NP (563(119) ml per 100 g; P = 0.035 versus CS18). Renal function was also better in CS2, CP and NP groups than in the CS18 group (mean(s.d.) serum creatinine fall 92(6), 79(9) and 64(17) versus 44(13) per cent respectively; P = 0.001). The AUC for serum creatinine was significantly lower with CS for 2 h than for 18 h (mean(s.d.) 1102(2600) versus 2156(401) micromol/l.h; P = 0.001), although values in CP and NP groups were not significantly different from those in the CS2 group (1354(300) and 1756(280) micromol/l.h respectively). Two hours of NP increased the adenosine 3'-triphosphate : adenosine 3'-diphosphate ratio to a significantly higher level than the preperfusion values in all other groups (P = 0.046).

CONCLUSION

NP with oxygenated blood was able to restore depleted ATP levels and reverse some of the deleterious effects of CS.

Tunnelled Catheters for the Haemodialysis Patient

Haemodialysis depends upon the establishment of a durable means of vascular access. Although the creation of a successful arterio-venous Fistulae (AVF) is the ideal, this is not always possible or practical. Tunnelled catheters play an important role as an interim/bridge technique for emergency access or while an AVF matures, but may be associated with significant morbidity. The aim of this review is to highlight recent evidence based developments in tunnelled catheters, including methods of placement, complications and possible management strategies.

Comparison of Techniques of Vascular Control in Laparoscopic Donor Nephrectomy: The Leicester Experience

BACKGROUND

The objective of this study was to compare the safety and efficacy of three different methods to secure the renal vessels during laparoscopic donor nephrectomy (LDN).

METHODS

Vessel lengths and intraoperative vascular complications were compared in a prospective series of 106 LDNs in which the vessels had been secured using a stapling device, metal clips, or polymer clips.

RESULTS

One hundred six patients underwent LDN (right = 25, left = 81). Renal vein lengths were not significantly different after stapling or using polymer clips (36 +/- 10 vs 37 +/- 9 mm; P = .463). Renal arterial length was shorter after stapling (30 +/- 7 mm) compared with both endoclips (34 +/- 10 mm; P = .030) and polymer clips (34 +/- 8 mm; P = .030). There was one major arterial bleed in the endoclip group, one episode of stapler malfunction, but no adverse events with polymer clips.

CONCLUSION

Polymer clips are safe and yield greater vessel lengths during LDN.

The aetiology and pathogenesis of chronic allograft nephropathy

Renal transplantation is the ultimate form of renal replacement therapy, and is the treatment of choice for many patients with end-stage renal failure. The advent of calcineurin inhibitor based immunosuppression resulted in the 1-year renal allograft failure rate dropping from around 50% twenty years ago to less than 10% in more recent times. Despite a massive improvement in renal allograft survival in the first year following transplantation 10-year graft survival can be as low as 50%. Chronic allograft nephropathy (CAN) is recognised as the main cause of renal allograft failure following the first year after transplantation. The diagnosis of CAN can only be made histologically. Typically biopsy specimens in grafts with CAN demonstrate an overall fibrotic appearance effecting the vascular endothelium, renal tubules, interstitium, and glomerulus. The risk factors for CAN are divided into alloimmune and alloimmune independent. Alloimmune dependent factors include acute cellular rejection, severity of rejection, subclinical rejection and HLA mismatch. Alloimmune independent factors such as delayed graft function, donor age, Cytomegalovirus infection, donor/recipient co-morbidity and of course calcineurin inhibitor toxicity are important in the development of CAN. The pathogenesis of CAN is complex, multifactorial, and unfortunately incompletely understood. There are a number of pivotal steps in the initiation and propagation of the fibrosis seen in biopsy specimens from kidneys with CAN. Endothelial activation in response to one or more of the aforementioned risk factors stimulates leukocyte activation and recruitment. Recruited leukocytes subsequently infiltrate through the endothelium and induce key effector cells to secrete excessive and abnormal extracellular matrix (ECM). Enhanced deposition of ECM is a histological hallmark of CAN. This paper aims to present a concise yet accurate and up-to-date review of the literature concerning the aetiological factors and pathological processes which are present in the generation of CAN.

