Erweiterung der Spenderpopulation bei Lebertransplantation: Klinischer Bedarf und Entwicklung eines Kleintier-Lebermaschinenperfusionssystems

Hintergrund. Für Patienten*innen mit fortgeschrittenen Leberkrankungen stellt die Le- bertransplantation derzeit die einzige kurative Therapieoption dar, allerdings deckt die Verfügbarkeit an geeigneten Spenderorganen nicht den Bedarf. Aus diesem Grund müssen sogenannte marginale Organe akzeptiert werden, die mit schlechteren Ergeb- nissen nach Transplantation assoziiert sind. Die normotherme ex vivo Maschinenper- fusion stellt eine Möglichkeit zur Evaluierung der Organfunktion und potentiell thera- peutischer Intervention vor Transplantation dar. Zuverlässige Kleintiermodelle zur Er- probung verschiedener Perfusionsbedingungen und pharmakologisch wirksamen Agenzien sind nur vereinzelt publiziert. Ziel dieser Arbeit war einerseits, die aktuelle Relevanz der Steatosis hepatis und des Alters in der Spenderpopulation zu analysie- ren und andererseits, einen experimentellen therapeutischen Ansatz im Kleintiermo- dell zu realisieren Methodik. Im klinischen Teil dieser Arbeit erfolgte eine retrospektive Datenanalyse aller 2652 Leberangebote an die Charité – Universitätsmedizin Berlin von 2010 bis 2016. Ausgewertet wurden Akzeptanz- und Ablehnungskriterien sowie die Ergebnisse nach Lebertransplantationen. Im experimentellen Teil der Arbeit wurde ein ex vivo Ma- schinenperfusionsmodell für Ratten-Lebertransplantate entwickelt und evaluiert. Ergebnisse. Insgesamt wurden im Analysezeitraum 80,2% der Organgebote abge- lehnt, wobei Organe von Spender*innen ≥ 65 Jahre seltener vermittelt wurden als von jüngeren. Die Rate an Lebertransplantationen, die aufgrund von Steatosis hepatis nicht realisiert werden konnten, stieg von 2010 mit 14,7% auf 63,6% im Jahr 2016, während die Gesamtprävalenz der Steatosis hepatis von 20,3% auf 30,8% zunahm. Das 1- und 3-Jahres-Überleben war weder nach Lebertransplantation alter noch steatotischer Transplantate reduziert. Es zeigte sich jedoch eine erhöhte Rate früher Minderfunktion bei steatotischen Transplantaten und eine höhere Retransplantations- rate bei Organen von Spendern ≥ 80 Jahre. Das druckgestützte normotherme ex vivo Maschinenperfusionsmodell der Rattenleber basierte auf einem proprietären Glasge- fäß, einem Oxygenator und einem Perfusat aus Kulturmedium supplementiert mit Rat- tenerythrozyten. Die Integration eines separaten Dialysekreislaufs konnte eine signifi- kante Reduktion des Kaliums im Perfusat erzielen. Durch Hinzunahme von Glycin wurde, gemessen an der Hämatoxylin-Eosin und Einzelstrang-DNA-Färbungen, eine Minimierung des Gewebsschadens erreicht. Bei Lebertransplantaten, welche nach Herzstillstand entnommen worden waren, führte die Kombination von Dialyse und Gly- cin zu einer signifikanten Reduktion der Alanin-Aminotransferase im Perfusat. Diskussion. Alte Spender*innen und Spender*innen mit Steatosis hepatis nehmen an Relevanz in der Spenderpopulation zu. Aus Mangel an Alternativen stellen sie eine aussichtsreiche Möglichkeit zur Erweiterung des Spenderpools dar, mit dem Risikos einer frühen Minderfunktion und einer erhöhten Retransplantationsrate. Ein Kleintier ex vivo Lebermaschinenperfusionsmodell, könnte genutzt werden, um Konzepte zur Einschätzung und Konditionierung marginaler Organe vor Transplantation zu evaluie- ren.Liver transplantation is currently the treatment of choice for patients with end-stage liver disease. The imbalance between supply and demand of liver allografts in Germany necessitates the acceptance of marginal organs, which are associated with poorer outcome after transplantation. Normothermic ex vivo liver machine perfusion is one option to evaluate organ quality and therapeutically intervene before transplantation. Only few small animal models to evaluate perfusion settings and pharmacological agents have been published. The objective was to firstly characterize the relevance of steatosis hepatis and donor age in the donor pool and secondly develop a therapeutic approach in a small animal model. Methods. In the clinical part of this work, a retrospective analysis of all 2652 liver offers to the Charité – Universitätsmedizin Berlin from 2010 to 2016 was performed. Acceptance and rejection criteria as well as the outcome after transplantation were analyzed. In the experimental part, an ex vivo machine perfusions system for the perfusion of rat livers was developed and evaluated. Results. During the respective time period, 80.2% of organ offers were declined. Organs from donors ≥ 65 years were allocated less frequently than from younger donors. Liver transplantations which were not realized, due to steatosis hepatis of the graft, increased from 14.7% in 2010 to 63.6% in 2016, while overall prevalence rose from 20.3% to 30.8. The 1- and 3-year patient survival was not reduced after transplantation of older or steatotic grafts. However, recipients of steatotic grafts were more likely to develop Early Allograft Dysfunction (EAD) and recipients of older donor grafts ≥80 years more often required a retransplantation. The pressure controlled normothermic ex vivo liver machine perfusion model was based on a proprietary glass receptacle, an oxygenator, and culture medium perfusate supplemented with rat erythrocytes. The addition of a dialysis resulted in reduced potassium and liver cell damage. Combining the dialysis with glycine resulted in the least cell damage in the hematoxylin-eosin and single-strand DNA stainings. Livers retrieved after cardiac death showed a reduction of alanine-aminotransferase levels when perfused with a dialysis and glycine. Discussion. Older donors and grafts with steatosis hepatis are increasing in relevance. Due to the lack of suitable alternatives, these allografts currently represent an opportunity to expand the donor pool. However, EAD and higher rates of retransplantation still necessitate cautious acceptance policies. Ex vivo liver machine perfusion with optimized perfusion settings could assist in evaluating organs before transplantation to reduce complications

