Assessment of Mitochondrial Respiration During Hypothermic Storage of Liver Biopsies Following Normothermic Machine Perfusion.

Organ quality can be assessed prior to transplantation, during normothermic machine perfusion (NMP) of the liver. Evaluation of mitochondrial function by high-resolution respirometry (HRR) may serve as a viability assessment concept in this setting. Freshly collected tissue is considered as optimal sample for HRR, but due to technical and personnel requirements, more flexible and schedulable measurements are needed. However, the impact of cold storage following NMP before processing biopsy samples for mitochondrial analysis remains unknown. We aimed at establishing an appropriate storage protocol of liver biopsies for HRR. Wedge biopsies of 5 human livers during NMP were obtained and assessed by HRR. Analysis was performed after 0, 4, 8, and 12 h of hypothermic storage (HTS) in HTK organ preservation solution at 4°C. With HTS up to 4 h, mitochondrial performance did not decrease in HTS samples compared with 0 h (OXPHOS, 44.62 [34.75-60.15] pmol·s-1·mg wet mass-1 vs. 43.73 [40.69-57.71], median [IQR], p > 0.999). However, at HTS beyond 4 h, mitochondrial respiration decreased. We conclude that HTS can be safely applied for extending the biopsy measurement window for up to 4 h to determine organ quality, but also that human liver respiration degrades beyond 4 h HTS following NMP.

The Predictive Value of Graft Viability and Bioenergetics Testing Towards the Outcome in Liver Transplantation.

Donor organ biomarkers with sufficient predictive value in liver transplantation (LT) are lacking. We herein evaluate liver viability and mitochondrial bioenergetics for their predictive capacity towards the outcome in LT. We enrolled 43 consecutive patients undergoing LT. Liver biopsy samples taken upon arrival after static cold storage were assessed by histology, real-time confocal imaging analysis (RTCA), and high-resolution respirometry (HRR) for mitochondrial respiration of tissue homogenates. Early allograft dysfunction (EAD) served as primary endpoint. HRR data were analysed with a focus on the efficacy of ATP production or P-L control efficiency, calculated as 1-L/P from the capacity of oxidative phosphorylation P and non-phosphorylating respiration L. Twenty-two recipients experienced EAD. Pre-transplant histology was not predictive of EAD. The mean RTCA score was significantly lower in the EAD cohort (-0.75 ± 2.27) compared to the IF cohort (0.70 ± 2.08; p = 0.01), indicating decreased cell viability. P-L control efficiency was predictive of EAD (0.76 ± 0.06 in IF vs. 0.70 ± 0.08 in EAD-livers; p = 0.02) and correlated with the RTCA score. Both RTCA and P-L control efficiency in biopsy samples taken during cold storage have predictive capacity towards the outcome in LT. Therefore, RTCA and HRR should be considered for risk stratification, viability assessment, and bioenergetic testing in liver transplantation.

Bioenergetic and Cytokine Profiling May Help to Rescue More DCD Livers for Transplantation.

The majority of organs used for liver transplantation come from brain-dead donors (DBD). In order to overcome the organ shortage, increasingly donation after circulatory death (DCD) organs are also considered. Since normothermic machine perfusion (NMP) restores metabolic activity and allows for in-depth assessment of organ quality and function prior to transplantation, such organs may benefit from NMP. We herein compare the bioenergetic performance through a comprehensive evaluation of mitochondria by high-resolution respirometry in tissue biopsies and the inflammatory response in DBD and DCD livers during NMP. While livers were indistinguishable by perfusate biomarker assessment and histology, our findings revealed a greater impairment of mitochondrial function in DCD livers after static cold storage compared to DBD livers. During subsequent NMPs, DCD organs recovered and eventually showed a similar performance as DBD livers. Cytokine expression analysis showed no differences in the early phase of NMP, while towards the end of NMP, significantly elevated levels of IL-1ß, IL-5 and IL-6 were found in the perfusate of DCD livers. Based on our results, we find it worthwhile to reconsider more DCD organs for transplantation to further extend the donor pool. Therefore, donor organ quality criteria must be developed, which may include an assessment of bioenergetic function and cytokine quantification.

