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Regenerative medicine is a multidisciplinary field where continued progress relies on the incorporation of a diverse set of technologies from a wide range of disciplines within medicine, science and engineering. This review describes how one such technique, mathematical modelling, can be utilised to improve the tissue engineering of organs and stem cell therapy. Several case studies, taken from research carried out by our group, ACTREM, demonstrate the utility of mechanistic mathematical models to help aid the design and optimisation of protocols in regenerative medicine.

The repair and reconstruction of bile ducts damaged by disease or trauma remains a vexing medical problem. In particular, surgeons have few options when it comes to a long segment reconstruction of the bile duct. Tissue-engineered substitutes, with properties similar to the native tissue, might represent a solution for the functional reconstruction of bile ducts. In particular, decellularized tissues and organs represent a suitable option for tissue engineering when specific scaffolds are needed. However, the optimal conditions to completely remove all the cellular components and minimally affect the structural and residual biochemical properties of the extracellular matrix are still to be found. This paper presents the characterization of rat bile ducts after implementing an established detergent-enzymatic decellularization method. One cycle was enough to generate a complete decellularized bile duct matrix, histologically and structurally similar to the native one. The network of collagen, reticular and elastic fibers, found in the native bile duct matrix was well preserved. Moreover, the decellularization approach did not affect the elastin content.

A tissue-engineered oesophageal scaffold could be very useful for the treatment of pediatric and adult patients with benign or malignant diseases such as carcinomas, trauma or congenital malformations. Here we decellularize rat oesophagi inside a perfusion bioreactor to create biocompatible biological rat scaffolds that mimic native architecture, resist mechanical stress and induce angiogenesis. Seeded allogeneic mesenchymal stromal cells spontaneously differentiate (proven by gene-, protein and functional evaluations) into epithelial- and muscle-like cells. The reseeded scaffolds are used to orthotopically replace the entire cervical oesophagus in immunocompetent rats. All animals survive the 14-day study period, with patent and functional grafts, and gain significantly more weight than sham-operated animals. Explanted grafts show regeneration of all the major cell and tissue components of the oesophagus including functional epithelium, muscle fibres, nerves and vasculature. We consider the presented tissue-engineered oesophageal scaffolds a significant step towards the clinical application of bioengineered oesophagi.

Objective We present our experience with uniportal videothoracoscopic surgery (VATS-U), examining its indications, limits, and results. Methods Since January 2009, 66 patients underwent VATS-U for the following indications: pneumothorax (n = 25), lung nodule (n = 15; n = 10 with preoperative radiolocalization), wedge biopsy (n = 15), hyperhidrosis (n = 10), and chest wall schwannoma (n = 1). The conversion rate to conventional video-assisted thoracic surgery (VATS), postoperative pain, complications, residual paraesthesia, and hospitalization were analyzed. Operative time, postoperative pain, and paraesthesia were retrospectively compared with a cohort of 172 cases of conventional multiportal VATS, performed in the same period. Results Conversion to traditional VATS was necessary in two cases (pulmonary nodule, n = 1; pneumothorax, n = 1). The mean pain score was 0.8, the mean operation time was 42 minutes, and 10 patients had postoperative paraesthesia that lasted a mean of 7 days. No postoperative complications were reported, and the mean postoperative hospital stay was 3 days (range, 1–6 days). The comparison between the VATS-U and the standard multiportal VATS group showed in the VATS-U group a lower but not statistically significant pain score and paraesthesia as well as a lower and statistically significant operative time. Conclusions Uniportal videothoracoscopic surgery has a wide range of indications: lung apex resections and pleurodesis for spontaneous pneumothorax treatment; pulmonary nodule assessment with or without preoperative localization; lung biopsy for interstitial diseases; unilateral or bilateral sympathectomy to treat hyperhidrosis; benign chest wall tumor evaluation. The limits of this technique are linked to pleural adhesions or lung nodules in difficult positions. In our experience, VATS-U results in minimal postoperative pain, allowing for fast functional recovery and a consequent short hospital stay; thus, we suggest that VATS-U is a valid alternative to traditional multiportal VATS for indications beyond cosmetic benefits. Prospective randomized trials are necessary to validate the advantages of uniportal VATS.

Nature Communications 5: Article number: 3562 (2014); Published 15 April 2014; Updated 21 March 2017 This Article is retracted by the authors. Nature Communications previously issued an Editorial Expression of Concern (http://www.nature.com/articles/ncomms13310) related to this Article, following the publication of a report commissioned by The Karolinska Institute and prepared by the Expert Group for Misconduct in Research at the Swedish Central Ethical Review Board.

Tissue-engineered tracheal transplants have been successfully performed clinically. However, before becoming a routine clinical procedure, further preclinical studies are necessary to determine the underlying mechanisms of in situ tissue regeneration. Here we describe a protocol using a tissue engineering strategy and orthotopic transplantation of either natural decellularized donor tracheae or artificial electrospun nanofiber scaffolds into a rat model. The protocol includes details regarding how to assess the scaffolds' biomechanical properties and cell viability before implantation. It is a reliable and reproducible model that can be used to investigate the crucial aspects and pathways of in situ tracheal tissue restoration and regeneration. The model can be established in

Decellularized tissues and organs represent a suitable option for tissue engineering when specific scaffolds are needed. However, the optimal conditions to completely remove all the cellular components and minimally affect the biochemical and structural properties of the extracellular matrix are still to be found. For this aim, bioreactors could be an alternative means to dynamically treat the biological samples, automatically controlling all the variables involved in the process and speeding up the entire procedure in order to deal with a suitable scaffold within a limited time period. This paper presents the characterization of rat tracheae decellularized in dynamic conditions, implementing a detergent-enzymatic method, previously considered. Only 6 cycles were enough to generate a tracheal matrix that was histologically and structurally similar to the native one. The network of collagen, reticular and elastic fibers was well preserved, such as the epithelial cilia, the luminal basement membrane and the main matrix components. The elastin content decreased, even if not significantly, after the decellularization protocol. Mechanical properties of the treated tissues were slightly affected by the procedure, and were partially recovered after crosslinking with genipin, a naturally-derived agent. The use of bioreactors could enhance the decellularization procedure of tissues/organs, but a careful selection of the processing parameters is needed in order to prevent large modifications compared to the native condition.

