Background

Liver transplantation (LTx) remains the only curative treatment for end-stage liver disease, yet the persistent shortage of donor organs continues to limit its availability. Normothermic machine perfusion (NMP) has emerged as a promising technique to improve the assessment and preservation of marginal livers, with the potential to expand the donor pool. However, despite the use of NMP, a considerable proportion of livers are ultimately deemed unsuitable for transplantation. Understanding the underlying reasons for graft discard after NMP is crucial to refine selection criteria, improve perfusion strategies and enhance clinical outcomes.

Methods

A retrospective analysis was performed using data from our institutional liver transplant database. From all donor livers subjected to NMP since the implementation of NMP in our centre in 2018, we identified those ultimately not transplanted. For these grafts, donor characteristics, perfusion parameters, histological findings and documented reasons for discard were evaluated. In addition, we determined the proportion of discarded livers subsequently utilized for scientific research purposes.

Results

Between 02/2018 and 01/2025, 97 liver allografts were defined as not transplantable after NMP. Mean donor age was 57.20 +/- 15.61 years, median donor risk index was 1.97. 39.17% of livers stemmed from non-heartbeating donors (DCD), 94.84% of donors were defined as extended criteria and 27.83% of livers were rescue or extended allocation offers. 60 livers met established discard criteria: donor malignancy (n = 4), fibrosis II and steatohepatitis of the liver in frozen section (n = 25), macrovesicular steatosis of 40% or more (n = 16) or no sufficient lactate clearance within 6 hours of perfusion (n = 33). Dysfunction of the NMP-device and a graft that could not be re-allocated occurred in one case, respectively. 35 grafts did not meet obligatory discard criteria, but rather accumulated multiple relative criteria (elevated transaminase and LDH levels, no bile production or a low bile pH, mild steatosis). 30 livers (30.92%) were used for further experimental studies after being declined for transplantation.

Conclusion

Though expanding the donor pool, a substantial proportion of livers is deemed untransplantable even after NMP. The reasons for discard proved to be diverse and multifactorial with histological findings and failure to meet functional perfusion criteria representing the most common reasons. Systematic evaluation of discard reasons may help refine selection algorithms to ameliorate selection in more marginal organs. Finally, the utilization of declined organs offers significant scientific value, which is currently not fully exploited, due to the lack of an appropriate legal framework.

BACKGROUND

Access to deceased donor liver transplantation (DDLT) is shaped by a complex interplay of demographic, clinical, and system-level factors. Normothermic liver machine perfusion (NLMP) has improved organ utilization, but its effect on candidate-level access to transplantation remains unclear. Herein, we aim to investigate whether the implementation of a clinical NLMP program improves access to DDLT.

METHODS

This retrospective cohort study included all adult (≥ 18 years) liver transplant (LT) candidates wait-listed for DDLT between February 2012 and January 2024 at the Medical University of Innsbruck. The exposure of interest was listing in the pre-NLMP era versus the NLMP era, with clinical NLMP implemented in February 2018. Multivariable Cox proportional hazards regression was performed to identify independent predictors of receiving a DDLT. Adjusted hazard ratios (aHR) with 95% confidence intervals (CI) are reported. Independent predictors of receiving a DDLT were identified using multivariable Cox proportional hazards regression, reporting adjusted hazard ratios (aHR) with 95% confidence intervals (CI).

RESULTS

A total of 870 patients were waitlisted during the study period, including 219 listed as female (25,17%) and 651 as male (74,83%). Female sex was not significantly associated with DDLT access (aHR = 0.89, 95% CI: 0.72–1.09; p = 0.24), despite significance in univariable analysis. However, body size (aHR = 1.01 per cm, 95% CI: 1.00–1.02; p = 0.028) was independently associated with higher transplant probability. Clinical urgency remained the strongest predictor: high urgency (HU) status (aHR = 8.05, 95% CI: 5.58–11.60; p < 0.001), higher laboratory MELD score (aHR = 1.03 per point, 95% CI: 1.02–1.04; p < 0.001), and standardized exception MELD (SE-MELD) points (aHR = 1.51, 95% CI: 1.18–1.94; p < 0.001) all significantly improved access to DDLT. Additionally, listing during the NLMP era was retained in the final multivariable model as an independent predictor associated with higher probability of receiving a DDLT (aHR = 1.24, 95% CI: 1.07–1.44; p = 0.005).

CONCLUSIONS

In this large, contemporary cohort of DDLT candidates, both biological and system-level factors significantly influenced DDLT access. Clinical urgency markers such as HU status, MELD score, and SE-MELD were strong predictors, underscoring the prioritization framework of current allocation policies. The association between NLMP era listing and improved transplant access highlights the potential impact of evolving organ preservation strategies on waitlist outcomes.

BACKGROUND

The global shortage of donor organs emphasizes the need to optimize not only transplantation but also the full spectrum of organ use, including recovery for research and other scientific purposes. Eurotransplant (ET), a collaborative network of eight European countries, and the United States (US), operating under the Organ Procurement and Transplantation Network (OPTN), represent two of the most comprehensive organ-sharing systems worldwide. Comparing their utilization metrics over a decade provides insight into differences in donor reporting, allocation efficiency, and the extent to which each system contributes to research potential. Organs that cannot be transplanted represent a valuable resource for advancing transplantation science, immunology, and regenerative medicine.

METHODS

We conducted a retrospective analysis using ET Annual Reports and the US OPTN and Scientific Registry of Transplant Recipients from 2014–2023. Outcomes included total reported organs, transplanted organs, nontransplanted organs, and organs used for research or other purposes. Data were normalized per million population (PMP) for direct comparison using Eurostat and US Census estimates to enable direct comparison between regions and over time. Descriptive statistics were calculated, and linear regression analyses were performed to evaluate temporal trends. Statistical significance was defined as p < 0.05.

RESULTS

ET reported a mean of 10,026 organs annually (74.2 ± 3.7 PMP), compared with 70,910 in the US (215.7 ± 43.0 PMP). Transplanted organs averaged 6,802 (50.3 ± 2.9 PMP) in ET versus 31,941 (97.3 ± 14.1 PMP) in the US, corresponding to 67.8 % vs 45.0 % of reported organs. Total nontransplanted organs averaged 3,224 (23.9 ± 1.9 PMP, 32.2 %) in ET and 38,969 (118.5 ± 29.1 PMP, 55.0 %) in the US. Within the US nontransplanted group, a mean of 4,944 organs (15.0 ± 4.6 PMP, 12.7 %) were recovered for research and 818 (2.49 ± 0.73 PMP, 2.1 %) for other purposes, categories not reported by ET. Linear regression showed significant annual increases in all categories in the US (p < 0.001). In ET, no significant temporal change was observed in reported or nontransplanted organs, whereas transplanted organs showed a significant decline per year (p = 0.024).