Ultrasound in augmented reality: a mixed-methods evaluation of head-mounted displays in image-guided interventions

Purpose: Augmented reality (AR) and head-mounted displays (HMD) in medical practice are current research topics. A commonly proposed use case of AR-HMDs is to display data in image-guided interventions. Although technical feasibility has been thoroughly shown, effects of AR-HMDs on interventions are not yet well researched, hampering clinical applicability. Therefore, the goal of this study is to better understand the benefits and limitations of this technology in ultrasound-guided interventions. Methods: We used an AR-HMD system (based on the first-generation Microsoft Hololens) which overlays live ultrasound images spatially correctly at the location of the ultrasound transducer. We chose ultrasound-guided needle placements as a representative task for image-guided interventions. To examine the effects of the AR-HMD, we used mixed methods and conducted two studies in a lab setting: (1) In a randomized crossover study, we asked participants to place needles into a training model and evaluated task duration and accuracy with the AR-HMD as compared to the standard procedure without visual overlay and (2) in a qualitative study, we analyzed the user experience with AR-HMD using think-aloud protocols during ultrasound examinations and semi-structured interviews after the task. Results: Participants (n = 20) placed needles more accurately (mean error of 7.4 mm vs. 4.9 mm, p = 0.022) but not significantly faster (mean task duration of 74.4 s vs. 66.4 s, p = 0.211) with the AR-HMD. All participants in the qualitative study (n = 6) reported limitations of and unfamiliarity with the AR-HMD, yet all but one also clearly noted benefits and/or that they would like to test the technology in practice. Conclusion: We present additional, though still preliminary, evidence that AR-HMDs provide benefits in image-guided procedures. Our data also contribute insights into potential causes underlying the benefits, such as improved spatial perception. Still, more comprehensive studies are needed to ascertain benefits for clinical applications and to clarify mechanisms underlying these benefits

