Reproducible Model for Kidney Autotransplantation in Pigs

Novel Kidney Auto Transplantation Technique for Ischemia-Reperfusion Studies

Large animal studies of long-term ischemia reperfusion are hampered by the use of immunosuppressive drugs to inhibit the influence of the allogeneic response. In small animals, this can be controlled by using inbred strains of the animal. For obvious reasons, this is not possible in large animals such as pigs. Since studies in pigs usually are the last step before first-in-man studies, this remains a problem trying to resemble a clinical situation. In the following short paper, we describe a novel auto kidney transplantation model that can be used for long term ischemia reperfusion studies. We also suggest a control setting to balance out the possible influence of an increased surgical trauma.

Normothermic machine perfusion of ischaemically damaged porcine kidneys with autologous, allogeneic porcine and human red blood cells

In porcine kidney auto-transplant models, red blood cells (RBCs) are required for ex-vivo normothermic machine perfusion (NMP). As large quantities of RBCs are needed for NMP, utilising autologous RBCs would imply lethal exsanguination of the pig that is donor and recipient-to-be in the same experiment. The purpose of this study was to determine if an isolated porcine kidney can also be perfused with allogeneic porcine or human RBCs instead. Porcine kidneys, autologous and allogeneic blood were obtained from a local slaughterhouse. Human RBCs (O-pos), were provided by our transfusion laboratory. Warm ischaemia time was standardised at 20 minutes and subsequent hypothermic machine perfusion lasted 1.5–2.5 hours. Next, kidneys underwent NMP at 37°C during 7 hours with Williams' Medium E and washed, leukocyte depleted RBCs of either autologous, allogeneic, or human origin (n = 5 per group). During perfusion all kidneys were functional and produced urine. No macroscopic adverse reactions were observed. Creatinine clearance during NMP was significantly higher in the human RBC group in comparison with the allogeneic group (P = 0.049) but not compared to the autologous group. The concentration of albumin in the urine was significantly higher in the human RBC group (P <0.001) compared to the autologous and allogeneic RBC group. Injury marker aspartate aminotransferase was significantly higher in the human RBC group in comparison with the allogeneic group (P = 0.040) but not in comparison with the autologous group. Renal histology revealed glomerular and tubular damage in all groups. Signs of pathological hyperfiltration and microvascular injury were only observed in the human RBC group. In conclusion, perfusion of porcine kidneys with RBCs of different origin proved technically feasible. However, laboratory analysis and histology revealed more damage in the human RBC group compared to the other two groups. These results indicate that the use of allogeneic RBCs is preferable to human RBCs in a situation where autologous RBCs cannot be used for NMP.

Postconditioning effects of argon or xenon on early graft function in a porcine model of kidney autotransplantation

BACKGROUND

Ischaemia-reperfusion injury is inevitable during renal transplantation and can lead to delayed graft function and primary non-function. Preconditioning, reconditioning and postconditioning with argon and xenon protects against renal ischaemia-reperfusion injury in rodent models. The hypothesis that postconditioning with argon or xenon inhalation would improve graft function in a porcine renal autotransplant model was tested.

METHODS

Pigs (n = 6 per group) underwent left nephrectomy after 60 min of warm ischaemia (renal artery and vein clamping). The procured kidney was autotransplanted in a separate procedure after 18 h of cold storage, immediately after a right nephrectomy. Upon reperfusion, pigs were randomized to inhalation of control gas (70 per cent nitrogen and 30 per cent oxygen), argon (70 per cent and 30 per cent oxygen) or xenon (70 per cent and 30 per cent oxygen) for 2 h. The primary outcome parameter was peak plasma creatinine; secondary outcome parameters included further markers of graft function (creatinine course, urine output), graft injury (aspartate aminotransferase, heart-type fatty acid-binding protein, histology), apoptosis and autophagy (western blot, terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) staining), inflammatory mediators and markers of cell survival/growth (mRNA and tissue protein quantification), and animal survival. Results are presented as median (i.q.r.). ANOVA and Kruskal-Wallis tests were used where indicated.