CONCLUSIONS

When adjusted for population, the US reports nearly three times more organs but transplants a smaller proportion compared with ET. ET’s higher utilization rate likely reflects selective reporting of higher-quality donors, whereas the US includes a broader donor pool and diverts many nontransplantable organs into research pathways, ensuring scientific benefit. These differences are also shaped by the underlying reporting and donation systems. Together, these findings suggest that ET could evolve toward a more comprehensive system by broadening donor reporting criteria and introducing a structured framework for organ use in research, thereby improving transparency and maximizing both clinical and scientific impact.

Background:

Micronutrient deficiencies are frequent in obese and post-bariatric patients, and a poor folate status has been linked to adverse hepatic outcomes. While metabolic-associated steatotic liver disease/-steatohepatitis (MASLD/MASH) improves in most bariatric patients, around 20% remain “non-responders” with ongoing fibrosis despite weight loss. A recent NHANES study showed that high serum folate was associated with a markedly lower risk of advanced fibrosis, suggesting a potential protective role. The mechanisms, however, remain poorly defined.

Objective:

We hypothesized that folate deficiency contributes to liver fibrosis progression, particularly in the context of macronutrient overload, and aimed to investigate this in a novel MAFLD/MASH animal model.

Methods:

Male Sprague-Dawley rats (n=6/group) received either a high-fat/high-fructose diet (HFFD) with standard folate content (10 mg FA/kg chow) or a folate-depleted HFFD (0.02 mg FA/kg). To further reduce bioavailable folate, half of each group received fortnightly low-dose Methotrexate (Mtx, 0.5 mg/kg), a folate antagonist known to induce liver injury. After 8 weeks, we performed histological analysis, flow cytometry of hepatic stellate cells (HSC, CD45- CD90-) and fibroblast precursors (CD45- CD90+), and characterization of hepatic immune subsets. Intestinal barrier function was assessed by transepithelial resistance (TEER) and permeability assays.

Results:

Preliminary data indicate that adequate dietary folate is associated with attenuated MAFLD activity. At a single-cell level, folate sufficiency reduced hepatic inflammation, HSC activation (αSMA, desmin protein expression), and antigen-presenting cell abundance. The absence of folate further aggravated inflammatory responses under HFFD compared to standard chow. While Mtx did not directly enhance fibrosis markers, it was associated with immune-modulatory effects and increased intestinal permeability, especially in the folate-depleted setting.

Conclusion:

Our findings suggest that the folate status might modulate key pathways in MAFLD/MASH progression. Adequate folate intake appears to dampen hepatic inflammation, reduce stellate cell activation, and stabilize immune homeostasis, whereas folate deficiency might increase vulnerability to fibrosis, particularly when combined with gut barrier dysfunction. These results highlight folate as a potentially modifiable factor in preventing progression of liver fibrosis in at-risk populations, warranting further mechanistic and translational studies.

Background

Obesity and metabolic associated fatty liver disease (MASLD) has been linked to increased intestinal permeability (IP) or "leaky gut". Metabolic-bariatric surgery (MBS) is an effective treatment for obesity and related metabolic disorders, but its impact on IP remains unclear.

Objectives

This study investigates the relationship between intestinal permeability and liver fibrosis in an obese MASH rat model following one-anastomosis gastric bypass (OAGB) compared to sham surgery.

Methods

Male Sprague Dawley rats (n=16) were fed a high-fat, high-cholesterol, high-fructose, and low-folate diet, combined with methotrexate injections (0.5 mg/kg, i.p., after 2, 4 and 6 weeks) to induce fibrotic steatohepatitis (MASH) and increased IP. Liver and intestine were evaluated after eight weeks in a group of 5 animals, further groups underwent either OAGB (n=6) or sham surgery (n=5), followed by another eight weeks on the same diet. Thereafter, MASLD and IP were assessed histologically in different small intestinal sections. Ussing chamber experiments evaluated tissue resistance and permeability.

Results

After 8 weeks rats developed fibrotic MASH with increased IP. OAGB significantly reduced body weight and fasting blood glucose compared to sham surgery. Rats with MASH showed lower gut tissue resistance compared to MAFL; those with fibrosis exhibited higher permeability than those without fibrosis. Ileum tissue resistance was significantly higher in OAGB than in sham rats and pre surgical rats. A negative correlation was found between tissue resistance in the jejunum and intestinal lamina propria mononuclear cells.

Conclusions

Bariatric surgery improved intestinal permeability and increased gut resistance in this rodent model. Higher IP was associated with MASH and fibrosis, suggesting that intestinal permeability may play a critical role in MASLD improvement following MBS.

BACKGROUND: The increasing demand for transplantable organs results in rising utilization of extended criteria donor organs (ECD). Normothermic machine perfusion (NMP) has emerged as a promising method to evaluate liver grafts under near-physiological conditions prior to transplantation. Despite these advances, there is a lack of easily assessable and non-invasive biomarkers to reliably predict graft viability and postoperative function. This study aims to assess the predictive value of selected perfusate-derived miRNAs during NMP for graft viability and the occurrence of early allograft dysfunction (EAD) following liver transplantation.

METHODS: In this study, a total of 33 liver grafts undergoing NMP between 2021 and 2024 at the Medical University of Vienna were analyzed. Perfusate samples were collected at three predefined time points: baseline (0 minutes), after 5 minutes, and after 60 minutes of perfusion. Expression levels of miRNA 122-5p, 151a-5p, and 192-5p were quantified using the commercially available hepatomiR^®Kit. For transplanted grafts, the incidence of EAD was assessed according to the criteria established by Olthoff et al. In addition, conventional perfusate markers including aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and lactate were measured for comparative analysis.

RESULTS: Out of the 33 livers evaluated, 22 grafts (66.7%) were transplanted, while 11 livers (33.3%) were discarded due to not meeting the required criteria that were previously established. 15 grafts (68.18%) out of the 22 transplanted livers developed EAD. No significant differences in miRNA expression were observed between transplanted and discarded livers. In contrast, miRNA levels were significantly elevated in grafts that subsequently developed EAD. Specifically, miRNA-122-5p levels were higher after 60 minutes of perfusion (p = 0.007), miRNA-151a-5p was elevated after 5 minutes (p = 0.026) and 60 minutes (p = 0.005), while miRNA-192-5p levels increased after 5 minutes (p = 0.021) and 60 minutes (p = 0.003). Receiver operating characteristic (ROC) analysis demonstrated strong predictive accuracy for EAD after 60 minutes of NMP, with an AUC of 0.857 for miRNA-122-5p, 0.867 for miRNA-151a-5p, and 0.886 for miRNA-192-5p. These values surpassed those of conventional markers such as AST (AUC 0.833) and LDH (AUC 0.786), whereas lactate did not show any predictive potential with an AUC of 0.478 after 60 minutes.