Tissue-engineered medical products are now entering the clinical testing phase of development. Therefore, an open discussion is warranted regarding ethical issues that may arise as these novel 'combination' products move forward, such as when to conduct clinical trials, how to regulate such trials, when and how to responsibly introduce these strategies into clinical practice and how to maintain a positive public perception of the tissue-engineering field as a whole. These issues are discussed, and recommendations are provided for conducting first-in-human clinical studies.

Summary Background In 2008, the first transplantation of a tissue-engineered trachea in a human being was done to replace an end-staged left main bronchus with malacia in a 30-year-old woman. We report 5 year follow-up results. Methods The patient was followed up approximately every 3 months with multidetector CT scan and bronchoscopic assessment. We obtained mucosal biopsy samples every 6 months for histological, immunohistochemical, and electron microscopy assessment. We also assessed quality of life, respiratory function, cough reflex test, and production and specificity of recipient antibodies against donor human leucocyte antigen. Findings By 12 months after transplantation, a progressive cicatricial stenosis had developed in the native trachea close to the tissue-engineered trachea anastomosis, which needed repeated endoluminal stenting. However, the tissue-engineered trachea itself remained open over its entire length, well vascularised, completely re-cellularised with respiratory epithelium, and had normal ciliary function and mucus clearance. Lung function and cough reflex were normal. No stem-cell-related teratoma formed and no anti-donor antibodies developed. Aside from intermittent bronchoscopic interventions, the patient had a normal social and working life. Interpretation These clinical results provide evidence that a tissue-engineering strategy including decellularisation of a human trachea, autologous epithelial and stem-cell culture and differentiation, and cell-scaffold seeding with a bioreactor is safe and promising. Funding European Commission, Knut and Alice Wallenberg Foundation, Swedish Research Council, ALF Medicine.

The incidence of chronic lung disease is increasing worldwide due to the spread of risk factors and ageing population. An important advance in treatment would be the development of a bioartificial lung where the blood-gas exchange surface is manufactured from a synthetic or natural scaffold material that is seeded with the appropriate stem or progenitor cells to mimic the functional tissue of the natural lung.Articles relating to bioartificial lungs were sourced through PubMed and ISI Web of Knowledge.There is a consensus that advances in bioartificial lung engineering will be beneficial to patients with chronic lung failure. Ultimate success will require the concerted efforts of researchers drawn from a broad range of disciplines, including clinicians, cell biologists, materials scientists and engineers.As a source of cells for use in bioartificial lungs it is proposed to use human embryonic stem cells; however, there are ethical and safety concerns regarding the use of these cells.There is a need to identify the optimum strategies for differentiating progenitor cells into functional lung cells; a need to better understand cell-biomaterial/ECM interactions and a need to understand how to harness the body's natural capacity to regenerate the lung.Biomaterial technologies for recreating the natural lung ECM and architecture need further development. Mathematical modelling techniques should be developed for determining optimal scaffold seeding strategies and predicting gas exchange performance.

The clinical outcome of transplantations of bioartificial tissues and organs depends on the presence of living cells. There are still no standard operative protocols that are simple, fast and reliable for confirming the presence of viable cells on bioartificial scaffolds prior to transplantation. By using mathematical modeling, we have developed a colorimetric-based system (colorimetric scale bar) to predict the cell viability and density for sufficient surface coverage. First, we refined a method which can provide information about cell viability and numbers in an in vitro setting: i) immunohistological staining by Phalloidin/DAPI and ii) a modified colorimetric cell viability assay. These laboratory-based methods and the developed colorimetric-based system were then validated in rat transplantation studies of unseeded and seeded tracheal grafts. This was done to provide critical information on whether the graft would be suitable for transplantation or if additional cell seeding was necessary. The potential clinical impact of the colorimetric scale bar was confirmed using patient samples. In conclusion, we have developed a robust, fast and reproducible colorimetric tool that can verify and warrant viability and integrity of an engineered tissue/organ prior to transplantation. This should facilitate a successful transplantation outcome and ensure patient safety.

Purpose of review To summarize the so far applied clinical methods of tracheal replacement, comparing pros and cons of conventional and tissue-engineered approaches. Recent findings Several strategies have been most recently described to replace the trachea-like aortic homografts, allotransplantation, and tissue engineering. Allotransplantation requires lifelong immunosuppression and this may be ethically questioned being not a lifesaving procedure. Tissue-engineered tracheal transplantation has been clinically applied using biological or bioartificial tubular or bifurcated scaffolds reseeded with mesenchymal stromal cells, and bioactive molecules boosting regeneration and promoting neovascularization. Summary Tracheal tissue engineering may be a promising alternative to conventional allotransplantation in adults and children. Different methods have been developed and are currently under active clinical investigation, and await long-term results.

