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Key Points Despite almost three decades of research on artificial and bioartificial liver support, appropriate, randomized, controlled, and adequately powered studies are rare Compared with the effect of a suitable orthotopic liver graft on a patient's clinical course, the clinical effects of extracorporeal liver support systems seem to be very limited The main issues for all liver support therapy concepts are the need for tissue vascularization and integration into the host circulation, and a lack of reliable sources of safe and metabolically active cells Strategies to overcome the conceptual limitations of (bio)artificial liver support devices include hepatocyte transplantation and various tissue engineering approaches (for example repopulation of decellularized organs, organ printing and induced organogenesis) Hepatocyte transplantation seems to be at least a temporary alternative treatment strategy in certain metabolic liver disorders, and might have a role in the treatment of acute liver failure and chronic liver disease Translation of regenerative medicine into the clinical routine, especially transplantation of recellularized liver grafts, seems possible but further intense research is needed This Review describes advances in artificial and bioartificial liver support systems and current developments. The evolving field of hepatocyte transplantation as a less invasive alternative to whole-organ transplantation is also reviewed, and a detailed overview of cutting-edge hepatic tissue engineering is included. Challenges and opportunities of the different approaches are analysed with respect to clinical relevance, as well as basic science concerns. The treatment of end-stage liver disease and acute liver failure remains a clinically relevant issue. Although orthotopic liver transplantation is a well-established procedure, whole-organ transplantation is invasive and increasingly limited by the unavailability of suitable donor organs. Artificial and bioartificial liver support systems have been developed to provide an alternative to whole organ transplantation, but despite three decades of scientific efforts, the results are still not convincing with respect to clinical outcome. In this Review, conceptual limitations of clinically available liver support therapy systems are discussed. Furthermore, alternative concepts, such as hepatocyte transplantation, and cutting-edge developments in the field of liver support strategies, including the repopulation of decellularized organs and the biofabrication of entirely new organs by printing techniques or induced organogenesis are analysed with respect to clinical relevance. Whereas hepatocyte transplantation shows promising clinical results, at least for the temporary treatment of inborn metabolic diseases, so far data regarding implantation of engineered hepatic tissue have only emerged from preclinical experiments. However, the evolving techniques presented here raise hope for bioengineered liver support therapies in the future.

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). 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. 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. 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.

Background Multimodal two-stage hepatectomy (mTSH) is used in patients with bilobar colorectal liver metastases (CRLM) that cannot be treated with one surgical procedure due to insufficient future liver remnant. Interval chemotherapy has been proposed to improve disease control in CRLM patients undergoing mTSH. We here present a narrative review of clinical studies on mTSH including the use of interval chemotherapy in patients with CRLM. Methods A systematic literature search of the PubMed databases as well as the ClinicalTrials.gov registry was performed. Results The use of interval chemotherapy during mTSH was reported in 23 studies and applied in 595 out of 1,461 patients with CRLM. Two studies report on the actual effects of this treatment, one study describes a trend towards improved disease progression rate. No serious adverse events caused by interval chemotherapy were observed. There is currently no randomized clinical trial investigating the efficacy and safety of interval chemotherapy during mTSH. Conclusion The currently available data indicate that interval chemotherapy does neither impair liver hypertrophy during mTSH nor cause procedure-associated complications in patients with CRLM. Results from randomized clinical trials on the potential positive effect on disease control are not yet available.

Considering the expected increase in the elderly population and the growing emphasis on aging-related biomedical research, the demand for aged laboratory animals has surged, challenging established husbandry practices. Our objective was to establish a cost-effective method for environmental enrichment, utilizing the liver as a representative organ to assess potential metabolic changes in response to differing enrichment levels. We conducted a six-month study involving 24 male Sprague Dawley rats, randomly assigned to four environmental enrichment groups. Two groups were housed in standard cages, while the others were placed in modified rabbit cages. Half of the groups received weekly playtime in an activity focused rat housing unit. We evaluated hormone levels, playtime behavior, and subjective handling experience. Additionally, liver tissue proteomic analysis was performed. Initial corticosterone levels and those after 3 and 6 months showed no significant differences. Yet, testosterone levels were lower in the control group by the end of the study (p = 0.007). We observed 1871 distinct proteins in liver tissue, with 77% being common across groups. In gene ontology analysis, no specific pathways were overexpressed. In semiquantitative analysis, we observed differences in proteins associated in lipid metabolism such as Apolipoprotein A-I and Acyl-CoA 6-desaturase, which were lower in the control group (p = 0.024 and p = 0.009). Rats in the intervention groups with weekly playtime displayed the least amount of reported distress during inspection or upon room entry and were less prone to accepting treats. Removing animals from their enclosure was most effortless for those in the large cage group. Over time, there was a decrease in conflicts among rats that interacted only twice weekly during playpen time. In summary, refining husbandry practices for aging rats is both simple and budget-friendly, with no apparent adverse effects on stress levels, animal development, or relevant metabolic changes in the liver.

Ischemia-reperfusion injury (IRI) constitutes a significant source of morbidity and mortality after orthotopic liver transplantation (OLT). The allograft is metabolically impaired during warm and cold ischemia and is further damaged by a paradox reperfusion injury after revascularization and reoxygenation. Short-term and long-term complications including post-reperfusion syndrome, delayed graft function, and immune activation have been associated with IRI. Due to the current critical organ shortage, extended criteria grafts are increasingly considered for transplantation, however, with an elevated risk to develop significant features of IRI. In recent years, ex vivo machine perfusion (MP) of the donor liver has witnessed significant advancements. Here, we describe the concept of hypothermic (oxygenated) machine perfusion (HMP/HOPE) approaches and highlight which allografts may benefit from this technology. This review also summarizes clinical applications and the main aspects of ongoing randomized controlled trials on hypothermic perfusion. The mechanistic aspects of IRI and hypothermic MP—which include tissue energy replenishment, optimization of mitochondrial function, and the reduction of oxidative and inflammatory damage following reperfusion—will be comprehensively discussed within the context of current preclinical and clinical evidence. Finally, we highlight novel trends and future perspectives in the field of hypothermic MP in the context of recent findings of basic and translational research.

