Pushing the boundaries of innovation: the potential of ex vivo organ perfusion from an interdisciplinary point of view.

Ex vivo machine perfusion (EVMP) is an emerging technique for preserving explanted solid organs with primary application in allogeneic organ transplantation. EVMP has been established as an alternative to the standard of care static-cold preservation, allowing for prolonged preservation and real-time monitoring of organ quality while reducing/preventing ischemia-reperfusion injury. Moreover, it has paved the way to involve expanded criteria donors, e.g., after circulatory death, thus expanding the donor organ pool. Ongoing improvements in EVMP protocols, especially expanding the duration of preservation, paved the way for its broader application, in particular for reconditioning and modification of diseased organs and tumor and infection therapies and regenerative approaches. Moreover, implementing EVMP for in vivo-like preclinical studies improving disease modeling raises significant interest, while providing an ideal interface for bioengineering and genetic manipulation. These approaches can be applied not only in an allogeneic and xenogeneic transplant setting but also in an autologous setting, where patients can be on temporary organ support while the diseased organs are treated ex vivo, followed by reimplantation of the cured organ. This review provides a comprehensive overview of the differences and similarities in abdominal (kidney and liver) and thoracic (lung and heart) EVMP, focusing on the organ-specific components and preservation techniques, specifically on the composition of perfusion solutions and their supplements and perfusion temperatures and flow conditions. Novel treatment opportunities beyond organ transplantation and limitations of abdominal and thoracic EVMP are delineated to identify complementary interdisciplinary approaches for the application and development of this technique.

Determinants of survival in patients on extracorporeal membrane oxygenation therapy due to severe covid-19.

BACKGROUND: Severe acute respiratory distress syndrome (ARDS) due to Coronavirus Disease-19 (COVID-19) is associated with high mortality. Although survival on mechanical circulatory support has improved, determinants for better prognosis are still unclear. Here, we report on the outcome of our patient population with the need for mechanical circulatory support due to severe COVID-19 (sCOVID-19) induced ARDS. METHODS: All patients treated with extracorporeal membrane oxygenation (ECMO) for severe ARDS due to sCOVID-19 were analysed. Patients > 18 years of age at the time of initiation of ECMO were included. Pre-existing comorbidities, complications during ECMO implantation, and ECMO runtime were reviewed. The latency to intubation, proning, tracheotomy, and ECMO implantation was analysed. Furthermore, the survival and non-survival population were compared to determine factors in favour of a better outcome. RESULTS: In total, 85 patients were treated with veno-venous membrane oxygenation (vv-ECMO) for severe ARDS in our medical centre. The patient population was predominantly male (83.5%) with a mean patient age of 54.9 years. A history of cardiovascular disease (p = .01), smoking (p < .05), need for vasopressor- (p < .05), and renal replacement therapy (p < .001) was associated with a worse prognosis. Overall survival was 50%. The survival population was significantly younger (p = .004), had a significantly higher body weight (p = .02) and body mass index (BMI) (p = .01). Furthermore, survival was significantly better when vv-ECMO was initiated within 48 h after admission (p < .001). CONCLUSIONS: Pre-existing cardiovascular disease, higher age, history of nicotine abuse, and development of renal failure are associated with poor outcome. Early start of vv-ECMO therapy may lead to better survival in sCOVID-19 patients, although complications during ECMO therapy are associated with a worse prognosis.

The role of ex-situ perfusion for thoracic organs.

PURPOSE OF REVIEW: Ex-situ machine perfusion for both heart (HTx) and lung transplantation (LuTx) reduces ischemia-reperfusion injury (IRI), allows for greater flexibility in geographical donor management, continuous monitoring, organ assessment for extended evaluation, and potential reconditioning of marginal organs. In this review, we will delineate the impact of machine perfusion, characterize novel opportunities, and outline potential challenges lying ahead to improve further implementation. RECENT FINDINGS: Due to the success of several randomized controlled trials (RCT), comparing cold storage to machine perfusion in HTx and LuTx, implementation and innovation continues. Indeed, it represents a promising interface for organ-specific therapies targeting IRI, allo-immune responses, and graft reconditioning. These mostly experimental efforts range from genetic approaches and nanotechnology to cellular therapies, involving mesenchymal stem cell application. Despite tremendous potential, prior to clinical transition, more data is needed. SUMMARY: Collectively, machine perfusion constitutes the vanguard in thoracic organ transplantation research with extensive potential for expanding the donor pool, enhancing transplant outcomes as well as developing novel therapy approaches.