CONCLUSIONS: Perfusate-derived miRNAs during NMP serve as non-invasive, sensitive predictors of early allograft dysfunction and outperform established biochemical parameters. Integration of HepatomiR levels into clinical viability assessment could improve organ selection when utilizing marginal grafts and therefore optimize graft survival after transplantation.

Introduction:

Normothermic machine perfusion (NMP) has emerged as a promising platform to preserve and evaluate donor livers prior to transplantation. However, the molecular processes underlying graft behavior during NMP remain poorly understood, particularly in marginal grafts that do not meet criteria for transplantation. To better characterize transcriptional changes during perfusion, we analyzed paired liver biopsies obtained before and after 12 hours of NMP in grafts not utilized for transplantation.

Methods:

Eighteen marginal donor livers that did not meet criteria for transplantation were subjected to NMP. Paired biopsies were collected prior to initiation of perfusion and after 12 hours. High-throughput sequencing of messenger RNA (mRNA) and microRNA (miRNA) was performed, followed by differential expression analysis. Regulatory interactions were predicted through in silico network modeling, and functional relevance was explored using Gene Ontology Biological Process (GO-BP) enrichment.

Results:

We identified 1,740 mRNA transcripts and 245 miRNAs with significant differential regulation during NMP. Network analysis revealed 29 mRNA targets associated with the regulation of eight miRNAs. The transcriptional profile was consistent with stress-biased regeneration, metabolic inflexibility, and endothelial activation. Specifically, strong downregulation of pyruvate dehydrogenase kinase 4 (PDK4) and acyl-CoA oxidase 1 (ACOX1) indicated suppression of fatty acid oxidation and increased glucose dependence, a maladaptive metabolic switch previously linked to ischemia–reperfusion and steatosis. Reduced growth hormone receptor expression suggested blunted growth hormone/insulin-like growth factor signaling, potentially impairing regenerative capacity. Endothelial destabilization was reflected by decreased expression of junctional regulators (MYLK, TMEM47, PCDH9, TENM2), which are involved in maintaining sinusoidal barrier integrity. Conversely, pro-stress and pro-apoptotic mediators including HSPA1B and BBC3/PUMA were upregulated, as were SERPINE1/PAI-1, RIPK2, ZC3H12A/MCPIP1, and CHKA, implicating proteotoxic stress, inflammatory signaling, thrombo-fibrotic priming, and enhanced phosphatidylcholine biosynthesis. Together, these transcriptional shifts suggest that livers failing viability testing enter a state of energetic strain, endothelial activation, and pro-inflammatory stress. GO-BP enrichment analysis corroborated these findings, with vascular regulation and metabolic pathways emerging as the most significantly modulated processes.

Conclusion:

Transcriptomic profiling of marginal liver grafts during NMP reveals a phenotype marked by impaired metabolic flexibility, blunted regenerative signaling, and endothelial activation, accompanied by heightened stress, apoptotic, and inflammatory pathways. These features likely contribute to the inability of such grafts to recover viability during perfusion. Understanding these maladaptive responses at the molecular level may guide targeted interventions to improve graft reconditioning, refine viability assessment, and expand the pool of usable donor livers.

The global demand for transplantable organs continues to rise, driving exploration of methods to extend preservation times and facilitate longer-distance transport. In this context, subzero preservation strategies may offer potential advantages by slowing metabolic processes and reducing tissue degradation. This study aimed to evaluate the feasibility of utilizing a novel organ preservation solution containing a nature-inspired anti-icing agent, XT-ViVo®, alongside the organ transporter TimeSeal®, for transport aboard a commercial transatlantic flight. To this end, porcine kidneys were harvested in Baltimore, USA, flushed with XT-ViVo®, stored at -5°C, and transported via a commercial aircraft to Innsbruck, Europe, using the TimeSeal® device designed to maintain exact target temperatures. After storage durations ranging from about 19.5 to 72.5 hours, graft function was assessed during six hours of Normothermic Machine Perfusion (NMP) using the Kidney Assist platform. Biopsies were collected before, during, and after perfusion to assess organ viability and mitochondrial activity via high-resolution respirometry. Additionally, biochemical analyses of perfusate and urine samples were performed, and microperfusion was evaluated noninvasively by hyperspectral imaging. The organ transporter appeared to maintain the temperature close to the target -5.0 °C with moderate variation, suggesting effective thermal stability during transport. During NMP, the kidneys showed stable hemodynamics post subzero storage with consistent flow rates, urine production, and a renal resistance index within expected physiological ranges. Oxygen consumption peaked after around two hours of reperfusion but appeared to taper off toward the end of the perfusion period. pH and lactate levels in perfusate samples remained within physiological range. Measurements of mitochondrial function indicated that while succinate was the dominant substrate, there was a gradual decline in oxidative phosphorylation capacity and ATP production efficiency as perfusion progressed, coupled with indications of increasing outer mitochondrial membrane impairment. Hyperspectral imaging demonstrated consistent microvascular perfusion throughout the six-hour perfusion. Collectively, these findings provide first preliminary evidence that the combined use of ice-free subzero preservation with XT-ViVo® and subsequent NMP may offer a clinically feasible approach for organ preservation and global organ transport.

Background: Hypothermic oxygenated machine perfusion (HOPE) improves outcomes after liver transplantation (LTx), yet standardized biomarkers for graft viability assessment during perfusion are lacking, as no readily available and easily assessable monitoring parameters exist currently.

Methods: This study included all patients who underwent LTx with grafts perfused via HOPE at the Medical University of Vienna between 2018 and 2023. HOPE was performed according to institutional standard operating procedures using University of Wisconsin machine perfusion solution. Blood gas analyses were obtained every 30 minutes for up to 120 minutes during perfusion. Hospitalization data was prospectively collected and retrospectively analyzed. Early allograft dysfunction (EAD) was the primary outcome parameter and defined according to Olthoff et al-.

