Analysis of DCD porcine kidney graft viability during sub-normothermic perfusion using magnetic resonance imaging and spectroscopy

Objective

Better preservation strategies for the storage of donation after circulatory death grafts could increase the number of kidneys available and improve patient survival. Warm (22°C and 37°C) ex-vivo perfusion has emerged as an alternative to hypothermia and a feasible strategy to recover/repair organs, but the underlying mechanism remains elusive. Here, using magnetic resonance imaging spectroscopy (MRIs), we evaluated kidney viability, and adenosine triphosphate (ATP) production during sub-normothermic ex-vivo kidney perfusion (22°C + O2) versus hypothermic machine perfusion (4°C and 4°C + O2) in a porcine kidney autotransplantation model.

Methods

To mimic donation after circulatory death (DCD), kidneys from 8-month-old pigs underwent 60 minutes of warm ischemia, prior to procurement. Kidneys were then perfused ex-vivo at 4°C with (4°C + O2), and without oxygen (4°C) or at 22°C (22°C + O2) before autotransplantation. During the ex-vivo perfusion, and after transplantation we assessed energy metabolites using MRIs. In addition, we performed Gadolinum (Gd) perfusion sequences. Each sample underwent histopathological analyzing and scoring. mRNA expression was analyzed on renal biopsies at various time points.

Results

Using MRI, we found that in pig kidney, total ATP content was 4 times higher during ex-vivo perfusion at sub-normothermic temperature compared to cold perfusion, with or without oxygen. At 22°C, ATP levels gradually increased up to 10 hrs of perfusion, then progressively declined. Similarly, AMP content was increased in SNOP perfused organs, then slowly consumed. over time. In addition, 22°C + O2 improved cortical and medullary perfusion (Gd elimination). Finally, sub-normothermic ex-vivo perfused graft had lower grade of histological damages 1 hour after transplantation compared to cold perfused organs (injury score 22°C + O2 : 8.8–12.2, 4°C : 13.5–18.8, 4°C + O2 : 17.5–18.5).

Conclusion

In kidneys, sub-normothermic perfusion improved graft viability when compared with hypothermic perfusions. These results suggest that sub-normothermic ex-vivo kidney perfusion might dampen the negative effect of warm ischemia and promote kidney metabolism such as ATP production. Future clinical studies will define the benefits of sub-normothermic ex-vivo kidney perfusion in improving kidney graft function, and patient's survival.

Preliminary experience with the new off-the-shelf 4 inner branches E-nside for the treatment of complex aortic disease

Objective

In case of complex aortic aneurysmal disease, fenestrated or branched EVAR (b/f-EVAR) is considered as a valid and safe alternative to open surgery. However, one the main limitation is the time required for manufacture, limiting its use in emergent situations. The new off-the-shelf 4 inner branches E-nside (Jotec, Hechingen, Germany) has been developed to offer a solution in such circumstances. The aim of this study was to report our preliminary monocentric experience with this new device.

Methods

Retrospective analysis of prospective data retrieved from 1 center between November 2020 and January 2022 was done. Endpoints were technical success, postoperative morbidity, rate of endoleak and any aneurysm-related re-interventions during follow-up.

Results

In this study, 15 patients (mean age 73 years, range 59–90) were identified. There was a majority of male (9/15) and all of them but 3 were asymptomatic. The mean aneurysmal diameter was 60 mm (range 50–100). There were 3 cases of juxtarenal aortic aneurysms (20%), 1 Crawford type I (7%), 4 type II (27%), 4 type III (27%) and 3 type IV (20%) aneurysms. In 7 cases, a 2-steps procedure was done with a TEVAR first followed by Enside implantation. There was a technical success in 93% with 1 open conversion for a mesenterical bypass. There was no death in the post-operative period. During the post-operative period, 33% of patients (5/15) presented complications with 3 complications related to the femoral or iliac access and 2 cases of spinal cord ischemia (13%). One case occurred in an emergent setting of a type III aneurysm rupture. The other case was the open conversion and the patient also developed a colic ischemia and finally died 4 months alter. The mean length of stay was 9 days. During the follow-up, 2 reinterventions were necessary, 1 for a type Ic endoleak with distal prolongation of the stent and 1 renal stent occlusion treated by relining. The overall target vessel patency was 98%.