Donor NK and T Cells in the Periphery of Lung Transplant Recipients Contain High Frequencies of Killer Cell Immunoglobulin-Like Receptor-Positive Subsets.

Introduction: For end-stage lung diseases, double lung transplantation (DLTx) is the ultimate curative treatment option. However, acute and chronic rejection and chronic dysfunction are major limitations in thoracic transplantation medicine. Thus, a better understanding of the contribution of immune responses early after DLTx is urgently needed. Passenger cells, derived from donor lungs and migrating into the recipient periphery, are comprised primarily by NK and T cells. Here, we aimed at characterizing the expression of killer cell immunoglobulin-like receptors (KIR) on donor and recipient NK and T cells in recipient blood after DLTx. Furthermore, we investigated the functional status and capacity of donor vs. recipient NK cells. Methods: Peripheral blood samples of 51 DLTx recipients were analyzed pre Tx and at T0, T24 and 3wk post Tx for the presence of HLA-mismatched donor NK and T cells, their KIR repertoire as well as activation status using flow cytometry. Results: Within the first 3 weeks after DLTx, donor NK and T cells were detected in all patients with a peak at T0. An increase of the KIR2DL/S1-positive subset was found within the donor NK cell repertoire. Moreover, donor NK cells showed significantly higher frequencies of KIR2DL/S1-positive cells (p<0.01) 3wk post DLTx compared to recipient NK cells. This effect was also observed in donor KIR+ T cells 3wk after DLTx with higher proportions of KIR2DL/S1 (p<0.05) and KIR3DL/S1 (p<0.01) positive T cells. Higher activation levels of donor NK and T cells (p<0.001) were detected compared to recipient cells via CD25 expression as well as a higher degranulation capacity upon activation by K562 target cells. Conclusion: Higher frequencies of donor NK and T cells expressing KIR compared to recipient NK and T cells argue for their origin in the lung as a part of a highly specialized immunocompetent compartment. Despite KIR expression, higher activation levels of donor NK and T cells in the periphery of recipients suggest their pre-activation during the ex situ phase. Taken together, donor NK and T cells are likely to have a regulatory effect in the balance between tolerance and rejection and, hence, graft survival after DLTx.

Towards Biohybrid Lung: Induced Pluripotent Stem Cell Derived Endothelial Cells as Clinically Relevant Cell Source for Biologization.

In order to provide an alternative treatment option to lung transplantation for patients with end-stage lung disease, we aim for the development of an implantable biohybrid lung (BHL), based on hollow fiber membrane (HFM) technology used in extracorporeal membrane oxygenators. Complete hemocompatibility of all blood contacting surfaces is crucial for long-lasting BHL durability and can be achieved by their endothelialization. Autologous endothelial cells (ECs) would be the ideal cell source, but their limited proliferation potential excludes them for this purpose. As induced pluripotent stem cell-derived ECs enable the generation of a large number of ECs, we assessed and compared their capacity to form a viable and confluent monolayer on HFM, while indicating physiologic EC-specific anti-thrombogenic and anti-inflammatory properties. ECs were generated from three different human iPSC lines, and seeded onto fibronectin-coated poly-4-methyl-1-pentene (PMP) HFM. Following phenotypical characterization, ECs were analyzed for their thrombogenic and inflammatory behavior with or without TNFα induction, using FACS and qRT-PCR. Complementary, leukocyte- and platelet adhesion assays were carried out. The capacity of the iPSC-ECs to reendothelialize cell-free monolayer areas was assessed in a scratch assay. ECs sourced from umbilical cord blood (hCBECs) were used as control. iPSC-derived ECs formed confluent monolayers on the HFM and showed the typical EC-phenotype by expression of VE-cadherin and collagen-IV. A low protein and gene expression level of E-selectin and tissue factor was detected for all iPSC-ECs and the hCBECs, while a strong upregulation of these markers was noted upon stimulation with TNFα. This was in line with the physiological and strong induction of leukocyte adhesion detected after treatment with TNFα, iPSC-EC and hCBEC monolayers were capable of reducing thrombocyte adhesion and repopulating scratched areas. iPSCs offer the possibility to provide patient-specific ECs in abundant numbers needed to cover all blood contacting surfaces of the BHL with a viable, non-thrombogenic and non-inflammatory monolayer. iPSC-EC clones can differ in terms of their reendothelialization rate, and pro-inflammatory response. However, a less profound inflammatory response may even be advantageous for BHL application. With the proven ability of the seeded iPSC-ECs to reduce thrombocyte adhesion, we expect that thrombotic events that could lead to BHL occlusion can be avoided, and thus, justifies further studies on enabling BHL long-term application.

