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Introduction: Endoscopic management of upper tract urothelial carcinoma (UTUC) is increasingly relevant with greater detection of low-grade disease and guidelines recommending kidney preservation for low-risk disease. Historically, laser or thermal ablation has served as the primary tool for endoscopic management of UTUC, however, chemoablation is rapidly being developed to serve as a primary or adjuvant treatment option, which warrants review. Areas Covered: The current literature was reviewed to compare the outcomes and clinical utility of endoscopic treatment modalities for low-grade UTUC, with a focus on mitomycin-containing reverse thermal gel (UGN-101). Expert Opinion: The overall outcomes of mitomycin-containing gel therapy are promising, but adverse effects such as ureteral stricture call for careful consideration when using this treatment. We believe it is reasonable to consider use of mitomycin-containing gel as an adjuvant chemotherapy with endoscopic laser resection of low-grade upper tract urothelial carcinoma. [ABSTRACT FROM AUTHOR]

Objective: To investigate whether ischemia alters donor kidney metabolism and whether these changes are associated with organ function. Background: An unmet need in kidney transplantation is the ability to predict posttransplant organ function before transplantation. Key to such viability testing is a profound understanding of the organ's complex biochemistry and how ischemia, inevitable during the transplantation process, influences this. Methods: First, metabolic changes in perfusate glucose, lactate, and 20 amino acids, induced by no, 1 hour of warm, or 22 hours of cold ischemia, were investigated during 4-hour perfusion of pig kidneys with autologous whole blood (n = 6/group), simulating the ischemia-reperfusion phase of transplantation. Next, we confirmed similar metabolic changes during normothermic preservation of pigs (n = 3/group; n = 4 for cold ischemia) and discarded human kidneys (n = 6) perfused with a red blood cell-based perfusate. Results: At 2 hours of perfusion with autologous whole blood, abundances of 17/20 amino acids were significantly different between groups, reflecting the type of ischemia. Amino acid changes at 15 minutes and 2 hours of perfusion correlated with future kidney function during perfusion. Similar metabolic patterns were observed during perfusion preservation of pig and discarded human donor kidneys, suggesting an opportunity to assess kidney viability before transplantation. Conclusions: Perfusate metabolite changes during normothermic kidney perfusion represent a unique noninvasive opportunity to assess graft viability. These findings now need validation in transplant studies. [ABSTRACT FROM AUTHOR]

Type 2 diabetes (T2D) is the leading cause of chronic kidney disease (CKD). In addition, the cardiovascular prevalence in diabetic patients is around 32.2%, with a two-fold increased mortality risk compared to those without diabetes. Recent investigations have shed light on the promising cardioprotective and nephroprotective benefits of sodium—glucose cotransporter-2 inhibitors (SGLT2i), glucagon-like peptide-1 receptor agonists (GLP-1RA), and nonsteroidal mineralocorticoid receptor antagonists (nsMRAs) for individuals with T2D. The evidence robustly indicates that SGLT2i and GLP-1RA significantly reduce the risk of CKD and cardiovascular disease (CVD), all while effectively managing blood glucose levels. Furthermore, combining SGLT2i with nsMRAs amplifies the benefits, potentially offering a more profound reduction in cardiovascular and renal outcomes. The data analysis strongly supports the integration of these pharmacological agents in the management strategies for CKD and CVD prevention among T2D patients, highlighting the importance of awareness among nephrologists, especially in regions with limited healthcare resources. [ABSTRACT FROM AUTHOR]

The transplant community is focused on prolonging the ex vivo preservation time of kidney grafts to allow for long-distance kidney graft transportation, assess the viability of marginal grafts, and optimize a platform for the translation of innovative therapeutics to clinical practice, especially those focused on cell and vector delivery to organ conditioning and reprogramming. We describe the first case of feasible preservation of a kidney from a donor after uncontrolled circulatory death over a 73-h period using normothermic perfusion and analyze hemodynamic, biochemical, histological, and transcriptomic parameters for inflammation and kidney injury. The mean pressure and flow values were 71.24 ± 9.62 mmHg and 99.65 ± 18.54 mL/min, respectively. The temperature range was 36.7°C–37.2°C. The renal resistance index was 0.75 ± 0.15 mmHg/mL/min. The mean pH was 7.29 ± 0.15. The lactate concentration peak increased until 213 mg/dL at 6 h, reaching normal values after 34 h of perfusion (8.92 mg/dL). The total urine output at the end of perfusion was 1.185 mL. Histological analysis revealed no significant increase in acute tubular necrosis (ATN) severity as perfusion progressed. The expression of KIM-1, VEGF, and TGFβ decreased after 6–18 h of perfusion until 60 h in which the expression of these genes increased again together with the expression of β-catenin, Ki67, and TIMP1. We show that normothermic perfusion can maintain a kidney graft viable ex vivo for 3 days, thus allowing a rapid translation of pre-clinical therapeutics to clinical practice.

Normothermic machine perfusion (NMP) has reshaped organ preservation in recent years. In this preclinical study, prolonged normothermic perfusions of discarded human kidney grafts were performed in order to investigate perfusion dynamics and identify potential quality and assessment indicators. Five human discarded kidney grafts were perfused normothermically (37°C) for 48 h using the Kidney Assist device with a red-blood-cell based perfusate with urine recirculation. Perfusion dynamics, perfusate and urine composition as well as injury markers were measured and analyzed. Donor age ranged from 41 to 68 years. All but one kidney were from brain dead donors. Perfusions were performed successfully for 48 h with all discarded kidneys. Median arterial flow ranged from 405 to 841 mL/min. All kidneys excreted urine until the end of perfusion (median 0.43 mL/min at the end of perfusion). While sodium levels were consistently lower in urine compared to perfusate samples, this was only seen for chloride and potassium in kidney KTX 2. Lactate, AST, LDH as well as proinflammatory cytokines increased over time, especially in kidneys KTX 3 and 4. Ex vivo normothermic perfusion is able to identify patterns of perfusion, biological function, and changes in inflammatory markers in heterogenous discarded kidney grafts. [ABSTRACT FROM AUTHOR]