The design and use of materials in the nanoscale size range for addressing medical and health-related issues continues to receive increasing interest. Research in nanomedicine spans a multitude of areas, including drug delivery, vaccine development, antibacterial, diagnosis and imaging tools, wearable devices, implants, high-throughput screening platforms, etc. using biological, nonbiological, biomimetic, or hybrid materials. Many of these developments are starting to be translated into viable clinical products. Here, we provide an overview of recent developments in nanomedicine and highlight the current challenges and upcoming opportunities for the field and translation to the clinic., This work was supported by the Deutscher Akademischer Austauschdienst (DAAD to Philipps Universität Marburg and Zhejiang University, Hangzhou), the Chinesisch Deutsches Zentrum für Wissenschaftsförderung (“CDZ” to Z.G. and W.J.P.), and the Chinese Academy of Science (CAS). Part of this work was supported by the National Natural Science Foundation (51390481, 81227902, 81625011), National Basic Research Program (2014CB931900) of China (to Y.S.), by the European Commission grant Futurenanoneeds (to V.P. and W.J.P.), by the Spanish Ministerio de Economia y Competitividad (CTQ2011-23167 and CTQ2014-59808R to R.A.A.P.), the Generalitat of Catalunya (2014-SGR-612 to R.A.A.P.), the Deutsche Forschungsgemeinschaft (DFG) (AL552/8-1 to R.T.), the Swiss National Science Foundation (NRP62 to P.H.), the Claude & Julianna Foundation (grant to P.H.), the National Science Foundation (NSF) grants CHE-1306928 (to R.P.) and ECS-0601345; CBET 0933384; CBET 0932823; and CBET 1036672 (to N.A.K.), Canadian Institute of Health Research (grant to W.C.W.C.), and Natural Sciences and Engineering Research Council of Canada (grant to W.C.W.C.). S.A. and B.P. acknowledge a fellowship from the Alexander von Humboldt Foundation. N.F. acknowledges the Lars Hiertas Minne Foundation. M.C. acknowledges Ikerbasque for a Research Fellow position. X.C. acknowledges the Intramural Research Program (IRP), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH). B.Z.T. acknowledges the Innovation and Technology Commission of Hong Kong (ITC-CNERC14SC01). The Pancreatic Cancer research of A.E.N. and H.M. was funded by the U.S. National Cancer Institute, NIH grant # U01CA198846. A.E. acknowledges Junta de Andalucía (Spain) for a Talentia Postdoc Fellowship, co-financed by the European Union's Seventh Framework Programme, grant agreement no 267226. A.G.S. acknowledges support by BOF (UGent) and FWO (Research Foundation Flanders). Part of this work was supported by the National Natural Science Foundation of China.

Item does not contain fulltext This report is to complement the original Fleischner Society recommendations for incidentally detected solid nodules by proposing a set of recommendations specifically aimed at subsolid nodules. The development of a standardized approach to the interpretation and management of subsolid nodules remains critically important given that peripheral adenocarcinomas represent the most common type of lung cancer, with evidence of increasing frequency. Following an initial consideration of appropriate terminology to describe subsolid nodules and a brief review of the new classification system for peripheral lung adenocarcinomas sponsored by the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS), and European Respiratory Society (ERS), six specific recommendations were made, three with regard to solitary subsolid nodules and three with regard to multiple subsolid nodules. Each recommendation is followed first by the rationales underlying the recommendation and then by specific pertinent remarks. Finally, issues for which future research is needed are discussed. The recommendations are the result of careful review of the literature now available regarding subsolid nodules. Given the complexity of these lesions, the current recommendations are more varied than the original Fleischner Society guidelines for solid nodules. It cannot be overemphasized that these guidelines must be interpreted in light of an individual's clinical history. Given the frequency with which subsolid nodules are encountered in daily clinical practice, and notwithstanding continuing controversy on many of these issues, it is anticipated that further refinements and modifications to these recommendations will be forthcoming as information continues to emerge from ongoing research.

Editorial Expression of Concern: Experimental orthotopic transplantation of a tissue-engineered oesophagus in rats

Background. We prospectively evaluated a clinical and endoscopic score, the tracheal endoscopic clinical score (TECS), developed as a disease-specified outcome measure in adult patients undergoing operation for subglottic stenosis. We also performed a retrospective chart review to identify preoperative and intraoperative risk factors for worse TECS. Methods. The TECS includes endoscopic (vocal cord and glottic function, anastomotic healing, and patency) and interview (respiration, voice, swallow) variables, and was administered at 6-month follow-up. Endoscopic and subjective domains were weighted to obtain a continuous TECS index ranging from 0 (best) to 1 (worse). The TECS and preoperative variables relationships were evaluated by univariate and multivariate analysis. Results. We collected data (January 2009 to December 2010) from 30 patients (mean age, 48.3 19 years) undergoing subglottic resection and primary reconstruction. Stenosis etiology was postintubation (n 8), idiopathic (n 2), tracheostomy (n 18), and malignant (n 2). Surgery included Pearson operation with (n 7) or without (n 23) a Liberman-Mathisen cricoplasty. Mean length of resected trachea was 30.5 13.5 mm, and mean hospital stay was 7.4 days. Mortality rate was 1 patient (3.3%). The univariate analysis showed positive correlation between 6-month TECS and degree of stenosis (McCaffrey and Cotton scale 0 to 4) stage 4, tracheostomy or T-tube at surgery, bottleneck-type transition stenosis, and resection length. At multivariate analysis, the presence of tracheostomy, bottleneck-type transition stenosis and resection length were indicators of worse postoperative functional result. Conclusions. The TECS seems to be a valid and simple instrument to identify preoperative variables predicting worse results and to assess postoperative outcome. Validation on larger series is necessary. (Ann Thorac Surg 2012;94:1065‐72) © 2012 by The Society of Thoracic Surgeons

ObjectiveOur objective was to investigate the capacity of a pumpless extracorporeal lung membrane (iLA) (Novalung; Novalung GmbH, Hechingen, Germany) to provide adequate respiratory support and the impact on morbidity/mortality during complex airway reconstruction.MethodsOnly patients unable to be ventilated via conventional intubation were eligible for the study. A larynx mask or orotracheal tubes were placed above the airway defect and the iLA was attached via femoral vessels (arteriovenous), providing extracorporeal gas exchange, apneic hyperoxygenation, and total tubeless airway reconstruction. Haptoglobulin, plasmin–antiplasmin complex, P-selectin activation, and interleukin 6 were measured before, during, and after iLA use and 72 hours postoperatively.ResultsFifteen consecutive patients (age, 42 ± 17 years) underwent elective (n = 7) or emergency (n = 8) reconstruction of the airway owing to a variety of disorders or defects. The iLA was left in place for 185 ± 61 minutes, diverted 1.70 ± 0.48 L/min of the cardiac output, and provided an arteriovenous carbon dioxide removal and oxygen transfer of 173 ± 94 and 144 ± 83 mL/min, respectively. The arterial oxygen tension/inspired oxygen fraction (314 ± 31 mm Hg), and arterial carbon dioxide tension (40 ± 6 mm Hg) remained stable throughout the entire operations. The following procedures were performed: redo slide tracheoplasties (n = 3), redo tracheoesophageal fistula repair (n = 1), sleeve lobectomies (n = 2), main carina reconstructions (n = 7), and anastomotic stenting and myocutaneous coverages (n = 2). Three patients required prolonged (9 ± 2 days) postoperative iLA support. Two (13%) patients died during the hospital stay. The use of iLA was associated with significant (P