Fucosylated lipid nanocarriers loaded with antibiotics efficiently inhibit mycobacterial propagation in human myeloid cells.

Antibiotic treatment of tuberculosis (TB) is complex, lengthy, and can be associated with various adverse effects. As a result, patient compliance often is poor, thus further enhancing the risk of selecting multi-drug resistant bacteria. Macrophage mannose receptor (MMR)-positive alveolar macrophages (AM) constitute a niche in which Mycobacterium tuberculosis replicates and survives. Therefore, we encapsulated levofloxacin in lipid nanocarriers functionalized with fucosyl residues that interact with the MMR. Indeed, such nanocarriers preferentially targeted MMR-positive myeloid cells, and in particular, AM. Intracellularly, fucosylated lipid nanocarriers favorably delivered their payload into endosomal compartments, where mycobacteria reside. In an in vitro setting using infected human primary macrophages as well as dendritic cells, the encapsulated antibiotic cleared the pathogen more efficiently than free levofloxacin. In conclusion, our results point towards carbohydrate-functionalized nanocarriers as a promising tool for improving TB treatment by targeted delivery of antibiotics.

Towards Biohybrid Lung Development-Fibronectin-Coating Bestows Hemocompatibility of Gas Exchange Hollow Fiber Membranes by Improving Flow-Resistant Endothelialization.

To provide an alternative treatment option for patients with end-stage lung disease, we aim for biohybrid lung development (BHL) based on hollow fiber membrane (HFM) technology used in extracorporeal membrane oxygenators. For long-term BHL application, complete hemocompatibility of all blood-contacting surfaces is indispensable and can be achieved by their endothelialization. Indeed, albumin/heparin (AH) coated HFM enables initial endothelialization, but as inexplicable cell loss under flow conditions was seen, we assessed an alternative HFM coating using fibronectin (FN). Therefore, endothelial cell (EC) adherence and viability on both coated HFM were analyzed by fluorescence-based staining. Functional leukocyte and thrombocyte adhesion assays were performed to evaluate hemocompatibility, also in comparison to blood plasma coated HFM as a clinically relevant control. To assess monolayer resistance and EC behavior under clinically relevant flow conditions, a mock circulation setup was established, which also facilitates imitation of lung-disease specific blood gas settings. Besides quantification of flow-associated cell loss, endothelial responses towards external stimuli, like flow exposure or TNFα stimulation, were analyzed by qRT-PCR, focusing on inflammation, thrombus formation and extracellular matrix production. Under static conditions, both coated HFM enabled the generation of a viable, confluent, non-inflammatory and anti-thrombogenic monolayer. However, by means of homogenous FN coating, cell retention and physiologic gene regulation towards an improved hemocompatible-and extracellular matrix producing phenotype, was significantly superior compared to the inhomogeneous AH coating. In summary, our adaptable in-house FN coating secures the endothelial requirements for long-term BHL application and may promote monolayer establishment on all other blood contacting surfaces of the BHL (e.g., cannulae).

Hypothermic preservation of endothelialized gas-exchange membranes.

Endothelialization of the blood contacting surfaces of blood-contacting medical devices, such as cardiovascular prostheses or biohybrid oxygenators, represents a plausible strategy for increasing their hemocompatibility. Nevertheless, isolation and expansion of autologous endothelial cells (ECs) usually requires multiple processing steps and time to obtain sufficient cell numbers. This excludes endothelialization from application in acute situations. Off-the-shelf availability of cell-seeded biohybrid devices could be potentially facilitated by hypothermic storage. In this study, the survival of cord-blood-derived endothelial colony forming cells (ECFCs) that were seeded onto polymethylpentene (PMP) gas-exchange membranes and stored for up to 2 weeks in different commercially available and commonly used preservation media was measured. While storage at 4°C in normal growth medium (EGM-2) for 3 days resulted in massive disruption of the ECFC monolayer and a significant decline in viability, ECFC monolayers preserved in Chillprotec could recover after up to 14 days with negligible effects on their integrity and viability. ECFC monolayers preserved in Celsior, HTS-FRS, or Rokepie medium showed a significant decrease in viability after 7 days or longer periods. These results demonstrated the feasibility of hypothermic preservation of ECFC monolayers on gas-exchange membranes for up to 2 weeks, with potential application on the preservation of pre-endothelialized oxygenators and further biohybrid cardiovascular devices.