Normothermic machine perfusion (NMP) has reshaped organ preservation in recent years. In this preclinical study, prolonged normothermic perfusions of discarded human kidney grafts were performed in order to investigate perfusion dynamics and identify potential quality and assessment indicators. Five human discarded kidney grafts were perfused normothermically (37°C) for 48 h using the Kidney Assist device with a red-blood-cell based perfusate with urine recirculation. Perfusion dynamics, perfusate and urine composition as well as injury markers were measured and analyzed. Donor age ranged from 41 to 68 years. All but one kidney were from brain dead donors. Perfusions were performed successfully for 48 h with all discarded kidneys. Median arterial flow ranged from 405 to 841 mL/min. All kidneys excreted urine until the end of perfusion (median 0.43 mL/min at the end of perfusion). While sodium levels were consistently lower in urine compared to perfusate samples, this was only seen for chloride and potassium in kidney KTX 2. Lactate, AST, LDH as well as pro-inflammatory cytokines increased over time, especially in kidneys KTX 3 and 4. Ex vivo normothermic perfusion is able to identify patterns of perfusion, biological function, and changes in inflammatory markers in heterogenous discarded kidney grafts.

Short bubble and subsequent surface oxygenation is an innovative oxygenation technique and alternative for membrane oxygenation during hypothermic machine perfusion (HMP). The metabolic effect of the interruption of surface oxygenation for 4 h (mimicking organ transport) during HMP was compared to continuous surface and membrane oxygenation in a pig kidney ex situ preservation model. After 30 min of warm ischemia by vascular clamping, a kidney of a ±40 kg pig was procured and subsequently preserved according to one of the following groups: (1) 22-h HMP + intermittent surface oxygenation (n = 12); (2) 22-h HMP + continuous membrane oxygenation (n = 6); and (3) 22-h HMP + continuous surface oxygenation (n = 7). Brief perfusate O2 uploading before kidney perfusion was either obtained by direct bubble (groups 1, 3) or by membrane (group 2) oxygenation. Bubble oxygenation during minimum 15 min was as efficient as membrane oxygenation in achieving supraphysiological perfusate pO2 levels before kidney perfusion. Metabolic tissue analysis (i.e., lactate, succinate, ATP, NADH, and FMN) during and at the end of the preservation period demonstrated similar mitochondrial protection between all study groups. Short bubble and subsequent intermittent surface oxygenation of the perfusate of an HMP-kidney might be an effective and cheap preservation strategy to protect mitochondria, eliminating the need/costs of a membrane oxygenator and oxygen source during transport. [ABSTRACT FROM AUTHOR]

This scoping review summarizes what is known about kidney metabolism during hypothermic perfusion preservation. Papers studying kidney metabolism during hypothermic (<12 °C) perfusion were identified (PubMed, Embase, Web of Science, Cochrane). Out of 14,335 initially identified records, 52 were included [dog (26/52), rabbit (2/52), pig (20/52), human (7/52)]. These were published between 1970–2023, partially explaining study heterogeneity. There is a considerable risk of bias in the reported studies. Studies used different perfusates, oxygenation levels, kidney injury levels, and devices and reported on perfusate and tissue metabolites. In 11 papers, (non)radioactively labeled metabolites (tracers) were used to study metabolic pathways. Together these studies show that kidneys are metabolically active during hypothermic perfusion, regardless of the perfusion setting. Although tracers give us more insight into active metabolic pathways, kidney metabolism during hypothermic perfusion is incompletely understood. Metabolism is influenced by perfusate composition, oxygenation levels, and likely also by pre-existing ischemic injury. In the modern era, with increasing donations after circulatory death and the emergence of hypothermic oxygenated perfusion, the focus should be on understanding metabolic perturbations caused by pre-existing injury levels and the effect of perfusate oxygen levels. The use of tracers is indispensable to understanding the kidney's metabolism during perfusion, given the complexity of interactions between different metabolites. [ABSTRACT FROM AUTHOR]

The use of high-risk renal grafts for transplantation requires the optimization of pretransplant assessment and preservation reconditioning strategies to decrease the organ discard rate and to improve short- and long-term clinical outcomes. Active oxygenation is increasingly recognized to play a central role in dynamic preservation strategies, independent of preservation temperature, to recondition mitochondria and to restore the cellular energy profile. The oxygen-related decrease in mitochondrial succinate accumulation ameliorates the harmful effects of ischemia-reperfusion injury. The differences between normothermic and hypothermic machine perfusion with regard to organ assessment, preservation, and reconditioning, as well as the logistic and economic implications, are factors to take into consideration for implementation at a local level. Therefore, these different techniques should be considered complementary to the perfusion strategy selected depending on functional intention and resource availability. This review provides an overview of the current clinical evidence of normothermic and oxygenated hypothermic machine perfusion, either as a continuous or end-ischemic preservation strategy, and future perspectives. [ABSTRACT FROM AUTHOR]

The increasing number of patients on the kidney transplant waiting list underlines the need to expand the donor pool and improve kidney graft utilization. By protecting kidney grafts adequately from the initial ischemic and subsequent reperfusion injury occurring during transplantation, both the number and quality of kidney grafts could be improved. The last few years have seen the emergence of many new technologies to abrogate ischemia–reperfusion (I/R) injury, including dynamic organ preservation through machine perfusion and organ reconditioning therapies. Although machine perfusion is gradually making the transition to clinical practice, reconditioning therapies have not yet progressed from the experimental setting, pointing towards a translational gap. In this review, we discuss the current knowledge on the biological processes implicated in I/R injury and explore the strategies and interventions that are being proposed to either prevent I/R injury, treat its deleterious consequences, or support the reparative response of the kidney. Prospects to improve the clinical translation of these therapies are discussed with a particular focus on the need to address multiple aspects of I/R injury to achieve robust and long-lasting protective effects on the kidney graft. [ABSTRACT FROM AUTHOR]

