Thrombogenicity assessment of perfusable tissue engineered constructs: a systematic review.

Vascular surgery faces a critical demand for novel vascular grafts that are biocompatible and thromboresistant. This urgency particularly applies to bypass operations involving small caliber vessels. In the realm of tissue engineering, the development of fully vascularized organs holds great promise as a solution to organ shortage for transplantation. To achieve this, it is imperative to (re-)construct a biocompatible and non-thrombogenic vascular network within these organs. In this systematic review, we identify, classify and discuss basic principles and methods used to perform in vitro/ex vivo dynamic thrombogenicity testing of perfusable tissue engineered organs and tissues. We conducted a pre-registered systematic review of studies published in the last 23 years according to PRISMA-P Guidelines, comprising a systematic data extraction, in-depth analysis and risk of bias assessment of 116 included studies. We identified shaking (n=28), flow loop (n=17), ex vivo (arterio-venous shunt, n=33) and dynamic in vitro models (n=38) as main approaches for thrombogenicity assessment. This comprehensive review unveils a prevalent lack of standardization and serves as a valuable guide in the design of standardized experimental setups.

Distinctive protein expression in elderly livers in a Sprague-Dawley rat model of normothermic ex vivo liver machine perfusion.

BACKGROUND: Liver grafts are frequently declined due to high donor age or age mismatch with the recipient. To improve the outcome of marginal grafts, we aimed to characterize the performance of elderly vs. young liver grafts in a standardized rat model of normothermic ex vivo liver machine perfusion (NMP). METHODS: Livers from Sprague-Dawley rats aged 3 or 12 months were procured and perfused for 6 h using a rat NMP system or collected as a reference group (n = 6/group). Tissue, bile, and perfusate samples were used for biochemical, and proteomic analyses. RESULTS: All livers cleared lactate during perfusion and continued to produce bile after 6 h of perfusion (614 mg/h). Peak urea levels in 12-month-old animals were higher than in younger animals. Arterial and portal venous pressure, bile production and pH did not differ between groups. Proteomic analysis identified a total of 1477 proteins with oxidoreductase and catalytic activity dominating the gene ontology analysis. Proteins such as aldehyde dehydrogenase 1A1 and 2-Hydroxyacid oxidase 2 were significantly more present in livers of older age. CONCLUSIONS: Young and elderly liver grafts exhibited similar viability during NMP, though proteomic analyses indicated that older grafts are less resilient to oxidative stress. Our study is limited by the elderly animal age, which corresponds to mature but not elderly human age typically seen in marginal human livers. Nevertheless, reducing oxidative stress could be a promising therapeutic target in the future.

On the relationship between viscoelasticity and water diffusion in soft biological tissues.

Magnetic resonance elastography (MRE) and diffusion-weighted imaging (DWI) are complementary imaging techniques that detect disease based on viscoelasticity and water mobility, respectively. However, the relationship between viscoelasticity and water diffusion is still poorly understood, hindering the clinical translation of combined DWI-MRE markers. We used DWI-MRE to study 129 biomaterial samples including native and cross-linked collagen, glycosaminoglycans (GAGs) with different sulfation levels, and decellularized specimens of pancreas and liver, all with different proportions of solid tissue, or solid fractions. We developed a theoretical framework of the relationship between mechanical loss and tissue-water mobility based on two parameters, solid and fluid viscosity. These parameters revealed distinct DWI-MRE property clusters characterizing weak, moderate, and strong water-network interactions. Sparse networks interacting weakly with water, such as collagen or diluted decellularized tissue, resulted in marginal changes in water diffusion over increasing solid viscosity. In contrast, dense networks with larger solid fractions exhibited both free and hindered water diffusion depending on the polarity of the solid components. For example, polar and highly sulfated GAGs as well as native soft tissues hindered water diffusion despite relatively low solid viscosity. Our results suggest that two fundamental properties of tissue networks, solid fraction and network polarity, critically influence solid and fluid viscosity in biological tissues. Since clinical DWI and MRE are sensitive to these viscosity parameters, the framework we present here can be used to detect tissue remodeling and architectural changes in the setting of diagnostic imaging. STATEMENT OF SIGNIFICANCE: The viscoelastic properties of biological tissues provide a wealth of information on the vital state of cells and host matrix. Combined measurement of viscoelasticity and water diffusion by medical imaging is sensitive to tissue microarchitecture. However, the relationship between viscoelasticity and water diffusion is still poorly understood, hindering full exploitation of these properties as a combined clinical biomarker. Therefore, we analyzed the parameter space accessible by diffusion-weighted imaging (DWI) and magnetic resonance elastography (MRE) and developed a theoretical framework for the relationship between water mobility and mechanical parameters in biomaterials. Our theory of solid material properties related to particle motion can be translated to clinical radiology using clinically established MRE and DWI.