Ex vivo limb perfusion for traumatic amputation in military medicine.

BACKGROUND: Limb loss has a drastic impact on a patient's life. Severe trauma to the extremities is common in current military conflicts. Among other aspects, "life before limb" damage control surgery hinders immediate replantation within the short post-traumatic timeframe, which is limited in part by the ischemic time for successful replantation. Ex vivo limb perfusion is currently being researched in animal models and shows promising results for its application in human limb replantation and allotransplantation. PRESENTATION OF THE HYPOTHESIS: The current lack of replantation possibilities in military operations with high rates of amputation can be addressed with the development of a portable ex vivo limb perfusion device, as there are several opportunities present with the introduction of this technique on the horizon. We hypothesize that ex vivo limb perfusion will enable overcoming the critical ischemic time, provide surgical opportunities such as preparation of the stump and limb, allow for spare-part surgery, enable rigorous antibiotic treatment of the limb, reduce ischemia-reperfusion injuries, enable a tissue function assessment before replantation, and enable the development of large limb transplant programs. TESTING THE HYPOTHESIS: Data from in vivo studies in porcine models are limited by the relatively short perfusion time of 24 h. In the military setting, notably longer perfusion times need to be realized. Therefore, future animal studies must focus especially on long-term perfusion, since this represents the military setting, considering the time for stabilization of the patient until evacuation to a tertiary treatment center. IMPLICATIONS OF THE HYPOTHESIS: The development and clinical introduction of ex vivo limb perfusion in the military setting could lead to a drastic reduction in the number of limb amputations among service members. Ex vivo limb perfusion enables replantation surgery in Role 4 facilities and changes the clinical setting from a highly urgent, life-threatening situation to a highly methodical, well-prepared starting point for optimal treatment of the wounded service member. With its introduction, the principle of "life before limb" will change to "life before limb before elective replantation/allotransplantation after ex vivo limb perfusion".

Identifying an optimal seeding protocol and endothelial cell substrate for biohybrid lung development.

Several key prerequisites need to be fulfilled for the development of a biohybrid lung, which can offer an actual alternative to lung transplantation. A major aspect is an optimized haemocompatibility of the device's artificial surfaces via endothelial cell seeding. In this study, four different types of polymeric gas exchange hollow fibre membranes (HFMs) were analysed utilizing four different seeding protocols in order to identify the ideal combination for sufficient long-term endothelialization. Human cord blood-derived endothelial cells (HCBECs) were used for the endothelialization of polypropylene HFMs with two different pore sizes and poly-4-methyl-1-pentene HFMs, both with and without heparin/albumin coating. The qualitative and quantitative impact of four different rotational seeding protocols regarding long-term HFM endothelialization and the impact of inflammatory stimulation on the seeded HCBECs were examined by fluorescence microscopy, cell counting, and analysis of relative expression levels of activation, shear stress, and thrombogenic state markers. Optimized endothelial cell seeding and long-term cultivation were only achieved using heparin/albumin-coated poly-4-methyl-1-pentene HFMs, applying 24 hr of rotational speed at 1 rpm followed by 120 hr of static culture. Neither cell-to-HFM contact nor the rotational cultivation procedure showed an impact on the physiological anti-thrombogenic and anti-inflammatory HCBEC activation status. Additionally, the cells maintained their physiological responsiveness towards inflammatory stimulation. Rotational seeding strategies and a seamless heparin/albumin coating of the HFMs are crucial requirements for a sufficient and long-lasting endothelialization and thus a key element in the future development and in vivo application of the biohybrid lung.

In-vitro evaluation of limitations and possibilities for the future use of intracorporeal gas exchangers placed in the upper lobe position.