Donor organ-shortage has resulted in the increased use of marginal grafts; however, normothermic machine perfusion (NMP) holds the potential for organ viability assessment and restoration of marginal grafts prior to transplantation. Additionally, cell-, oxygen carrier-free and antioxidants-supplemented solutions could potentially prevent adverse effects (transfusion reactions, inflammation, hemolysis), associated with the use of autologous packed red blood cell (pRBC)-based perfusates. This study compared 6 h NMP of porcine kidneys, using an established pRBC-based perfusate (pRBC, n = 7), with the novel cell- and oxygen carrier-free organ preservation solution Ecosol, containing taurine (Ecosol, n = 7). Despite the enhanced tissue edema and tubular injury in the Ecosol group, related to a suboptimal molecular mass of polyethylene glycol as colloid present in the solution, functional parameters (renal blood flow, intrarenal resistance, urinary flow, pH) and oxygenation (arterial pO2, absence of hypoxia-inducible factor 1-alpha) were similar to the pRBC group. Furthermore, taurine significantly improved the antioxidant capacity in the Ecosol group, reflected in decreased lactate dehydrogenase, urine protein and tubular vacuolization compared to pRBC. This study demonstrates the feasibility of 6 h NMP using a taurine containing, cell- and oxygen carrier-free perfusate, achieving a comparable organ quality to pRBC perfused porcine kidneys. [ABSTRACT FROM AUTHOR]

Normothermic ex-vivo machine perfusion provides a powerful tool to improve donor kidney preservation and a route for the delivery of pharmacological or gene therapeutic interventions prior to transplantation. However, perfusion at normothermic temperatures requires adequate tissue oxygenation to meet the physiological metabolic demand. For this purpose, the addition of appropriate oxygen carriers (OCs) to the perfusion solution is essential to ensure a sufficient oxygen supply and reduce the risk for tissue injury due to hypoxia. It is crucial that the selected OCs preserve the integrity and low immunogenicity of the graft. In this study, the effect of two OCs on the organ's integrity and immunogenicity was evaluated. Porcine kidneys were perfused ex-vivo for four hours using perfusion solutions supplemented with red blood cells (RBCs) as conventional OC, perfluorocarbon (PFC)-based OC, or Hemarina-M101 (M101), a lugworm hemoglobin-based OC named HEMO2life®, recently approved in Europe (i.e., CE obtained in October 2022). Perfusions with all OCs led to decreased lactate levels. Additionally, none of the OCs negatively affected renal morphology as determined by histological analyses. Remarkably, all OCs improved the perfusion solution by reducing the expression of pro-inflammatory mediators (IL-6, IL-8, TNFα) and adhesion molecules (ICAM-1) on both transcript and protein level, suggesting a beneficial effect of the OCs in maintaining the low immunogenicity of the graft. Thus, PFC-based OCs and M101 may constitute a promising alternative to RBCs during normothermic ex-vivo kidney perfusion.

Introduction: On the United States' Organ Transplantation Waitlist, approximately 17 people die each day waiting for an organ. The situation continues to deteriorate as the discrepancy between harvested organs and the number of patients in need is increasing. Static cold storage is the clinical standard method for preserving a harvested organ but is associated with several drawbacks. Machine perfusion of an organ has been shown to improve preservation quality as well as preservation time over static cold storage. While there are machine perfusion devices clinically available, they are costly and limited to specific organs and preservation solutions. This study presents a versatile oxygenating perfusion system (VOPS) that supplies oxygen and pulsatile perfusion. Materials and Methods: Experiments evaluated the system's performance with a human kidney mimicking hydraulic analog using multiple compressed oxygen supply pressures and aqueous solutions with viscosities ranging from 1 to 6.5 cP, which simulated viscosities of commonly used organ preservation solutions. Results and Conclusions: The VOPS produced mean flow rates ranging from 0.6 to 28.2 mL/min and perfusion pressures from 4.8 to 96.8 mmHg, which successfully achieved the desired perfusion parameters for human kidneys. This work provides evidence that the VOPS described herein has the versatility to perfuse organs using many of the clinically available preservation solutions. [ABSTRACT FROM AUTHOR]

The ideal composition of the perfusate for normothermic kidney perfusion is unknown, though the perfusate commonly used to perfuse human kidneys contains leukocyte-depleted packed red blood cells (RBC), as this is believed to prevent excessive inflammation. We performed a systematic search identifying 19 articles reporting on cytokine levels during normothermic pig or human kidney perfusion. Cytokine levels varied widely across the reported studies. No direct comparisons of perfusate cytokines during perfusion with RBC or whole blood were performed, and no data on how these levels are influenced by ischemia are available. Therefore, we compared perfusate IL-6, IL-1β, TNF-α, TGF-β, IL-10, IL-8, and CCL2 levels during 4 h normothermic pig kidney perfusion with a whole blood- or RBC-based perfusate. Kidneys were exposed to either 1 h of warm or 22 h of cold ischemia. We found no evidence of different perfusate cytokine or gene expression levels in whole blood or RBC perfusions. There was no clear evidence to suggest that cytokine concentrations differ between ischemically injured kidneys and controls. In conclusion, pro-inflammatory and anti-inflammatory cytokines and chemokines are detectable in the perfusate and urine of kidneys undergoing normothermic perfusion. It is unclear how cytokine levels change in different ischemic conditions and whether the use of a leukocyte filter plays a role. [ABSTRACT FROM AUTHOR]

Oxygenated machine perfusion of human organs has been shown to improve both preservation quality and time duration when compared to the current gold standard: static cold storage. However, existing machine perfusion devices designed for preservation and transportation of transplantable organs are too complicated and organ-specific to merit use as a solution for all organs. This work presents a novel, portable, and nonelectronic device potentially capable of delivering oxygenated machine perfusion to a variety of organs. An innovative pneumatic circuit system regulates a compressed oxygen source that cyclically inflates and deflates silicone tubes, which function as both the oxygenator and perfusion pump. Different combinations of silicone tubes in single or parallel configurations, with lengths ranging from 1.5 to 15.2 m, were evaluated at varying oxygen pressures from 27.6 to 110.3 kPa. The silicone tubes in parallel configurations produced higher peak perfusion pressures (70% increase), mean flow rates (102% increase), and oxygenation rates (268% increase) than the single silicone tubes that had equivalent total lengths. While pumping against a vascular resistance element that mimicked a kidney, the device achieved perfusion pressures (8.4–131.6 mmHg), flow rates (2.0–40.2 mL min−1), and oxygenation rates (up to 388 μmol min−1) that are consistent with values used in previous kidney preservation studies. The nonelectronic device achieved those perfusion parameters using 4.4 L min−1 of oxygen to operate. These results demonstrate that oxygenated machine perfusion can be successfully achieved without any electronic components. [ABSTRACT FROM AUTHOR]