Bioengineered tissues created for transplant will be expected to survive and contribute to function over the lifetime of the individual. To evaluate potential intrinsic changes and degradation of the extracellular matrix of decellularized human tissue scaffolds, human decellularized tracheas were evaluated over a one year period in vitro . Human tracheas were decellularized and stored for one year in phosphate-buffered saline at 4 °C in the presence of antibiotics and anti-mycotics, and their structural, mechanical, and angiogenic properties compared to baseline values. Results showed that stored human decellularized tracheas were increasingly degraded resulting in a loss of extracellular matrix architecture – in particular of collagenous and elastic fiber structure –and decreased mechanical and angiogenic properties. The mechanical alterations of the extracellular matrix but not the deterioration and microstructure were not improved by using a natural cross-linking agent. These findings demonstrate that human decellularized tracheas, stored for one year in phosphate-buffered saline solution at 4 °C, would not meet the demands for a tissue engineering matrix and likely would not yield a suitable graft for lifelong implantation. The degradation phenomenon observed in vitro may be further enhanced in vivo , having clinical relevance for tissues that will be transplanted long-term and this should be carefully evaluated in pre-clinical settings.

In tissue engineering approach, the scaffold plays a key role for a suitable outcome of cell-scaffold interactions and for the success of tissue healing and regeneration. As a consequence, the characterization of scaffold properties and the in vivo evaluation of tissue responses and effects result to be essential in the development of suitable implantable device. Among the in vivo methods, the chick embryo chorioallantoic membrane (CAM) assay represents a rather simple and cost-effective procedure to study the biocompatibility responses of graft materials. CAM is indeed characterized by low experiment costs, simplicity, relative speed in obtaining the expected results, limited ethical concern, no need of high-level technical skill, and the absence of a mature immune system, resulting in an inexpensive, simple, and practical method to evaluate and characterize tissue-engineered constructs. The results till now obtained suggest that CAM assay can be used as a pre-screening assay, before in vivo animal studies, to determine whether the scaffold is liable to cause an adverse reaction and to evaluate its future enhancement of existing materials for tissue engineering. A review of the more recent results related to the use of CAM for in vivo biomaterial property evaluation is herein reported.

Mesenchymal stromal cells (MSCs), a rare heterogeneous subset of pluripotent stromal cells that can be easily isolated from different adult tissues, in vitro expanded and differentiated into multiple lineages, are immune privileged and, more important, display immunomodulatory capacities. Because of this, they are the preferred cell source in tissue-engineered replacements, not only in autogeneic conditions, where they do not evoke any immune response, but especially in the setting of allogeneic organ and tissue replacements. However, more preclinical and clinical studies are requested to completely understand MSC's immune biology and possible clinical applications. We herein review the immunogenicity and immunomodulatory properties of MSCs, their possible mechanisms and potential clinical use for tissue-engineered organ and tissue replacement.

Recent technical advances in the domains of anesthesia, cardiovascular and thoracic surgery, and synthetic materials manufacturing coupled with more oncological extended tumor indications have unlocked the door to the surgical treatment of pulmonary, mediastinal, or other rare tumors involving intrathoracic vessels. In 1987, Dartevelle et al1 first described a consecutive and large series of patients with mediastinal or lung malignancies and superior vena cava (SVC) involvement treated with SVC resection by using polytetrafluoroethylene tubular grafts for reconstruction. Open surgery requires a high level of technical expertise and vigilant attention to patient selection and perioperative management to minimize complications, which are reported even in highly specialized centers.1,2 During the past decade, operative mortality for these procedures has ranged between 0% and 7.7%, with long-term patency rates of about 70%-100%.3-9 However, proper patient selection is critical for clinical success. We will outline the role of surgery for selected patients with locally advanced but completely resectable non-small cell lung cancers (NSCLC) or mediastinal tumors (MT) involving invading the SVC and/or the innominate vein (IV).

The use of synthetic degradable or permanent polymers and biomaterials has not yet helped to achieve successful clinical whole-airway replacement. A novel, clinically successful approach involves tissue engineering (TE) replacement using three-dimensional biologic scaffolds composed of allogeneic extracellular scaffolds derived from nonautologous sources and recellularized with autologous stem cells or differentiated cells. In this paper, we discuss this novel approach and review information that can lead to a better understanding of stem cell recruitment and/or mobilization and site-specific tissue protection, which can be pharmacologically boosted in humans.

Prosthetic replacements, autologous tissue transfer and allografts have so far failed to offer functional solutions for the treatment of long circumferential tracheal defects and loss of a functioning larynx. Interest has therefore turned increasingly to the field of tissue-engineering which applies the principles and methods of bioengineering, material science, cell transplantation and life sciences in an effort to develop in vitro biological substitutes able to restore, maintain or improve tissue and organ function.This article gives an overview of the tissue-engineering approach to airway replacement and will describe the encouraging results obtained so far in tracheal regeneration. The recent advances in the field of tissue-engineering have provided a new attractive approach towards the concept of functional substitutes and may represent an alternative to the shortage of suitable grafts for reconstructive airway surgery. We summarize fundamental questions, as well as future directions in airway tissue engineering.The replacement of active movement, as would be necessary to replace an entire larynx introduces another order of magnitude of complexity, although progress in this area is starting to bear fruit. In addition, the stem cell field is advancing rapidly, opening new avenues for this type of therapy.