[Position paper of the Berlin-Brandenburg Surgical Society-On the future of surgical further training]. / Positionspapier der Berlin-Brandenburgischen Chirurgischen Gesellschaft ­ zur Zukunft der chirurgischen Weiterbildung.

BACKGROUND: Surgical further training faces the challenging task of reconciling technological advancements and patient safety, particularly in the context of the planned hospital reform. Additionally, the generation shift and evolving expectations of Generations Y and Z in the workplace present further challenges. In response to these demands, the Berlin-Brandenburg Surgical Society (Berlin-Brandenburgische Chirurgische Gesellschaft, BCG) initiated a structured discussion and developed a position paper during the Neuhardenberg talks (Neuhardenberger Gespräche). METHODOLOGY: Within the framework of the Neuhardenberg talks, four sessions with keynote presentations and discussions took place. Based on the main discussion points, theses and positions were subsequently formulated and digitally voted on. RESULTS: The results reveal a clear consensus favoring flexible working hours models, earlier specialization options and the integration of external rotations in surgical further training. Regarding talent acquisition and early recruitment of residents, there was a clear consensus supporting the promotion of employee engagement and structured early recruitment of students. There was unanimous agreement on the introduction of training associations as an effective means to ensure high-quality surgical further training. DISCUSSION: One of the central points in the discussions was that high-quality surgical further training will only be achievable within training associations, especially given the impending hospital reform. The BCG plans to develop a modular further training association to make surgical further training in Berlin/Brandenburg fit for the future.

Optimizing environmental enrichment for Sprague Dawley rats: Exemplary insights into the liver proteome.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. DISCUSSION: 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.

Chemistry matters: A side-by-side comparison of two chemically distinct methacryloylated dECM bioresins for vat photopolymerization.

Decellularized extracellular matrix (dECM) is an excellent natural source for 3D bioprinting materials due to its inherent cell compatibility. In vat photopolymerization, the use of dECM-based bioresins is just emerging, and extensive research is needed to fully exploit their potential. In this study, two distinct methacryloyl-functionalized, photocrosslinkable dECM-based bioresins were prepared from digested porcine liver dECM through functionalization with glycidyl methacrylate (GMA) or conventional methacrylic anhydride (MA) under mild conditions for systematic comparison. Although the chemical modifications did not significantly affect the structural integrity of the dECM proteins, mammalian cells encapsulated in the respective hydrogels performed differently in long-term culture. In either case, photocrosslinking during 3D (bio)printing resulted in transparent, highly swollen, and soft hydrogels with good shape fidelity, excellent biomimetic properties and tunable mechanical properties (~ 0.2-2.5 kPa). Interestingly, at a similar degree of functionalization (DOF ~ 81.5-83.5 %), the dECM-GMA resin showed faster photocrosslinking kinetics in photorheology resulting in lower final stiffness and faster enzymatic biodegradation compared to the dECM-MA gels, yet comparable network homogeneity as assessed via Brillouin imaging. While human hepatic HepaRG cells exhibited comparable cell viability directly after 3D bioprinting within both materials, cell proliferation and spreading were clearly enhanced in the softer dECM-GMA hydrogels at a comparable degree of crosslinking. These differences were attributed to the additional hydrophilicity introduced to dECM via methacryloylation through GMA compared to MA. Due to its excellent printability and cytocompatibility, the functional porcine liver dECM-GMA biomaterial enables the advanced biofabrication of soft 3D tissue analogs using vat photopolymerization-based bioprinting.