RESULTS

Peak plasma creatinine levels were similar between the groups: control 20·8 (16·4-23·1) mg/dl, argon 21·4 (17·1-24·9) mg/dl and xenon 19·4 (17·5-21·0) mg/dl (P = 0·607). Xenon was associated with an increase in autophagy and proapoptotic markers. Creatinine course, urine output, injury markers, histology, survival and inflammatory mediators were not affected by the intervention.

CONCLUSION

Postconditioning with argon or xenon did not improve kidney graft function in this experimental model. Surgical relevance Ischaemia-reperfusion injury is inevitable during renal transplantation and can lead to delayed graft function and primary non-function. Based on mainly small animal experiments, noble gases (argon and xenon) have been proposed to minimize this ischaemia-reperfusion injury and improve outcomes after transplantation. The hypothesis that postconditioning with argon or xenon inhalation would improve graft function was tested in a porcine kidney autotransplantation model. The peak plasma creatinine concentration was similar in the control, argon and xenon groups. No other secondary outcome parameters, including animal survival, were affected by the intervention. Xenon was associated with an increase in autophagy and proapoptotic markers. Despite promising results in small animal models, postconditioning with argon or xenon in a translational model of kidney autotransplantation was not beneficial. Clinical trials would require better results.

Plasmatic Villin 1 Is a Novel In Vivo Marker of Proximal Tubular Cell Injury During Renal Ischemia-Reperfusion

BACKGROUND

Early detection of acute kidney injury (AKI), a common condition with a high mortality risk, can be facilitated by specific and reliable biomarkers. Villin 1, a protein typically found in the brush borders of proximal tubular cells, has been detected in urine of patients with AKI, but its possible release in plasma remains unexplored.

METHODS

We measured the presence of villin 1 by immunohistochemistry on kidney sections and by Western blotting in plasma samples from rats subjected to renal ischemia-reperfusion injury, pigs subjected to renal transplantation and liver transplantation patients that developed AKI. Moreover, rats were treated with necrostatin-1, an inhibitor of programmed necrosis (necroptosis), which occurs in renal tubular cells during AKI. Villin 1 levels were compared with other renal injury markers (creatinine, aspartate transaminase, and heart-type fatty acid binding protein).

RESULTS

During AKI, plasmatic villin 1 levels corresponded with the severity of kidney injury and dysfunction. Its detection in plasma was associated with a redistribution in the kidney tissue. Unlike the levels of other markers, plasmatic villin 1 decreased already after a short (3 hours) treatment with necrostatin-1 during renal ischemia-reperfusion injury. The presence of plasmatic villin 1 was confirmed in patients who experienced AKI after liver transplantation.

CONCLUSIONS

Villin 1 is released in plasma during AKI and shows potential as an early marker for proximal tubular injury/necrosis and warrants further investigation.

Establishment of laparoscopic live donor nephrectomy in a porcine model: techniques and outcomes in 44 pigs

BACKGROUND

Laparoscopic live donor nephrectomy has replaced open donor nephrectomy in most patients due to numerous benefits. A live animal model is required to equip surgeons with the necessary skills to perform such a procedure with minimal risk of complications. The aim of this study was to establish the technique for laparoscopic live donor nephrectomy in a porcine (Sus scrofa) model.

MATERIALS AND METHODS

This study was approved by the Animal Ethics Committee of the university. Forty-four pigs underwent laparoscopic live donor nephrectomy. The left kidney was removed with a standardized four-port technique, with a small suprapubic incision to facilitate kidney delivery.

RESULTS

All 44 procedures were performed successfully, with no intraoperative complications or conversion to open surgery. There was no apparent damage to any of the kidney grafts. The mean surgical time was 118.3 (±20.7) minutes. There was a small, but statistically insignificant, decrease in surgical time throughout the duration of the study. Several subjects had minor variations in the anatomy of the renal vasculature.

CONCLUSIONS

This series has developed and proven a training model for laparoscopic donor nephrectomy in pigs. This training model will allow surgeons to develop laparoscopic proficiency in a live donor, to be used in conjunction with human cadaveric training.

