Histidine-tryptophan-ketoglutarate (HTK) is associated with reduced graft survival in pancreas transplantation

Histidine-tryptophan-ketoglutarate for pancreas allograft preservation: the Indiana University experience

Histidine-tryptophan-ketoglutarate solution (HTK) has been scrutinized for use in pancreas transplantation. A recent case series and a United Network for Organ Sharing data base review have suggested an increased incidence of allograft pancreatitis and graft loss with HTK compared to the University of Wisconsin solution (UW). Conversely, a recent randomized, controlled study failed to show any significant difference between HTK and UW for pancreas allograft preservation. This study was a retrospective review of all pancreas transplants performed at Indiana University between 2003 and 2009 comparing preservation with HTK or UW. Data included recipient and donor demographics, 7-day, 90-day and 1-year graft survival, peak 30-day serum amylase and lipase, HbA1c and C-peptide levels. Of the 308 pancreas transplants, 84% used HTK and 16% UW. There were more SPK compared to pancreas after kidney and pancreas transplant alone in the HTK group. Donor and recipient demographics were similar. There was no significant difference in 7-day, 90-day or 1-year graft survival, 30-day peak serum amylase and lipase, HbA1c or C-peptide. No clinically significant difference between HTK and UW for pancreas allograft preservation was identified. Specifically, in the context of low-to-moderate flush volume and short cold ischemia time (<or=10 h), no increased incidence of allograft pancreatitis or graft loss was observed.

Donor intervention and organ preservation: where is the science and what are the obstacles?

The organ shortage is widely acknowledged as the most critical factor hindering the full realization of success for solid organ transplantation. Innovation in the areas of donor management and organ preservation offers the most realistic hope to improve both the quality and size of the current organ supply. Although the basic science dissecting the complex processes of brain death and ischemia/reperfusion injury is replete with exciting discoveries, the clinical science investigating donor management and organ preservation is sparse in contrast. This review will survey the current landscape of trials to mitigate organ injury through interventions administered to donors in vivo or organs ex vivo. Consideration will then be given to the scientific, logistical and ethical obstacles that impede the transformation of laboratory breakthroughs into innovative treatments that simultaneously improve organ quality and supply.

A comparison of hypothermic machine perfusion versus static cold storage in an experimental model of renal ischemia reperfusion injury

INTRODUCTION

There is increasing support for the use of hypothermic machine perfusion (HMP) in an attempt to reduce preservation injury. However, experimental evidence is needed to further examine the effects of HMP on renal ischemia reperfusion injury.

METHODS

Porcine kidneys were subjected to 10 min of warm ischemia followed by 18 hr of static cold storage with hyperosomolar citrate (HOC), histidine-tryptophan-ketoglutarate (HTK), or University of Wisconsin (UW) solutions or 18 hr HMP with Kidney Perfusion Solution using the Lifeport perfusion system. Renal function, oxidative damage, and morphology were assessed during 3 hr of reperfusion with autologous blood using an isolated organ perfusion system.

RESULTS

During reperfusion, intrarenal resistance was significantly lower in the HMP group compared with HOC and UW (area under the curve; HMP 3.8+/-1.7, HOC 9.1+/-4.3, UW 7.7+/-2.2, HTK 5.6+/-1.9 mm Hg/min; P=0.006), and creatinine clearance was significantly higher compared with the UW group (area under the curve creatinine clearance; HMP 9.8+/-7.3, HOC 2.2+/-1.7, UW 1.8+/-1.0, HTK 2.1+/-1.8 mL/min/100 g; P=0.004). Tubular function was significantly improved in the HMP group (P<0.05); however, levels of lipid peroxidation were significantly higher (P=0.005).

CONCLUSION

HMP demonstrated a reduced level of preservation injury compared with the static techniques resulting in improved renal and tubular function and less tubular cell inflammation during reperfusion.

Organ donation and utilization in the United States, 1999-2008

Despite the Organ Donation Breakthrough Collaborative's work to engage the transplant community and the suggested positive impact from these efforts, availability of transplanted organs over the past 5 years has declined. Living kidney, liver and lung donations declined from 2004 to 2008. Living liver donors in 2008 dropped to less than 50% of the peak (524) in 2001. There were more living donors that were older and who were unrelated to the recipient. Percentages of living donors from racial minorities remained unchanged over the past 5 years, but percentages of Hispanic/Latino and Asian donors increased, and African American donors decreased. The OPTN/UNOS Living Donor Transplant Committee restructured to enfranchise organ donors and recipients, and to seek their perspectives on living donor transplantation. In 2008, for the first time in OPTN history, deceased donor organs decreased compared to the prior year. Except for lung donors, deceased organ donation fell from 2007 to 2008. Donation after cardiac death (DCD) has accounted for a nearly 10-fold increase in kidney donors from 1999 to 2008. Use of livers from DCD donors declined in 2008 to 2005 levels. Understanding health risks associated with the transplantation of organs from 'high-risk' donors has received increased scrutiny.