Normothermic machine perfusion (NMP) of kidneys in combination with an optimized perfusate composition may increase donor organ preservation quality, especially in the case of marginal donor grafts. Optimization of currently employed perfusates is still a subject of present research. Due to the advantages of being cell-free, easy to store, and having minimal antigenicity, hemoglobin-based oxygen carriers, such as HBOC-301 (Oxyglobin®, Hemoglobin Oxygen Therapeutics LLC, Souderton, PA, USA), offer an alternative to the commonly used perfusates based on packed red blood cells (pRBC). As previously described, using HBOC results in formation of methemoglobin (metHb) as an adverse effect, inducing hypoxic conditions during the perfusion. As a potential counterpart to metHb formation, the application of the antioxidant ascorbic acid (VitC) is of high interest. Therefore, this study was conducted in four experimental groups, to compare the effect of NMP with (1) HBOC or (3) pRBC, and additionally examine a beneficial effect of VitC in both groups (2) HBOC + VitC and (4) pRBC + VitC. All groups were subjected to NMP for 6 h at a pressure of 75 mmHg. Kidneys in the HBOC groups had a significantly lower renal blood flow and increasing intrarenal resistance, with reduced renal function in comparison to the pRBC groups, as demonstrated by significantly lower creatinine clearance and higher fractional sodium excretion rates. Clinical chemistry markers for tissue damage (LDH, lactate) were higher in the HBOC groups, whereas no significant histological differences were observed. Although the application of VitC decreased oxidative stress levels, it was not able to significantly increase the outcome parameters mentioned above in either group. This study demonstrated that HBOC-301 is inferior to pRBCs in our porcine kidney NMP model, independent of additional VitC administration. Oxidative stress and fragmentation of the hemoglobin polymers could be detected as a possible reason for these results, hence further research, focusing on the use of cell-free oxygen carriers that do not exhibit this complex of issues, is required. [ABSTRACT FROM AUTHOR]

Donor organ-shortage has resulted in the increased use of marginal grafts; however, normothermic machine perfusion (NMP) holds the potential for organ viability assessment and restoration of marginal grafts prior to transplantation. Additionally, cell-, oxygen carrier-free and antioxidants-supplemented solutions could potentially prevent adverse effects (transfusion reactions, inflammation, hemolysis), associated with the use of autologous packed red blood cell (pRBC)-based perfusates. This study compared 6 h NMP of porcine kidneys, using an established pRBC-based perfusate (pRBC, n = 7), with the novel cell- and oxygen carrier-free organ preservation solution Ecosol, containing taurine (Ecosol, n = 7). Despite the enhanced tissue edema and tubular injury in the Ecosol group, related to a suboptimal molecular mass of polyethylene glycol as colloid present in the solution, functional parameters (renal blood flow, intrarenal resistance, urinary flow, pH) and oxygenation (arterial pO2, absence of hypoxia-inducible factor 1-alpha) were similar to the pRBC group. Furthermore, taurine significantly improved the antioxidant capacity in the Ecosol group, reflected in decreased lactate dehydrogenase, urine protein and tubular vacuolization compared to pRBC. This study demonstrates the feasibility of 6 h NMP using a taurine containing, cell- and oxygen carrier-free perfusate, achieving a comparable organ quality to pRBC perfused porcine kidneys.

The advantages of oxygenated perfusion are continuing to be demonstrated by many groups focused on improving the efficacy of tissue preservation for transplant, bioreactors for studies of basic tissue physiology, and closed-loop resuscitation. This work presents a novel and portable device that supplies oxygenated and pulsatile perfusion, both of which are regulated by a single pump-oxygenator component comprised of silicone tubes that are cyclically inflated/deflated with compressed oxygen. In this study, pump variables (oxygen supply pressure and length of a silicone tube) were evaluated against hydraulic elements that mimicked the vascular resistance of kidneys, livers, and hearts. The perfusion pressures, flow rates, and oxygenation rates produced by the device were characterized for all configurations of pump variables, and the pulse rates were tuned to improve performance. The device supplied perfusion pressures ranging from 3.5 to 109 mmHg, flow rates ranging from 1.4 to 71.8 mL min−1, and oxygenation rates up to 316.6 µmol min−1. From those results, it was determined that the device was capable of achieving perfusion parameters used in previous kidney, liver, and heart preservation studies. Ultimately, this research demonstrated the efficacy of a novel device that is designed to supply oxygenated perfusion across a range of applications. [ABSTRACT FROM AUTHOR]

Introduction: On the United States’ Organ Transplantation Waitlist, approximately 17 people die each day waiting for an organ. The situation continues to deteriorate as the discrepancy between harvested organs and the number of patients in need is increasing. Static cold storage is the clinical standard method for preserving a harvested organ but is associated with several drawbacks. Machine perfusion of an organ has been shown to improve preservation quality as well as preservation time over static cold storage. While there are machine perfusion devices clinically available, they are costly and limited to specific organs and preservation solutions. This study presents a versatile oxygenating perfusion system (VOPS) that supplies oxygen and pulsatile perfusion. Materials and Methods: Experiments evaluated the system’s performance with a human kidney mimicking hydraulic analog using multiple compressed oxygen supply pressures and aqueous solutions with viscosities ranging from 1 to 6.5 cP, which simulated viscosities of commonly used organ preservation solutions. Results and Conclusions: The VOPS produced mean flow rates ranging from 0.6 to 28.2 mL/min and perfusion pressures from 4.8 to 96.8 mmHg, which successfully achieved the desired perfusion parameters for human kidneys. This work provides evidence that the VOPS described herein has the versatility to perfuse organs using many of the clinically available preservation solutions.