From morbidity reduction to cost-effectiveness: Enhanced recovery after surgery (ERAS) society recommendations in minimal invasive liver surgery.

PURPOSE: Minimal-invasive liver surgery (MILS) reduces surgical trauma and is associated with fewer postoperative complications. To amplify these benefits, perioperative multimodal concepts like Enhanced Recovery after Surgery (ERAS), can play a crucial role. We aimed to evaluate the cost-effectiveness for MILS in an ERAS program, considering the necessary additional workforce and associated expenses. METHODS: A prospective observational study comparing surgical approach in patients within an ERAS program compared to standard care from 2018-2022 at the Charité - Universitätsmedizin Berlin. Cost data were provided by the medical controlling office. ERAS items were applied according to the ERAS society recommendations. RESULTS: 537 patients underwent liver surgery (46% laparoscopic, 26% robotic assisted, 28% open surgery) and 487 were managed by the ERAS protocol. Implementation of ERAS reduced overall postoperative complications in the MILS group (18% vs. 32%, p = 0.048). Complications greater than Clavien-Dindo grade II incurred the highest costs (€ 31,093) compared to minor (€ 17,510) and no complications (€13,893; p < 0.001). In the event of major complications, profit margins were reduced by a median of € 6,640. CONCLUSIONS: Embracing the ERAS society recommendations in liver surgery leads to a significant reduction of complications. This outcome justifies the higher cost associated with a well-structured ERAS protocol, as it effectively offsets the expenses of complications.

Extended Right Hepatectomy following Clearance of the Left Liver Lobe and Portal Vein Embolization for Curatively Intended Treatment of Extensive Bilobar Colorectal Liver Metastases: A Single-Center Case Series.

BACKGROUND: Two-staged hepatectomy (TSH) including portal vein embolization (PVE) may offer surgical treatment for extensive bilobar colorectal liver metastases (CRLM). This study aimed to investigate the feasibility and outcomes of extended right hepatectomy (ERH) within TSH including PVE for patients with extended CRLM. METHODS: We retrospectively collected data of patients who underwent TSH for extended CRLM between 2015 and 2021 at our institution. Clearance of the left liver lobe (clear-up, CU) associated with PVE was followed by ERH. RESULTS: Minimally invasive (n = 12, 46%, MIH) or open hepatectomy (n = 14, 54%, OH) was performed. Postoperative major morbidity and 90-day mortality were 54% and 0%. Three-year overall survival was 95%. Baseline characteristics, postoperative and long-term outcomes were comparable between MIH and OH. However, hospital stay was significantly shorter after MIH (8 vs. 15 days, p = 0.008). Additionally, the need for intraoperative transfusions tended to be lower in the MIH group (17% vs. 50%, p = 0.110). CONCLUSIONS: ERH following CU and PVE for extended CRLM is feasible and safe in laparoscopic and open approaches. MIH for ERH may result in shorter postoperative hospital stays. Further high-volume, multicenter studies are required to evaluate the potential superiority of MIH.

Endoscopic and surgical treatment of necrotizing pancreatitis-a comparison of short- and long-term outcome.