Morbidity Rates With Reduced Mycophenolate Mofetil Dosage: A Single-Center Experience

OBJECTIVE

Mycophenolate Mofetil (MMF) is a key component of available immunosuppressant regimens for transplantation. Traditionally a dose of 2 g/d is utilized, with the incidence of side effects, most notably gastrointestinal, being well known to transplant teams. The aim of this study was to assess the incidence of side effects and rejection rates with reduced doses compared to standard regimens of MMF.

METHODS

Case notes of 117 renal transplants performed from 2002 to 2004 were reviewed retrospectively for the incidence of side effects and rejection rates for MMF doses of 1 g twice a day (n = 86) versus 500 mg twice a day (n = 27).

RESULTS

All patients received MMF, steroids, and a calcineurin inhibitor or sirolimus. The incidence of side effects was higher at 1 g twice a day. Seventy-nine percent of the patients required dose reductions due to side effects. The incidence of acute rejection episodes was similar in both groups.

CONCLUSION

The balance between adequate immunosuppression, side effects, and the risk of rejection is a constant dilemma faced by transplant surgeons. This study showed a reduced side effect profile with similar rejection rates when using a lower-dose regimen of MMF. This may have implications for future immunosuppressive protocols.

Effects of arterial pressure in an experimental isolated haemoperfused porcine kidney preservation system

Background

Normothermic preservation provides metabolic support to an ischaemically damaged organ before use as a kidney transplant. Optimal conditions for ex vivo preservation have not yet been established. This study examined the effects of arterial pressure on renal preservation using isolated haemoperfused kidneys.

Methods

An isolated organ preservation system, developed using cardiopulmonary bypass technology, was used to perfuse porcine kidneys with normothermic oxygenated blood. Groups of kidneys (n = 6) were perfused at a mean arterial pressure of 95, 75 or 55 mmHg.

Results

Kidneys perfused at the higher mean arterial pressures of 95 and 75 mmHg demonstrated improved renal function: mean(s.d.) area under the curve (AUC) for creatinine clearance 71(19) and 55(30) respectively versus 14(12) in the 55-mmHg group, P = 0·002; AUC for serum creatinine 938(140) and 1290(394) versus 2404(595), P = 0·003. The higher perfusion pressures were also associated with better acid–base homeostasis and improved renal haemodynamics.

Conclusion

Mean arterial pressures of either 95 or 75 mmHg were capable of sustaining physiological renal function, but kidneys in the 95-mmHg group demonstrated superior renal function overall.

Primary endoluminal stenting of transplant renal artery stenosis from cadaver and non-heart-beating donor kidneys

This study evaluated the efficacy of primary endovascular stenting in cases of transplant renal artery stenosis (TRAS) from cadaver and non-heart-beating donor kidneys. Patients with TRAS (n = 13) from a single-centre transplant population (n = 476) were treated by primary percutaneous angioplasty and endovascular stenting. The short-term efficacy of this intervention is demonstrated in terms of serum creatinine, glomerular filtration rate (GFR) biochemical, anti-hypertensive medications and mean arterial blood pressure control. Stenting for TRAS was performed in male (n = 10) and female (n = 3) recipients. The median age at transplantation was 55 yr (range 10-67 yr). Stenting occurred at a median duration of 410 d post-transplantation (range 84-5799 d). Mean serum creatinine (pre, 247 micromol/L; post, 214 micromol/L; p = 0.002), GFR (pre, 82.6 mL/min; post, 100.9 mL/min; p < 0.001), arterial blood pressure (pre, 104 mmHg; post, 97 mmHg; p = 0.036) and the number of anti-hypertensive medications required (pre, 3.4; post, 3.0; p = 0.002) showed significant improvement after post-endovascular therapy. There were no serious complications encountered. Primary endovascular stenting of TRAS produces a significant improvement in biochemical parameters of renal graft function and in blood pressure stability, with the benefit of low patient morbidity and single arterial puncture. Primary endoluminal stenting of TRAS is a safe and effective procedure for the treatment of TRAS.