Hyperspectral Imaging as a Tool for Viability Assessment During Normothermic Machine Perfusion of Human Livers: A Proof of Concept Pilot Study.

Normothermic machine perfusion (NMP) allows for ex vivo viability and functional assessment prior to liver transplantation (LT). Hyperspectral imaging represents a suitable, non-invasive method to evaluate tissue morphology and organ perfusion during NMP. Liver allografts were subjected to NMP prior to LT. Serial image acquisition of oxygen saturation levels (StO2), organ hemoglobin (THI), near-infrared perfusion (NIR) and tissue water indices (TWI) through hyperspectral imaging was performed during static cold storage, at 1h, 6h, 12h and at the end of NMP. The readouts were correlated with perfusate parameters at equivalent time points. Twenty-one deceased donor livers were included in the study. Seven (33.0%) were discarded due to poor organ function during NMP. StO2 (p < 0.001), THI (p < 0.001) and NIR (p = 0.002) significantly augmented, from static cold storage (pre-NMP) to NMP end, while TWI dropped (p = 0.005) during the observational period. At 12-24h, a significantly higher hemoglobin concentration (THI) in the superficial tissue layers was seen in discarded, compared to transplanted livers (p = 0.036). Lactate values at 12h NMP correlated negatively with NIR perfusion index between 12 and 24h NMP and with the delta NIR perfusion index between 1 and 24h (rs = -0.883, p = 0.008 for both). Furthermore, NIR and TWI correlated with lactate clearance and pH. This study provides first evidence of feasibility of hyperspectral imaging as a potentially helpful contact-free organ viability assessment tool during liver NMP.

Distal Pancreatic Resection with Splenectomy in the Rat: A Pancreatic Fistula Model to Investigate Postsurgical Damage?

BACKGROUND: Postoperative pancreatic fistula (POPF) is a major complication in pancreatic surgery and can cause considerable postoperative morbidity. Advanced surgical-technical approaches to prevent POPF did not yield a substantial improvement. To investigate innovative treatments, experimental animal models of distal pancreatic resection and pancreaticoduodenectomy are of fundamental importance. After a failed attempt to replicate a previously described rat model for pancreatic fistula induction, we proceeded to distal pancreatic resection with splenectomy to provoke pancreatic leakage and generate a suitable animal model. METHODS: Distal pancreatic resection with splenectomy was performed in 40 rats. The rats were sacrificed on postoperative day (POD) 1, 2, 4, 6, 8, or 10, and the abdominal cavity was explored. Ascites probes were collected pre- and postoperatively for the detection of pancreas amylase and lipase. Tissue samples from the naïve pancreas (POD 0) and the postoperatively harvested remnant were evaluated histologically. The extent of necrosis was determined, and samples were examined for neutrophil infiltration. TUNEL staining served for the verification of necrosis in distinct cases. Immunohistochemistry of Ki67, von Willebrand factor, and CD68 was performed to evaluate proliferation, blood-vessel sprouting, and macrophage invasion. RESULTS: The rats showed no clinical symptoms or severe complications in the postoperative course up to 10 days. Abdominal exploration revealed adhesions in the upper abdomen, but no intra-abdominal fluid accumulations were found. Signs of inflammation and tissue damage were evident at the pancreatic resection margin on histological examination whereas the naïve pancreatic tissue was widely unaffected. Statistically significant differences were seen between the preoperative and postoperative extent of necrosis, the presence of neutrophil infiltrate, and levels of ascitic amylase and lipase. Immunohistochemical staining on Ki67, von Willebrand factor, and CD68 did not reveal any workable results on nonstatistical examination, and it was therefore not considered for further analyses. CONCLUSION: Creating a functional animal model of pancreatic fistula that reflects the clinical and pathophysiological impact of pancreatic leakage in humans has not been achieved. Our approach of left pancreatic resection recapitulated inflammation and tissue damage, early events in the development of fistulas, and it could be suitable for the experimental testing of novel targeting methods.

Cell-Based Regeneration and Treatment of Liver Diseases.