If controllable, stem cell activation following injury has the therapeutic potential for supporting regeneration in acute or chronic wounds. Human dermally-derived stem cells (FmSCs) were exposed to the cytokines interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α (TNF-α) in the presence of erythropoietin (EPO). Cells were cultured under ischemic conditions and phenotypically characterized using flow cytometry. Topical EPO application was performed in three independent clinical wound healing attempts. The FmSCs expressed the receptor for EPO. EPO had a strong inhibitory effect on FmSC growth in the absence of IL-6 and TNF-α. With IL-6, the EPO effects were reversed to that of growth stimulation. TNF-α had the strongest stimulatory effect. In contrast, IL-1β had an inhibitory effect. Topically applied EPO considerably enhanced wound healing and improved wound conditions of acute and chronic wounds. Site specificity of stem cell activation is mediated by IL-6 and TNF-α. In trauma, EPO ceases its inhibitory role and reverts to a clinically relevant boosting function. EPO may be an important therapeutic tool for the topical treatment of acute and chronic wounds.

There are a variety of airway diseases with different clinical settings, which may extend from a surgical approach to total organ replacement. Tissue engineering involves modifying cells or tissues in order to repair, regenerate, or replace tissue in the body and seems to be a promising approach for airway replacement. The successful implantation of stem-cell-based tissue-engineered trachea in a young woman with end-stage post-tuberculosis left main bronchus collapse serves as a prototype for the airway tissue-engineered-based approach. The trachea indeed could represent a perfect model system to investigate the translational aspects of tissue engineering, largely due to its low-oxygen needs. This review highlights the anatomy of the airways, the various disease conditions that cause damage to the airways, elaborates on the essential components of the tissue-engineering approach, and discusses the success of the revolutionary trachea transplantation approach.

In June 2008, the world’s first whole tissue-engineered organ – the windpipe – was successfully transplanted into a 31-year-old lady, and about 18 months following surgery she is leading a near normal life without immunosuppression. This outcome has been achieved by employing three groundbreaking technologies of regenerative medicine: (i) a donor trachea first decellularized using a detergent (without denaturing the collagenous matrix), (ii) the two main autologous tracheal cells, namely mesenchymal stem cell derived cartilage-like cells and epithelial respiratory cells and (iii) a specifically designed bioreactor that reseed, before implantation, the in vitro pre-expanded and pre-differentiated autologous cells on the desired surfaces of the decellularized matrix. Given the long-term safety, efficacy and efforts using such a conventional approach and the potential advantages of regenerative implants to make them available for anyone, we have investigated a novel alternative concept how to fully avoid in vitro cell replication, expansion and differentiation, use the human native site as micro-niche, potentiate the human body’s site-specific response by adding boosting, permissive and recruitment impulses in full respect of sociological and regulatory prerequisites. This tissue-engineered approach and ongoing research in airway transplantation is reviewed and presented here.

ObjectiveWe sought to determine the relative contributions of epithelial cells and mesenchymal stem cell–derived chondrocytes to the survival of tissue-engineered airway transplants in pigs.MethodsNonimmunogenic tracheal matrices were obtained by using a detergent-enzymatic method. Major histocompatibility complex–unmatched animals (weighing 65 ± 4 kg) were divided into 4 groups (each n = 5), and 6 cm of their tracheas were orthotopically replaced with decellularized matrix only (group I), decellularized matrix with autologous mesenchymal stem cell–derived chondrocytes externally (group II), decellularized matrix with autologous epithelial cells internally (group III), or decellularized matrix with both cell types (group IV). Autologous cells were recovered, cultured, and expanded. Mesenchymal stem cells were differentiated into chondrocytes by using growth factors. Both cell types were seeded simultaneously with a dual-chamber bioreactor. Animals were not immunosuppressed during the entire study. Biopsy specimens and blood samples were taken from recipients continuously, and animals were observed for a maximum of 60 days.ResultsMatrices were completely covered with both cell types within 72 hours. Survival of the pigs was significantly affected by group (P < .05; group I, 11 ± 2 days; group II, 29 ± 4 days; group III, 34 ± 4 days; and group IV, 60 ± 1 days). Cause of death was a combination of airway obstruction and infection (group I), mainly infection (group II), or primarily stenosis (group III). However, pigs in group IV were alive, with no signs of airway collapse or ischemia and healthy epithelium. There were no clinical, immunologic, or histologic signs of rejection despite the lack of immunosuppression.ConclusionsWe confirm the clinical potential of autologous cell– and tissue-engineered tracheal grafts, and suggest that the seeding of both epithelial and mesenchymal stem cell–derived chondrocytes is necessary for optimal graft survival.

ObjectiveWe sought to bioengineer a nonimmunogenic tracheal tubular matrix of 6 cm in length and test its structural, functional, and immunologic properties in vitro and in vivo.MethodsTwelve-centimeter tracheal segments were harvested from Yorkshire boars. Half of each segment was subjected to a detergent–enzymatic method (containing sodium deoxycholate/DNase lavations) of decellularization for as many cycles as needed, and the other half was stored in phosphate-buffered saline at 4°C as a control. Bioengineered and control tracheas were then implanted in major histocompatibility complex–unmatched pigs (allograft) or mice (xenograft) heterotopically for 30 days. Structural and functional analysis and immunostaining were performed after each detergent–enzymatic method cycle and transplantation.ResultsCompared with control tracheas, bioengineered matrices displayed no major histocompatibility complex class I and II antigens after 17 detergent–enzymatic method cycles, without significant (P > .05) differences in their strain ability (rupture force, 56.1 ± 3.3 vs 55.5 ± 2.4 N; tissue deformation at 203% ± 13% vs 200% ± 8% or 12.2 ± 0.8 vs 12 ± 0.5 cm; and applied maximum force, 173.4 ± 3.2 vs 171.5 ± 4.6 N). Thirty days after implantation, significantly (P < .01) smaller inflammatory reactions (392 vs 15 macrophages/mm2 and 874 vs 167 T lymphocytes/mm2) and P-selectin expressions (1/6 vs 6/6) were observed in both the xenograft and allograft models with bioengineered matrices compared with those seen with control tracheas. There was no development of anti-pig leukocyte antigen antibodies or increase in both IgM and IgG content in mice implanted with bioengineered tracheas.ConclusionsBioengineered tracheal matrices displayed similar structural and mechanical characteristics to native tracheas and excite no immune response to 30 days when implanted as allografts or xenografts. This method holds great promise for the future of tissue-engineered airway replacement.

