Renal preservation

Liver Transplantation Today: Where We Are Now and Where We Are Going

Liver transplantation was made a reality through the bravery, innovation, and persistence of Dr. Thomas Starzl. His death in 2017, at the age of 90, makes us pause to consider how far the field has come since its inception by this remarkable pioneer. It also is an opportunity to evaluate the continued novel innovations which contribute to the growth and potential for liver transplantation in the future. The liver transplant community in 2017 continued to be most significantly challenged by an overwhelming disparity between the need for liver transplant and the shortage of donor organs. The many ways in which this critical shortage are being addressed are examined in this article. The continued debate about equitable and efficacious organ allocation, "the liver wars," has dominated much of the recent past, while efforts to optimize current organ availability have also been aggressively pursued. Efforts to optimize the use of marginal and expanded criteria organs have escalated in recent years and have been accompanied by rigorous scientific evaluation. The ongoing opioid epidemic, combined with the approval and availability of highly effective hepatitis C treatment options, has allowed the increased use of HCV positive organs in HCV positive and negative recipients. Machine perfusion, both cold and warm, has moved solidly into the liver transplant world potentiating optimization of marginal donors and also offering potential modulation of liver grafts (ie, gene therapy, stem cell therapy, and defatting). Finally, pharmacological and mechanical interventions in DCD procurement techniques have contributed to improved outcomes in DCD transplants. All of these are explored in this article as a tribute to innovative spirit of Dr. Starzl and his continued impact on liver transplant today.

Hypothermic machine perfusion in kidney transplantation

PURPOSE OF REVIEW

This article summarizes novel developments in hypothermic machine perfusion (HMP) as an organ preservation modality for kidneys recovered from deceased donors.

RECENT FINDINGS

HMP has undergone a renaissance in recent years. This renewed interest has arisen parallel to a shift in paradigms; not only optimal preservation of an often marginal quality graft is required, but also improved graft function and tools to predict the latter are expected from HMP. The focus of attention in this field is currently drawn to the protection of endothelial integrity by means of additives to the perfusion solution, improvement of the HMP solution, choice of temperature, duration of perfusion, and machine settings. HMP may offer the opportunity to assess aspects of graft viability before transplantation, which can potentially aid preselection of grafts based on characteristics such as perfusate biomarkers, as well as measurement of machine perfusion dynamics parameters.

SUMMARY

HMP has proven to be beneficial as a kidney preservation method for all types of renal grafts, most notably those retrieved from extended criteria donors. Large numbers of variables during HMP, such as duration, machine settings and additives to the perfusion solution are currently being investigated to improve renal function and graft survival. In addition, the search for biomarkers has become a focus of attention to predict graft function posttransplant.

Limb preservation for reimplantation. a review

Although reimplantation of severed limbs and other parts of the body has become prevalent in recent years, the questions of how best to preserve limbs for reimplantation and how to determine if a transected part is viable have not been fully answered. The problem of preservation involves combating direct anoxic damage to tissue as well as combating the changes in the vascular system that lead to the "no reflow phenomenon." Current information concerning kidney preservation as well as experimental and clinical reports on limb preservation are reviewed in this article, and suggestions are made for further investigations.

Failure of perfusion with oxygenated Krebs-Ringer solution to preserve the eccrine function of the vascular endothelium in bone

An ex vivo canine tibia preparation was perfused at a constant rate with aerated (95% O2-5% CO2) Krebs-Ringer solution for 24 h. Bolus injections of norepinephrine (0.125-0.5 micrograms) were given and then acetylcholine (5 x 10(-5) M) was used to stimulate endothelial production of smooth muscle relaxing factors. Following 1 h of perfusion the addition of acetylcholine resulted in significant attenuation of the response to norepinephrine (p < 0.001). After 4 h perfusion acetylcholine did not attenuate the norepinephrine response, but addition of L-arginine (the precursor of endothelial-derived relaxing factor) resulted in significant attenuation in the presence of acetylcholine (p < 0.005). At 6, 12, and 24 h the acetylcholine did not attenuate the norepinephrine response. It is concluded that normothermic, continuous perfusion with oxygenated Krebs-Ringer solution results in normal endothelial eccrine activity up to 1 h. Following this period there is substrate depletion but endothelial eccrine function can be demonstrated for up to 4 h. At 6 h this function cannot be demonstrated, suggesting degradation of the functional integrity of the endothelium.