Results: A total of 158 patients were included in the analysis, of whom 44 (27.8%) developed EAD. Grafts that developed EAD exhibited significantly lower sodium concentrations at all measured time points, whereas lactate levels were elevated in EAD grafts at 60 and 90 minutes during HOPE. Sodium and lactate measurements at 90 minutes demonstrated the highest predictive value for EAD, with areas under the receiver operating characteristic curve of 0.741 and 0.633, respectively. Optimal cut-off values were identified as 85 mmol/L for sodium and 4.3 mmol/L for lactate at 90 minutes. Based on these thresholds, a low-risk cohort (high sodium, low lactate) exhibited an EAD incidence of 17.6%, whereas a high-risk cohort (low sodium, high lactate) showed a markedly higher incidence of 69.2% (p ≤0,001).

Conclusion: Assessment of sodium and lactate levels at 90 minutes during HOPE effectively identifies high-risk donor grafts prior to LTx. Accordingly, the evaluation of these readily available perfusate biomarkers prior to decision for transplantation might improve patient outcome.

Introduction: Kidney transplantation remains the gold standard treatment for end-stage renal dysfunction. However, the prolonged shortage of suitable donors further compounded by the increasing utilization of extended-criteria donors emphasizes the urgent need for advancements in organ preservation techniques. While static cold storage (SCS) is widely adopted due to its cost-effectiveness and simplicity, it still requires further optimization. Preclinical evidence suggests that methane (CH₄) has potent anti-inflammatory, antioxidative, and mitochondrial-stabilizing properties, indicating potential utility as a bioactive additive in preservation solutions. This study aimed to develop a clinically relevant porcine kidney transplantation model to investigate the efficacy of methane-enriched Custodiol (HTK) solution in improving SCS outcomes.

Methods: Under general anaesthesia and mechanical ventilation, pigs underwent left nephrectomy followed by recovery (approval no. V/3262/2022). Retrieved kidneys were perfused and stored for 16 hours at 4°C in either standard HTK or methane-enriched HTK solution (HTK+CH₄; enriched with 25 L of 2.1% CH₄-air mixture; n=5/group). Kidneys were then reimplanted, and contralateral nephrectomy performed following reinduction of anesthesia. Following transplantation, animals were monitored for 24 hours, assessing renal artery flow (RAF), urine output (UO), serum creatinine levels, systemic haemodynamics, diuretic requirements, renal myeloperoxidase (MPO) enzyme activity and kidney mitochondrial function.

Results: There was no significant difference in systemic haemodynamics between the two groups. However, kidneys preserved in HTK+CH₄ demonstrated superior perfusion, as evidenced by consistently higher RAF and lower renal vascular resistance throughout the post-transplantation period. Furthermore, the HTK+CH₄ group required less diuretic support and exhibited improved UO and urine specific gravity, along with lower serum creatinine levels, all indicating enhanced renal function. Renal inflammation, as reflected by MPO activity, was significantly reduced, and mitochondrial outer membrane integrity was better preserved in kidneys stored in HTK+CH₄.

Conclusions: This translational porcine model effectively facilitates the evaluation of organ preservation strategies. Our findings suggest that methane-enriched HTK solution confers significant renoprotective effects, enhancing graft function and perfusion in the context of kidney transplantation.

Introduction

Infective endocarditis is an increasingly prevalent, often fatal disease. When affecting the mitral or tricuspid valve, repair should be performed whenever possible, using a synthetic annuloplasty ring. Currently used rings do not offer any antibacterial features. Therefore, systemic antibiosis remains the only antimicrobial treatment option. In this study we developed a fully absorbable magnesium (Mg)-based annuloplasty ring covered with silver (Ag) nanoparticle (AgNP)-loaded electrospun polycaprolactone (PCL) providing local antibacterial activity. Initial in vitro and in vivo biocompatibility studies of the Mg alloy ZX00 and the AgNP-PCL coverage were performed before long-term functionality and safety were assessed in a sheep model.

Methods

In vitro biocompatibility and hemocompatibility assays were performed. AgNP-PCL was tested for in vitro antibacterial activity. ZX00 was implanted subcutaneously in rat and rabbit models for histopathological, µCT, inflammatory and mechanical bending assessments. To ensure orthotopic implant functionality, the rings were implanted in sheep hearts in the mitral position. Widely used Edwards mitralrings were used as controls. Echocardiography, hemograms, blood chemistry, organ histopathological assessments, immunohistochemistry and mass spectrometry (ICP-MS) studies were conducted.

Results

Excellent in vitro and in vivo biocompatibility of ZX00 and AgNP-PCL as well as significant in vitro antibacterial activity of AgNP-PCL was observed (>99% reduction of bacteria). Exceptional suture retention of the newly developed Mg ring was demonstrated through successful implantation in sheep hearts. Implants degraded homogeneously (55 ± 6% implant volume reduction after one year of implantation) and showed remarkable ingrowth behavior comparable to clinically available rings. Echocardiography showed preserved mitral valve function (mean pressure gradient: 1.37 ± 0.52 mmHg) during the entire one-year follow-up period. Toxicological safety could be demonstrated through monthly hematological assessments as well as histopathological analysis of parenchymatous organs. Finally, mass spectrometric screenings of Ag revealed no significant accumulation of AgNP in parenchymatous organs compared to control animals. The relevant patent of the invention was published in August 2025 (Publication Number: WO/2025/176798).

Conclusion

This newly developed, antibacterial and biodegradable annuloplasty ring presents a promising new option for the surgical treatment of infective endocarditis, whenever repair of the valve is possible.

Normothermic machine perfusion (NMP) allows liver preservation under near-physiological conditions and thus may, serve as a platform for ex situ therapeutic interventions. Liver-directed adeno-associated viruses (AAV) hold promise for treating genetic liver diseases, yet highly specific vectors remain limited and are lacking. We applied Oxford Nanopore Technology (ONT) for direct sequencing of vector DNA and RNA in an NMP model to optimize AAV-based gene therapy protocols.

Porcine livers (n=4) were subjected to NMP (organOx Metra) for 48h, and eYFP-labeled AAV3B was administered to the perfusate. Serial perfusate samples were evaluated for organ function. Tissue biopsies were collected before vector administration and after 3h, 24h, and 48h for real-time confocal microscopy and immunofluorescent staining to assess eYFP protein, or cryopreserved for ONT-based quantification of AAV3B cDNA and gDNA.
ONT sequencing confirmed high-quality AAV3B vector preparation. All livers were successfully perfused for 48h with preserved organ function, as indicated by lactate clearance and low liver transaminase and LDH levels.