The lack of donor organs has led to the development of alternative "destination therapies", such as a bio-artificial lung (BA) for end-stage lung disease. Ultimately aiming at a fully implantable BA, general capabilities and limitations of different oxygenators were tested based on the model of BA positioning at the right upper lobe. Three different-sized oxygenators (neonatal, paediatric, and adult) were tested in a mock circulation loop regarding oxygenation and decarboxylation capacities for three respiratory pathologies. Blood flows were imitated by a roller pump, and respiration was imitated by a mechanical ventilator with different FiO2 applications. Pressure drops across the oxygenators and the integrity of the gas-exchange hollow fibers were analyzed. The neonatal oxygenator proved to be insufficient regarding oxygenation and decarboxylation. Despite elevated pCO2 levels, the paediatric and adult oxygenators delivered comparable sufficient oxygen levels, but sufficient decarboxylation across the oxygenators was ensured only at flow rates of 0.5 L min. Only the adult oxygenator indicated no significant pressure drops. For all tested conditions, gas-exchange hollow fibers remained intact. This is the first study showing the general feasibility of delivering sufficient levels of gas exchange to an intracorporeal BA via patient's breathing, without damaging gas-exchange hollow fiber membranes.

Local Anesthetics delivered through Pleural Drainages improve Pain and Lung Function after Cardiac Surgery.

OBJECTIVE: Pleural tubes after coronary artery bypass graft (CABG) surgery usually cause pain resulting interalia in an impact of postoperative breathing. Therefore, the influence of intrapleural lidocaine application through special double-lumen chest tubes with respect to pain relief and lung function was investigated and compared with placebo. METHODS: In this study, 40 patients who underwent CABG got intrapleural injection either with 2% lidocaine (n = 20) or placebo (0.9% saline solution) (n = 20) on the first 2 days after surgery. Pain was measured by pain intensity numeric rating scale (NRS) (0 = no pain; 10 = the most intense pain) and lung function by portable spirometer. RESULTS: On the first postoperative day (POD1), mean pain reduction was NRS 1.9 for the lidocaine group with an improvement of the forced expiratory volume in 1 second (FEV1) of 0.51 L. Similar results were shown on the second postoperative day (POD2) with a decreased pain level of mean NRS 1.65 and an FEV1 improvement of 0.26 L. In comparison, results of the placebo group showed no significant pain reduction, neither on the POD1 (NRS 0.35; p = 0.429) nor on the POD2 (NRS 0.55; p = 0.159). Also, there was no significant influence of FEV1 after placebo on the POD1 (FEV1 = 0.048 L; p = 0.70) or on the POD2 (FEV1 = 0.0135 L; p = 0.925). CONCLUSION: Intrapleural application of lidocaine is a safe and feasible method to reduce drainage-related pain and improving lung function after CABG.

Low Immunogenic Endothelial Cells Maintain Morphological and Functional Properties Required for Vascular Tissue Engineering.

The limited availability of native vessels suitable for the application as hemodialysis shunts or bypass material demands new strategies in cardiovascular surgery. Tissue-engineered vascular grafts containing autologous cells are considered ideal vessel replacements due to the low risk of rejection. However, endothelial cells (EC), which are central components of natural blood vessels, are difficult to obtain from elderly patients of poor health. Umbilical cord blood represents a promising alternative source for EC, but their allogeneic origin corresponds with the risk of rejection after allotransplantation. To reduce this risk, the human leukocyte antigen class I (HLA I) complex was stably silenced by lentiviral vector-mediated RNA interference (RNAi) in EC from peripheral blood and umbilical cord blood and vein. EC from all three sources were transduced by 93.1% ± 4.8% and effectively, HLA I-silenced by up to 67% compared to nontransduced (NT) cells or transduced with a nonspecific short hairpin RNA, respectively. Silenced EC remained capable to express characteristic endothelial surface markers such as CD31 and vascular endothelial cadherin important for constructing a tight barrier, as well as von Willebrand factor and endothelial nitric oxide synthase important for blood coagulation and vessel tone regulation. Moreover, HLA I-silenced EC were still able to align under unidirectional flow, to take up acetylated low-density lipoprotein, and to form capillary-like tube structures in three-dimensional fibrin gels similar to NT cells. In particular, addition of adipose tissue-derived mesenchymal stem cells significantly improved tube formation capability of HLA I-silenced EC toward long and widely branched vascular networks necessary for prevascularizing vascular grafts. Thus, silencing HLA I by RNAi represents a promising technique to reduce the immunogenic potential of EC from three different sources without interfering with EC-specific morphological and functional properties required for vascular tissue engineering. This extends the spectrum of available cell sources from autologous to allogeneic sources, thereby accelerating the generation of tissue-engineered vascular grafts in acute clinical cases.

