Pathologies comprising more than half the length of the trachea are a challenge to the reconstructive surgeon. Innovative tracheal transplantation techniques aim to offer the patient a curative solution with a sustained improvement in quality of life. This review summarizes the authors' experience with the rabbit as a versatile model for research regarding tracheal transplantation. Because of the segmental blood supply of the trachea, it is not feasible to transplant the organ together with a well-defined vascular pedicle. As such, the key element of successful tracheal transplantation is the creation of a new blood supply. This vascularized construct is created by prelaminating the rabbit trachea heterotopically, within the lateral thoracic fascia. After prelamination, the construct and its vascular pedicle are transferred to the orthotopic position in the neck. This model has become gold standard because of the advantages of working with rabbits, the anatomy of the rabbit trachea, and the reliability of the lateral thoracic artery flap. In this paper, the key elements of surgery in the rabbit are discussed, as well as the tracheal anastomosis and the harvest of the lateral thoracic artery flap. Practical tips and tricks are presented. The data described in this review represent the fundaments of ongoing translational research in the center over the past twenty years.

RationaleReceptor-interacting protein kinase 1 (RIPK1) is a key mediator of regulated cell death (including apoptosis and necroptosis) and inflammation, both drivers of chronic obstructive pulmonary disease (COPD) pathogenesis.ObjectiveWe aimed to define the contribution of RIPK1 kinase-dependent cell death and inflammation in the pathogenesis of COPD.MethodsWe assessedRIPK1expression in single-cell RNA-sequencing data from human and mouse lungs and validated RIPK1 levels in lung tissue of COPD patientsviaimmunohistochemistry. Next, we assessed the consequences of genetic and pharmacological inhibition of RIPK1 kinase activity in experimental COPD, usingRipk1S25D/S25Dkinase deficient mice and the RIPK1 kinase inhibitor GSK'547.Measurements and main resultsRIPK1expression increased in alveolar type I (AT1), AT2, ciliated and neuroendocrine cells in human COPD. RIPK1 protein levels were significantly increased in airway epithelium of COPD patients, compared to never smokers and smokers without airflow limitation. In mice, exposure to cigarette smoke (CS) increasedRipk1expression similarly in AT2 cells, and further in alveolar macrophages and T cells. Genetic and/or pharmacological inhibition of RIPK1 kinase activity significantly attenuated airway inflammation upon acute and subacute CS-exposure, as well as airway remodeling, emphysema and apoptotic and necroptotic cell death upon chronic CS-exposure. Similarly, pharmacological RIPK1 kinase inhibition significantly attenuated elastase-induced emphysema and lung function decline. Finally, RNA-sequencing on lung tissue of CS-exposed mice revealed downregulation of cell death and inflammatory pathways upon pharmacological RIPK1 kinase inhibition.ConclusionsRIPK1 kinase inhibition is protective in experimental models of COPD and may represent a novel promising therapeutic approach.

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Background: Chronic Obstructive Pulmonary Disease (COPD) is characterized by a progressive and abnormal inflammatory response in the lungs, mainly caused by cigarette smoking. Animal models exposed to cigarette smoke (CS) are used to mimic human COPD but the use of different CS protocols makes it difficult to compare the immunological and structural consequences of using a nose-only or whole-body CS exposure system. We hypothesized that when using a standardized CS exposure protocol based on particle density and CO (carbon monoxide) levels, the whole-body CS exposure system would generate a more severe inflammatory response than the nose-only system, due to possible sensitization, uptake of gases through the skin or uptake of tar particles stuck on the skin via grooming. Methods: In this study focusing on early COPD, mice were exposed twice daily 5 days a week to CS either with a nose-only or whole-body exposure system for 14 weeks to assess lung remodeling and inflammation. Data was analyzed with a one-way ANOVA with Bonferroni post-hoc test or Kruskal-Wallis with Dunn’s test for multiple comparison depending on respectively parametric or non-parametric datasets.Results: Both CS exposure systems induced a similar degree of lung function impairment and morphological alterations. Interestingly, an enhanced lymphoid presence in the bronchoalveolar lavage and lymph nodes with a higher mRNA expression of interleukin 6 and keratinocyte chemoattractant in the lungs were found with the whole-body system. Conclusion: Our data indicate that the inflammatory outcomes are more severe in the whole-body CS exposure compared to the nose-only system, but lung remodeling and lung function impairment are similarly affected. These observations can assist researchers to make an appropriate choice between the two CS exposure systems in designing their future studies in early drug interventions.

Background Primary graft dysfunction resulting from ischaemia-reperfusion injury (IRI) remains a major obstacle after lung transplantation (LTx) and is associated with morbidity and mortality. Continuous release of inflammatory cytokines, due to the process of ischaemia and reperfusion, triggers a complex cascade of apoptosis and necrosis resulting in graft dysfunction. Previous studies demonstrated successful graft improvement by cytokine filtration during ex vivo lung perfusion (EVLP). We hypothesize that plasma cytokine filtration with CytoSorb® during in vivo graft perfusion immediately after implantation may attenuate IRI after left LTx in a porcine model. Materials and Methods Left porcine lung transplantation was performed with allografts preserved for 24 hours at 4 °C. In the treatment group [T] (n = 7), a veno-venous shunt was created to insert the cytokine filter (CytoSorbents, Berlin, Germany). In the sham group [S] (n = 4) the shunt was created without the filter. Haemodynamic parameters, lung mechanics, blood gases and plasma cytokines were assessed during 6-hours in vivo reperfusion. Results During 6 hours of reperfusion, significant differences in plasma pro-inflammatory cytokine (IFN-α, IFN-γ, and IL-6) concentrations were observed between [T] and [S], but surprisingly with higher plasma levels in the [T] group. Plasma concentrations of other pro-inflammatory cytokines (IL-1β, IL-12p40, IL-4, IL-6, IL-8, IFN-α, IFN-γ, and TNF-α) and anti-inflammatory cytokines (IL-10) did not find any evidence for a difference. Furthermore, our study failed to show meaningful difference in haemodynamics and blood gases. Also, no statistically significant differences were found between [T] and [S] in biopsies and wet-to-dry ratio at the end of the experiment. Conclusions In our porcine left lung transplantation model cytokine filtration did not achieve the intended effect. This is in contrast to previous studies with CytoSorb® use during ex vivo lung perfusion as a surrogate LTx model. Our findings might highlight the fact that the theoretical benefit of inserting an additional cytokine adsorber to improve graft function in clinical practice should be critically evaluated with further studies.