Acellular Perfusate is an Adequate Alternative to Packed Red Blood Cells During Normothermic Human Kidney Perfusion

Background

Brief normothermic machine perfusion is increasingly used to assess and recondition grafts before transplant. During normothermic machine perfusion, metabolic activity is typically maintained using red blood cell (RBC)-based solutions. However, the utilization of RBCs creates important logistical constraints. This study explored the feasibility of human kidney normothermic perfusion using William's E-based perfusate with no additional oxygen carrier.

Methods

Sixteen human kidneys declined for transplant were perfused with a perfusion solution containing packed RBCs or William's E medium only for 6 h using a pressure-controlled system. The temperature was set at 37 °C. Renal artery resistance, oxygen extraction, metabolic activity, energy metabolism, and histological features were evaluated.

Results

Baseline donor demographics were similar in both groups. Throughout perfusion, kidneys perfused with William's E exhibited improved renal flow (P = 0.041) but similar arterial resistance. Lactic acid levels remained higher in kidneys perfused with RBCs during the first 3 h of perfusion but were similar thereafter (P = 0.95 at 6 h). Throughout perfusion, kidneys from both groups exhibited comparable behavior regarding oxygen consumption (P = 0.41) and reconstitution of ATP tissue concentration (P = 0.55). Similarly, nicotinamide adenine dinucleotide levels were preserved during perfusion. There was no evidence of histological damage caused by either perfusate.

Conclusions

In human kidneys, William's E medium provides a logistically convenient, off-the-shelf alternative to packed RBCs for up to 6 h of normothermic machine perfusion.

Short-term hypercaloric carbohydrate loading increases surgical stress resilience by inducing FGF21

Dietary restriction promotes resistance to surgical stress in multiple organisms. Counterintuitively, current medical protocols recommend short-term carbohydrate-rich drinks (carbohydrate loading) prior to surgery, part of a multimodal perioperative care pathway designed to enhance surgical recovery. Despite widespread clinical use, preclinical and mechanistic studies on carbohydrate loading in surgical contexts are lacking. Here we demonstrate in ad libitum-fed mice that liquid carbohydrate loading for one week drives reductions in solid food intake, while nearly doubling total caloric intake. Similarly, in humans, simple carbohydrate intake is inversely correlated with dietary protein intake. Carbohydrate loading-induced protein dilution increases expression of hepatic fibroblast growth factor 21 (FGF21) independent of caloric intake, resulting in protection in two models of surgical stress: renal and hepatic ischemia-reperfusion injury. The protection is consistent across male, female, and aged mice. In vivo, amino acid add-back or genetic FGF21 deletion blocks carbohydrate loading-mediated protection from ischemia-reperfusion injury. Finally, carbohydrate loading induction of FGF21 is associated with the induction of the canonical integrated stress response (ATF3/4, NF-kB), and oxidative metabolism (PPARγ). Together, these data support carbohydrate loading drinks prior to surgery and reveal an essential role of protein dilution via FGF21.

Sodium Hydrosulfide Treatment During Porcine Kidney Ex Vivo Perfusion and Transplantation

Background

In rodents, hydrogen sulfide (H2S) reduces ischemia-reperfusion injury and improves renal graft function after transplantation. Here, we hypothesized that the benefits of H2S are conserved in pigs, a more clinically relevant model.

Methods

Adult porcine kidneys retrieved immediately or after 60 min of warm ischemia (WI) were exposed to 100 µM sodium hydrosulfide (NaHS) (1) during the hypothermic ex vivo perfusion only, (2) during WI only, and (3) during both WI and ex vivo perfusion. Kidney perfusion was evaluated with dynamic contrast-enhanced MRI. MRI spectroscopy was further employed to assess energy metabolites including ATP. Renal biopsies were collected at various time points for histopathological analysis.

Results

Perfusion for 4 h pig kidneys with Belzer MPS UW + NaHS resulted in similar renal perfusion and ATP levels than perfusion with UW alone. Similarly, no difference was observed when NaHS was administered in the renal artery before ischemia. After autotransplantation, no improvement in histologic lesions or cortical/medullary kidney perfusion was observed upon H2S administration. In addition, AMP and ATP levels were identical in both groups.

Conclusions

In conclusion, treatment of porcine kidney grafts using NaHS did not result in a significant reduction of ischemia-reperfusion injury or improvement of kidney metabolism. Future studies will need to define the benefits of H2S in human, possibly using other molecules as H2S donors.

Modified Tail Vein and Penile Vein Puncture for Blood Sampling in the Rat Model

Blood samples are required in most experimental animal designs to assess various hematological parameters. This paper presents two procedures for blood collection in rats: the lateral tail vein puncture and the dorsal penile vein puncture, which offer significant advantages over other previously described techniques. This study shows that these two procedures allow for fast sampling (under 10 min) and yield sufficient blood volumes for most assays (202 μL ± 67.7 μL). The dorsal penile vein puncture must be done under anesthesia, whereas the lateral tail vein puncture can be done on a conscious, restrained animal. Alternating these two techniques, therefore, enables blood draw in any situation. While it is always recommended for an operator to be assisted during a procedure to ensure animal welfare, these techniques require only a single operator, unlike most blood sampling methods that require two. Moreover, whereas these previously described methods (e.g., jugular stick, subclavian vein blood draw) require extensive prior training to avoid harm to or death of the animal, tail vein and dorsal penile vein puncture are rarely fatal. For all these reasons, and according to the context (e.g., for studies including male rats, during the perioperative or immediate postoperative period, for animals with thin tail veins), both techniques can be used alternately to enable repeated blood draws.