Cellular Differentiation of Human Monocytes Is Regulated by Time-Dependent Interleukin-4 Signaling and the Transcriptional Regulator NCOR2.

Human in vitro generated monocyte-derived dendritic cells (moDCs) and macrophages are used clinically, e.g., to induce immunity against cancer. However, their physiological counterparts, ontogeny, transcriptional regulation, and heterogeneity remains largely unknown, hampering their clinical use. High-dimensional techniques were used to elucidate transcriptional, phenotypic, and functional differences between human in vivo and in vitro generated mononuclear phagocytes to facilitate their full potential in the clinic. We demonstrate that monocytes differentiated by macrophage colony-stimulating factor (M-CSF) or granulocyte macrophage colony-stimulating factor (GM-CSF) resembled in vivo inflammatory macrophages, while moDCs resembled in vivo inflammatory DCs. Moreover, differentiated monocytes presented with profound transcriptomic, phenotypic, and functional differences. Monocytes integrated GM-CSF and IL-4 stimulation combinatorically and temporally, resulting in a mode- and time-dependent differentiation relying on NCOR2. Finally, moDCs are phenotypically heterogeneous and therefore necessitate the use of high-dimensional phenotyping to open new possibilities for better clinical tailoring of these cellular therapies.

First results of HeartWare left ventricular assist device implantation with tunnelling of the outflow graft through the transverse sinus.

OBJECTIVES: The number of left ventricular assist device (LVAD) implants for the treatment of advanced heart failure is increasing tremendously. The main therapeutic goal of this operation is to provide a bridge to transplant for patients awaiting a donor heart. In 2011, we developed a novel, minimally invasive surgical technique for LVAD implantation. To avoid possible outflow graft injuries during redo sternotomies as well as to provide a more physiological outflow towards the aortic arch, a further modification of this approach was made with outflow graft tunnelling through the transverse sinus. METHODS: More than 500 LVADs were implanted at Hannover Medical School between 2008 and 2015. From September 2012 to December 2015, we used this novel technique in 17 consecutive bridge-to-transplant patients and analysed their clinical outcomes retrospectively. Baseline characteristics were obtained for all patients, and outcome data were collected from a review of electronic medical records. Subsequently, we compared the results of a data analysis of a group of 86 patients with a minimally invasive left thoracotomy LVAD implantation with the results from patients in a control group receiving a conventional outflow graft placement between May 2009 and January 2015. RESULTS: Our data demonstrate that the outcomes and adverse events of the operated group were comparable to those of the control group. Three patients of the study group died within the first year (3 of 17, 18%); survival to 3 years was 84%. The adverse events were similar in both groups. The study group had 3 ischaemic strokes (18%) and 1 LVAD thrombosis (6%). Five patients had LVAD thrombosis (5 of 86, 6%) and 6 in the control group had ischaemic strokes (6 of 86, 7%). The average in-hospital stay was 35.4 days for the study group and 27.4 days for the control group. Three patients from the study group and 5 from the control group had cardiac transplants. The average time until cannulation and start of extracorporeal circulation was 56 min in the study group and 96 min in the control group. Re-thoracotomy was necessary in 2 patients from the control group, whereas none was necessary in the study group. CONCLUSIONS: LVAD implantation with outflow graft tunnelling through the transverse sinus is an innovative technique to prevent outflow graft damage in case of cardiac resternotomy. The results of this study show that there are no significant differences in pump speed or flow, adverse events or patient outcomes compared with the standard implant techniques. The theoretical benefits of this novel technique are the reduced risk in redo cases and the physiological direction of blood flow. Consequently, this procedure might be particularly suitable for younger patients who received an LVAD as a bridge-to-transplant option.

First series of left ventricular assist device exchanges to HeartMate 3.