Endothelial Nitric Oxide Synthase and Endothelin-1 Expression in the Early Post-Porcine Kidney Autotransplantation Period

BACKGROUND

The aim of this study was the assessment of endothelial nitric oxide synthase (eNOS) and endothelin-1 (EDN-1) expression in porcine kidneys on the 14th and 30th days after the autotransplantation procedure.

METHODS

The research was conducted on 12 animals that underwent a left renal transplantation procedure with further standardized rinsing and 24-hour storage in 4°C; subsequently, the kidneys were implanted in the right retroperitoneal space after right-sided nephrectomy. Removed kidneys were examined (group 0). Six randomly chosen animals (group 1) were under observation for 14 days and 6 others (group 2) for 30 days.

RESULTS

After these observation periods, euthanasia was performed on the animals and 4-g samples were collected from the renal cortex and medulla. The Western blot technique was used to detect the eNOS and EDN-1 expression at the protein level. The obtained results are presented as absolute values of integrated optical density. Stable graft function was observed in all animals from the 2nd day after the procedure. eNOS in group 1 reached the mean value of 1.064 and was statistically significantly lower than in group 2 (2.085) or in the control group 0 (3.318). In the case of EDN-1 expression on 14th day after transplantation, the medium level was reported (0.248), which was similar to group 0 (0.216), whereas group 2 presented values 2 times higher (0.743).

CONCLUSIONS

A lowered eNOS level in the organ was observed on the 14th day after autotransplantation of a pig kidney; further enzyme normalization is associated with increased EDN-1 expression.

Toll-like receptors 2 and 4 in pigs' kidneys early after autotransplantation procedure

OBJECTIVES

The aim of this paper was to evaluate mRNA expression of Toll-like receptors 2 (TLR2) and 4 (TLR4) and the adaptor protein myeloid differentiation primary-response protein 88 (MyD88) in pigs' kidneys 14 and 30 days after autotransplantation.

METHODS

The research was conducted on 12 animals that underwent left renal transplantation procedure with further standardized rinsing with Biolasol solution and 24 hours' storage in 4°C; subsequently the kidneys were implanted in the right retroperitoneal space after right-side nephrectomy. Six randomly chosen animals (group I) were under observation for 14 days, the other 6 (group II) for 30 days. After these observation periods, the animals were killed and 4-g samples were collected from the renal cortex and medulla.

RESULTS

Expression of mRNA in homogenates of collected samples were determined with the use of reverse-transcription polymerase chain reaction analysis. Obtained results in both groups, presented in relation to GAPDH, were compared with the use of Mann-Whitney U test. Stable graft function was observed in all animals from the 2nd day after the procedure. TLR2 in group I reached the mean value of 3.64 and was statistically significantly higher than in group II (2.19). Inverse proportion was observed in case of mRNA for TLR4: group II presented 2 times higher value than group I (0.25 vs 0.11). Similarly, significant difference was observed in MyD88 (group I, 0.067; group II, 0.45).

CONCLUSIONS

At 14 days after autotransplantation of a pig kidney, mRNA expression for TLR2 is dominant; later, expression increases for TLR4 and MyD88.

Neutrophil gelatinase-associated lipocalin, a new biomarker candidate in perfusate of machine-perfused kidneys: a porcine pilot experiment