Conclusion

The use of the off-the-shelf 4 inner branches E-nside appears to be safe with good technical success for the treatment of complex aortic aneurysmal disease. It is associated with an acceptable rate of complications and allows for treatment of a wide variety of diseases in an emergent setting. Further patients and longer follow-up are required to better evaluate the exact role of this new device.

Design of the OptiSurg trial: Multicenter open-label randomized controlled trial of time restricted feeding (TRF) vs regular dietary advices in patient undergoing femoral endarterectomy

Objective

Vascular patients suffer some of the highest complications rates. Surprisingly, there is no uniformly accepted medical therapy to reduce complications in these patients. Time restricted feeding (TRF) is an approach that emphasizes energy intake limited to certain windows of time within the 24-hour cycle, without restrictions on any calories or macronutrients. In healthy young human, TRF improves cardio-metabolic fitness. However, there is a lack of research on TRF in patient undergoing surgery, and suffering from cardiovascular diseases. This study aims to investigate the feasibility and efficacy of a pre-operative 2-week, 10-hour TRF in patient undergoing vascular surgery.

Methods

The OptiSurg Study is a randomized open-label clinical trial, that plan to enroll 40 patients, undergoing elective femoral endarterectomy. Only Fontaine stage II peripheral artery disease, and a BMI ≥ 20 kg/m2 are included. Patients are randomized with a 1:1 ratio to either the control or intervention group. The control group receives diet nutritional counselling (standard of care, SOC). The intervention group receives the same SOC and a self-selected 10-hour TRE window. After the surgery, patients will be on SOC only, and followed every 3 months up to 1 year. Primary endpoint is a composite of death, myocardial infarction, stroke, and surgical re-intervention at 1 month post-operative. Blood glucose, body weight, body composition, biomarkers (neuroendocrine, inflammatory and metabolic), sleep and quality of life will also be examined. Temporal calorie intake is monitored with the smartphone application myCircadianClock preoperatively. VascuQoL-6 is used to monitor quality of life.

Results

9 participants were enrolled since the start of the recruitment in February 2021, 4 were randomized in the 8 hours TRF intervention, and 5 to SOC. They all completed the study: 7 men and 2 women, age 73, 53–87 (median, min-max) years. Using the myCircadianClock app, adherence to the TRF was >90% (Figure 1).

Conclusion

Our preliminary experience seems to demonstrate that a 2-week TRF regimen before vascular surgery is feasible. The complete results will be disseminated through future peer-reviewed manuscripts, reports and presentations.

Ex vivo analysis of graft viability using 31P magnetic resonance imaging spectroscopy

Objective

Expansion in organ supply has been proposed through the use of organs after circulatory death (donation after circulatory death [DCD]) in order to face the chronic shortage of kidneys for transplantation. However, many DCD grafts are discarded because of long warm ischemia times, and the absence of reliable non-invasive means to determine kidney viability. P magnetic resonance imaging (pMRI) spectroscopy is a noninvasive method to detect high-energy phosphate metabolites, such as ATP. However, the reliability of pMRI to predict kidney energy state, and its viability before transplantation remain also unknown.

Methods

To mimic DCD, pig kidneys underwent 0, 30 min or 60 min of warm ischemia, before oxygenated hypothermic machine perfusion (HMP). During the ex vivo perfusion, we assessed energy metabolites and Gadolinium elimination using pMRI. Each sample underwent histopathological scoring.

