Oxygenated machine perfusion preservation of predamaged kidneys with HTK and Belzer machine perfusion solution: an experimental study in pigs

Design of a Multiparametric Perfusion Bioreactor System for Evaluating Sub-Normothermic Preservation of Rat Abdominal Wall Vascularized Composite Allografts

Static cold storage (SCS), the current clinical gold standard for organ preservation, provides surgeons with a limited window of time between procurement and transplantation. In vascularized composite allotransplantation (VCA), this time limitation prevents many viable allografts from being designated to the best-matched recipients. Machine perfusion (MP) systems hold significant promise for extending and improving organ preservation. Most of the prior MP systems for VCA have been built and tested for large animal models. However, small animal models are beneficial for high-throughput biomolecular investigations. This study describes the design and development of a multiparametric bioreactor with a circuit customized to perfuse rat abdominal wall VCAs. To demonstrate its concept and functionality, this bioreactor system was employed in a small-scale demonstrative study in which biomolecular metrics pertaining to graft viability were evaluated non-invasively and in real time. We additionally report a low incidence of cell death from ischemic necrosis as well as minimal interstitial edema in machine perfused grafts. After up to 12 h of continuous perfusion, grafts were shown to survive transplantation and reperfusion, successfully integrating with recipient tissues and vasculature. Our multiparametric bioreactor system for rat abdominal wall VCA provides an advanced framework to test novel techniques to enhance normothermic and sub-normothermic VCA preservations in small animal models.

Enhanced immunosuppression improves early allograft function in a porcine kidney transplant model of donation after circulatory death

It remains controversial whether renal allografts from donation after circulatory death (DCD) have a higher risk of acute rejection (AR). In the porcine large animal kidney transplant model, we investigated the AR and function of DCD renal allografts compared to the non-DCD renal allografts and the effects of increased immunosuppression. We found that the AR was significantly increased along with elevated MHC-I expression in the DCD transplants receiving low-dose immunosuppression; however, AR and renal function were significantly improved when given high-dose immunosuppressive therapy postoperatively. Also, high-dose immunosuppression remarkably decreased the mRNA levels of ifn-g, il-6, tgf-b, il-4, and tnf-a in the allograft at day 5 and decreased serum cytokines levels of IFN-g and IL-17 at day 4 and day 5 after operation. Furthermore, Western blot analysis showed that higher immunosuppression decreased phosphorylation of signal transducer and activator of transcription 3 and nuclear factor kappa-light-chain-enhancer of activated B cells-p65, increased phosphorylation of extracellular-signal-regulated kinase, and reduced the expression of Bcl-2-associated X protein and caspase-3 in the renal allografts. These results suggest that the DCD renal allograft seems to be more vulnerable to AR; enhanced immunosuppression reduces DCD-associated AR and improves early allograft function in a preclinical large animal model.

Ex vivo machine perfusion for renal graft preservation

Kidney transplantation is the treatment of choice for end-stage renal disease. Despite its superiority over dialysis, the persisting organ shortage remains a major drawback. Additional sources to increase the donor pool are grafts recovered from extended criteria donors (ECD) and donation after circulatory death (DCD). Although transplantation of marginal grafts demonstrates promising outcomes, increased rates of primary non-function, delayed graft function, and reduced graft survival have been reported. Cold ischemic injury, caused by static cold storage is a significant risk factor for poor outcome. Machine perfusion (MP) at various temperatures bears the potential to improve organ preservation, assessment, and repair. While hypothermic machine perfusion (HMP) is well established in clinical practice, modified HMP, subnormothermic machine perfusion (SMP), and normothermic machine perfusion (NMP) are novel emerging strategies with the potential to significantly improve the outcome of marginal kidney grafts. This review summarizes findings and recent advances from pre-clinical and clinical machine perfusion studies, organized by temperature, and discusses potential future developments for graft assessment and repair.

Maximizing kidneys for transplantation using machine perfusion: from the past to the future: A comprehensive systematic review and meta-analysis

BACKGROUND

The two main options for renal allograft preservation are static cold storage (CS) and machine perfusion (MP). There has been considerably increased interest in MP preservation of kidneys, however conflicting evidence regarding its efficacy and associated costs have impacted its scale of clinical uptake. Additionally, there is no clear consensus regarding oxygenation, and hypo- or normothermia, in conjunction with MP, and its mechanisms of action are also debated. The primary aims of this article were to elucidate the benefits of MP preservation with and without oxygenation, and/or under normothermic conditions, when compared with CS prior to deceased donor kidney transplantation.