BACKGROUND: Acute necrotizing pancreatitis is still related to high morbidity and mortality rates. Minimal-invasive treatment options, such as endoscopic necrosectomy, may decrease peri-interventional morbidity and mortality. This study aims to compare the initial operative with endoscopic treatment on long-term parameters, such as endocrine and exocrine functionality, as well as mortality and recurrence rates. METHODS: We included 114 patients, of whom 69 were treated with initial endoscopy and 45 by initial surgery. Both groups were further assessed for peri-interventional and long-term parameters. RESULTS: In the post-interventional phase, patients in the group of initial surgical treatment (IST) showed significantly higher rates of renal insufficiency (p < 0.001) and dependency on invasive ventilation (p < 0.001). The in-house mortality was higher in the surgical group, with 22% vs. 10.1% in the group of patients following initial endoscopic treatment (IET; p = 0.077). In long-term follow-up, the overall mortality was 45% for IST and 31.3% for IET (p = 0.156). The overall in-hospital stay and intensive care unit (ICU) stay were significantly shorter after IET (p < 0.001). In long-term follow-up, the prevalence of endocrine insufficiency was 50% after IST and 61.7% after IET (p = 0.281). 57.1% of the patients following IST and 16.4% of the patients following IET had persistent exocrine insufficiency at that point (p = < 0.001). 8.9% of the IET and 27.6% of the IST patients showed recurrence of acute pancreatitis (p = 0.023) in the long-term phase. CONCLUSION: In our cohort, an endoscopic step-up approach led to a reduced in-hospital stay and peri-interventional morbidity. The endocrine function appeared comparable in both groups, whereas the exocrine insufficiency seemed to recover in the endoscopic group in the long-term phase. These findings advocate for a preference for endoscopic treatment of acute necrotizing pancreatitis whenever feasible.

Proteomic analysis of decellularized mice liver and kidney extracellular matrices.

BACKGROUND: The extracellular matrix (ECM) is a three-dimensional network of proteins that encases and supports cells within a tissue and promotes physiological and pathological cellular differentiation and functionality. Understanding the complex composition of the ECM is essential to decrypt physiological processes as well as pathogenesis. In this context, the method of decellularization is a useful technique to eliminate cellular components from tissues while preserving the majority of the structural and functional integrity of the ECM. RESULTS: In this study, we employed a bottom-up proteomic approach to elucidate the intricate network of proteins in the decellularized extracellular matrices of murine liver and kidney tissues. This approach involved the use of a novel, perfusion-based decellularization protocol to generate acellular whole organ scaffolds. Proteomic analysis of decellularized mice liver and kidney ECM scaffolds revealed tissue-specific differences in matrisome composition, while we found a predominantly stable composition of the core matrisome, consisting of collagens, glycoproteins, and proteoglycans. Liver matrisome analysis revealed unique proteins such as collagen type VI alpha-6, fibrillin-2 or biglycan. In the kidney, specific ECM-regulators such as cathepsin z were detected. CONCLUSION: The identification of distinct proteomic signatures provides insights into how different matrisome compositions might influence the biological properties of distinct tissues. This experimental workflow will help to further elucidate the proteomic landscape of decellularized extracellular matrix scaffolds of mice in order to decipher complex cell-matrix interactions and their contribution to a tissue-specific microenvironment.

Short-term postoperative outcomes of lymphadenectomy for cholangiocarcinoma, hepatocellular carcinoma and colorectal liver metastases in the modern era of liver surgery: Insights from the StuDoQ|Liver registry.

INTRODUCTION: The clinical role of lymphadenectomy (LAD) as part of hepatic resection for malignancies of the liver remains unclear. In this study, we aimed to report on the use cases and postoperative outcomes of liver resection and simultaneous LAD for hepatic malignancies (HM). MATERIALS AND METHODS: Clinicopathological data from patients who underwent surgery at 13 German centers from 2017 to 2022 (n = 3456) was extracted from the StuDoQ|Liver registry of the German Society of General and Visceral Surgery. Propensity-score matching (PSM) was performed to account for the extent of liver resection and patient demographics. RESULTS: LAD was performed in 545 (16%) cases. The most common indication for LAD was cholangiocarcinoma (CCA), followed by colorectal liver metastases (CRLM) and hepatocellular carcinoma (HCC). N+ status was found in 7 (8%), 59 (35%), and 56 cases (35%) for HCC, CCA, and CRLM, respectively (p < 0.001). The LAD rate was highest for robotic-assisted resections (28%) followed by open (26%) and laparoscopic resections (13%), whereas the number of resected lymph nodes was equivalent between the techniques (p = 0.303). LAD was associated with an increased risk of liver-specific postoperative complications, especially for patients with HCC. CONCLUSION: In this multicenter registry study, LAD was found to be associated with an increased risk of liver-specific complications. The highest rate of LAD was observed among robotic liver resections.