OBJECTIVES: Left ventricular assist device (LVAD) exchange is becoming a standard surgical procedure. The exchange procedure is an opportunity to upgrade patients to a new generation pump that offers advanced reduction of adverse events or longer battery hours. METHODS: We performed an analysis of 6 consecutive patients who underwent LVAD exchange to HeartMate 3 either from a HeartWare or HeartMate (HM) II device. Minimally invasive operations were performed through a lateral thoracotomy. Follow-up time was 6 months after LVAD exchange. RESULTS: We present 4 patients with the HM II and 2 patients with the HeartWare ventricular assist device (HVAD) who underwent LVAD exchange to HM III. The average age was 57.5 years. At the time of the LVAD exchange, all patients were classified as Interagency Registry for Mechanically Assisted Circulatory Support level 3. In 5 cases, LVAD infection led to LVAD exchange (83%, 5/6). The remaining patient underwent LVAD exchange due to pump thrombosis (16%, 1/6). The 6-month survival rate after LVAD exchange was 100% (6/6). None of the patients was postoperatively supported by extracorporeal membrane oxygenation. No patient experienced postoperative relevant bleeding. One patient suffered minor cerebral bleeding (16.6%, 1/6). At the 6-month follow-up examination, 1 patient reported a single syncope and several low-flow alarms (1/6). The remaining 5 patients showed no adverse events or technical malfunctions of the VAD (5/6). CONCLUSIONS: LVAD exchanges from HM II as well from HVAD to HM 3 are proven to be technically feasible. Due to the advantages and technical improvements of the new-generation pumps, this procedure is an excellent opportunity to give patients access to a superior generation of assist device.

Endothelialization and characterization of titanium dioxide-coated gas-exchange membranes for application in the bioartificial lung.

Fouling on the gas-exchange hollow-fiber membrane (HFM) of extracorporeal membrane oxygenation (ECMO) devices by blood components and pathogens represents the major hurdle to their long-term application in patients with lung deficiency or unstable hemodynamics. Although patients are treated with anticoagulants, deposition of blood proteins onto the membrane surface may still occur after few days, leading to insufficient gas transfer and, consequently, to device failure. The aim of this study was to establish an endothelial cell (EC) monolayer onto the gas-exchange membrane of an ECMO device with a view to developing a hemocompatible bioartificial lung. Poly(4-methyl-1-pentene) (PMP) gas-exchange membranes were coated with titanium dioxide (TiO2), using the pulsed vacuum cathodic arc plasma deposition (PVCAPD) technique, in order to generate a stable interlayer, enabling cell adhesion onto the strongly hydrophobic PMP membrane. The TiO2 coating reduced the oxygen transfer rate (OTR) of the membrane by 22%, and it successfully mediated EC attachment. The adhered ECs formed a confluent monolayer, which retained a non-thrombogenic state and showed cell-to-cell, as well as cell-to-substrate contacts. The established monolayer was able to withstand physiological shear stress and possessed a "self-healing" capacity at areas of induced monolayer disruption. The study demonstrated that the TiO2 coating mediated EC attachment and the establishment of a functional EC monolayer. STATEMENT OF SIGNIFICANCE: Surface endothelialization is considered an effective approach to achieve complete hamocompatibility of blood-contacting devices. Several strategies to enable endothelial cell adhesion onto stents and vascular prostheses have already been described in the literature. However, only few studies investigated the feasibility of establishing an endothelial monolayer onto the gas exchange membrane of ECMO devices, using peptides or proteins that were weakly adsorbed via dip coating techniques. This study demonstrated the effectiveness of an alternative and stable titanium dioxide coating for gas-exchange membranes, which enabled the establishment of a confluent, functional and non-activated endothelial monolayer, while maintaining oxygen permeability.

Developing a biohybrid lung - sufficient endothelialization of poly-4-methly-1-pentene gas exchange hollow-fiber membranes.

Working towards establishing a biohybrid lung with optimized hemocompatibility, this study analyzed the feasibility of establishing flow-resistant endothelium on heparin/albumin coated poly-4-methly-1-pentene hollow fiber gas exchange membranes (PMP-HFs). The seeding efficiency and proliferation of human cord blood derived endothelial cells (HCBEC) on PMP-HFs were analyzed under static conditions by WST-8 cell proliferation assay and fluorescence microscopy. The HCBEC monolayer integrity under different flow conditions was also assessed. Endothelial-specific phenotype verification, expression activation levels and thrombogenic state markers were quantified by real-time RT-PCR for cell-to-PMP-HF contact under static and dynamic conditions. The results demonstrated the feasibility of establishing a viable, confluent, and flow-resistant endothelial monolayer on the blood-contact surface of PMP-HFs, which maintained a physiological response to TNFα-stimulation and flow conditions. The endothelial phenotype, expression levels of adhesion molecules and thrombogenic state markers were unaffected by cell-to-PMP-HFs contact. These results represent a significant step towards establishing a biohybrid lung.