METHODS

Clinical (observational studies and prospective trials) and animal (experimental) articles exploring the use of renal MP were assessed (EMBASE, Medline, and Cochrane databases). Meta-analyses were conducted for the comparisons between hypothermic MP (hypothermic machine perfusion [HMP]) and CS (human studies) and normothermic MP (warm (normothermic) perfusion [WP]) compared with CS or HMP (animal studies). The primary outcome was allograft function. Secondary outcomes included graft and patient survival, acute rejection and parameters of tubular, glomerular and endothelial function. Subgroup analyses were conducted in expanded criteria (ECD) and donation after circulatory (DCD) death donors.

RESULTS

A total of 101 studies (63 human and 38 animal) were included. There was a lower rate of delayed graft function in recipients with HMP donor grafts compared with CS kidneys (RR 0.77; 95% CI 0.69-0.87). Primary nonfunction (PNF) was reduced in ECD kidneys preserved by HMP (RR 0.28; 95% CI 0.09-0.89). Renal function in animal studies was significantly better in WP kidneys compared with both HMP (standardized mean difference [SMD] of peak creatinine 1.66; 95% CI 3.19 to 0.14) and CS (SMD of peak creatinine 1.72; 95% CI 3.09 to 0.34). MP improves renal preservation through the better maintenance of tubular, glomerular, and endothelial function and integrity.

CONCLUSIONS

HMP improves short-term outcomes after renal transplantation, with a less clear effect in the longer-term. There is considerable room for modification of the process to assess whether superior outcomes can be achieved through oxygenation, perfusion fluid manipulation, and alteration of perfusion temperature. In particular, correlative experimental (animal) data provides strong support for more clinical trials investigating normothermic MP.

Mechanistic analysis of nonoxygenated hypothermic machine perfusion's protection on warm ischemic kidney uncovers greater eNOS phosphorylation and vasodilation

Protection of endothelial cell function may explain the benefits of nonoxygenated hypothermic machine perfusion (MP) for marginal kidney preservation. However, this hypothesis remains to be tested with a preclinical model. We postulated that MP protects the nitric oxide (NO) signaling pathway, altered by static cold storage (CS), and improves renal circulation recovery compared to CS. The endothelium releases the vasodilator NO in response to flow via either increased endothelial NO synthase (eNOS) expression (KLF2-dependent) or activation of eNOS by phosphorylation (via Akt, PKA or AMPK). Using a porcine model of kidney transplantation, including 1 h of warm ischemia and preserved 24 h by CS or MP (n=5), we reported that MP did not alter the cortical levels of KLF2 and eNOS at the end of preservation, but significantly increased eNOS activating phosphorylation compared to CS. eNOS phosphorylation appeared AMPK-dependent and was concomitant to an increased NO-dependent vasodilation of renal arteries measured, ex situ, at the end of preservation. In vivo, laser Doppler showed that cortical microcirculation was improved at reperfusion in MP kidneys. In conclusion, we demonstrate for the first time, in a large-animal model, that MP protects the NO signaling pathway, confirming the value of MP for marginal kidney preservation.

Oxygen consumption during oxygenated hypothermic perfusion as a measure of donor organ viability