The enduring kidney graft shortage has led to the increasing use of expanded-criteria donors as well as kidneys donated after cardiac death, triggering the revival of machine perfusion preservation. Indeed, machine perfusion not only preserves these kidneys better than static cold storage, but also has the potential to evaluate them. The presence of certain biomarkers, among them aspartate aminotransferase (AST) and heart-type fatty acid binding protein (H-FABP), has been demonstrated in the perfusate of human kidneys, making them potentially useful as biomarkers of graft quality. Neutrophil gelatinase-associated lipocalin (NGAL) which is believed to be released upon renal tubular cell injury is another biomarker candidate. However, because it is also released from neutrophils, it is currently unclear whether NGAL is a direct or indirect, inflammatory-mediated marker of kidney injury. To resolve this issue we established a pilot experiment to study the concentrations of AST, H-FABP, and NGAL in the perfusates of 6 porcine kidneys that were exposed to incremental periods of warm ischemia before machine perfusion for 22 hours. An ex vivo porcine model was chosen because preclinical large animal work remains necessary to refine machine perfusion technology and because the presence of these markers in perfusates of porcine kidneys had not been shown previously. All 3 biomarkers were detectable in the cold acellular perfusate; their release seemed to be proportionate to the degree of warm injury, albeit that this must be confirmed in a larger sample. In conclusion, NGAL is directly released by ischemically damaged kidneys, independent of neutrophil activation. In addition to NGAL, the determination of AST and H-FABP in perfusates of machine-perfused porcine kidneys is also feasible. Determination of these markers may be added to the arsenal of research tools for preclinical preservation research.

Laparoscopic surgery for kidney orthotopic transplant in the pig model

The authors report that a laparoscopic technique could facilitate orthotopic kidney transplantation in selected patients.

Background and Objectives:

Laparoscopic surgery has rapidly expanded in surgical practice with well-accepted benefits of minimal incision, less analgesia, better cosmetics, and quick recovery. The surgical technique for kidney transplantation has remained unchanged since the first successful kidney transplant in the 1950s. Over the past decade, there were only a few case reports of kidney transplantation by laparoscopic or robotic surgery. Therefore, the aim of this study is to develop a laparoscopic technique for kidney transplantation at the region of the native kidney.

Methods:

After initial development of the laparoscopic technique for kidney transplant in cadaveric pigs, 5 live pigs (Sus scrofa, weighing 45–50 kg) underwent laparoscopic kidney transplant under general anesthesia. First, laparoscopic donor nephrectomy was performed, and then the kidney was perfused and preserved with cold Ross solution. The orthotopic auto-transplant was subsequently performed using the laparoscopic technique. The blood flow of the kidney graft was assessed using Doppler ultrasonography, and urine output was monitored.

Results:

The laparoscopic kidney transplant was successful in 4 live pigs. Immediate urine output was observed in 3 pigs. The blood flow in the kidney was adequate, as determined using Doppler ultrasonography.

Conclusion:

It has been shown that laparoscopic kidney orthotopic transplant is feasible and safe in the pig model. Immediate kidney graft function can be achieved. A further study will be considered to identify the potential surgical morbidity and mortality after recovery in a pig model before translating the technique to clinical human kidney transplantation.

Laparoscopic kidney orthotopic transplant: preclinical study in the pig model

BACKGROUND

Laparoscopic surgery has rapidly expanded in clinical practice replacing conventional open surgery over the last three decades. Laparoscopic donor nephrectomy has been favored due to its multiple benefits. The aim of this study was to explore the safety and feasibility of kidney transplantation by a laparoscopic technique in a pig model.

MATERIALS AND METHODS

The study was approved by the university animal ethics committee. Eight female pigs (Sus Scrofra, weighing 45-50 kg) were divided into 2 groups: group I included 4 animals that underwent laparoscopic kidney orthotopic transplantation on the left side. The right kidney was remained functional in situ. The pigs recovered and were observed for 1 week. In the 4 hosts group II pigs underwent a laparoscopic kidney transplantation on the left side. With simultaneous clipping of the right ureter. After recovery, the pigs were observed for 4 weeks. A laparotomy for examination was performed prior to euthanasia.

RESULTS

All 4 group I pigs survived for 1 week. The laparotomy showed normal graft perfusion with wall patent renal artery and vein as well as satisfactory urine output upon transection of ureter in 3 hosts. Renal artery stenosis occurred in one pig. In The Immediate kidney graft function was achieved in 3 group II pigs. The fourth died following extubation due to laryngospasm despite a functional graft. The average creatinine levels were 195.5 μmol/L on day 3; 224.5 μmol/L at week 1; 127 μmol/L at week 2; 182.7 umol/L at week 3; and 154.7 umol/L at week 4.