Survival and spirometry outcomes after lung transplantation from donors aged 70 years and older.

BACKGROUND: Mediocre donation rates and increasing demand for lung transplantation leads transplant centers to consider extended-criteria donor lungs. Arguably, the largest remaining non-utilized lung donor segment is the elderly individual, already considered for visceral organ donation but not thoracic. So far, transplantation of donor lungs aged ≥ 70 years is rarely reported, and recipient outcomes are unknown. Accordingly, we report a single-center series of lung transplantations from donors aged ≥ 70 years and compare outcomes with contemporary lung transplantations from younger donors. METHODS: All bilateral lung transplantations performed at our center between March 2011 and July 2014 were analyzed, and 2 cohorts were built according to lung donor age. RESULTS: A total of 440 bilateral lung transplantations were performed from 413 donors aged <70 years, and 27 donors aged ≥70 years. Donor characteristics did not differ in sex, donor time on mechanical ventilation before retrieval, or donor partial pressure of arterial oxygen/fraction of inspired oxygen ratio. Older donors were significantly less often positive for smoking history (43.7% vs 14.8%, p = 0.003) or for abnormal bronchoscopy results (52.9% vs 15.8%, p = 0.002). Recipients receiving donor lungs aged <70 years were younger than those receiving older donor lungs ≥ 70 (49.8 [range, 35-58] vs 58 [range, 53-62] years, p < 0.0001). Underlying diagnoses did not differ significantly between the groups. Post-operative mechanical ventilation times (15 [range, 10-59] vs 27.5 [range, 10-75.8] hours), intensive care unit stays (3 [range, 1-5] vs 3 [range, 1-8] days), and total hospital lengths of stay (24 [range, 22-40.5] vs 24 [range, 22-40] days) of the recipients did not differ significantly between the two groups. The percentage predicted forced expiratory volume in 1 second was 86.5% ± 26.2% 12 months after transplantation of younger lungs vs 72.2% ± 23.8% (p = 0.01) after transplantation of older lungs. Differentiating the spirometry findings according to underlying diseases showed significantly lower forced expiratory volume in 1 second values after transplantation of donor lungs aged ≥70 only in idiopathic pulmonary fibrosis recipients but not in emphysema patients. Patient survival up to 36 months was not significantly different, with 1-year survival being 92.9% for younger vs 95.5% for older donor lungs. CONCLUSION: Use of donor lungs aged ≥70 years for transplantation is safe, without compromising survival. However, spirometry findings after transplantation with donors ≥70 years indicate better functional outcomes in emphysema recipients than in idiopathic pulmonary fibrosis recipients.

In vitro comparison of biological and synthetic materials for skeletal chest wall reconstruction.

BACKGROUND: Various biological and synthetic materials have been proposed for use in skeletal chest wall reconstruction (SCWR). Because of the lack of studies allowing a direct comparison of SCWR materials, their clinical use often depends on the surgeon's preference and experience. The aim of this study was to analyze 6 synthetic and 3 biological materials frequently used in SCWR with respect to their cytotoxicity, bacterial adhesion, surface characteristics, and mechanical properties to facilitate data-driven decisions. METHODS: The effect of the SCWR materials and their extracts on the metabolism of human skeletal muscle cells (SkMCs), dermal fibroblasts, adipose cells, and osteoblasts was analyzed in vitro. Bacterial adhesion was quantified by incubating samples in bacterial suspensions (Staphylococcus epidermidis, S aureus, and Escherichia coli), followed by counting colony-forming units and performing scanning electron microscopy. Moreover, the mechanical properties of the materials were analyzed under uniaxial tensile loading to failure. RESULTS: The metabolism of all cell types seeded on the SCWR materials was reduced compared with untreated cells. With the exception of Vypro (Ethicon, Somerville, NJ), whose extracts significantly reduced fibroblast viability, no cytotoxic leachable substances were detected. Biological materials were less cytotoxic compared with synthetic ones, but they demonstrated increased bacterial adhesion. Synthetic materials demonstrated higher elongation to failure than did biological materials. CONCLUSIONS: Biological and synthetic SCWR materials showed significant differences in their cytotoxicity, bacterial adhesion, and biomechanical properties, suggesting that they may be used for different indications in SCWR. Further comparable in vivo studies are needed to analyze their performance in different indications of clinical application.