Impact of complexity in minimally invasive liver surgery on enhanced recovery measures: prospective study.

BACKGROUND: Adherence to enhanced recovery after surgery (ERAS) protocols is crucial for successful liver surgery. The aim of this study was to assess the impact of minimally invasive liver surgery complexity on adherence after implementing an ERAS protocol. METHODS: Between July 2018 and August 2021, a prospective observational study involving minimally invasive liver surgery patients was conducted. Perioperative treatment followed ERAS guidelines and was recorded in the ERAS interactive audit system. Kruskal-Wallis and ANOVA tests were used for analysis, and pairwise comparisons utilized Wilcoxon rank sum and Welch's t-tests, adjusted using Bonferroni correction. RESULTS: A total of 243 patients were enrolled and categorized into four groups based on the Iwate criteria: low (n = 17), intermediate (n = 81), advanced (n = 74) and expert difficulty (n = 71). Complexity correlated with increased overall and major morbidity rate, as well as longer length of stay (all P < 0.001; standardized mean difference = 0.036, 0.451, 0.543 respectively). Adherence to ERAS measures decreased with higher complexity (P < 0.001). Overall adherence was 65.4%. Medical staff-centred adherence was 79.9%, while patient-centred adherence was 38.9% (P < 0.001). Complexity significantly affected patient-centred adherence (P < 0.001; standardized mean difference (SMD) = 0.420), but not medical staff-centred adherence (P = 0.098; SMD = 0.315). Postoperative phase adherence showed major differences among complexity groups (P < 0.001, SMD = 0.376), with mobilization measures adhered to less in higher complexity cases. CONCLUSION: The complexity of minimally invasive liver surgery procedures impacts ERAS protocol adherence for each patient. This can be addressed using complexity-adjusted cut-offs and 'gradual adherence' based on the relative proportion of cut-off values achieved.

miRNA as potential biomarkers after liver transplantation: A systematic review.

BACKGROUND: Liver transplantation is a life-saving therapy for end-stage liver disease patients, but acute cellular rejection (ACR) and graft complications remain significant postoperative challenges. Early and accurate diagnosis is crucial for timely intervention and improved patient outcomes, but their diagnosis rely currently on invasive biopsy sampling, thus prompting the search for non-invasive Biomarkers. MicroRNA (miRNA) have emerged as promising biomarkers in various pathological conditions, and their potential utility in diagnosing acute cellular rejection after liver transplantation has gained significant interest. METHODS: This systematic review of PubMed, Web of Science, and the ClinicalTrials.gov registry analyzes studies exploring miRNA as biomarkers for ACR and graft dysfunction in liver transplantation (PROSPERO ID CRD42023465278). The Cochrane Collaboration tool for assessing risk of bias was employed. Population data, identified miRNA and their dynamic regulation, as well as event prediction were compared. Data extraction and quality assessment were performed independently by two reviewers. RESULTS: Thirteen studies were included in this systematic review. Various investigated miRNAs were upregulated in association with acute cellular rejection, like miR-122, miR-155, miR-181, miR-483-3p, and miR-885-5p, demonstrating great biomarker potential. Additionally, several studies conducted target gene analysis, revealing insights into cellular mechanisms linked to ACR. Moreover, various miRNA were also capable of predicting different organ complications following transplantation, expanding their versatility. Remaining challenges include the standardization of miRNA profiling, the need for functional validation, and the necessity for long-term studies. CONCLUSION: The results highlight the potential of miRNA as specific, non-invasive biomarkers for ACR and graft dysfunction following liver transplantation. However, further research is needed to validate these findings and establish standardized diagnostic panels to incorporate them into clinical practice and explore miRNA-based therapies in the future.