SUMMARY: Assessment of donor kidney quality is based on clinical scores or requires biopsies for histological assessment. Noninvasive strategies to identify and predict graft outcome at an early stage are, therefore, needed. We evaluated the perfusate of donation after brain death (DBD) kidneys during nonoxygenated hypothermic machine perfusion (HMP). In particular, we compared perfusate protein profiles of good outcome (GO) and suboptimal outcome (SO) 1‐year post‐transplantation. Samples taken 15 min after the start HMP (T1) and before the termination of HMP (T2) were analysed using quantitative liquid chromatography–tandem mass spectrometry (LC‐MS/MS). Hierarchical clustering of the 100 most abundant proteins showed discrimination between grafts with a GO and SO at T1. Elevated levels of proteins involved in classical complement cascades at both T1 and T2 and a reduced abundance of lipid metabolism at T1 and of cytoskeletal proteins at T2 in GO versus SO was observed. ATP‐citrate synthase and fatty acid‐binding protein 5 (T1) and immunoglobulin heavy variable 2‐26 and desmoplakin (T2) showed 91% and 86% predictive values, respectively, for transplant outcome. Taken together, DBD kidney HMP perfusate profiles can distinguish between outcome 1‐year post‐transplantation. Furthermore, it provides insights into mechanisms that could play a role in post‐transplant outcomes. [ABSTRACT FROM AUTHOR]

Cystinosis is an autosomal recessive metabolic disease that belongs to the family of lysosomal storage disorders. The defective gene is CTNS, which encodes the lysosomal cystine transporter, cystinosin. Cystine accumulates in all tissues and leads to organ damage including end-stage renal disease. In this review, we outline the studies that support that genetic rescue of cystinosis could be an achievable goal, even though cystinosis is a multi-compartmental disease and cystinosin an intracellular transmembrane protein. Using the mouse model of cystinosis, the Ctns(-/-) mice, we showed that transplanted hematopoietic stem cells (HSCs) were able to act as vehicles for the delivery of a functional Ctns gene to the different organs and led to the significant decrease of the tissue cystine content and tissue preservation. Ex vivo gene-modified Ctns(-/-) HSC transplantation using a lentiviral vector containing CTNS complementary DNA (cDNA) was also successful in the Ctns(-/-) mice and built the foundations for a clinical trial for autologous HSC transplantation for cystinosis. The capacity of HSCs for rescuing non-hematopoietic disease is controversial, and new insights into regenerative medicine could be gained from unraveling the underlying mechanism of action.

Normothermic machine perfusion (NMP) of kidneys in combination with an optimized perfusate composition may increase donor organ preservation quality, especially in the case of marginal donor grafts. Optimization of currently employed perfusates is still a subject of present research. Due to the advantages of being cell-free, easy to store, and having minimal antigenicity, hemoglobin-based oxygen carriers, such as HBOC-301 (Oxyglobin®, Hemoglobin Oxygen Therapeutics LLC, Souderton, PA, USA), offer an alternative to the commonly used perfusates based on packed red blood cells (pRBC). As previously described, using HBOC results in formation of methemoglobin (metHb) as an adverse effect, inducing hypoxic conditions during the perfusion. As a potential counterpart to metHb formation, the application of the antioxidant ascorbic acid (VitC) is of high interest. Therefore, this study was conducted in four experimental groups, to compare the effect of NMP with (1) HBOC or (3) pRBC, and additionally examine a beneficial effect of VitC in both groups (2) HBOC + VitC and (4) pRBC + VitC. All groups were subjected to NMP for 6 h at a pressure of 75 mmHg. Kidneys in the HBOC groups had a significantly lower renal blood flow and increasing intrarenal resistance, with reduced renal function in comparison to the pRBC groups, as demonstrated by significantly lower creatinine clearance and higher fractional sodium excretion rates. Clinical chemistry markers for tissue damage (LDH, lactate) were higher in the HBOC groups, whereas no significant histological differences were observed. Although the application of VitC decreased oxidative stress levels, it was not able to significantly increase the outcome parameters mentioned above in either group. This study demonstrated that HBOC-301 is inferior to pRBCs in our porcine kidney NMP model, independent of additional VitC administration. Oxidative stress and fragmentation of the hemoglobin polymers could be detected as a possible reason for these results, hence further research, focusing on the use of cell-free oxygen carriers that do not exhibit this complex of issues, is required.

The limiting factor in conventional quality assessments of transplanted organs, namely the invasiveness of tissue sample collection, has prompted much research on the field of transplantology to focus on the development of alternative evaluation methods of organ quality. In the present project, we undertake the challenge to address the need for a new analytical solution for graft quality assessments by using a novel metabolomic diagnostic protocol based on low‐invasive solid‐phase microextraction. Solid‐phase microextraction probes of ca. 0.2 mm coated with 4 mm long mixed‐mode extraction phase were inserted into rabbit kidneys immediately following euthanasia and after 2, 4, 6, and 21 h of preservation. Liquid chromatography–mass spectrometry analysis of the extracts was performed with the use of a reversed phase column and a Q‐Exactive Focus mass spectrometer operated in positive ionization mode. Statistical analysis of significantly changing compounds revealed metabolic profile changes in kidneys induced by ischemia and oxidative stress as a function of the duration of cold storage. The most pronounced alterations were reflected in levels of essential amino acids and purine nucleosides. Our findings demonstrate that the proposed approach may be successfully used to monitor changes in the metabolic profile of organs over time of preservation. [ABSTRACT FROM AUTHOR]

The use of blood for normothermic and subnormothermic kidney preservation hinders the translation of these approaches and promising therapeutics. This study evaluates whether adding hydrogen sulfide donor AP39 to Hemopure, a blood substitute, during subnormothermic perfusion improves kidney outcomes. After 30 min of renal pedicle clamping, porcine kidneys were treated to 4 h of static cold storage (SCS-4 °C) or subnormothermic perfusion at 21 °C with Hemopure (H-21 °C), Hemopure + 200 nM AP39 (H200nM-21 °C) or Hemopure + 1 µM AP39 (H1µM-21 °C). Then, kidneys were reperfused with Hemopure at 37 °C for 4 h with metabolic support. Perfusate composition, tissue oxygenation, urinalysis and histopathology were analyzed. During preservation, the H200nM-21 °C group exhibited significantly higher urine output than the other groups and significantly higher tissue oxygenation than the H1µM-21 °C group at 1 h and 2h. During reperfusion, the H200nM-21 °C group exhibited significantly higher urine output and lower urine protein than the other groups. Additionally, the H200nM-21 °C group exhibited higher perfusate pO2 levels than the other groups and significantly lower apoptotic injury than the H-21 °C and the H1µM-21 °C groups. Thus, subnormothermic perfusion at 21 °C with Hemopure + 200 nM AP39 improves renal outcomes. Additionally, our novel blood-free model of ex vivo kidney preservation and reperfusion could be useful for studying other therapeutics.