Chronic thromboembolic pulmonary hypertension (CTEPH), which has a natural history with low long-term survival, is increasingly being diagnosed. Pulmonary endarterectomy (PE) is the treatment of choice, which can be curative. This technique consists of a true endarterectomy through a midline sternotomy with extracorporeal circulation and periods of hypothermic circulatory arrest. The following procedures should be performed before surgery: transesophageal echocardiogram, ventilation-perfusion pulmonary scintigraphy, right cardiac catheterism, pulmonary angiography and helicoidal computed tomography. Surgery should be indicated in CTEPH as soon as the diagnosis is made, before arteriopathy develops in the non-obstructed regions and CTEPH becomes severe. The only absolute contraindication to PE is the presence of obstructive or restrictive, severe underlying pulmonary disease. There are no inaccessible grades of embolic obstruction, or grade of right ventricular failure or level of pulmonary vascular resistance (PVR) that are inoperable. However, prognosis worsens with greater preoperative pulmonary pressure and greater postoperative PVR. Mortality in PE is 4-10% and the main cause of postoperative death is the persistence of high pulmonary pressures and PVR, followed by reperfusion edema, which requires prolongation of mechanical ventilation, the use of pulmonary vasodilators and, sometimes, extracorporeal respiratory support. In the long-term, 75% of patients undergoing PE show good functional results and half recover adequate exercise tolerance. Pulmonary transplantation is an alternative for patients unsuitable for PE, although with worse results and greater mortality.

Background The purpose of this study was to evaluate the long-term clinical and immunologic outcome of cryopreserved arterial allograft (CAA) revascularization of intrathoracic vessels invaded by malignancies. Methods Since January 2002, consecutive patients whose intrathoracic vessels were invaded by malignancies were operated on and revascularizion made using human lymphocyte antigen (HLA)– and ABO-mismatched CAAs. Immunologic studies were performed preoperatively, and 1, 3, 6, 12, and 24 months postoperatively. Postoperative oral anticoagulation therapy was not given. Results Twenty-six patients aged 53.1 ± 15 years with a nonsmall-cell lung cancer (n = 10), invasive mediastinal tumors (n = 7), pulmonary artery sarcoma (n = 3), laryngeal (n = 2), or other rare lung neoplasms (n = 4) underwent operation. Cardiopulmonary bypass was used in 10 cases (38%), and all resections were pathologically complete. Revascularization was either for venous (n = 12) or arterial (n = 14) vessels, and a total of 30 allografts revascularized the superior vena cava (n = 6), pulmonary artery (n = 7), innominate vein (n = 3) or artery (n = 2), ascendent (n = 4) or descending (n = 1) aorta, and subclavian vein (n = 3) or artery (n = 4). Hospital morbidity and mortality were 50% (n = 13) and 3.8% (n = 1), respectively, all CAA unrelated. With a median follow-up of 18 months (range, 3 to 60+), 5-year survival and allograft patency were 84% and 95%, respectively. Preoperative anti-HLA antibodies were detected in 2 patients (7.7%) and a postoperative anti-HLA antibody response, clinically irrelevant, in 1 of 24 patients (4%). Conclusions Revascularization of intrathoracic venous and arterial vessels in patients with malignancies using HLA- and ABO-mismatched CAA is technically feasible and clinically attractive because of no infection risk and postoperative anticoagulation, and excellent long-term survival, patency, and nonimmunogeneicity.

The aim of this study was to determine the optimal positive end-expiratory pressure (PEEP) required during extracorporeal lung membrane support (interventional lung assist [iLA]; Novalung GmbH, Hechingen, Germany). Twenty healthy pigs were initially (4 h) mechanically ventilated with a tidal volume (V(T)) of 10 mL/Kg, respiratory rate (RR) of 20 breaths/min, PEEP of 5 cm H(2)O, and fraction of inspired O(2) (FiO(2)) of 1.0. Thereafter, the iLAs were placed arteriovenously transfemorally and settings reduced to reach near static ventilation (V(T) 12 cm H(2)O, and this without hemodynamical imbalance. This study suggests that the iLA may provide adequate gas exchange during static ventilation only with PEEP levels > 10 cm H(2)O, and this without pulmonary or systemic hemodynamic imbalance.

A small experimental animal model of postobstructive pulmonary hypertension (PH) providing insights in the physiopathology of this disease was developed.Male Lewis rats were anesthetized and aleatory manipulated via a left thoracotomy with (group I, n = 10) or without (group II, n = 10) ligation of the left pulmonary artery. Animals were followed for 2 weeks and then sacrificed. Hemodynamic parameters and blood gases were recorded at baseline and 2 weeks after surgical procedure.Group I animals developed a significant (P0.01) PH (mean pulmonary artery pressure, 32 +/- 6 versus 16 +/- 2 mm Hg; pulmonary vascular resistance, 46 +/- 3 versus 21 +/- 2 mm Hg/mL/min; reduction of cardiac output, 75 +/- 3 versus 105 +/- 4 mL/min), compared to group II animals, and had a significant (P0.01) worse gas exchange (partial arterial pressure of O(2): 91 +/- 3 versus 439 +/- 24 mm Hg; partial arterial pressure of CO(2): 54 +/- 3 versus 42 +/- 2 mm Hg, on a fraction of inspired oxygen of 1.0), right ventricle hypertrophy (ventricle to left ventricle/septum ratio, 0.56 +/- 0.04 versus 0.45 +/- 0.04, P0.02) and less tolerance test (immobility time, 123 +/- 11 versus 61 +/- 8 s, P0.01) than group II animals. Histologically, ligated lungs showed postobstructive pulmonary vasculopathic abnormalities and bronchial-pulmonary artery hypertrophy, and the contralateral lung had initial signs of small vessel arteriopathy.The experimental model generated here successfully reproduced a PH morphologically and functionally similar to clinical postembolic PH and might be used for evaluating the physiopathology of postobstructive PH.