Cystathionine-γ-lyase overexpression modulates oxidized nicotinamide adenine dinucleotide biosynthesis and enhances neovascularization

Objective

Hydrogen sulfide is a proangiogenic gas produced primarily by the transsulfuration enzyme cystathionine-γ-lyase (CGL). CGL-dependent hydrogen sulfide production is required for neovascularization in models of peripheral arterial disease. However, the benefits of increasing endogenous CGL and its mechanism of action have not yet been elucidated.

Methods

Male whole body CGL-overexpressing transgenic (CGLTg) mice and wild-type (WT) littermates (C57BL/6J) were subjected to the hindlimb ischemia model (age, 10-12 weeks). Functional recovery was assessed via the treadmill exercise endurance test. Leg perfusion was measured by laser Doppler imaging and vascular endothelial-cadherin immunostaining. To examine the angiogenic potential, aortic ring sprouting assay and postnatal mouse retinal vasculature development studies were performed. Finally, comparative metabolomics analysis, oxidized/reduced nicotinamide adenine dinucleotide (NAD+/NADH) analysis, and quantitative real-time polymerase chain reaction were performed on CGLWT and CGLTg gastrocnemius muscle.

Results

The restoration of blood flow occurred more rapidly in CGLTg mice. Compared with the CGLWT mice, the median ± standard deviation running distance and time were increased for the CGLTg mice after femoral artery ligation (159 ± 53 m vs 291 ± 74 m [P < .005] and 17 ± 4 minutes vs 27 ± 5 minutes [P < .05], respectively). Consistently, in the CGLTg ischemic gastrocnemius muscle, the capillary density was increased fourfold (0.05 ± 0.02 vs 0.20 ± 0.12; P < .005). Ex vivo, the endothelial cell (EC) sprouting length was increased in aorta isolated from CGLTg mice, especially when cultured in VEGFA (vascular endothelial growth factor A)-only media (63 ± 2 pixels vs 146 ± 52 pixels; P < .05). Metabolomics analysis demonstrated a higher level of niacinamide, a precursor of NAD+/NADH in the muscle of CGLTg mice (61.4 × 106 ± 5.9 × 106 vs 72.4 ± 7.7 × 106 area under the curve; P < .05). Similarly, the NAD+ salvage pathway gene expression was increased in CGLTg gastrocnemius muscle. Finally, CGL overexpression or supplementation with the NAD+ precursor nicotinamide mononucleotide improved EC migration in vitro (wound closure: control, 35% ± 9%; CGL, 55% ± 11%; nicotinamide mononucleotide, 42% ± 13%; P < .05).

Conclusions

Our results have demonstrated that CGL overexpression improves the neovascularization of skeletal muscle on hindlimb ischemia. These effects correlated with changes in the NAD pathway, which improved EC migration.

In vivo magnetic resonance <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msup><mml:mrow/> <mml:mrow><mml:mn>31</mml:mn></mml:mrow> </mml:msup> </mml:mrow> </mml:math> P-Spectral Analysis With Neural Networks: 31P-SPAWNN

PURPOSE

We have introduced an artificial intelligence framework, 31P-SPAWNN, in order to fully analyze phosphorus-31 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msup><mml:mrow/> <mml:mrow><mml:mn>31</mml:mn></mml:mrow> </mml:msup> </mml:mrow> <mml:annotation>$$ {}^{31} $$</mml:annotation></mml:semantics> </mml:math> P) magnetic resonance spectra. The flexibility and speed of the technique rival traditional least-square fitting methods, with the performance of the two approaches, are compared in this work.

THEORY AND METHODS

Convolutional neural network architectures have been proposed for the analysis and quantification of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msup><mml:mrow/> <mml:mrow><mml:mn>31</mml:mn></mml:mrow> </mml:msup> </mml:mrow> <mml:annotation>$$ {}^{31} $$</mml:annotation></mml:semantics> </mml:math> P-spectroscopy. The generation of training and test data using a fully parameterized model is presented herein. In vivo unlocalized free induction decay and three-dimensional <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msup><mml:mrow/> <mml:mrow><mml:mn>31</mml:mn></mml:mrow> </mml:msup> </mml:mrow> <mml:annotation>$$ {}^{31} $$</mml:annotation></mml:semantics> </mml:math> P-magnetic resonance spectroscopy imaging data were acquired from healthy volunteers before being quantified using either 31P-SPAWNN or traditional least-square fitting techniques.

RESULTS

The presented experiment has demonstrated both the reliability and accuracy of 31P-SPAWNN for estimating metabolite concentrations and spectral parameters. Simulated test data showed improved quantification using 31P-SPAWNN compared with LCModel. In vivo data analysis revealed higher accuracy at low signal-to-noise ratio using 31P-SPAWNN, yet with equivalent precision. Processing time using 31P-SPAWNN can be further shortened up to two orders of magnitude.

CONCLUSION

The accuracy, reliability, and computational speed of the method open new perspectives for integrating these applications in a clinical setting.

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.

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 &gt;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.