Minimal Invasive Versus Open Surgery for Colorectal Liver Metastases: A Multicenter German StuDoQ|Liver Registry-Based Cohort Analysis in Germany.

Objective: To compare the outcome of minimally invasive liver surgery (MILS) to open liver surgery (OLS) for resection of colorectal liver metastases (CRLM) on a nationwide level. Background: Colorectal cancer is the third most common malignancy worldwide. Up to 50% of all patients with colorectal cancer develop CRLM. MILS represents an attractive alternative to OLS for treatment of CRLM. Methods: Retrospective cohort study using the prospectively recorded German Quality management registry for liver surgery. Propensity-score matching was performed to account for variance in the extent of resection and patient demographics. Results: In total, 1037 patients underwent liver resection for CRLM from 2019 to 2021. MILS was performed in 31%. Operative time was significantly longer in MILS (234 vs 222 minutes, P = 0.02) compared with OLS. After MILS, median length of hospital stay (LOS) was significantly shorter (7 vs 10 days; P < 0.001). Despite 76% of major resections being OLS, postoperative complications and 90-day morbidity and mortality did not differ. The Pringle maneuver was more frequently used in MILS (48% vs 40%, P = 0.048). After propensity-score matching for age, body mass index, Eastern Cooperative Oncology Group, and extent of resection, LOS remained shorter in the MILS cohort (6 vs 10 days, P < 0.001) and operative time did not differ significantly (P = 0.2). Conclusion: MILS is not the standard for resection of CRLM in Germany. Drawbacks, such as a longer operative time remain. However, if technically possible, MILS is a reasonable alternative to OLS for resection of CRLM, with comparable postoperative complications, reduced LOS, and equal oncological radicality.

Correction: Felsenstein M. et al. Perineural Invasion in Pancreatic Ductal Adenocarcinoma (PDAC): A Saboteur of Curative Intended Therapies? J. Clin. Med. 2022, 11, 2367.

In the original publication [...].

Papain-Based Solubilization of Decellularized Extracellular Matrix for the Preparation of Bioactive, Thermosensitive Pregels.

Solubilized, gel-forming decellularized extracellular matrix (dECM) is used in a wide range of basic and translational research and due to its inherent bioactivity can promote structural and functional tissue remodeling. The animal-derived protease pepsin has become the standard proteolytic enzyme for the solubilization of almost all types of collagen-based dECM. In this study, pepsin was compared with papain, α-amylase, and collagenase for their potential to solubilize porcine liver dECM. Maximum preservation of bioactive components and native dECM properties was used as a decisive criterion for further application of the enzymes, with emphasis on minimal destruction of the protein structure and maintained capacity for physical thermogelation at neutral pH. The solubilized dECM digests, and/or their physically gelled hydrogels were characterized for their rheological properties, gelation kinetics, GAG content, proteomic composition, and growth factor profile. This study highlights papain as a plant-derived enzyme that can serve as a cost-effective alternative to animal-derived pepsin for the efficient solubilization of dECM. The resulting homogeneous papain-digested dECM preserved its thermally triggered gelation properties similar to pepsin digests, and the corresponding dECM hydrogels demonstrated their enhanced bioadhesiveness in single-cell force spectroscopy experiments with fibroblasts. The viability and proliferation of human HepaRG cells on dECM gels were similar to those on pure rat tail collagen type I gels. Papain is not only highly effective and economically attractive for dECM solubilization but also particularly interesting when digesting human-tissue-derived dECM for regenerative applications, where animal-derived materials are to be avoided.