T-cell–mediated rejection (TCMR) remains a major cause of kidney transplant failure, despite being considered treatable. Its impact reflects a limited understanding of the underlying molecular mechanisms and their clinical consequences. To address this, we induced acute TCMR in mouse kidney transplants and profiled molecular changes using single-nucleus RNA sequencing (snRNA-seq), spatial transcriptomics and immunofluorescence. Results were compared with human snRNA-seq data from TCMR and stable allografts, as well as single-cell deconvolution analysis of bulk transcriptomic data from kidney transplant biopsies. Here we show that TCMR induces injured epithelial cell states in mouse kidney allografts, particularly in proximal tubules and thick ascending limbs. Spatial transcriptomics of these injured epithelial states demonstrated heterogeneous localization, interactions with immune cells and cellular microenvironments. Cross-species analysis confirmed similar severely injured epithelial states in human samples, whose abundances correlated with transplant survival and persisted despite TCMR resolution. Collectively, our results identify epithelial injury cell states as a determinant of outcome after TCMR. T-cell–mediated rejection (TCMR) remains a major cause of kidney transplant failure with incompletely understood mechanisms. Here the authors use single-nucleus RNA sequencing, spatial transcriptomics and immunofluorescence to show that injured kidney epithelial cell states associate with poor transplant outcomes after T-cell–mediated rejection.

Background Colorectal cancer with liver metastasis affects both men and women. However, therapeutic strategies and long-term outcomes could be influenced by patients’ sex, due to variations in tumour biology, lifestyle, and dietary habits. By conducting a comprehensive comparative analysis, this study aims to detail differences in tumour characteristics, postoperative complications, recurrence rates, and survival outcomes between sexes. Methods Single-centre retrospective analysis between 2010 and 2022 of all patients undergoing liver surgery for colorectal liver metastases (CRLM) at the Department of Surgery, Charité– Universitätsmedizin Berlin. Patients were stratified by sex. Statistical analysis was performed using R V4.2. Results We analysed 642 patients who underwent hepatic resections for CRLM. Baseline patient characteristics were comparable between sexes: However, significant differences ( p  < 0.001) were noted in body mass index (BMI), with females exhibiting lower BMIs (median BMI in females: 23.7 kg/m² vs. males: 26.5 kg/m²). Primary tumour locations varied significantly ( p  = 0.008), with females presenting more sigmoid colon tumours (37%), while males predominantly had rectal tumours (35%). RAS mutation rates were higher in females (54%) than males (34%, p  = 0.005). A higher prevalence of bilobar metastases were evident in men (62%, p  = 0.011), yet surgical techniques and complications showed comparable distributions. The time for resection was longer in males (median 304 min vs. 290 min in females); however, conversion to open surgery took place more often in females (5.2% vs. 2.3% in males). Postoperative complications and survival rates showed no significant differences by patients’ sex. Conclusion Distinct sex-related patterns in tumour characteristics and postoperative outcomes in patients with CRLM were observed, emphasizing the need for further investigations to understand and address gender-based disparities for more personalized clinical management in the future. Trial registration This research was conducted with ethical approval from the relevant institutional review board Ethikkommission der Charité– Universitätsmedizin Berlin’ (reference numbers EA2/006/16 and EA4/084/17). No other registration applied.

Vascularized composite allotransplants (VCAs) have unique properties because of diverse tissue components transplanted en mass as a single unit. In addition to surgery, this type of transplant also faces enormous immunological challenges that demand a detailed analysis of all aspects of alloimmune responses, organ preservation, and injury, as well as the immunogenicity of various tissues within the VCA grafts to further improve graft and patient outcomes. Moreover, the side effects of long-term immunosuppression for VCA patients need to be carefully balanced with the potential benefit of a non-life-saving procedure. In this review article, we provide a comprehensive update on limb and face transplantation, with a specific emphasis on the alloimmune responses to VCA, established and novel immunosuppressive treatments, and patient outcomes.

All memory T cells mount an accelerated response on antigen reencounter, but significant functional heterogeneity is present within the respective memory T-cell subsets as defined by CCR7 and CD45RA expression, thereby warranting further stratification. Here we show that several surface markers, including KLRB1, KLRG1, GPR56, and KLRF1, help define low, high, or exhausted cytokine producers within human peripheral and intrahepatic CD4 + memory T-cell populations. Highest simultaneous production of TNF and IFN-γ is observed in KLRB1 + KLRG1 + GPR56 + CD4 T cells. By contrast, KLRF1 expression is associated with T-cell exhaustion and reduced TNF/IFN-γ production. Lastly, TCRβ repertoire analysis and in vitro differentiation support a regulated, progressive expression for these markers during CD4 + memory T-cell differentiation. Our results thus help refine the classification of human memory T cells to provide insights on inflammatory disease progression and immunotherapy development. Despite the current human CD4 memory T cell stratification by CD45RA/CCR7, functional heterogeneities still exist within the respective subsets. Here the authors show that several surface markers, including KLRB1, KLRG1, GPR56 and KLRF1, help to further refine the subsetting of human CD4 memory T cells and provide insights for their differentiation.