Hypothermic machine perfusion (HMP) for the preservation of kidneys, recovered from extended criteria organ donors (ECDs), presents the opportunity for assessing ex vivo parameters that may have value in predicting postimplantation organ viability. Organ perfusion and vascular resistance are the parameters most frequently cited as the basis for the decision to use or discard a donor kidney. The limitation of these measures is emphasized by the observation that a significant percentage of ECD kidneys with poor perfusion parameters can provide life-sustaining function after transplantation. It has been suggested that whole organ oxygen consumption (OC) during oxygenated HMP may better reflect the proportion of viable tissue in the organ and more reliably predict posttransplant organ function. Our study correlates renal OC and renal vascular resistance (RVR) during oxygenated HMP with postpreservation glomerular filtration rates (GFRs) in rodent kidneys after 24 hours of oxygenated HMP. Kidneys from adult rodents were preserved for 24 hours using oxygenated HMP and static cold storage (SCS). During oxygenated HMP preservation, organ OC, renal organ flow rates, and RVR were serially measured. After the preservation period, organs were mounted onto a Langendorff device for warming to normal body temperature and measurement of GFR. Oxygen consumption and RVR during HMP were correlated with postpreservation GFR. Oxygen consumption during oxygenated HMP was significantly correlated (r2 = 0.871; p < 0.05) with postpreservation GFR, suggesting that higher OC predicts better postpreservation GFR. In contrast, RVR was poorly correlated with postpreservation GFR (r2 = 0.258; p = 0.199). Glomerular filtration rate in SCS kidneys was 0.002 ± 0.003 ml/min/g. We demonstrate that measurement of organ OC during oxygenated HMP may have significant value in predicting postpreservation organ function.

A basic consideration for porcine liver preservation using a novel continuous machine perfusion device

INTRODUCTION

The aims of this study were to compare extracellular and intracellular-type University of Wisconsin (UW) solutions for liver grafts and to assess oxygenation in this perfusion system.

MATERIALS AND METHODS

The organ preservation system consisted of 3 circulating systems for the portal vein, hepatic artery, and maintenance of the perfusion solution. The portal vein or hepatic artery system had a roller pump, a flow meter, and a pressure sensor. In this study, we perfused livers with UW or extracellular type UW-gluconate at 4°C-6°C for 4 hours. The flow rates at the entrance were 0.5 mL/min/g liver in the portal vein and 0.2 mL/min/liver in the hepatic artery. Orthotopic liver transplantation was performed in pigs: group 1-a, grafts procured after acute hemorrhagic shock were preserved by a solution without O(2); group 1-b, grafts were preserved with O(2); group 2-a, grafts were perfused using intracellular type solution (UW); and group 2-b, grafts were perfused using extracellular-type solution (UW-gluconate).

RESULTS

Effluent aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) levels in group 1-b were lower than those in group 1-a. Survival rates in group 2-a and group 2-b were 1/4 and 3/3, respectively. Effluent AST and LDH levels in the perfusate of group 2-b were lower than group 2-a. Histological study revealed necrosis of hepatocytes and sinusoidal congestion in group 2-a.

CONCLUSION

A beneficial effect of extracellular-type solution with oxygenation in a novel continuous machine preservation system yielded well-preserved liver graft function.

Delayed graft function in the kidney transplant

Acute kidney injury occurs with kidney transplantation and too frequently progresses to the clinical diagnosis of delayed graft function (DGF). Poor kidney function in the first week of graft life is detrimental to the longevity of the allograft. Challenges to understand the root cause of DGF include several pathologic contributors derived from the donor (ischemic injury, inflammatory signaling) and recipient (reperfusion injury, the innate immune response and the adaptive immune response). Progressive demand for renal allografts has generated new organ categories that continue to carry high risk for DGF for deceased donor organ transplantation. New therapies seek to subdue the inflammatory response in organs with high likelihood to benefit from intervention. Future success in suppressing the development of DGF will require a concerted effort to anticipate and treat tissue injury throughout the arc of the transplantation process.

The role of perfluorocarbon in organ preservation

Perfluorocarbons (PFCs) are inert solutions that have a high capacity for dissolving oxygen. There has been a continuing level of research into the delivery of oxygen during solid organ preservation with the use of PFCs. The one- and two-layer methods have been used as static storage techniques, proving particularly successful for pancreas preservation. They can also be formulated as an emulsion for continual perfusion or as a simple flush solution. The success of PFCs in organ preservation seems to be somewhat organ and species dependant, and further experimental evidence is needed to establish their application.

Optimising post-conditioning time of marginal donor livers

BACKGROUND

Due to the discrepancy between organ donors and receptors, the use of marginal livers (e.g., non-heart-beating-donor grafts) for transplantation purpose increased. The potential of a short-term aerobic machine perfusion (post-conditioning) for "less than optimal" grafts after cold storage (CS) was recently demonstrated. In our study, the optimal time course of post-conditioning (PC) is to be evaluated.