At a dose of 1×10¹³ vg/kg, AAV transduction was successfully detected by eYFP fluorescence in tissue biopsies after 24h and 48h, but not as early as 3h after vector application. The addition of a poloxamer (Pluronic) enhanced AAV3B transduction efficiency, while a reduced dose of 2×10^12 vg/kg with Pluronic achieved comparable efficiency to the high-dosage protocol without it.

In conclusion, AAV administration during liver NMP is feasible, well tolerated, and establishes NMP as a powerful platform for the development of AAV-based gene-directed therapies.

Background: Normothermic machine perfusion (NMP) has emerged as a promising strategy to evaluate liver graft viability prior to transplantation and may serve as a tool for future organ repair strategies. As a prerequisite, reliable experimental models to study and quantify liver injury are warranted.

Methods: To identify a model in which a notable but not detrimental degree of damage is inflicted on livers prior to NMP in a standardized setting, porcine livers (Sus domesticus, 70–95 kg, total n=7) underwent 24 h of cold ischemia time (CIT) at 4 °C (n=3). Biopsies were collected at baseline and after 24 h of storage, formalin-fixed, and histologically graded for structural injury (H&E). Markers of apoptosis, proliferation, and immune activation were analyzed using immunohistochemistry (IHC). Functional outcomes were measured during subsequent NMP (OrganOx® Metra), comparing livers after 24h vs. 0h of CIT.

Results: After 24 h of CIT, histological evaluation revealed only discrete increase of vacuolization (score 0h: 1±1.5 vs. 24h 2±1; n.s.), and an absence of graft necrosis, architecture destruction, and apoptosis (all p>0.05, respectively). Likewise, IHC displayed no significant alterations in markers indicating apoptosis (Caspase-3, Bcl-2), proliferation (Ki-67), or endothelial activation (ICAM-1, TLR4, VEGFRII), concerning both staining intensity and the proportion of positive cells (all p>0.05). Furthermore, lymphocyte subset composition (CD3, CD25, CD4, FoxP3) remained unaltered. Reperfusion of livers after 24h of CIT resulted in elevated lactate levels following NMP initiation (24h: 109.8 ± SD vs 0h: 65 ± SD, p>0.05), which gradually declined over 24h of NMP. Pronounced hepatocyte damage was indicated by high ALT (24h CIT: 734.6U/L ± SD vs 0h CIT: 43U/L ± SD, p<0.058) and AST (24h CIT: 10224.3 U/L ±SD vs 0h CIT: 111 U/L ±SD, p<0.058) levels.

Conclusion: A 24-h period of cold ischemia at 4 °C, although twice the duration typically applied clinically, did not induce major morphologically detectable damage. Functional assessment during NMP indicated moderate but not extensive impairment, suggesting a reproducible and suitable experimental model for NMP research. These findings highlight the value of NMP-based viability testing with functional readouts to evaluate grafts subjected to prolonged CIT.

Background: A promising strategy to meet the growing demand for organ donations is the allocation of extended criteria or marginal donor grafts. However, the use of suboptimal liver allografts poses a significant risk for serious postoperative complications. While hypothermic oxygenated machine perfusion (HOPE) has been shown to significantly improve postoperative outcomes by ameliorating ischemia reperfusion injury (IRI), the reduced metabolism in the cold limits the possibility to assess organ quality during machine perfusion, i.e. prior to transplantation. Mitochondrial flavin mononucleotide (FMN) and glycocalyx component syndecan-1 (Sdc-1) have previously been investigated as potential biomarkers of liver viability and have shown promising success in prediction of postoperative early allograft dysfunction (EAD) and other outcome parameters.

Methods: FMN and Sdc-1 concentrations in HOPE perfusates of 40 liver allografts were measured via fluorescence spectroscopy and enzyme-linked immunosorbent essay (ELISA), respectively. Previously reported cut-off values of 10.65 ng/mL after five minutes of perfusion for FMN and 808 ng/mL after 60 minutes for Sdc-1 were used for risk stratification. With a sequential combination of FMN and Sdc-1, refined risk groups could be investigated in order to further improve the prediction of postoperative outcomes in liver transplantation.

Results: Early allograft dysfunction (EAD) was largely absent in the low-risk cohort, occurring in only 9% of patients with FMN concentrations below the threshold (2/22) and 27% of those with sub-threshold Sdc-1 levels (7/26). In contrast, among high-risk individuals, EAD was observed in 52% of cases with elevated FMN (13/25) and 58% with elevated Sdc-1 (7/12). Intriguingly, no instances of EAD were documented when both biomarkers remained below their respective cut-off values (0/12). Conversely, simultaneous elevation of FMN and Sdc-1 was associated with a markedly higher incidence of EAD, affecting 67% of patients (6/9). When only one biomarker exceeded the threshold, FMN demonstrated superior predictive performance, with EAD occurring in 58% of such cases, compared with 33% for isolated Sdc-1 elevation.

Conclusion: FMN and Sdc-1 levels assessed during HOPE serve as reliable biomarkers for predicting EAD following liver transplantation. Their combined evaluation markedly enhances predictive specificity and may provide additional support for clinical decision making.

Background:

Orthotopic liver transplantation (OLT) remains the only curative treatment for end-stage liver disease, but the shortage of suitable organs and limitations of current donor assessment tools restrict optimal allocation. Traditional laboratory markers lack predictive accuracy for donor organ quality. The hepatomiR® P-score, based on circulating microRNAs (miR-122-5p, miR-151a-5p, miR-192-5p), has shown prognostic value in hepatic surgery, but its role in donor evaluation for OLT remains unexplored.

Methods:

Between 2016 and 2021, 89 brain-dead donors and 60 corresponding recipients at the Medical University of Vienna were prospectively studied. Donor blood samples were collected before procurement, and recipient samples pre-OLT, 30 minutes post-reperfusion, and on postoperative day 1. Plasma microRNA levels were quantified using the hepatomiR® kit to calculate P-scores. Donor histology, laboratory parameters, and clinical outcomes were analyzed. Early allograft dysfunction (EAD) was defined by a model of early allograft function (MEAF) score ≥8.

Results:

Donors with higher P-scores were more frequently associated with non-utilization (75% vs. 31.1%, p=0.014) and grafts leading to EAD (33.3% vs. 3.9%, p=0.031). Median P-scores were significantly higher in recipients versus donors (0.515 vs. 0.245, p<0.001), particularly in non-malignant indications. Perioperative dynamics revealed a rapid P-score increase as early as 30 minutes after reperfusion, correlating with MEAF (r=0.413, p=0.001). At reperfusion, P-score predicted EAD with an AUC of 0.833, outperforming routine laboratory tests. No correlation was observed between donor P-score and histological steatosis or fibrosis.