Laryngeal and tracheal transplantation have been proposed as treatments for irreversible airway disease for many years. Despite much research, there has only been one true laryngeal transplant reported. Although this was in many ways a success, several barriers remain before full clinical trials. There are issues over patient selection, reinnervation, immunosuppression, and cost-benefit. For the trachea, where finely tuned neuromuscular activity is not an issue, tissue-engineering probably represents the future. This overview discusses the arguments for and against laryngeal and tracheal transplantation and suggests ways of overcoming these barriers.

Das Bronchialkarzinom ist eine der haufigsten Krebserkrankungen in den Industrie landern, vorrangig bei Mannern, in zunehmendem Mase jedoch auch bei Frauen. Die einzig kurative Therapie besteht in der kompletten chirurgischen Resektion des Tumors. Hierbei sind die prazise praoperative Diagnostik mit moglichst exaktem Tumorstaging sowie die interdisziplinare Diskussion und Festlegung der weiteren individuellen Therapie essenziell fur ein modernes Therapiekonzept. Die operative Therapie des Bronchialkarzinoms ist heute stadienabhangig haufig in adjuvante und neoadjuvante Therapieschemata eingebunden und bedarf einer regen Kommunikation mit Pneumologen, Onkologen und Strahlentherapeuten. Chirurgische Uber legungen zur Therapie der einzelnen Tumorstadien werden prasentiert und die daraus resultierenden Operationsindikationen beschrieben. Daruber hinaus erlautert der Beitrag sowohl die invasiven Stagingtechniken als auch die praoperative Evaluation der Lungenfunktion.

The purpose of this study was to evaluate the feasibility of integrating an artificial, pumpless extracorporeal membrane ventilator (Novalung) to near static mechanical ventilation and its efficacy in patients with severe postresectional acute respiratory distress syndrome (ARDS) unresponsive to optimal conventional treatment.Indications were severe postresectional and unresponsive acute respiratory distress syndrome, hemodynamic stability, and no significant peripheral arterial occlusive disease or heparin-induced thrombocytopenia. Management included placement of the arteriovenous femoral transcutaneous interventional lung-assist membrane ventilator, lung rest at minimal mechanical ventilator settings, and optimization of systemic oxygen consumption and delivery.Among 239 pulmonary resections performed between 2005 and 2006, 7 patients (2.9%) experienced, 4 +/- 0.8 days after 5 pneumonectomies and 2 lobectomies, a severe (Murray score, 2.9 +/- 0.3) acute respiratory distress syndrome unresponsive to 4 +/- 2 days of conventional therapy. The interventional lung-assist membrane ventilator was left in place 4.3 +/- 2.5 days, and replaced only once for massive clotting. During this time, 29% +/- 0.3% or 1.4 +/- 0.36 L/min of the cardiac output perfused the device, without hemodynamic impairment. Using a sweep gas flow of 10.7 +/- 3.8 L/min, the device allowed an extracorporeal carbon dioxide removal of 255 +/- 31 mL/min, lung(s) rest (tidal volume, 2.7 +/- 0.8 mL/kg; respiratory rate, 6 +/- 2 beats/min; fraction of inspired oxygen, 0.5 +/- 0.1), early (24 hours) significant improvement of respiratory function, and reduction of plasmatic interleukin-6 levels (p0.001) and Murray score (1.25 +/- 0.1; p0.003). All but 1 patient (14%) who died of multiorgan failure were weaned from mechanical ventilation 8 +/- 3 days after removal of the interventional lung-assist membrane ventilator, and all of them were discharged from the hospital.The integration of this device to near static mechanical ventilation of the residual native lung(s) is feasible and highly effective in patients with severe and unresponsive acute respiratory distress syndrome after pulmonary resection.

The currently available surgical options to repair the diaphragm are associated with significant risks of defect recurrence, lack of growth potential and restored functionality. A tissue engineered diaphragm has the potential to improve surgical outcomes for patients with congenital or acquired disorders. Here we show that decellularized diaphragmatic tissue reseeded with bone marrow mesenchymal stromal cells (BM-MSCs) facilitates in situ regeneration of functional tissue. A novel bioreactor, using simultaneous perfusion and agitation, was used to rapidly decellularize rat diaphragms. The scaffolds retained architecture and mechanical properties and supported cell adhesion, proliferation and differentiation. Biocompatibility was further confirmed in vitro and in vivo. We replaced 80% of the left hemidiaphragm with reseeded diaphragmatic scaffolds. After three weeks, transplanted animals gained 32% weight, showed myography, spirometry parameters, and histological evaluations similar to native rats. In conclusion, our study suggested that reseeded decellularized diaphragmatic tissue appears to be a promising option for patients in need of diaphragmatic reconstruction.

OBJECTIVE To investigate whether deep (

Objective: Complete resection of advanced pulmonary malignancies infiltrating the heart or the great vessels may require the application of cardiopulmonary bypass (CPB). Extracorporal circulation, however, is known to cause lung injury and may be harmful especially in pneumonectomies. Methods: Over a period of 10 years extended pulmonary resections requiring cardiopulmonary bypass were analyzed in a retrospective study. Results: From August 1993 to August 2003, 13 patients underwent an extended pulmonary resection for curative indications, requiringsupportbyCPB.Underlyingdiseasesweresarcomas(n = 8),non-smallcelllungcarcinomas(n = 3),andothers(n = 2).Pneumonectomies were performed in nine and lobectomies in four cases. In the majority of cases, several cardiac structures, predominantly the left atrium (n = 9), were affected. In four patients (31%), the indication for a CPB-supported procedure was not electively planned, but made intraoperatively. Complete en-bloc resection (R0) was achieved in 12 of 13 cases (92%). The 30-day mortality rate was 15% (n = 2). Major complications observed were acute lung injury (n = 4), right heart failure (n = 1), and multi-organ failure (n = 1). The cumulative survival at 1, 3, and 5 years in patients presenting with sarcomas was 62.5% compared to 33%, 0%, and 0%, respectively, in patients with non-small cell carcinoma (n = 3). Conclusions: Our results encourage the application of CPB in extended pulmonary resections to achieve complete resections. In carefully selected patients, especially those with sarcomas, the radical surgical procedure associated with increased pulmonary complications allows for significantly prolonged survival and quality of life. # 2005 Elsevier B.V. All rights reserved.