MATERIALS AND METHODS

Livers from male Wistar rats were withdrawn 30 min after cardiac arrest and flushed with histidine tryptophan ketoglutarate (HTK) solution. Then they were stored in HTK at 4 degrees C for 18 h. After 16 h, some livers were put on PC by cold perfusion with HTK for 0.5, 1, 2 or 3 h. Afterwards, the viability of the organs was estimated by warm reperfusion (2 h) in vitro.

RESULTS

After 1 h of PC, a significant increase in bile production and a decrease in enzyme release could be detected in comparison to CS. The adenosine triphosphate content of the PC livers after 1 h of treatment was significant higher than in CS organs. No markers for apoptosis could be detected after 1 h PC.

CONCLUSION

It can be concluded that a PC of 1 h after cold storage can ameliorate the organ viability of marginal livers. The extension or abbreviation of PC time seems to have no further beneficial effects.

Influence of flow and addition of oxygen during porcine liver hypothermic machine perfusion

INTRODUCTION

In contrast with kidneys, data on hypothermic machine perfusion (HMP) of livers remain scarce. Optimal liver HMP is poorly defined. Superiority of liver HMP over simple cold storage (SCS), the current standard preservation, must be proven before HMP is applied clinically. In this study, morphology and adenosine triphosphate (ATP) contents of HMP livers at different flows and with versus without O(2) studied in a porcine ex vivo model were compared to SCS.

METHODS

Pig livers were procured, flushed with HTK and preserved via SCS or HMP at 3 HMP settings: high flow (HF); low flow (LF); low flow + O(2) (300 mm Hg) (LFO). HMP livers were perfused via the hepatic artery (HA) and portal vein (PV) with KPS-1 TM at 4 degrees C to 6 degrees C for 24 hours with HF: PV: 3 to 5 mm Hg, 1 mL/g liver/min for HA and 25 mm Hg; LF: PV: 3 to 5 mm Hg, 0.5 ml/g liver/min with HA: 20 mm Hg. Morphology and ATP levels were measured in preserved liver tissues.

RESULTS

Throughout the SCS preservation, livers remained intact. In HMP livers, vacuoles appeared after 4 hours of preservation in the HF group and after 12 hours in the LF livers. LFO livers remained intact with limited vacuoles. Compared to SCS, HMP livers showed dilated sinusoids, particularly in the HF group. ATP remained relatively constant or even increased during HMP, particularly in the LF group, whereas ATP decreased after SCS.

CONCLUSION

Among the various HMP settings, HMP with LFO was superior. ATP levels were the highest in LF. In contrast with all HMP groups, SCS showed the lowest ATP levels, indicating that HMP has the potential to better preserve energy stores.

Perspectives in organ preservation

Maintaining organ viability after donation until transplantation is critically important for optimal graft function and survival. To date, static cold storage is the most widely used form of preservation in every day clinical practice. Although simple and effective, it is questionable whether this method is able to prevent deterioration of organ quality in the present era with increasing numbers of organs retrieved from older, more marginal, and even non-heart-beating donors. This review describes principles involved in effective preservation and focuses on some basic components and methods of abdominal organ preservation in clinical and experimental transplantation. Concepts and developments to reduce ischemia related injury are discussed, including hypothermic machine perfusion. Despite the fact that hypothermic machine perfusion might be superior to static cold storage preservation, organs are still exposed to hypothermia induced damage. Therefore, recently some groups have pointed at the beneficial effects of normothermic machine perfusion as a new perspective in organ preservation and transplantation.

Hypothermic perfusion preservation: the future of organ preservation revisited?

Hypothermic perfusion preservation (HPP) was an integral step in the development of early clinical transplantation programmes, and considerable progress was made in understanding the basic principles underlying the technique. In subsequent years, the development of better preservation solutions for cold hypoxic storage, along with pragmatic choices made on grounds of costs and logistics, saw a fall in the application of HPP. More recently, the acute shortage of suitable organ donors and the inevitable pressure to use organs from sub-optimal (or expanded criteria) donors, has forced a re-evaluation of HPP, and the development of a new generation of HPP machines and associated perfusion solutions. This review sets out the historical development of HPP across the range of organs in which the method was originally investigated, describes the biological benefits and drawbacks associated with HPP, and sets out the most recent literature on the topic (including comments on the interest in use of higher temperatures in organ perfusion).