Conclusion:

The hepatomiR® P-score identifies high-risk donor grafts and predicts EAD more accurately than conventional biomarkers at early time points. Its rapid responsiveness to ischemia-reperfusion injury and standardized measurement support its utility as a complementary tool in donor assessment. Incorporation of hepatomiR® into clinical practice may refine graft selection and improve OLT outcomes.

Background/Objective: Post-implantation syndrome (PIS) is a benign and self-limited acute-phase inflammatory response to endovascular interventions such as Thoracic Endovascular Aortic Repair (TEVAR). Despite the absence of a precise definition, PIS is characterized by fever and elevated inflammatory parameters. The development of PIS has been associated with prolonged hospital stay, increased costs and a greater likelihood for rehospitalization. The aim of this study was to analyze the impact of PIS on the overall morbidity and mortality rate following TEVAR and to detect possible risk factors for the development of PIS after TEVAR.

Methods: Primary elective TEVAR procedures for aneurysm or penetrating aortic ulcer of the descending thoracic aorta between January 2017 and Dezember 2023 were analysed in this single-centre retrospective observational study. The peak levels of CRP, leukocytes, procalcitonin were examined both before and after intervention. Welch two-sample t-test and Pearson's Chi-squared test with Yates' continuity correction were performed. A multivariant logistic regression analysis was performed to assess potential risk factors. PIS was defined as postinterventional temperature >38°C, and a leucocyte count >12 000/ml or a CRP level >10 mg/dl.

Results: 186 TEVAR procedures were performed, 24.7% (n=46) met the inclusion criteria. 30.4 % (n=14) cases of PIS were identified. Patients with PIS showed significantly increased temperatures (POD 1, 2, 3, 4. with p-values <0.02) as well as increased peak levels of CRP (POD 3 with p=0.004), and leucocytes (POD4 with p= 0.028). Patients with PIS demonstrated a trend towards prolonged ICU (2.14 d vs. 1.03 d p= 0.110) and hospital (6.64 d vs. 5.66 d p=0.102) stays compared to patients without PIS. In our cohort, stent graft material did not have a statistically significant influence on the development of PIS.

Conclusion: Our results are comparable to studies with larger collectives on PIS after abdominal endovascular aortic repair. PIS was not associated with an increased mortality rate. It is imperative that further studies with larger sample sizes be conducted to analyze PIS after TEVAR.

Background
Aortic stenosis (AS) imposes chronic left ventricular (LV) pressure overload, leading to hypertrophy, remodeling, and without intervention ultimately to heart failure. Surgical aortic valve replacement (SAVR) relieves outflow obstruction and induces reverse remodeling, characterized by partial restoration of LV´s pre–pressure overload state.

Methods
We studied 164 patients undergoing SAVR, with comprehensive assessments at four timepoints. Evaluations included heart failure status, quality-of-life scores, echocardiography (aortic flow velocity, regurgitation, valve area, LV ejection fraction -LVEF, LV and atrial volumes, wall thickness), biomarkers of myocardial stretch and injury, renal and hepatic function, lipid profile, circulating mRNAs and histological analysis of perioperative LV biopsies.

Results
Women presented with more pronounced baseline LV hypertrophy but exhibited faster and more pronounced reverse remodeling than men, with greater reductions in LV mass and septal thickness indexed. Despite higher age and worse heart failure scores at baseline, women achieved superior structural recovery after one year. However, women had lower glomerular filtration rate, higher creatinine, and greater susceptibility to renal dysfunction. LVEF improved significantly in both sexes. N-terminal pro-B-type natriuretic peptide was higher in women at baseline and postoperatively, consistent with longer hypertension exposure and greater myocardial stretch. Transcriptomic profiling of total blood identified sex-specific molecular patterns. Differentially expressed mRNAs were enriched in pathways regulating extracellular matrix remodeling, fibroblast activation, angiogenesis, immune signaling, and oxidative stress. In women, early post-SAVR enrichment included matrix-degrading enzymes (MMP14, ADAM9) and angiogenic/fibrotic regulators (PDGFC, WNT pathways), while men showed enrichment of oxidative stress- and membrane transport–related transcripts (GLRX5, DNAJ30, FZD5).

Conclusion
The timely performed SAVR restores normal flow dynamics, improves LV structure and function, and enhances functional status and quality of life. Gender-specific differences were evident: women demonstrated greater reverse remodeling despite higher age and worse baseline parameters yet were more vulnerable to renal impairment. Integrating molecular and structural data may enable early identification of non-responders and guide personalized therapeutic strategies after SAVR.

Surgical education in Austria faces significant challenges. A growing shortage of specialists, evolving training requirements, and increasing strain on clinical resources threaten the long-term quality of patient care. Innovative teaching approaches are, therefore, urgently required.

At the Center for Biomedical Research and Translational Surgery, Medical University of Vienna, we have established a concept called SMART Medical Training that offers medical students, beginning in their 5th semester, early hands-on access to complex surgical skills, including robotic-assisted techniques. Within our elective surgical training courses, students practice vascular suturing under the supervision of experienced cardiac and vascular surgeons. Training is performed on synthetic grafts, ex-vivo porcine hearts, and innovative biological and 3D-printed vessel models, providing an advanced level of exposure that has traditionally been reserved for surgical residents.

A key innovation of this program is the integration of digital evaluation methods. Motion analysis (video-based and wearable tremor detection) and eye-tracking for cognitive performance assessment enable objective, quantitative monitoring of individual learning progress. These data allow for personalized training optimization and establish novel, measurable performance parameters for surgical education. Our current research focuses on refining these evaluation strategies to create an optimized, data-driven training environment for surgical teaching.

This approach represents a paradigm shift in surgical education: combining realistic, high-level practice with digital performance assessment to bridge the gap between undergraduate training and residency. By promoting early skill acquisition and implementing objective evaluation tools, this program contributes to the modernization of surgical education and to securing the next generation of highly qualified surgeons in Austria.

Nerve injury induces the reprogramming of adult Schwann cells (SCs) into a distinct repair phenotype essential for peripheral nerve regeneration. Current understanding of the underlying regenerative mechanisms is largely based on rodent models, while translational progress is hampered by limited validation in human systems. To address this need, we aim to reveal the functional heterogeneity and temporal dynamics of cell populations within injured human peripheral nerves. We performed single-cell RNA sequencing on cultured human sural nerve explants at days 1, 4, 8 and 12 post-excision and validated the findings using immunofluorescence staining of nerve sections and isolated human SC cultures. Single-cell RNA sequencing successfully captured cell type-specific and time-resolved gene expression changes in the nerve explants. We were able to confirm the transition of SCs into a repair state and demonstrate immunomodulatory properties associated with distinct SC subtypes. Thus, this ex vivo injury model represents a valuable human-based platform to study early cellular and molecular responses following peripheral nerve injury. We are currently analyzing additional donor samples across multiple time points to build a detailed, temporally resolved single-cell atlas of the injured human sural nerve.