The liver, in combination with a functional biliary system, is responsible for maintaining a great number of vital body functions. However, acute and chronic liver diseases may lead to irreversible liver damage and, ultimately, liver failure. At the moment, the best curative option for patients suffering from end-stage liver disease is liver transplantation. However, the number of donor livers required by far surpasses the supply, leading to a significant organ shortage. Cellular therapies play an increasing role in the restoration of organ function and can be integrated into organ transplantation protocols. Different types and sources of stem cells are considered for this purpose, but highly specific immune cells are also the focus of attention when developing individualized therapies. In-depth knowledge of the underlying mechanisms governing cell differentiation and engraftment is crucial for clinical implementation. Additionally, novel technologies such as ex vivo machine perfusion and recent developments in tissue engineering may hold promising potential for the implementation of cell-based therapies to restore proper organ function.

Ex Vivo Mesenchymal Stem Cell Therapy to Regenerate Machine Perfused Organs.

Transplantation represents the treatment of choice for many end-stage diseases but is limited by the shortage of healthy donor organs. Ex situ normothermic machine perfusion (NMP) has the potential to extend the donor pool by facilitating the use of marginal quality organs such as those from donors after cardiac death (DCD) and extended criteria donors (ECD). NMP provides a platform for organ quality assessment but also offers the opportunity to treat and eventually regenerate organs during the perfusion process prior to transplantation. Due to their anti-inflammatory, immunomodulatory and regenerative capacity, mesenchymal stem cells (MSCs) are considered as an interesting tool in this model system. Only a limited number of studies have reported on the use of MSCs during ex situ machine perfusion so far with a focus on feasibility and safety aspects. At this point, no clinical benefits have been conclusively demonstrated, and studies with controlled transplantation set-ups are urgently warranted to elucidate favorable effects of MSCs in order to improve organs during ex situ machine perfusion.

Long-term outcome after hand and forearm transplantation - a retrospective study.

Between 2000 and 2014, five patients received bilateral hand (n = 3), bilateral forearm (n = 1), and unilateral hand (n = 1) transplants at the Innsbruck Medical University Hospital. We provide a comprehensive report of the long-term results at 20 years. During the 6-20 years follow-up, 43 rejection episodes were recorded in total. Of these, 27.9% were antibody-related with serum donor-specific alloantibodies (DSA) and skin-infiltrating B-cells. The cell phenotype in rejecting skin biopsies changed and C4d-staining increased with time post-transplantation. In the long-term, a change in hand appearance was observed. The functional outcome was highly depending on the level of amputation. The number and severity of rejections did not correlate with hand function, but negatively impacted on the patients´ well-being and quality of life. Patient satisfaction significantly correlated with upper limb function. One hand allograft eventually developed severe allograft vasculopathy and was amputated at 7 years. The patient later died due to progressive gastric cancer. The other four patients are currently rejection-free with moderate levels of immunosuppression. Hand transplantation remains a therapeutic option for carefully selected patients. A stable immunologic situation with optimized and individually adopted immunosuppression favors good compliance and patient satisfaction and may prevent development of DSA.

Restoring Mitochondrial Function While Avoiding Redox Stress: The Key to Preventing Ischemia/Reperfusion Injury in Machine Perfused Liver Grafts?

Mitochondria sense changes resulting from the ischemia and subsequent reperfusion of an organ and mitochondrial reactive oxygen species (ROS) production initiates a series of events, which over time result in the development of full-fledged ischemia-reperfusion injury (IRI), severely affecting graft function and survival after transplantation. ROS activate the innate immune system, regulate cell death, impair mitochondrial and cellular performance and hence organ function. Arresting the development of IRI before the onset of ROS production is currently not feasible and clinicians are faced with limiting the consequences. Ex vivo machine perfusion has opened the possibility to ameliorate or antagonize the development of IRI and may be particularly beneficial for extended criteria donor organs. The molecular events occurring during machine perfusion remain incompletely understood. Accumulation of succinate and depletion of adenosine triphosphate (ATP) have been considered key mechanisms in the initiation; however, a plethora of molecular events contribute to the final tissue damage. Here we discuss how understanding mitochondrial dysfunction linked to IRI may help to develop novel strategies for the prevention of ROS-initiated damage in the evolving era of machine perfusion.

Subcutaneous administration of a neutralizing IL-1ß antibody prolongs limb allograft survival.