The transplant community is focused on prolonging the ex vivo preservation time of kidney grafts to allow for long-distance kidney graft transportation, assess the viability of marginal grafts, and optimize a platform for the translation of innovative therapeutics to clinical practice, especially those focused on cell and vector delivery to organ conditioning and reprogramming. We describe the first case of feasible preservation of a kidney from a donor after uncontrolled circulatory death over a 73-h period using normothermic perfusion and analyze hemodynamic, biochemical, histological, and transcriptomic parameters for inflammation and kidney injury. The mean pressure and flow values were 71.24 ± 9.62 mmHg and 99.65 ± 18.54 mL/min, respectively. The temperature range was 36.7°C-37.2°C. The renal resistance index was 0.75 ± 0.15 mmHg/mL/min. The mean pH was 7.29 ± 0.15. The lactate concentration peak increased until 213 mg/dL at 6 h, reaching normal values after 34 h of perfusion (8.92 mg/dL). The total urine output at the end of perfusion was 1.185 mL. Histological analysis revealed no significant increase in acute tubular necrosis (ATN) severity as perfusion progressed. The expression of KIM-1, VEGF, and TGFβ decreased after 6-18 h of perfusion until 60 h in which the expression of these genes increased again together with the expression of β -catenin, Ki67, and TIMP1. We show that normothermic perfusion can maintain a kidney graft viable ex vivo for 3 days, thus allowing a rapid translation of pre-clinical therapeutics to clinical practice., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Montagud-Marrahi, Luque, Ros, Ajami, Cuadrado-Payan, Estrella, Arancibia, Sánchez-Etayo, Bohils, Marrero, Fundora, Ramírez-Bajo, Banon-Maneus, Rovira, Larque, Campistol, Diekmann and Musquera.)

Cold preservation is the standard of care for renal grafts. However, research on alternatives like perfusion at higher temperatures and supplementing preservation solutions with hydrogen sulfide (H2S) has gained momentum. In this study, we investigated whether adding H2S donor AP39 to porcine blood during subnormothermic perfusion at 21 °C improves renal graft outcomes. Porcine kidneys were nephrectomized after 30 min of clamping the renal pedicles and treated to 4 h of static cold storage (SCS) on ice or ex vivo subnormothermic perfusion at 21 °C with autologous blood alone (SNT) or with AP39 (SNTAP). All kidneys were reperfused ex vivo with autologous blood at 37 °C for 4 h. Urine output, histopathology and RNAseq were used to evaluate the renal graft function, injury and gene expression profiles, respectively. The SNTAP group exhibited significantly higher urine output than other groups during preservation and reperfusion, along with significantly lower apoptotic injury compared to the SCS group. The SNTAP group also exhibited differential pro-survival gene expression patterns compared to the SCS (downregulation of pro-apoptotic genes) and SNT (downregulation of hypoxia response genes) groups. Subnormothermic perfusion at 21 °C with H2S-supplemented blood improves renal graft outcomes. Further research is needed to facilitate the clinical translation of this approach.

University of Wisconsin (UW) solution is not optimal for preservation of marginal organs. Polyethylene glycol (PEG) could improve protection. Similarly formulated solutions containing either 15 or 20 g/L PEG 20 kDa or 5, 15 and 30 g/L PEG 35 kDa were tested in vitro on kidney endothelial cells, ex vivo on preserved kidneys, and in vivo in a pig kidney autograft model. In vitro, all PEGs provided superior preservation than UW in terms of cell survival, adenosine triphosphate (ATP) production, and activation of survival pathways. Ex vivo, tissue injury was lower with PEG 20 kDa compared to UW or PEG 35 kDa. In vivo, function recovery was identical between UW and PEG 35 kDa groups, while PEG 20 kDa displayed swifter recovery. At three months, PEG 35 kDa 15 and 30 g/L animals had worse outcomes than UW, while 5 g/L PEG 35 kDa was similar. PEG 20 kDa was superior to both UW and PEG 35 kDa in terms of function and fibrosis development, with low activation of damage pathways. PEG 20 kDa at 15 g/L was superior to 20 g/L. While in vitro models did not discriminate between PEGs, in large animal models of transplantation we showed that PEG 20 kDa offers a higher level of protection than UW and that longer chains such as PEG 35 kDa must be used at low doses, such as found in Institut George Lopez (IGL1, 1g/L). [ABSTRACT FROM AUTHOR]

Background: Kidney transplantation following uncontrolled donation after circulatory death (uDCD) presents a high risk of delayed graft function due to prolonged warm ischemia time. In order to minimise the effects of ischemia/reperfusion injury during warm ischemia, normothermic recirculation recently replaced in situ perfusion prior to implantation in several institutions. The aim of this study was to compare these preservation methods on kidney graft outcomes.Methods: The primary endpoint was the one-year measured graft filtration rate (mGFR). We collected retrospective data from 64 consecutive uDCD recipients transplanted over a seven-year period in a single centre.Results: Thirty-two grafts were preserved by in situ perfusion and 32 by normothermic recirculation. The mean ± SD mGFR at 1 year post-transplantation was 43.0 ± 12.8 mL/min/1.73 m2 in the in situ perfusion group and 53.2 ± 12.8 mL/min/1.73 m2 in the normothermic recirculation group (p = 0.01). Estimated GFR levels were significantly higher in the normothermic recirculation group at 12 months (p = 0.01) and 24 months (p = 0.03) of follow-up. We did not find any difference between groups regarding patient and graft survival, delayed graft function, graft rejection, or interstitial fibrosis.Conclusions: Function of grafts preserved by normothermic recirculation was better at 1 year and the results suggest that this persists at 2 years, although no difference was found in short-term outcomes. Despite the retrospective design, this study provides an additional argument in favour of normothermic recirculation. [ABSTRACT FROM AUTHOR]

