Reduced glutathione in the liver as a potential viability marker in non-heart-beating donors

Advances in the management of the explanted donor liver

Liver transplantation is the best therapy in end-stage liver disease. Donor organ shortage and efforts to expand the donor organ pool are permanent issues given that advances in perioperative management and immunosuppressive therapy have brought the procedure into widespread clinical use. The management of organ procurement, including donor preconditioning and adequate organ storage, has a key role in transplantation. However, the organ procurement process can differ substantially between transplant centres, depending on local and national preferences. Advances in the field have come from experimental and clinical research on dynamic storage systems, such as machine perfusion devices, as an alternative to static cold storage. Determination of the clinical significance of these new systems is a topic worthy of future investigations.

Current status and recent advances of liver transplantation from donation after cardiac death

The last decade saw increased organ donation activity from donors after cardiac death (DCD). This contributed to a significant proportion of transplant activity. Despite certain drawbacks, liver transplantation from DCD donors continues to supplement the donor pool on the backdrop of a severe organ shortage. Understanding the pathophysiology has provided the basis for modulation of DCD organs that has been proven to be effective outside liver transplantation but remains experimental in liver transplantation models. Research continues on how best to further increase the utility of DCD grafts. Most of the work has been carried out exploring the use of organ preservation using machine assisted perfusion. Both ex-situ and in-situ organ perfusion systems are tested in the liver transplantation setting with promising results. Additional techniques involved pharmacological manipulation of the donor, graft and the recipient. Ethical barriers and end-of-life care pathways are obstacles to widespread clinical application of some of the recent advances to practice. It is likely that some of the DCD offers are in fact probably “prematurely” offered without ideal donor management or even prior to brain death being established. The absolute benefits of DCD exist only if this form of donation supplements the existing deceased donor pool; hence, it is worthwhile revisiting organ donation process enabling us to identify counter remedial measures.

Contribution of large pig for renal ischemia-reperfusion and transplantation studies: the preclinical model

Animal experimentation is necessary to characterize human diseases and design adequate therapeutic interventions. In renal transplantation research, the limited number of in vitro models involves a crucial role for in vivo models and particularly for the porcine model. Pig and human kidneys are anatomically similar (characterized by multilobular structure in contrast to rodent and dog kidneys unilobular). The human proximity of porcine physiology and immune systems provides a basic knowledge of graft recovery and inflammatory physiopathology through in vivo studies. In addition, pig large body size allows surgical procedures similar to humans, repeated collections of peripheral blood or renal biopsies making pigs ideal for medical training and for the assessment of preclinical technologies. However, its size is also its main drawback implying expensive housing. Nevertheless, pig models are relevant alternatives to primate models, offering promising perspectives with developments of transgenic modulation and marginal donor models facilitating data extrapolation to human conditions.

Machine perfusion at 20°C reduces preservation damage to livers from non-heart beating donors

We previously reported that machine perfusion (MP) performed at 20°C enhanced the preservation of steatotic rat livers. Here, we tested whether rat livers retrieved 30 min after cardiac arrest (NHBDs) were better protected by MP at 20°C than with cold storage. We compared the recovery of livers from NHBDs with organs obtained from heart beating donors (HBDs) preserved by cold storage. MP technique: livers were perfused for 6h with UW-G modified at 20°C. Cold storage: livers were perfused in situ and preserved with UW solution at 4°C for 6h. Both MP and cold storage preserved livers were reperfused with Krebs-Heinselet buffer (2h at 37°C). AST and LDH release and mitochondrial glutamate dehydrogenase (GDH) levels were evaluated. Parameters assessed included: bile production and biliary enzymes; tissue ATP; reduced and oxidized glutathione (GSH/GSSG); protein-SH group concentration. Livers preserved by MP at 20°C showed significantly lower hepatic damage at the end of reperfusion compared with cold storage. GDH release was significantly reduced and bile production, ATP levels, GSH/GSSG and protein-SH groups were higher in livers preserved by MP at 20°C than with cold storage. The best preserved morphology and high glycogen content was obtained with livers submitted to MP at 20°C. Liver recovery using MP at 20°C was comparable to recovery with HBDs. MP at 20°C improves cell survival and gives a better-quality of preservation for livers obtained from NHBDs and may provide a new method for the successful utilization of marginal livers.

Navigated liver biopsy using a novel soft tissue navigation system versus CT-guided liver biopsy in a porcine model: a prospective randomized trial

RATIONALE AND OBJECTIVES

The aim of this prospective, randomized animal study was to compare a new computer guided needle-based navigation system for liver biopsy with conventional computed tomography (CT)-guided liver biopsy. Computer-navigated interventions provide continuous needle tracking during motion and deformation from patient respiration and movement.

MATERIALS AND METHODS

Twenty artificial tumors of about 5 mm in diameter were injected into the livers of five pigs, each at a different site. Each tumor was targeted by conventional CT-guided and computer navigated intervention. Intervention was considered complete after successful tumor biopsy. Data on procedure time, number of CT scans performed, accuracy, and success rate were recorded.