CONCLUSION

Laparoscopic kidney transplantation was feasible and safe in a pig model with immediate graft function. This study will provide further evidence to support application of laparoscopic technique to human kidney transplant.

Role of warm ischemia on innate and adaptive responses in a preclinical renal auto-transplanted porcine model

Background

Deceased after cardiac arrest donor are an additional source of kidney graft to overcome graft shortage. Deciphering the respective role of renal warm and cold ischemia is of pivotal interest in the transplantation process.

Methods

Using a preclinical pig model of renal auto-transplantation, we investigated the consequences of warm and cold ischemia on early innate and adaptive responses as well as graft outcome. Kidneys were subjected to either 60 min-warm ischemia (WI) or auto-transplanted after cold storage for 24 h at 4°C (CS), or both conditions combined (WI + CS). Renal function, immune response and cytokine expression, oxidative stress and cell death were investigated at 3 h, 3 and 7 days (H3, D3 and D7) after reperfusion. At 3 months, we focused on cell infiltration and tissue remodelling.

Results

WI + CS induced a delayed graft function linked to higher tubular damage. Innate response occurred at D3 associated to a pro-oxidative milieu with a level dependent on the severity of ischemic injury whereas adaptive immune response occurred only at D7 mainly due to CS injuries and aggravated by WI. Graft cellular death was an early event detected at H3 and seems to be one of the first ischemia reperfusion injuries. These early injuries affect graft outcome on renal function, cells infiltration and fibrosis development.

Conclusions

The results indicate that the severe ischemic insult found in kidneys from deceased after cardiac arrest donor affects kidney outcome and promotes an uncontrolled deleterious innate and adaptive response not inhibited 3 months after reperfusion.

Pig kidney transplantation: an up-to-date guideline

BACKGROUND

Swine and human beings have many aspects in common that make swine a well-characterized large animal model for kidney transplantation (KTx). However, pigs have some peculiar anatomical characteristics that standardized techniques must adapt to. The aim of this study was to prepare an up-to-date guideline for porcine KTx.

METHODS

To achieve this goal, we performed a Medline search using the terminology 'kidney' or 'renal' and 'transplantation' and 'pig' or 'swine' or 'porcine'. We found over 1,300 published articles since 1963. Only 13 studies focused on the surgical aspect. Furthermore, we reviewed related books and articles about swine anatomical characteristics and surgery. Finally, our experimental experiences of KTx during the last few decades were added to this collection.

RESULTS

Proper hosting, fasting, anesthesia, medical therapy and monitoring can prevent postoperative complications. Explantation with a Carrel patch of the aorta facilitates the implantation and prevents future stenosis. Native nephrectomy makes the follow-up of the implanted organ more precise. KTx in the infrarenal fossa via end-to-side anastomosis to the aorta and inferior vena cava followed by ureteroureterostomy are the recommended options for KTx in pigs compared to other possible methods.

CONCLUSION

Pigs, with respect to their characterizations, constitute one of the best large animal models for KTx. Preoperative preparations are as important as the intra- and postoperative management. Using the most adaptable methods of surgery with respect to the specific anatomical characteristics of pigs can prevent undermining the studies and avoid preventable complications and pitfalls.

Contribution of large pig for renal ischemia-reperfusion and transplantation studies: the preclinical model

Animal experimentation is necessary to characterize human diseases and design adequate therapeutic interventions. In renal transplantation research, the limited number of in vitro models involves a crucial role for in vivo models and particularly for the porcine model. Pig and human kidneys are anatomically similar (characterized by multilobular structure in contrast to rodent and dog kidneys unilobular). The human proximity of porcine physiology and immune systems provides a basic knowledge of graft recovery and inflammatory physiopathology through in vivo studies. In addition, pig large body size allows surgical procedures similar to humans, repeated collections of peripheral blood or renal biopsies making pigs ideal for medical training and for the assessment of preclinical technologies. However, its size is also its main drawback implying expensive housing. Nevertheless, pig models are relevant alternatives to primate models, offering promising perspectives with developments of transgenic modulation and marginal donor models facilitating data extrapolation to human conditions.