Complications after pancreas transplantation

PURPOSE OF REVIEW

The history of transplantation of the pancreas, unlike that of transplantation of other abdominal organs, has largely been shaped by the associated surgical complications. After more than three decades of progress, surgical-technical pancreas graft failure rates have decreased to approximately 8%. The most recent developments in this area are systematically reviewed in this article.

RECENT FINDINGS

Vascular graft thrombosis remains, by far, the most common cause of technical graft failure. Recent reports suggested that pancreas preservation with histidine-tryptophan-ketoglutarate solution (HTK) might be a risk factor for reperfusion pancreatitis, graft thrombosis and decreased short- and long-term graft survival. It remains unclear whether these results are, at least in part, related to HTK flush volumes and extended preservation (e.g.,>12 h). For selected thrombosed pancreas grafts, there has been renewed interest in pharmacological, interventional, and surgical salvage. For selected recipients with early pancreas graft thrombosis not amenable to a salvage intervention, transplant pancreatectomy in conjunction with immediate retransplantation has emerged as a viable option. For graft thrombosis prevention, the enhanced backtable pancreas vascular reconstruction techniques (e.g., gastroduodenal artery revascularization) proposed by some authors await more formal study. For prevention of native vascular complications in high-risk recipients, several technical modifications have been reported. Developments with respect to other surgical complications (wound infection, pancreatitis, leak, and bleeding) have been more incremental.

CONCLUSION

Recent evidence underscores the importance of judicious donor and recipient selection and of optimization of preservation and surgical factors for excellent short- and long-term pancreas transplant outcomes.

Pharmacological strategies against cold ischemia reperfusion injury

IMPORTANCE OF THE FIELD

Good organ preservation is a determinant of graft outcome after revascularization. The necessity of increasing the quality of organ preservation, as well as of extending cold storage time, has made it necessary to consider the use of pharmacological additives.

AREAS COVERED IN THIS REVIEW

The complex physiopathology of cold-ischemia-reperfusion (I/R) injury--and in particular cell death, mitochondrial injury and endoplasmic reticulum stress--are reviewed. Basic principles of the formulation of the different preservation solutions are discussed.

WHAT THE READER WILL GAIN

Current strategies and new trends in static organ preservation using additives such as trimetazidine, polyethylene glycols, melatonin, trophic factors and endothelin antagonists in solution are presented and discussed. The benefits and mechanisms responsible for enhancing organ protection against I/R injury are also discussed. Graft preservation was substantially improved when additives were added to the preservation solutions.

TAKE HOME MESSAGE

Enrichment of preservation solutions by additives is clinically useful only for short periods. For longer periods of cold ischemia, the use of such additives becomes insufficient because graft function deteriorates as a result of ischemia. In such conditions, the preservation strategy should be changed by the use of machine perfusion in normothermic conditions.

Multicenter analysis of novel and established variables associated with successful human islet isolation outcomes

Islet transplantation is a promising therapy used to achieve glycometabolic control in a select subgroup of individuals with type I diabetes. However, features that characterize human islet isolation success prior to transplantation are not standardized and lack validation. We conducted a retrospective analysis of 806 isolation records from 14 pancreas-processing laboratories, considering variables from relevant studies in the last 15 years. The outcome was defined as post-purification islet equivalent count, dichotomized into yields > or =315 000 or < or =220 000. Univariate analysis showed that donor cause of death and use of hormonal medications negatively influenced outcome. Conversely, pancreata from heavier donors and those containing elevated levels of surface fat positively influence outcome, as did heavier pancreata and donors with normal amylase levels. Multivariable logistic regression analysis identified the positive impact on outcome of surgically intact pancreata and donors with normal liver function, and confirmed that younger donors, increased body mass index, shorter cold ischemia times, no administration of fluid/electrolyte medications, absence of organ edema, use of University of Wisconsin preservation solution and a fatty pancreas improves outcome. In conclusion, this multicenter analysis highlights the importance of carefully reviewing all donor, pancreas and processing parameters prior to isolation and transplantation.

Machine perfusion or cold storage in organ transplantation: indication, mechanisms, and future perspectives

Most organs are currently preserved by cold storage (CS) prior to transplantation. However, as more so called marginal donor organs are utilized, machine perfusion has regained clinical interest. Recent studies have demonstrated advantages of pulsatile perfusion over CS preservation for kidney transplantation. However, it remains unclear whether there is a significant benefit of one preservation method over the other in general, or, whether the utilization of particular preservation approaches needs to be linked to organ characteristics. Proposed protective mechanisms of pulsatile perfusion remain largely obscure. It can be speculated that pulsatile perfusion may not only provide nutrition and facilitate the elimination of toxins but also trigger protective mechanisms leading to the amelioration of innate immune responses. Those aspects may be of particular relevance when utilizing grafts with suboptimal quality which may have an increased vulnerability to ischemia/reperfusion injury and compromised repair mechanisms. This review aims to enunciate the principles of organ perfusion and preservation as they relate to indication, aspects of organ protection and to highlight future developments.