Rise of tissue- and species-specific 3D bioprinting based on decellularized extracellular matrix-derived bioinks and bioresins.

Thanks to its natural complexity and functionality, decellularized extracellular matrix (dECM) serves as an excellent foundation for creating highly cell-compatible bioinks and bioresins. This enables the bioprinted cells to thrive in an environment that closely mimics their native ECM composition and offers customizable biomechanical properties. To formulate dECM bioinks and bioresins, one must first pulverize and/or solubilize the dECM into non-crosslinked fragments, which can then be chemically modified as needed. In bioprinting, the solubilized dECM-derived material is typically deposited and/or crosslinked in a layer-by-layer fashion to build 3D hydrogel structures. Since the introduction of the first liver-derived dECM-based bioinks, a wide variety of decellularized tissue have been employed in bioprinting, including kidney, heart, cartilage, and adipose tissue among others. This review aims to summarize the critical steps involved in tissue-derived dECM bioprinting, starting from the decellularization of the ECM to the standardized formulation of bioinks and bioresins, ultimately leading to the reproducible bioprinting of tissue constructs. Notably, this discussion also covers photocrosslinkable dECM bioresins, which are particularly attractive due to their ability to provide precise spatiotemporal control over the gelation in bioprinting. Both in extrusion printing and vat photopolymerization, there is a need for more standardized protocols to fully harness the unique properties of dECM-derived materials. In addition to mammalian tissues, the most recent bioprinting approaches involve the use of microbial extracellular polymeric substances in bioprinting of bacteria. This presents similar challenges as those encountered in mammalian cell printing and represents a fascinating frontier in bioprinting technology.

Toward a 3D Printed Perfusable Islet Embedding Structure: Technical Notes and Preliminary Results.

To date, islet transplantation to treat type 1 diabetes mellitus remains unsuccessful in long-term follow-up, mainly due to failed engraftment and reconstruction of the islet niche. Alternative approaches, such as islet embedding structures (IESs) based on 3D printing have been developed. However, most of them have been implanted subcutaneously and only a few are intended for direct integration into the vascular system through anastomosis. In this study, we 3D printed a proof-of-concept IES using gelatin methacrylate biocompatible ink. This structure consisted of a branched vascular system surrounding both sides of a central cavity dedicated to islets of Langerhans. Furthermore, we designed a bioreactor optimized for these biological structures. This bioreactor allows seeding and perfusion experiments under sterile and physiological conditions. Preliminary experiments aimed to analyze if the vascular channel could successfully be seeded with mature endothelial cells and the central cavity with rat islets. Subsequently, the structures were used for a humanized model seeding human endothelial progenitor cells (huEPC) within the vascular architecture and human islets co-cultured with huEPC within the central cavity. The constructs were tested for hemocompatibility, suture strength, and anastomosability. The 3D printed IES appeared to be hemocompatible and anastomosable using an alternative cuff anastomosis in a simple ex vivo perfusion model. While rat islets alone could not successfully be embedded within the 3D printed structure for 3 days, human islets co-cultivated with huEPC successfully engrafted within the same time. This result emphasizes the importance of co-culture, nursing cells, and islet niche. In conclusion, we constructed a proof-of-concept 3D printed islet embedding device consisting of a vascular channel that is hemocompatible and perspectively anastomosable to clinical scale blood vessels. However, there are numerous limitations in this model that need to be overcome to transfer this technology to the bedside.

Development and systematic evaluation of decellularization protocols in different application models for diaphragmatic tissue engineering.