The influence of the COVID-19 pandemic on surgical therapy and care: a cross-sectional study

Background: Due to the COVID-19 pandemic, an extensive reorganisation of healthcare resources was necessary-with a particular impact on surgical care across all disciplines. However, the direct and indirect consequences of this redistribution of resources on surgical therapy and care are largely unknown. Methods: We analysed our prospectively collected standardised digital quality management document for all surgical cases in 2020 and compared them to the years 2018 and 2019. Periods with high COVID-19 burdens were compared with the reference periods in 2018 and 2019. Results: From 2018 to 2020, 10,723 patients underwent surgical treatment at our centres. We observed a decrease in treated patients and a change in the overall patient health status. Patient age and length of hospital stay increased during the COVID-19 pandemic (p = 0.004 and p = 0.002). Furthermore, the distribution of indications for surgical treatment changed in favour of oncological cases and less elective cases such as hernia repairs (p < 0.001). Postoperative thromboembolic and pulmonary complications increased slightly during the COVID-19 pandemic. There were slight differences for postoperative overall complications according to Clavien-Dindo, with a significant increase of postoperative mortality (p = 0.01). Conclusion: During the COVID-19 pandemic we did not see an increase in the occurrence, or the severity of postoperative complications. Despite a slightly higher rate of mortality and specific complications being more prevalent, the biggest change was in indication for surgery, resulting in a higher proportion of older and sicker patients with corresponding comorbidities. Further research is warranted to analyse how this changed demographic will influence long-term patient care

Early Allograft Dysfunction Increases Hospital Associated Costs After Liver Transplantation—A Propensity Score–Matched Analysis

Concepts to ameliorate the continued mismatch between demand for liver allografts and supply include the acceptance of allografts that meet extended donor criteria (ECD). ECD grafts are generally associated with an increased rate of complications such as early allograft dysfunction (EAD). The costs of liver transplantation for the health care system with respect to specific risk factors remain unclear and are subject to change. We analyzed 317 liver transplant recipients from 2013 to 2018 for outcome after liver transplantation and hospital costs in a German transplant center. In our study period, 1-year survival after transplantation was 80.1% (95% confidence interval: 75.8%-84.6%) and median hospital stay was 33 days (interquartile rage: 24), with mean hospital costs of euro115,924 (SD euro113,347). There was a positive correlation between costs and laboratory Model for End-Stage Liver Disease score (r(s) = 0.48, P < 0.001), and the development of EAD increased hospital costs by euro26,229. ECD grafts were not associated with a higher risk of EAD in our cohort. When adjusting for recipient-associated risk factors such as laboratory Model for End-Stage Liver Disease score, recipient age, and split liver transplantation with propensity score matching, only EAD and cold ischemia increased total costs. Conclusion: Our data show that EAD leads to significantly higher hospital costs for liver transplantation, which are primarily attributed to recipient health status. Strategies to reduce the incidence of EAD are needed to control costs in liver transplantation

Ex vivo machine perfusion: current applications and future directions in liver transplantation

Background: Liver transplantation is the only curative treatment option for end-stage liver disease; however, its use remains limited due to a shortage of suitable organs. In recent years, ex vivo liver machine perfusion has been introduced to liver transplantation, as a means to expand the donor organ pool. Purpose: To present a systematic review of prospective clinical studies on ex vivo liver machine perfusion, in order to assess current applications and highlight future directions. Methods: A systematic literature search of both PubMed and ISI web of science databases as well as the ClinicalTrials.gov registry was performed. Results: Twenty-one articles on prospective clinical trials on ex vivo liver machine perfusion were identified. Out of these, eight reported on hypothermic, eleven on normothermic, and two on sequential perfusion. These trials have demonstrated the safety and feasibility of ex vivo liver machine perfusion in both standard and expanded criteria donors. Currently, there are twelve studies enrolled in the clinicaltrials.gov registry, and these focus on use of ex vivo perfusion in extended criteria donors and declined organs. Conclusion: Ex vivo liver machine perfusion seems to be a suitable strategy to expand the donor pool for liver transplantation and holds promise as a platform for reconditioning diseased organs