Metabolism in hypothermically perfused human kidney carcinoma: utilization and production of amino acids and glucose

The metabolism of human kidney carcinoma was studied during hypothermic perfusion. Ten kidneys with carcinomas of different size were perfused in a Gambro perfusion machine for 6 days at +8 degrees C to +10 degrees C. The tumourous kidneys were allocated to one of two groups depending on the relative size of the tumour. Tumours occupying more than 40% of the total kidney volume were designated as "large tumours" and tumours occupying less than 40% as "small tumours". The net glucose uptake was greater during perfusion of kidneys with large tumours than during perfusion of kidneys with small tumours. A lower gluconeogenesis was found in kidneys with large tumours compared to perfusion of kidneys with small tumours and this could explain a large part of the difference in net glucse uptake. The uptake of fatty acids per unit kidney weight was lower during perfusion of kidneys with large tumours. A considerable uptake and release of amino acids were found in both groups. The uptake of proline, aspartate, glycine, and arginine as well as the release of alanine and serine was lower during perfusion of kidneys with large tumours. The nitrogen balance was negative in both groups, with a net release of amino acids to the perfusate. The results suggest a higher glucose uptake, a lower gluconeogenesis, a lower fatty acid uptake and a decreased metabolization of amino acids in the tumour compared to the renal tissue. The model appears promising for studies of human kidney carcinomas at various experimental conditions.

Flow and function in machine-preserved kidneys

One hundred machine-preserved cadaver kidneys were transplanted irrespective of their flow rates on the preservation machine. Twenty-five per cent had flows of below 100 ml/min and 11 per cent had flows of below 80 ml/min. There was no correlation between the flow rate and function at 1, 3 or 12 months. There was no difference in the flow rate between those kidneys which functioned immediately and those which never functioned. A fall in flow rate was associated with acute tubular necrosis of longer duration but eventual function was not impaired. There was a higher incidence of early aggressive rejection in kidneys which functioned immediately. Preservation failure per se is a rare cause of primary non-function. Adherence to a policy of ignoring the flow characteristics of machine-preserved kidneys could make up to 25 per cent more kidneys available for transplantation.

Bilateral cervical transplantation of canine kidneys for study of canine renal preservation

Bilateral cervical autotransplantation of canine kidneys is described for comparative study of renal preservation techniques. Data are obtained from kidneys preserved by (1) initial intravascular flushing with modified Collins' C3 solution (Ursol) followed by cold storage, and (2) pulsatile perfusion (MOX 100). Preharvest condition of the donor and ischemia times are identical, thus eliminating major sources of potential data variation. Renal function studies performed at periodic intervals demonstrated better initial function for machine preservation but no difference after one to two-month period.

Maintenance of insulin release from pancreatic islets stored in the cold for up to 5 weeks

Insulin content and release were measured from hand-dissected pancreatic islets from noninbred ob/ob mice after 1-5 wk storage in tissue culture medium 199 at various temperatures and glucose concentrations. After storage of islets for 1 wk at 37 degrees, 22 degrees, or 8 degrees C in 18 mM glucose medium and preincubation with 1 mM glucose, glucose-stimulated insulin release during the subsequent incubation was only 20-35% of that of fresh islets. The addition of a 4-h period at 37 degrees C with 18 mM glucose between the cold storage and perincubation restored glucose-stimulated insulin release from 8 degrees C stored islets to fresh-islet levels. Release throughout the 1-18 mM glucose range was strikingly parallel to that of fresh islets. Exposure of fresh islets to the same 4-h period increased basal release but did not affect maximal release. When islets were stored at 8 degrees C with 18 mM glucose for more than 1 wk, a short period at 37 degrees C every week was necessary for maintenance of release. After 5 wk of this procedure, glucose-stimulated insulin release was one-third that of fresh islets, or similar to that of islets stored for only 1 wk at 37 degrees C. Storage at 8 degrees C for 1 wk with 3 mM glucose, or continuously for 3 or 5 wk with 18 mM glucose, maintained islet insulin content, whereas release was lost. Thus, glucose-stimulated insulin release is best maintained by storage of pancreatic islets in tissue culture medium with a high concentration of glucose at 8 degrees C with short weekly periods at 37 degrees C.