Pancreatic duct: A suitable route to oxygenate tissue during pancreas hypothermic preservation?

The effectiveness of Two-Layer Method has been questioned recently. In this study we hypothesized that pancreatic duct might be an appropriate route to oxygenate the organ and prevent cold ischemic injury. Male Sprague-Dawley rats were employed for the pancreas procurement. Pancreata were removed after 20ml ductal injection of cold Hank's Balanced Salt Solution (HBSS), or pre-oxygenated solutions of HBSS (O-HBSS), perfluorocarbon (O-PFC), and emulsified PFC (O-ePFC) and then preserved in HBSS for 24h. Spectrophotometric analysis was performed to measure ATP, adenosine diphosphate (ADP), and adenosine monophosphate (AMP). To standardize metabolite data, values were reported in terms of 'per gram protein of pancreatic tissue'. Protein was measured according to Lowry et al. ADP/ATP ratio, total adenylates and energy charge (EC) were calculated. There was a significant decrease in tissue ATP after hypothermic preservation. Pancreatic tissues lost 47.8% of their ATP values just in the first hour of preservation and 98.5% of their ATP values within 12h of preservation and ductal oxygenation could not prevent the ischemia. Unlike the other groups, ductal injection of oxygenated PFC could slow the total adenylates reduction rate that no significant difference was detected (9.6+/-2.9 vs. 14.8+/-2.1mol/g protein, NS) after 12h of preservation. Ductal injection of oxygenated PFC significantly reduced ADP/ATP ratio (8.57+/-0.6 vs. 14.2+/-2.4, p<0.03) and improved intracellular energy charge (0.36+/-0.05 vs. 0.22+/-0.03, p<0.001) as compared to HBSS group. The findings indicate that the pancreatic duct might be a suitable route for pancreatic oxygenation.

Histidine-tryptophan-ketoglutarate (HTK) is associated with reduced graft survival of deceased donor kidney transplants

Single-center studies have reported equivalent outcomes of kidney allografts recovered with histidine-tryptophan-ketoglutarate (HTK) or University of Wisconsin (UW) solution. However, these studies were likely underpowered and often unadjusted, and multicenter studies have suggested HTK preservation might increase delayed graft function (DGF) and reduce graft survival of renal allografts. To further inform clinical practice, we analyzed the United Network for Organ Sharing (UNOS) database of deceased donor kidney transplants performed from July 2004 to February 2008 to determine if HTK (n = 5728) versus UW (n = 15 898) preservation impacted DGF or death-censored graft survival. On adjusted analyses, HTK preservation had no effect on DGF (odds ratio [OR] 0.99, p = 0.7) but was associated with an increased risk of death-censored graft loss (hazard ratio [HR] 1.20, p = 0.008). The detrimental effect of HTK was a relatively late one, with a strong association between HTK and subsequent graft loss in those surviving beyond 12 months (HR 1.43, p = 0.007). Interestingly, a much stronger effect was seen in African-American recipients (HR 1.55, p = 0.024) than in Caucasian recipients (HR 1.18, p = 0.5). Given recent studies that also demonstrate that HTK preservation reduces liver and pancreas allograft survival, we suggest that the use of HTK for abdominal organ recovery should be reconsidered.

Organ donation and utilization in the United States: 1998-2007

Organ transplantation remains the only life-saving therapy for many patients with organ failure. Despite the work of the Organ Donation and Transplant Collaboratives, and the marked increases in deceased donors early in the effort, deceased donors only rose by 67 from 2006 and the number of living donors declined during the same time period. There continue to be increases in the use of organs from donors after cardiac death (DCD) and expanded criteria donors (ECD). This year has seen a major change in the way organs are offered with increased patient safety measures in those organ offers made by OPOs using DonorNet. Unfortunately, the goals of 75% conversion rates, 3.75 organs transplanted per donor, 10% of all donors from DCD sources and 20% growth of transplant center volume have yet to be reached across all donation service areas (DSAs) and transplant centers; however, there are DSAs that have not only met, but exceeded, these goals. Changes in organ preservation techniques took place this year, partly due to expanding organ acceptance criteria and increasing numbers of ECDs and DCDs. Finally, the national transplant environment has changed in response to increased regulatory oversight and new requirements for donation and transplant provider organizations.