Prevalence of Steatosis Hepatis in the Eurotransplant Region: Impact on Graft Acceptance Rates

Due to the shortage of liver allografts and the rising prevalence of fatty liver disease in the general population, steatotic liver grafts are considered for transplantation.This condition is an important risk factor for the outcome after transplantation.We here analyze the characteristics of the donor pool offered to the Charité –Universitätsmedizin Berlin from 2010 to 2016 with respect to liver allograft nonacceptance and steatosis hepatis. Of the 2653 organs offered to our center, 19.9% (n=527) were accepted for transplantation, 58.8% (n=1561) were allocated to other centers, and 21.3% (n = 565) were eventually discarded from transplantation. In parallel to an increase of the incidence of steatosis hepatis in the donor pool from 20% in 2010 to 30% in 2016, the acceptance rates for steatotic organs increased in our center from 22.3% to 51.5% in 2016 (p 0.001) having less than 30% macrovesicular steatosis hepatis. However, by 2016, the number of canceled transplantations due to higher grades of steatosis hepatis had significantly increased from 14.7% (n = 15) to 63.6% (42; p < 0.001).The rising prevalence of steatosis hepatis in the donor pool has led to higher acceptance rates of steatotic allografts. Nonetheless, steatosis hepatis remains a predominant phenomenon in discarded organs necessitating future concepts such as organ reconditioning to increase graft utilization

Use and accuracy of decision support systems using artificial intelligence for tumor diseases: a systematic review and meta-analysis

Background: For therapy planning in cancer patients multidisciplinary team meetings (MDM) are mandatory. Due to the high number of cases being discussed and significant workload of clinicians, Clinical Decision Support System (CDSS) may improve the clinical workflow. Methods: This review and meta-analysis aims to provide an overview of the systems utilized and evaluate the correlation between a CDSS and MDM. Results: A total of 31 studies were identified for final analysis. Analysis of different cancers shows a concordance rate (CR) of 72.7% for stage I-II and 73.4% for III-IV. For breast carcinoma, CR for stage I-II was 72.8% and for III-IV 84.1%, P≤ 0.00001. CR for colorectal carcinoma is 63% for stage I-II and 67% for III-IV, for gastric carcinoma 55% and 45%, and for lung carcinoma 85% and 83% respectively, all P>0.05. Analysis of SCLC and NSCLC yields a CR of 94,3% and 82,7%, P=0.004 and for adenocarcinoma and squamous cell carcinoma in lung cancer a CR of 90% and 86%, P=0.02. Conclusion: CDSS has already been implemented in clinical practice, and while the findings suggest that its use is feasible for some cancers, further research is needed to fully evaluate its effectiveness

In vitro recellularization of decellularized bovine carotid arteries using human endothelial colony forming cells

Background: Many patients suffering from peripheral arterial disease (PAD) are dependent on bypass surgery. However, in some patients no suitable replacements (i.e. autologous or prosthetic bypass grafts) are available. Advances have been made to develop autologous tissue engineered vascular grafts (TEVG) using endothelial colony forming cells (ECFC) obtained by peripheral blood draw in large animal trials. Clinical translation of this technique, however, still requires additional data for usability of isolated ECFC from high cardiovascular risk patients. Bovine carotid arteries (BCA) were decellularized using a combined SDS (sodium dodecyl sulfate) -free mechanical-osmotic-enzymatic-detergent approach to show the feasibility of xenogenous vessel decellularization. Decellularized BCA chips were seeded with human ECFC, isolated from a high cardiovascular risk patient group, suffering from diabetes, hypertension and/or chronic renal failure. ECFC were cultured alone or in coculture with rat or human mesenchymal stromal cells (rMSC/hMSC). Decellularized BCA chips were evaluated for biochemical, histological and mechanical properties. Successful isolation of ECFC and recellularization capabilities were analyzed by histology. Results: Decellularized BCA showed retained extracellular matrix (ECM) composition and mechanical properties upon cell removal. Isolation of ECFC from the intended target group was successfully performed (80% isolation efficiency). Isolated cells showed a typical ECFC-phenotype. Upon recellularization, co-seeding of patient-isolated ECFC with rMSC/hMSC and further incubation was successful for 14 (n = 9) and 23 (n = 5) days. Reendothelialization (rMSC) and partial reendothelialization (hMSC) was achieved. Seeded cells were CD31 and vWF positive, however, human cells were detectable for up to 14 days in xenogenic cell-culture only. Seeding of ECFC without rMSC was not successful. Conclusion: Using our refined decellularization process we generated easily obtainable TEVG with retained ECM- and mechanical quality, serving as a platform to develop small-diameter (< 6 mm) TEVG. ECFC isolation from the cardiovascular risk target group is possible and sufficient. Survival of diabetic ECFC appears to be highly dependent on perivascular support by rMSC/hMSC under static conditions. ECFC survival was limited to 14 days post seeding