BACKGROUND: Tissue engineered bioscaffolds based on decellularized composites have gained increasing interest for treatment of various diaphragmatic impairments, including muscular atrophies and diaphragmatic hernias. Detergent-enzymatic treatment (DET) constitutes a standard strategy for diaphragmatic decellularization. However, there is scarce data on comparing DET protocols with different substances in distinct application models in their ability to maximize cellular removal while minimizing extracellular matrix (ECM) damage. METHODS: We decellularized diaphragms of male Sprague Dawley rats with 1 % or 0.1 % sodium dodecyl sulfate (SDS) and 4 % sodium deoxycholate (SDC) by orbital shaking (OS) or retrograde perfusion (RP) through the vena cava. We evaluated decellularized diaphragmatic samples by (1) quantitative analysis including DNA quantification and biomechanical testing, (2) qualitative and semiquantitative analysis by proteomics, as well as (3) qualitative assessment with macroscopic and microscopic evaluation by histological staining, immunohistochemistry and scanning electron microscopy. RESULTS: All protocols produced decellularized matrices with micro- and ultramorphologically intact architecture and adequate biomechanical performance with gradual differences. The proteomic profile of decellularized matrices contained a broad range of primal core and ECM-associated proteins similar to native muscle. While no outstanding preference for one singular protocol was determinable, SDS-treated samples showed slightly beneficial properties in comparison to SDC-processed counterparts. Both application modalities proved suitable for DET. CONCLUSION: DET with SDS or SDC via orbital shaking or retrograde perfusion constitute suitable methods to produce adequately decellularized matrices with characteristically preserved proteomic composition. Exposing compositional and functional specifics of variously treated grafts may enable establishing an ideal processing strategy to sustain valuable tissue characteristics and optimize consecutive recellularization. This aims to design an optimal bioscaffold for future transplantation in quantitative and qualitative diaphragmatic defects.

Internal drainage for interdisciplinary management of anastomotic leakage after pancreaticogastrostomy.

BACKGROUND: Anastomotic leakage and postoperative pancreatic fistula (POPF) may occur after pancreatic head resection, also in the setting of pancreato-gastric reconstruction. For adequate complication management, a variety of non-standardized treatments are available. Still, data on clinical evaluation of endoscopic methods remain scarce. Based on our interdisciplinary experience on endoscopic treatment of retro-gastric fluid collections after left-sided pancreatectomies, we developed an innovative endoscopic concept with internal peri-anastomotic stent placement for patients with anastomotic leakage and/or peri-anastomotic fluid collection. METHODS: Over the period of 6 years (2015-2020) we retrospectively evaluated 531 patients after pancreatic head resections at the Department of Surgery, Charité-Unversitätsmedizin Berlin. Of these, 403 received reconstruction via pancreatogastrostomy. We identified 110 patients (27.3%) with anastomotic leakage and/or peri-anastomotic fluid collection and could define four treatment groups which received either conservative treatment (C), percutaneous drainage (PD), endoscopic drainage (ED), and/or re-operation (OP). Patients were grouped in a step-up approach for descriptive analyses and in a stratified, decision-based algorithm for comparative analyses. The study's primary endpoints were hospitalization (length of hospital stay) and clinical success (treatment success rate, primary/secondary resolution). RESULTS: We characterized an institutional, post-operative cohort with heterogenous complication management following pancreato-gastric reconstruction. The majority of patients needed interventional treatments (n = 92, 83.6%). Of these, close to one-third (n = 32, 29.1%) were treated with endoscopy-guided, peri-anastomotic pigtail stents for internal drainage as either primary, secondary and/or tertiary treatment modality. Following a decision-based algorithm, we could discriminate superior primary-(77,8% vs 53.7%) and secondary success rates (85.7% vs 68.4%) as well as earlier primary resolutions (11.4 days, 95%CI (5.75-17.13) vs 37.4 days, 95%CI (27.2-47.5)] in patients receiving an endoscopic compared to percutaneous management. CONCLUSION: This study underscores the importance of endoscopy-guided approaches for adequate treatment of anastomotic leakage and/or peri-anastomotic fluid collections after pancreatoduodenectomy. We herein report a novel, interdisciplinary concept for internal drainage in the setting of pancreato-gastric reconstruction.