RESULTS

All tumors (100%) were biopsied successfully. Mean procedural time was comparable between the two techniques (20 ± 9 minutes conventional versus 20 ± 8 minutes navigation). Mean number of CT scans were 1.2 ± 0.4 with navigation and 6.1 ± 3.8 with the conventional technique (P < .01). The dose-length product in the conventional group was significantly higher (212 ± 116 mGy × cm) than in the navigated group (78 ± 22 mGy × cm; P < .001). Mean number of capsule penetrations was 4 ± 1 with navigation versus 2 ± 1 with the conventional technique (P < .001).

CONCLUSION

Computer-navigated liver biopsy may provide a promising and innovative device for easy, rapid, and successful liver biopsies with low morbidity. Further technical improvements and clinical studies in humans are required.

Liver transplantation: Issues for the next 20 years

The growing numbers of potential transplant recipients on waiting lists is increasingly disproportionate to the supply of cadaveric donor organs. The hope for the next 20 years is that supply will satisfy demand. This requires both a reduction in indications for the procedure and an increase in the transplants performed. A multi-pronged approach is needed to increase cadaveric organ donation, generating enthusiasm for donation among both the general public and hospital staff. Accurate assessment of marginal grafts with stringent criteria known to predict graft function will diminish wastage of organs. Methods of rehabilitating marginal grafts during extracorporeal perfusion will increase organ availability. Supply of non-heart beating donors can be greatly expanded and protocols developed with ethical consent to optimize their initial function despite warm ischemia. Splitting livers that fulfill selection criteria, thus providing for two recipients, should be universally applied with acceptable incentives to those units who do not directly benefit. A proportion of recipients, though not those transplanted for autoimmune disease, will be spared the side-effects of immunosuppression thanks to immune tolerance. Protocols for close monitoring of those patients for rejection during treatment withdrawal must be carefully observed. In addition to gene therapy, it is highly likely that hepatocyte transplantation will replace orthotopic grafting in patients without cirrhosis, especially for inherited metabolic diseases. It is much more difficult to envisage that heterologous stem cell transplantation or xenotransplantation will have clinical impact in the next 20 years, although research in those areas has obvious long-term potential.

A novel biomarker for retinal degeneration: vitreous body neurofilament proteins

Retinal degeneration leads to release of cell-type specific proteins into the adjacent compartment. Here we investigated whether the neurofilament heavy chain protein (NfH) could be measured from the vitreous body and anterior chamber fluid. This prospective study included 85 patients who underwent vitrectomy (44 retinal detachment, 12 macular hole, 15 epiretinal gliosis, 8 organ donors) or trabelectomy (six glaucoma). The cut-off level was calculated from the organ donors. An established enzyme-linked immunosorbent assay (ELISA, SMI35) was used for quantification of NfH (190-210 kDa). Measurable levels of NfH were detected from the vitreous body homogenate, but not from the anterior chamber fluid. The cut-off level was 0.29 ng/mL. A significant proportion of patients suffering from retinal detachment (43.2%, mean 0.74 ng/mL) had vitreous body NfH levels above cut-off when compared to organ donors (0%, 0.12 ng/mL, p = 0.02), epiretinal sclerosis (1.6%, 0.05 ng/mL, p = 0.01), macular hole (0%, 0.04 ng/mL, p = 0.004). Following retinal detachment, vitreous NfH-SMI35 levels correlated with time from onset (R = -0.3, p < 0.05), persisting for up to 2 years. This study shows that NfH can be quantified from the human vitreous body and may be a useful novel biomarker for retinal degeneration. The method can be applied for investigating the dynamics of retinal degeneration and the response to neuroprotective strategies in a broad range of retinal diseases in either clinical or experimental research.

Exact CT-based liver volume calculation including nonmetabolic liver tissue in three-dimensional liver reconstruction

Exact preoperative determination of the liver volume is of great importance prior to hepatobiliary surgery, especially in living donated liver transplantation (LDLT) and extended hepatic resections. Modern surgery-planning systems estimate these volumes from segmented image data. In an experimental porcine study, our aim was (1) to analyze and compare three volume measurement algorithms to predict total liver volume, and (2) to determine vessel tree volumes equivalent to nonmetabolic liver tissue. Twelve porcine livers were examined using a standardized three-phase computed tomography (CT) scan and liver volume was calculated computer-assisted with the three different algorithms. After hepatectomy, livers were weighed and their vascular system plasticized followed by CT scan, CT reconstruction and re-evaluation of total liver and vessel volumes with the three different algorithms. Blood volume determined by the plasticized model was at least 1.89 times higher than calculated by multislice CT scans (9.7% versus 21.36%, P=0.028). Analysis of 3D-CT-volumetry showed good correlation between the actual and the calculated liver volume in all tested algorithms with a high significant difference in estimating the liver volume between Heymsfield versus Heidelberg (P=0.0005) and literature versus Heidelberg (P=0.0060). The Heidelberg algorithm reduced the measuring error with deviations of only 1.2%. The present results suggest a safe and highly predictable use of 3D-volumetry in liver surgery for evaluating liver volumes. With a precise algorithm, the volume of remaining liver or single segments can be evaluated exactly and potential operative risks can therefore be better calculated. To our knowledge, this study implies for the first time a blood pool, which corresponds to nonmetabolic liver tissue, of more than 20% of the whole liver volume.