To assess the application of a hypothermic machine perfusion device (LifePort) in kidney transplantation from donation after cardiac death (DCD) donors, 24 pairs of DCD kidneys were randomly divided into two groups: one of the paired kidneys from the same donor was perfused with the LifePort machine (hypothermic machine perfusion [HMP]), and the contralateral kidney was prepared using common static cold preservation (CCP). The two groups were compared with respect to the incidence of delayed graft function (DGF), level of graft function, and pathological changes in time-zero biopsy specimens. The incidence of DGF was 16.7 and 37.5% in the HMP and CCP groups, respectively; the difference between the two groups was statistically significant ( P < 0.05). The incidence of acute rejection was 4.1 (1/24) and 8.3% (2/24) in the HMP and CCP groups, respectively; this difference was not statistically significant ( P > 0.05). Forty-eight kidney patients were followed up for 6 months, and the two groups of recipients all survived, yielding a survival rate of 100%. The mean 6-month serum creatinine levels were 98.7 ± 23.6 µmol/L in the HMP group and 105.3 ± 35.1 µmol/L in the CCP group; there was no significant difference between the two groups. HMP can reduce the incidence of DGF in DCD kidneys, and this effect is greater for expanded criteria donors kidneys. HMP can also improve early renal function. [ABSTRACT FROM AUTHOR]

Introduction: We sought to assess the long-term results of conservative treatment for upper urinary tract carcinoma (UUTC) with regard to tumour recurrence and preservation of renal unit. Methods: From October 1987 to January 2014, 65 patients (median age 68 years) were diagnosed with UUTC and underwent endoscopic and open surgical techniques. Thirteen patients had bilateral disease and one had a single kidney. The primary approach was endoscopic in 37 reno-ureteral units (20 percutaneous resections, 17 ureteroscopies). Open surgery was performed in 19 cases. A total of 20 patients received mitomycin C. Results: Superficial stage pTa or T1 was noted in 37 patients, infiltrating stage pT2 and pT3 in seven and inverted papilloma in one. The stage of the tumour was impossible to classify in 20. With a median followup of 75.12 months (interquartile range [IQR] 144.71-17.41), the kidney preservation, recurrence, specific survival, and global survival rates were 78.5% (51/65), 40.0% (26/65), 92.3% (60/65), and 69.2% (45/65), respectively. From the patients who had recurrence, 15 were salvaged with radical nephroureterectomy (RNU). The bladder tumour recurrence rate after the surgery was 30.76% (20/65). At the end of the followup, five patients had died of UUTC progression and 16 from other causes. Postoperative complications included one case of fistula, one case of stricture, and one case of nephrectomy due to bleeding. Conclusions: In selected cases, conservative management is a safe and feasible alternative to RNU, with the advantage of renal unit preservation. [ABSTRACT FROM AUTHOR]

Introduction: Radical nephroureterectomy with an ipsilateral bladder cuff is the referent standard for management of muscle-invasive, high-grade, or bulky upper-tract urothelial carcinoma (UTUC). Nonetheless, certain patients with UTUC have imperative or elective indications for kidney preservation thereby lending to more conservative strategies for management of this disease. Areas covered: A review of the PubMED and Medline databases was performed to identify original scientific and review articles discussing retrograde ureteroscopic or percutaneous antegrade resection of UTUC tumors published between 1995 and 2016. Comparative studies with radical nephroureterectomy were also included. Expert commentary: Endoscopic ablative treatments via retrograde or antegrade approaches may appropriately treat small, solitary, and low risk UTUC tumors. Recurrences in the ipsilateral upper-tract and bladder distal to the original tumor can occur following nephron-sparing treatments and therefore a vigilant surveillance program with a compliant patient is essential when pursuing this treatment approach. [ABSTRACT FROM AUTHOR]

Normothermic ex-vivo machine perfusion provides a powerful tool to improve donor kidney preservation and a route for the delivery of pharmacological or gene therapeutic interventions prior to transplantation. However, perfusion at normothermic temperatures requires adequate tissue oxygenation to meet the physiological metabolic demand. For this purpose, the addition of appropriate oxygen carriers (OCs) to the perfusion solution is essential to ensure a sufficient oxygen supply and reduce the risk for tissue injury due to hypoxia. It is crucial that the selected OCs preserve the integrity and low immunogenicity of the graft. In this study, the effect of two OCs on the organ's integrity and immunogenicity was evaluated. Porcine kidneys were perfused ex-vivo for four hours using perfusion solutions supplemented with red blood cells (RBCs) as conventional OC, perfluorocarbon (PFC)-based OC, or Hemarina-M101 (M101), a lugworm hemoglobin-based OC named HEMO 2 life®, recently approved in Europe (i.e., CE obtained in October 2022). Perfusions with all OCs led to decreased lactate levels. Additionally, none of the OCs negatively affected renal morphology as determined by histological analyses. Remarkably, all OCs improved the perfusion solution by reducing the expression of pro-inflammatory mediators (IL-6, IL-8, TNFα) and adhesion molecules (ICAM-1) on both transcript and protein level, suggesting a beneficial effect of the OCs in maintaining the low immunogenicity of the graft. Thus, PFC-based OCs and M101 may constitute a promising alternative to RBCs during normothermic ex-vivo kidney perfusion., Competing Interests: The authors JHB and CF declared that they were editorial board members of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 Rother, Horgby, Schmalkuche, Burgmann, Nocke, Jägers, Schmitz, Bräsen, Cantore, ZLC, Ferenz, Blasczyk and Figueiredo.)