Results

Using pMRI, we found that in pig kidney, ATP was rapidly generated in presence of oxygen (100 kPa), which remained stable up to 22 h. Warm ischemia (60 min) induced significant histological damages, delayed cortical and medullary Gadolinium elimination (perfusion), and reduced ATP levels, but not its precursors (AMP). Finally, ATP levels and kidney perfusion both inversely correlated with the severity of kidney histological injury.

Conclusion

ATP levels, and kidney perfusion measurements using pMRI, are biomarkers of kidney injury after warm ischemia. Future work will define the role of pMRI in predicting kidney graft viability and patient's survival.

Hydrogen sulfide (H2S) reduces oxygen and ATP consumption in the isolated perfused pig kidney

Objective

Organ donation after circulatory death [DCD] has the potential to reduce the shortage of kidneys available for transplantation. However, many DCD grafts are discarded because of long warm ischemia times. Strategies reducing oxygen demand may minimize damages caused by ischemia/reperfusion injury. Ex-vivo, Hydrogen sulfide (H2S) reduces oxygen and ATP consumption of the isolated perfused kidney, reduces inflammation and improves renal function following ischemia reperfusion injury in rodents. However, the benefits and applicability of H2S in clinically relevant model remain unknown.

Methods

To mimic DCD, pig kidneys underwent 0 or 60 min of warm ischemia, before oxygenated hypothermic machine perfusion (HMP). NaHS (100µM), an H2S donor, was added to the perfusion media or injected as an intra-arterial bolus before warm ischemia. After 2 hours of HMP, kidneys were transplanted and reperfused for 1 hour before harvest. Kidney function was assesses before, after and during ex vivo perfusion by measuring energy metabolites, Gadolinium elimination by pMRI and histopathological scoring.

Results

Warm ischemia (60 min) induced significant histological damages, delayed cortical and medullary Gadolinium elimination (perfusion), and reduced ATP levels, but not its precursors (AMP). As expected, ATP levels and kidney perfusion both inversely correlated with the severity of kidney histological injury. NaHS reduced metabolism during warm ischemia, and seemed to increase kidney ATP levels and viability after reperfusion.

Conclusion

Our preliminary data suggest that the H2S donor NaHS reduces kidney metabolism and protects from warm ischemia. Further experiments will identify the best administration protocol and the clinical relevance of H2S supplementation in the context of organ preservation.

Brief dietary protein dilution using carbohydrate rich drink protects from kidney ischemia and reperfusion injuries trough IGF-1

Objective

Lifelong low-protein, high-carbohydrate diets extend lifespan in rodent. Consistently in human, the administration of oral carbohydrate drinks the day before surgery might improve clinical outcome. However, the fundamental questions of what represents a macronutritionally balanced diet, and how this impact surgical stress remain unanswered.

Methods

Here, we induced dietary protein dilution by giving mice ad libitum access to 50% sucrose water, without any food restriction. Mice were randomized into four regimens: regular diet (17,6 % protein, Ctrl), and a low protein diet (5.6% protein, LP), with or without high sucrose water (50% sucrose) for 7 days. At the end of the preconditioning, calorimetric data, fasting blood glucose, IGF1, glucose tolerance, and finally resistance to renal failure following a bilateral renal ischemia-reperfusion was evaluated.

Results

We demonstrate that access to carbohydrate drinks promotes dietary protein restriction despite a total caloric intake that was twice higher. This short-term self-restriction in daily protein, independent of caloric intake, improved insulin sensitivity, reduced serum triglyceride, and enhanced mitochondrial respiration as well as energy expenditure. Importantly, a 7-day pre-conditioning protein dilution regimen promotes recovery following kidney ischemia and reperfusion (IRI), a model of surgical stress. This protection from kidney IRI inversely correlated with pre-operative protein intake, but not carbohydrate or fat. The benefit of a low protein, high-carbohydrate regimen was independent of the protein sensing pathway eIF2α/ATF4, NRF2 and hydrogen sulfide, but instead required Insulin-like growth factor 1 (IGF1) downregulation.

Conclusion

These results support further clinical studies of a low protein diet combined with carbohydrate drinks prior to surgery.