The lymphatic vasculature plays a critical role in tissue homeostasis by facilitating the clearance of cellular debris, excess fluid or particles following injury, as well as orchestrating immune responses. Given their central function in immune surveillance and wound exudate clearance, lymphatic endothelial cells (LECs) inevitably interact with biomaterials employed in small diameter vascular graft (SDVG) implantation. However, the impact of various biomaterials on physiological and pathological lymphangiogenesis, and the cellular responses of LECs, remains poorly characterized. Therefore, the current study systematically investigates the effects of distinct vascular graft materials—including decellularized umbilical arteries (dUCAs), biodegradable polyurethane, and clinically used expanded polytetrafluoroethylene (ePTFE)—on LECs and the process of lymphangiogenesis. Using immortalized LECs (LEC-TERT), both direct and indirect material interactions were assessed using cell viability, proliferation, lymphvasculogenesis and two- and three-dimensional migration assays, as well as immunocytochemistry, scanning electron microscopy (SEM), and gene expression analyses. The findings demonstrated a marked reduction in LEC-TERT viability and function upon exposure to ePTFE, suggesting a mechanistic link to the suboptimal healing frequently associated with ePTFE-SDVGs in clinical settings. In contrast, both polyurethane and dUCA promoted improved LEC responses in several experimental metrics, with polyurethane exerting a particularly favorable influence on the lymphangiogenic potential. In summary, the results demonstrated that polyurethane and dUCA were superior biomaterial candidates for supporting physiological lymphatic integration and function in vascular graft applications.

Introduction: Biomaterials from decellularized human placental extracellular matrix (dhpECM) offer unique clinical potential due to their rich protein composition, anti-inflammatory properties, and accessibility. This study compares isolated placental regions to identify proteomic characteristics, compartment–specific cell–matrix interactions, and biophysical properties for the rational selection of tissue-mimetic bioinks for cardiac regeneration and soft-tissue models.

Methods: The dhpECMs, derived from four placental compartments—amnion, basal plate, chorion, and umbilical cord—were formulated as hydrogels. Mass‑spectrometry proteomics was used to assess matrisome similarity to native cardiac tissue and to predict tissue specificity through rank-based gene enrichment analysis. Cell–matrix crosstalk was evaluated in primary human cardiac fibroblasts using RT-qPCR to validate in silico predictions. Rheology quantified thermal gelation behavior, viscoelasticity, and flow properties. Printability was validated on a custom in‑gel extrusion bioprinter.

Results: Proteomics revealed distinct, compartment-specific tissue compositions and matrisomes with high batch-to-batch consistency, overlapping with cardiac ECM constituents, including collagens, glycoproteins, and other matricellular proteins. Bioinformatics ranked umbilical‑cord matrices as closest to native atrial and ventricular tissue. Gene enrichment confirmed the umbilical cord as a candidate, as cardiac terms were significantly enriched in the umbilical cord dataset (Score > 3; FDR < 0.05), with the most substantial enrichment among the hydrogels. Cardiac fibroblasts exhibited hydrogel‑dependent transcriptional responses; qPCR trends corroborated in silico rankings, confirming umbilical cord-derived matrices moderating fibroblast activation markers (aSMA, POSTN) while controlling matrix (COL1A1, COL3A1) and adhesion (ITGAV, ITGB1) expression, modulating cardiac fibrosis relative to other placental ECM groups and controls. The rheology of hydrogels was assessed by characterizing thermogelation (G′ > G″), shear thinning, and a printable yield regime, which enables continuous filament deposition and leads to stable 3D printed constructs.

Discussion: This proteomics-driven, rheology-anchored pipeline can rationally select placenta-derived ECM bioinks with high biochemical fidelity to cardiac tissue and extrusion-ready mechanics. The identified compartment-specific umbilical cord ECM supports the development of stable, cytocompatible constructs for cardiac regeneration research. The applied workflow provides a transferable framework for scaffold selection across various soft-tissue engineering applications.

Metabolic bariatric surgery leads to effective weight loss and to metabolic improvement in most cases. However, one fifth of bariatric patients experience onset of post-operative liver fibrosis with underlying mechanisms remaining unclear. Post-surgical malnutrition, including serum folic acid (FA) deficiency is commonplace. Folates have key roles in DNA-synthesis, as well as in epigenetic and immune regulations. A link between serum FA levels and liver status has been described, leading to the hypothesis that FA deficiency may contribute to post-operative liver fibrosis.

Hepatic stellate cells (HSC) are the main player in liver fibrosis. While predominantly quiescent in healthy liver, they become activated in response to damage signals, differentiating into myofibroblasts that produce high levels of extracellular matrix (ECM) proteins, leading to fibrosis. While fibrosis is reversible, targeted treatment options are currently limited, and elucidating mechanism of HSC activation is key.

In this project we are developing an in vitro model using the human immortalized HSC LX-2 line to study the role of bioavailable 5-methyltetrahydrofolate (5-MTHF) in HSC activation. Preliminary results suggest that in the LX-2 in vitro model, 5-MTHF has no effect on expression of fibrosis-associated markers. During their activation, HSC undergo metabolic reprogramming. Therefore, metabolomics studies will be performed to investigate changes in cellular metabolism in folate-depleted conditions or following 5-MTHF treatment in the presence of pro-fibrotic stimuli. Moreover, co-cultures with patient-derived CD14+ monocytes are to be carried out to examine the involvement of myeloid cells in HSC activation as well as a potential immune-modulating role for folates in this interaction.

Over the past decades, notable progress has been made in designing artificial small-diameter vascular grafts (SDVGs). However, the perivascular adipose tissue (PVAT) and its role in the healing process of synthetic SDVGs remains widely uninvestigated, despite its substantial role in blood vessel homeostasis. The current study evaluates electrospun thermoplastic polyurethane (TPU) SDVGs using combined in vitro and in vivo approaches to examine the bidirectional interaction between the biomaterial and PVAT during graft healing.