One of the main issues in kidney transplantation is the optimal functional preservation of the organ until its transplantation into the appropriate recipient. Despite intensive efforts, the functional preservation period remains limited to hours. During this time, as a result of cellular injury, various proteins, peptides, and other molecules are released by the organ into the preservation medium. In this study, we used proteomic techniques to analyze the protein profiles of preservation solutions in which organs had been preserved prior to their transplantation. Samples were obtained from the preservation solutions of 25 deceased donor kidneys scheduled for transplantation. The protein profiles of the solutions were analyzed using 2D gel electrophoresis/MALDI-TOF and LC-MS/MS. We identified and quantified 206 proteins and peptides belonging to 139 different groups. Of these, 111 proteins groups were belonging to kidney tissues. This study used proteomic techniques to analyze the protein profiles of organ preservation solutions. These findings will contribute to the development of improved preservation solutions to effectively protect organs for transplantation. [ABSTRACT FROM AUTHOR]

Kidney grafts are often preserved initially in static cold storage ( CS) and subsequently on hypothermic machine perfusion ( MP). However, the impact of CS/ MP time on transplant outcome remains unclear. We evaluated the effect of prolonged CS/ MP time in a single-center retrospective cohort of 59 donation after circulatory death ( DCD) and 177 matched donation after brain death ( DBD) kidney-alone transplant recipients. With mean overall CS/ MP times of 6.0 h/30.0 h, overall incidence of delayed graft function ( DGF) was higher in DCD transplants (30.5%) than DBD transplants (7.3%, P < 0.0001). In logistic regression, DCD recipient ( P < 0.0001), longer CS time ( P = 0.0002), male recipient ( P = 0.02), and longer MP time ( P = 0.08) were associated with higher DGF incidence. In evaluating the joint effects of donor type ( DBD vs. DCD), CS time (<6 vs. ≥6 h), and MP time (<36 vs. ≥36 h) on DGF incidence, one clearly sees an unfavorable effect of MP time ≥36 h ( P = 0.003) across each donor type and CS time stratum, whereas the unfavorable effect of CS time ≥6 h ( P = 0.01) is primarily seen among DCD recipients. Prolonged cold ischemia time had no unfavorable effect on renal function or graft survival at 12mo post-transplant. Long CS/ MP time detrimentally affects early DCD/ DBD kidney transplant outcome when grafts were mainly preserved by MP; prolonged CS time before MP has a particularly negative impact in DCD kidney transplantation. [ABSTRACT FROM AUTHOR]

Background Efficient and effective perfusion during organ procurement is required for the best prevention of donor organ injury preceding transplantation. However, current organ preservation solutions, including hydroxyethyl starch (HES)–based University of Wisconsin (UW) solution, do not always yield the best outcomes. Our previous study demonstrated that replacing HES with hyperbranched polyglycerol (HPG) reduced donor heart injury during cold storage. The current research was designed to examine the advantages of HPG-based solution for cold kidney perfusion. Methods Perfusion efficiency of HPG versus UW solution was tested using mouse kidneys at 4°C. The blood washout was evaluated by using a semiquantitative scoring system and tissue damage by histologic analysis. The interaction of HPG or UW solution with human red blood cells (RBCs) was examined by measuring RBC sedimentation and aggregation. Results The lower viscosity of HPG solution was correlated with faster and more efficient perfusion through donor kidneys as compared with UW. HPG solution was also more effective than UW in removing RBCs from the kidney and was associated with less tissue damage to donor kidneys. In vitro UW solution caused significant RBC sedimentation and hyperaggregation, whereas HPG showed minimal impact on RBC sedimentation and prevented RBC aggregation. Conclusions This experimental study demonstrated that compared with UW, HPG solution was more efficient and effective in the removal of the blood from donor kidneys and offered better protection from donor tissue damage, suggesting that the HPG solution is a promising candidate to supplant standard UW solution for donor kidney perfusion in transplantation. [ABSTRACT FROM AUTHOR]

Background: In kidney transplantation, the conditions of organ preservation following removal influence function recovery. Current static preservation procedures are generally based on immersion in a cold-storage solution used under atmospheric air (approximately 78 kPa N2, 21 kPa O2, 1 kPa Ar). Research on static cold-preservation solutions has stalled, and modifying the gas composition of the storage medium for improving preservation was considered. Organoprotective strategies successfully used noble gases and we addressed here the effects of argon and xenon on graft preservation in an established preclinical pig model of autotransplantation.Methods: The preservation solution Celsior saturated with pure argon (Argon-Celsior) or xenon (Xenon-Celsior) at atmospheric pressure was tested versus Celsior saturated with atmospheric air (Air-Celsior). The left kidney was removed, and Air-Celsior (n = 8 pigs), Argon-Celsior (n = 8) or Xenon-Celsior (n = 6) was used at 4 °C to flush and store the transplant for 30 h, a duration that induced ischemic injury in our model when Air-Celsior was used. Heterotopic autotransplantation and contralateral nephrectomy were performed. Animals were followed for 21 days.Results: The use of Argon-Celsior vs. Air-Celsior: (1) improved function recovery as monitored via creatinine clearance, the fraction of excreted sodium and tubulopathy duration; (2) enabled diuresis recovery 2-3 days earlier; (3) improved survival (7/8 vs. 3/8 pigs survived at postoperative day-21); (4) decreased tubular necrosis, interstitial fibrosis, apoptosis and inflammation, and preserved tissue structures as observed after the natural death/euthanasia; (5) stimulated plasma antioxidant defences during the days following transplantation as shown by monitoring the "reduced ascorbic acid/thiobarbituric acid reactive substances" ratio and Hsp27 expression; (6) limited the inflammatory response as shown by expression of TNF-alpha, IL1-beta and IL6 as observed after the natural death/euthanasia. Conversely, Xenon-Celsior was detrimental, no animal surviving by day-8 in a context where functional recovery, renal tissue properties and the antioxidant and inflammation responses were significantly altered. Thus, the positive effects of argon were not attributable to the noble gases as a group.Conclusions: The saturation of Celsior with argon improved early functional recovery, graft quality and survival. Manipulating the gas composition of a preservation medium constitutes therefore a promising approach to improve preservation. [ABSTRACT FROM AUTHOR]