Dual versus single vessel normothermic ex vivo perfusion of rat liver grafts using metamizole for vasodilatation

Background: Normothermic ex vivo liver perfusion (NEVLP) is a promising strategy to increase the donor pool in liver transplantation. Small animal models are essential to further investigate questions regarding organ preservation and reconditioning by NEVLP. A dual vessel small animal NEVLP (dNEVLP) model was developed using metamizole as a vasodilator and compared to conventional portovenous single vessel NEVLP (sNEVLP). Methods: Livers of male Wistar rats were perfused with erythrocyte-supplemented culture medium for six hours by either dNEVLP via hepatic artery and portal vein or portovenous sNEVLP. dNEVLP was performed either with or without metamizole treatment. Perfusion pressure and flow rates were constantly monitored. Transaminase levels were determined in the perfusate at the start and after three and six hours of perfusion. Bile secretion was monitored and bile LDH and GGT levels were measured hourly. Histopathological analysis was performed using liver and bile duct tissue samples after perfusion. Results: Hepatic artery pressure was significantly lower in dNEVLP with metamizole administration. Compared to sNEVLP, dNEVLP with metamizole treatment showed higher bile production, lower levels of transaminases during and after perfusion as well as significantly lower necrosis in liver and bile duct tissue. Biochemical markers of bile duct injury showed the same trend. Conclusion: Our miniaturized dNEVLP system enables normothermic dual vessel rat liver perfusion. The administration of metamizole effectively ameliorates arterial vasospasm allowing for six hours of dNEVLP, with superior outcome compared to sNEVLP

Surface modification of decellularized bovine carotid arteries with human vascular cells significantly reduces their thrombogenicity

Background: Since autologous veins are unavailable when needed in more than 20% of cases in vascular surgery, the production of personalized biological vascular grafts for implantation has become crucial. Surface modification of decellularized xenogeneic grafts with vascular cells to achieve physiological luminal coverage and eventually thromboresistance is an important prerequisite for implantation. However, ex vivo thrombogenicity testing remains a neglected area in the field of tissue engineering of vascular grafts due to a multifold of reasons. Methods: After seeding decellularized bovine carotid arteries with human endothelial progenitor cells and umbilical cord-derived mesenchymal stem cells, luminal endothelial cell coverage (LECC) was correlated with glucose and lactate levels on the cell supernatant. Then a closed loop whole blood perfusion system was designed. Recellularized grafts with a LECC > 50% and decellularized vascular grafts were perfused with human whole blood for 2 h. Hemolysis and complete blood count evaluation was performed on an hourly basis, followed by histological and immunohistochemical analysis. Results: While whole blood perfusion of decellularized grafts significantly reduced platelet counts, platelet depletion from blood resulting from binding to re-endothelialized grafts was insignificant (p = 0.7284). Moreover, macroscopic evaluation revealed thrombus formation only in the lumen of unseeded grafts and histological characterization revealed lack of CD41 positive platelets in recellularized grafts, thus confirming their thromboresistance. Conclusion: In the present study we were able to demonstrate the effect of surface modification of vascular grafts in their thromboresistance in an ex vivo whole blood perfusion system. To our knowledge, this is the first study to expose engineered vascular grafts to human whole blood, recirculating at high flow rates, immediately after seeding