Cytokine-expression profiles revealed IL-1ß highly upregulated in rejecting skin of limb allografts. We investigate the effect of intragraft treatment with a neutralizing IL-1ß antibody in limb transplantation. Following allogenic hind-limb transplantation, Lewis rats were either left untreated or treated with anti-lymphocyte serum + tacrolimus (baseline); baseline immunosuppression + anti-IL-1ß (1 mg/kg once/week, 6-8 subcutaneous injections) into the transplanted or contralateral limb. Endpoint was rejection grade III or day 100. Graft rejection was assessed by histology, immunohistochemistry, flow cytometry phenotyping of immune cells, and monitoring cytokine expression. Anti-IL-1ß injections into the allograft or contralateral limb resulted in a significant delay of rejection onset (controls: 58.60 ± 0.60; group 3: 75.80 ± 10.87, P = .044; group 4: 73.00 ± 6.49, P = .008) and prolongation of graft survival (controls: 64.60 ± 0.87; group 3: 86.60 ± 5.33, P = .002; group 4: 93.20 ± 3.82, P = .002), compared to controls. Although the phenotype of the graft infiltrating immune cells did not differ between groups, significantly decreased skin protein levels of IL-1ß, IL-4, IL-13, IP-10, MCP-1, and MCP-3 in long-term-survivors indicate an overall decrease of chemoattraction and infiltration of immune cells as the immunosuppressive mechanism of anti-IL-1ß. Inhibition of IL-1ß with short-term systemic immunosuppression prolongs limb allograft survival and represents a promising target for immunosuppression in extremity transplantation.

Ischemia/reperfusion injury in vascularized tissue allotransplantation: tissue damage and clinical relevance.

PURPOSE OF REVIEW: Ischemia and reperfusion injury (IRI) in vascularized tissue allotransplantation (VCA) remain largely undefined. Because VCA is comprised of different tissues, the sensitivity towards IRI may not be uniform. We, herein, attempt to address mechanistic aspects of IRI in VCA and provide a summary on potential technologies and targets for amelioration or treatment of IRI in this novel field. RECENT FINDINGS: IRI results in a loosened architecture of musculature, hypertrophic, centrally located cell nuclei as well as a high degree of neovascularization. Mitochondria in muscle tissue show a high degree of degeneration after prolonged ischemia whereas the ultrastructure remains normal after short cold ischemia time (CIT). Muscle cell necrosis accompanied by a diffuse inflammatory infiltrate and vasculopathy of small vessels is observed after 30 h of CIT. Nerves revealed a high degree of separation and vacuolization of myelin lamellae because of Wallerian degeneration. Approaches to minimize IRI include use of novel preservation solutions, administration of antioxidative and anti-inflammatory molecules/drugs as well as the implementation of machine perfusion in the setting of VCA. SUMMARY: Hand and face transplantations are logistically challenging procedures. Optimal planning and a highly congruent and motivated team are key to keep ischemia times to a minimum. In addition to pharmacological approaches, machine perfusion seems promising to help circumvent logistic problems and expand the donor pool in VCA.

Diagnosing skin rejection in vascularized composite allotransplantation: advances and challenges.

Refinements in microsurgical techniques coupled with advances in immunosuppressive and immunomodulatory protocols have enabled broader clinical application of vascularized composite allotransplantation (VCA) with encouraging immunological, functional, and esthetic results. However, skin rejection remains a significant obstacle and a serious complication for VCA recipients. Clinical and histopathological features of rejection in VCA have been described in a number of studies, which led to the development of an international consensus on the classification guidelines of rejection in the context of VCA. Nevertheless, currently available diagnostic modalities still have several limitations and shortcomings that can pose a significant diagnostic challenge, particularly when signs of rejection are found to be equivocal. In this review, we provide a critical analysis of these advances and challenges in diagnosing skin rejection. Specifically, we highlight the gaps in understanding of rejection mechanisms, the shortfalls in correlating cellular, molecular, and clinicopathologic markers with rejection grades, deficiencies in defining chronic rejection, and antibody-mediated rejection after VCA, as well as providing an outlook on novel concepts, such as the utilization of advanced computational analyses and cross-disciplinary diagnostic approaches.