In vitro, vascular and perivascular related cells were cultured on TPU grafts for up to seven days and analyzed via cell viability assays, immunofluorescence (IF) staining, scanning electron microscopy (SEM) and qPCR. For in vivo assessment, prostheses were implanted into male Sprague Dawley rats for one week or three months (n = 6 per group), with SHAM-operated animals (n = 6) serving as controls. Cellularization of the implants was assessed using immunohistochemistry and SEM. Furthermore, qPCR was used to analyze inflammation-related genes and adipocyte subtype markers in graft-surrounding PVAT.

Viability of in vitro seeded cells increased over three days, confirming TPU’s cytocompatibility. Cell attachment to the graft as well as maintenance of their typical phenotype was demonstrated by SEM and immunofluorescence staining. Notably, IF staining revealed increased adiponectin expression in PVAT-derived cells, while endothelial cells showed reduced ICAM-1 and VCAM-1 expression compared to unchanged levels in cells seeded on tissue culture plates (TCP). These observations were supported by qPCR, which revealed elevated adiponectin levels approximately 18% higher than in the control TCP group, and downregulated TNF-alpha on TPU.

In vivo, H&E staining and SEM demonstrated rapid cell coverage of implanted grafts within one week, further validated by IF staining of CD34⁺ endothelial progenitor cells on the luminal surface. Gene expression analysis revealed a temporal divergence between compartments: anti-inflammatory markers increased within graft tissue over time, whereas pro-inflammatory markers such as TNF-alpha were elevated in adjacent PVAT by 20% at 3 months. Moreover, PVAT displayed a distinct immune cell response, with both innate (CD11c, MPO, Arg-1) and adaptive immune (FoxP3, T-bet) markers being dynamically regulated following graft implantation. Concurrently, significant alterations in adipocyte marker expression indicated a reorganization of PVAT composition, with partial transition from white-like to brown-like phenotypes during graft integration.

The present study highlights the dual role of TPU-based SDVGs, which support endothelialization while actively shaping local immune and adipose tissue response. An initial pro-inflammatory response is followed by a shift toward protective adipokine secretion, adipocyte browning, and reduced graft inflammation, accompanied by SMC stabilization and perivascular tissue formation with vasa vasorum–like features. By uncovering PVAT’s contribution to graft healing, these findings emphasize the importance of investigating PVAT responses to biomaterials when developing SDVGs to ensure long-term patency.

Background and Aim: Colorectal cancer ranks as the third most commonly diagnosed cancer and is the second leading cause of cancer-related deaths worldwide, which highlights the urgent need for the development of new treatments. One promising avenue is the use of so-called humanized mouse models to investigate the interactions between the human immune system and tumors. In this setting, the project focuses on tumor-infiltration and tumor-induced changes of human monocyte subsets: classical, intermediate, non-classical, and CD56+ monocytes.

Methods: Generation of a human immune system in immunocompromised NSG-QUAD mice was achieved by sub-lethal irradiation and intrahepatic injection of human CD34+ hematopoietic stem cells (HSCs) isolated from human cord blood. Afterwards, colorectal cancer was induced by orthotopic injection of human HCT-116 Luc2 cells and tumor growth was monitored in vivo by bioluminescent imaging. The monocyte subsets were isolated from a healthy donor, separated by their CD14, CD16 and CD56 expression in fluorescence-activated cell sorting (FACsorting), were membrane-labeled and then intravenously injected into the tumor-bearing mice. At the end of the experiment, the characterization of the generated human immune system and the monocyte distribution were assessed by flow cytometric analysis of mouse blood and bone marrow. Furthermore, membrane-labeled human monocytes were re-isolated from colorectal tumors by tissue dissociation and FACsorting. RNA isolation and sequencing were conducted of the sorted monocyte subsets before and after tumor infiltration.

Results: Humanization of NSG-QUAD mice with human CD34+ HSCs was successful, with an average human engraftment of 34% in blood and 49% in bone marrow, and a developed human immune system as characterized by flow cytometry. The orthotopic induction of colorectal cancer promoted the development of tumors in the humanized mouse model over 3 weeks, followed by adoptive cell transfer of isolated human monocyte subsets. RNA sequencing confirmed the subset identity of FACsorted classical, intermediate, non-classical and CD56+ monocytes before transfer into the tumor-bearing mice. However, the RNA integrity of the re-isolated, tumor-infiltrating monocytes did not allow further analysis of the possible changes in the gene expression of the monocyte subsets.

Conclusions: We have successfully established a xenograft model of orthotopically growing human CRC cells in humanized mice with adoptive transfer of human monocyte subsets. We are currently improving the reisolation of tumor-infiltrating monocytes for profiling by RNA sequencing.

BACKGROUND: The current state of the art to assess myocardial viability in ex-situ heart perfusion (ESHP) is serial lactate measurements. The information about myocardial function and cell damage is limited. Microdialysis is able to measure markers of cell injury and metabolites in the interstitial fluid. The study aimed to investigate the feasibility of this analysis tool in a porcine ESHP model.

METHODS: 12 german domestic pigs were used as heart and blood donors. To simulate different organ donation procedures two protocols were established: Control group (n=6) and “donation after circulatory death” (DCD) (n=6). Microdialysis catheters (CMA 20 Elite 10mm, CMA Microdialysis AB, Kista, Sweden) were inserted in the myocardium of the left ventricle. Semi-continuous perfusate samples were taken every 10 minutes. Lactate, pyruvate, and glycerol were analysed subsequently with the ISCUSflex (CMA Microdialysis AB, Kista, Sweden). The groups were compared at baseline (in-situ) and 20, 60, 180, and 360 minutes of ex-situ heart perfusion using t-test.

RESULTS: Interstitial levels of lactate, pyruvate, and glycerol did not differ at baseline.
Lactate increased significantly in the DCD group with the highest values after 20 minutes of ESHP (Control 1.28 (±0.56) mmol/L vs. DCD 7.31 (±0.11) mmol/l, p<0.001) and correlated with perfusate lactate levels. Pyruvate increased significantly faster in the DCD group (20min: Control 26.41 (±23.97) µmol/l vs. DCD 162.8 (±124.4) µmol/l, p=0.04; 360min: Control 129.58 (±72.46) µmol/l vs. DCD 455.93 (±104.59) µmol/l, p<0.001). Glycerol was stable during ESHP in the Control group, but was significantly higher in the DCD group with a rapid increase directly after reperfusion (20min: DBD 105 µmol/l (±71.73) vs. DCD 783.79 (±280.02) µmol/l, p<0.001).

CONCLUSIONS: Microdialysis in ESHP is feasible and able to detect metabolic changes in tissue. Especially, glycerol as a marker of cell injury is able to give additional information quickly.