Antibody-mediated rejection in hand transplantation.

Clinical relevance of antibody-mediated rejection (ABMR) in vascularized composite allotransplantation (VCA) has not been defined. We herein describe a novel type of donor-specific antibody (DSA) and B-cell-associated rejection in hand transplantation. In 2003, a bilateral forearm transplantation was performed on a 42-year-old male patient. In 2012, the patient presented with edematous hands and forearms without skin lesions. Punch skin biopsies revealed rejection grade Banff II. Immunohistochemical analysis identified large aggregates of CD20 + lymphocytes with an architecture resembling lymph nodes. De novo DSA was found at a high level. Steroid treatment was ineffective, but administration of rituximab resulted in complete remission of clinical symptoms, evaporation of B-cell aggregates, and disappearance of DSA. We herein report the first case of what we suggest is an ABMR in VCA occurring at 9 years after forearm transplantation. Rituximab therapy successfully reversed the event.

Lymphoid neogenesis in skin of human hand, nonhuman primate, and rat vascularized composite allografts.

The mechanisms of skin rejection in vascularized composite allotransplantation (VCA) remain incompletely understood. The formation of tertiary lymphoid organs (TLO) in hand transplantation has been recently described. We assess this phenomenon in experimental and clinical VCA rejection. Skin biopsies of human (n = 187), nonhuman primate (n = 11), and rat (n = 15) VCAs were analyzed for presence of TLO. A comprehensive immunohistochemical assessment (characterization of the cell infiltrate, expression of adhesion molecules) including staining for peripheral node addressin (PNAd) was performed and correlated with rejection and time post-transplantation. TLO were identified in human, nonhuman primate, and rat skin samples. Expression of PNAd was increased in the endothelium of vessels upon rejection in human skin (P = 0.003) and correlated with B- and T-lymphocyte numbers and LFA-1 expression. PNAd expression was observed at all time-points after transplantation and increased significantly after year 5. In nonhuman primate skin, PNAd expression was found during inflammatory conditions early and late after transplantation. In rat skin, PNAd expression was strongly associated with acute rejection and time post-transplantation. Lymphoid neogenesis and TLO formation can be uniformly found in experimental and human VCA. PNAd expression in vascular endothelium correlates with skin rejection and T- and B-cell infiltration.

The impact and relevance of techniques and fluids on lung injury in machine perfusion of lungs.

Primary graft dysfunction (PGD) is a common complication after lung transplantation. A plethora of contributing factors are known and assessment of donor lung function prior to organ retrieval is mandatory for determination of lung quality. Specialized centers increasingly perform ex vivo lung perfusion (EVLP) to further assess lung functionality and improve and extend lung preservation with the aim to increase lung utilization. EVLP can be performed following different protocols. The impact of the individual EVLP parameters on PGD development, organ function and postoperative outcome remains to be fully investigated. The variables relate to the engineering and function of the respective perfusion devices, such as the type of pump used, functional, like ventilation modes or physiological (e.g. perfusion solutions). This review reflects on the individual technical and fluid components relevant to EVLP and their respective impact on inflammatory response and outcome. We discuss key components of EVLP protocols and options for further improvement of EVLP in regard to PGD. This review offers an overview of available options for centers establishing an EVLP program and for researchers looking for ways to adapt existing protocols.

Prediction of Biliary Complications After Human Liver Transplantation Using Hyperspectral Imaging and Convolutional Neural Networks: A Proof-of-concept Study.

BACKGROUND: Biliary complications (BCs) negatively impact the outcome after liver transplantation. We herein tested whether hyperspectral imaging (HSI) generated data from bile ducts (BD) on reperfusion and machine learning techniques for data readout may serve as a novel approach for predicting BC. METHODS: Tissue-specific data from 136 HSI liver images were integrated into a convolutional neural network (CNN). Fourteen patients undergoing liver transplantation after normothermic machine preservation served as a validation cohort. Assessment of oxygen saturation, organ hemoglobin, and tissue water levels through HSI was performed after completing the biliary anastomosis. Resected BD segments were analyzed by immunohistochemistry and real-time confocal microscopy. RESULTS: Immunohistochemistry and real-time confocal microscopy revealed mild (grade I: 1%-40%) BD damage in 8 patients and moderate (grade II: 40%-80%) injury in 1 patient. Donor and recipient data alone had no predictive capacity toward BC. Deep learning-based analysis of HSI data resulted in >90% accuracy of automated detection of BD. The CNN-based analysis yielded a correct classification in 72% and 69% for BC/no BC. The combination of HSI with donor and recipient factors showed 94% accuracy in predicting BC. CONCLUSIONS: Deep learning-based modeling using CNN of HSI-based tissue property data represents a noninvasive technique for predicting postoperative BC.

Handheld hyperspectral imaging as a tool for the post-mortem interval estimation of human skeletal remains.

In forensic medicine, estimating human skeletal remains' post-mortem interval (PMI) can be challenging. Following death, bones undergo a series of chemical and physical transformations due to their interactions with the surrounding environment. Post-mortem changes have been assessed using various methods, but estimating the PMI of skeletal remains could still be improved. We propose a new methodology with handheld hyperspectral imaging (HSI) system based on the first results from 104 human skeletal remains with PMIs ranging between 1 day and 2000 years. To differentiate between forensic and archaeological bone material, the Convolutional Neural Network analyzed 65.000 distinct diagnostic spectra: the classification accuracy was 0.58, 0.62, 0.73, 0.81, and 0.98 for PMIs of 0 week-2 weeks, 2 weeks-6 months, 6 months-1 year, 1 year-10 years, and >100 years, respectively. In conclusion, HSI can be used in forensic medicine to distinguish bone materials >100 years old from those <10 years old with an accuracy of 98%. The model has adequate predictive performance, and handheld HSI could serve as a novel approach to objectively and accurately determine the PMI of human skeletal remains.

Transcriptomic signatures during normothermic liver machine perfusion correspond with graft quality and predict the early graft function.

BACKGROUND: A better understanding of the molecular events during liver normothermic machine perfusion (NMP) is warranted to develop a data-based approach for the identification of biomarkers representative of graft quality and posttransplant outcome. We analysed the dynamic transcriptional changes during NMP and linked them to clinical and biochemical parameters. METHODS: 50 livers subjected to NMP for up to 24 h were enrolled. Bulk RNA sequencing was performed in serial biopsies collected pre and during NMP, and after reperfusion. Perfusate was sampled to monitor liver function. qPCR and immunohistochemistry were performed to validate findings. Molecular profiles were compared between transplanted and non-transplanted livers, and livers with and without early allograft dysfunction. FINDINGS: Pathways related to immune and cell stress responses, cell trafficking and cell regulation were activated during NMP, while cellular metabolism was downregulated over time. Anti-inflammatory responses and genes involved in tissue remodelling were induced at later time-points, suggesting a counter-response to the immediate damage. NMP strongly induced a gene signature associated with ischemia-reperfusion injury. A 7-gene signature corresponds with the benchmarking criteria for transplantation or discard at 6 h NMP (area under curve 0.99). CD274 gene expression (encoding programmed cell-death ligand-1) showed the highest predictive value. LEAP2 gene expression at 6 h NMP correlated with impaired graft function. INTERPRETATION: Assessment of gene expression markers could serve as a reliable tool to evaluate liver quality during NMP and predicts early graft function after transplantation. FUNDING: The research was supported by "In Memoriam Dr. Gabriel Salzner Stiftung", Tiroler Wissenschaftsfond, Jubiläumsfonds-Österreichische Nationalbank and MUI Start grant.

Standardizing skin biopsy sampling to assess rejection in vascularized composite allotransplantation.

Over 70 hands and 20 faces have been transplanted during the past 13 yr, which have shown good to excellent functional and esthetic outcomes. However, (skin) rejection episodes complicate the post-operative courses of hand and face transplant recipients and are still a major obstacle to overcome after reconstructive allotransplantation. This article summarizes all relevant information on the skin component and rejection of a vascularized composite allograft. As more and more centers plan to implement a vascularized composite allotransplantation (VCA) program, we further develop guidelines and recommendations on collection and processing of skin biopsies from hand and face allograft recipients. This will help to standardize post-operative monitoring, avoid pitfalls for those new in the field and facilitate comparison of data on VCA between centers.