Primary tumours of the trachea can be benign or malignant and account for fewer than 0.1% of tumours. However, they are a diagnostic and therapeutic challenge. Benign tumours are usually misdiagnosed as asthma or chronic lung disease, and can delay diagnosis for months or years. Because of their rapid growth and onset of haemoptysis, malignant tumours are often diagnosed earlier than benign tumours and patients thus often present with locally advanced disease. Inappropriate treatment is an equally frustrating issue. Modern techniques for tracheal surgery-laryngotracheal, tracheal, or carinal resection-combined with radiotherapy, can be offered curatively with low perioperative risks. Nevertheless, the low numbers of patients undergoing resection and the associated poor survival in epidemiological studies over the past two decades have shown that surgery is rarely considered outside referral centres, with radiotherapy or another form of local treatment (eg, endotracheal stents, debridement, brachytherapy) generally preferred. The liberal use of these other techniques should be avoided because surgery has the potential to cure all patients with benign and low-grade tumours and most patients with malignant primary tracheal tumours, and other techniques are usually palliative at best.

Objective We sought to grow in vitro functional smooth muscle cells, chondrocytes, and respiratory epithelium on a biologic, directly vascularized matrix as a scaffold for tracheal tissue engineering. Methods Ten- to 15-cm–long free jejunal segments with their own vascular pedicle were harvested and acellularized from donor pigs (n = 10) and used as a vascular matrix. Autologous costal chondrocytes, smooth muscle cells, and respiratory epithelium and endothelial progenitor cells were first cultured in vitro and then disseminated on the previously acellularized vascular matrix. Histologic, immunohistologic, molecular imaging, and Western blotting studies were then performed to assess cell viability. Results The endothelial progenitor cells re-endothelialized the matrix to such an extent that endothelial cell viability was uniformly documented through 2-(18F)-fluoro-2′-deoxyglucose positron emission tomography. This vascularized scaffold was seeded with functional (according to Western blot analysis) smooth muscle cells and successfully reseeded with viable ciliated respiratory epithelium. Chondrocyte growth and production of extracellular cartilaginous matrix was observed as soon as 2 weeks after their culture. Conclusions The fundamental elements for a bioartificial trachea were successfully engineered in vitro in a direct vascularized 10- to 15-cm–long bioartificial matrix. Future experimental work will be directed to give them a 3-dimensional aspect and a biomechanical profile of a functioning trachea.

The ultimate target of regenerative medicine approaches (tissue engineering and cell therapy) for irreversible diseases of the respiratory tract is to replace or restore tissues or organ function. In this chapter we will describe the basic developmental biology of the respiratory system, and highlight the endogenous and exogenous stem or progenitor cells that are involved in tissue regeneration and homeostasis in the respiratory tract. We will also review the different therapeutic approaches to understand how a reconstituted complex whole tissue or organ can remodel, regenerate, and repair via specific mechanisms. We describe a mesenchymal stem-cell-like mucoepidermoid tumor cell population (MEi cells) in the human respiratory tract; and provide an overview of the innovative applications that nanotechnology can offer to accelerate the field of TE and cell therapy.

Tissue engineering has the potential to help many adults and children affected by esophageal disorders such as cancer, Barrett’s esophagus, malformations, trauma, etc. Current surgical treatment is a complex procedure where the esophagus is replaced with either colon or stomach. Related mortality and morbidity is high, and functional outcomes are poor. A tissue-engineered graft could eliminate the need to use the patients’ own tissue and could result in a better clinical outcome. Tissue engineering approaches are also used to facilitate mucosal and submucosal healing after endoscopic removal of superficial cancer or precancerous lesions. This chapter describes the anatomy, physiology, and pathology of the esophagus, and summarizes the efforts made so far in the world of tissue engineering of the esophagus. We describe the use of biological and synthetic scaffolds and discuss results from many large and small animal publications. Lastly, we present two clinical studies that have been published to date, where either extra cellular matrix or oral mucosal cell sheets were transplanted to the wound bed after interventional endoscopy. In conclusion, the field of regenerative medicine and tissue engineering has the potential to save many lives, but much effort still needs to be made.

Regenerative medicine is a promising and growing field for the treatment of both acute and chronic diseases affecting the respiratory tract. It focuses on the repair, replacement, or regeneration of cells, tissues, or organ dysfunction, which can be a result of many causes, including congenital defects, disease, trauma, and aging. This can be applied as a multidisciplinary approach to create and/or restore functional three-dimensional tissues or organs, which uses a combination of stem cells, scaffolds, and signaling molecules (tissue engineering), or direct application of cells to the site of injury or disorder (cell therapy). Tissue engineering might not be an ideal system for treating highly complex and multifunctional organ like the lung when targeting clinical application. Hence, cell therapy may be a more suitable treatment option because this can be applied by local or systemic administration combining with or without bioactive molecules such as erythropoietin. In this chapter, in the context of respiratory diseases, we will review the current research and clinical outcomes that involve the different approaches.

Recent anesthetic and surgical advances have remarkably reduced the frequency of airway complications after tracheobronchial resections, yet the end-to-side reimplantation of a main, lobar, or intermedius bronchus onto the trachea or the side of the contralateral main bronchus still represents a major technical challenge with high anastomotic morbidity and procedure-related mortality.1 We present the results of a simplified anastomotic technique for end-to-side reimplantation of the lobar or intermedius bronchus onto the trachea or contralateral main bronchus after extensive bronchial sleeve resections or carinal lobectomy.

Stem cells contribute to regeneration of tissues and organs. Cells with stem cell-like properties have been identified in tumors from a variety of origins, but to our knowledge there are yet no reports on tumor-related stem cells in the human upper respiratory tract. In the present study, we show that a tracheal mucoepidermoid tumor biopsy obtained from a 6 year-old patient contained a subpopulation of cells with morphology, clonogenicity and surface markers that overlapped with bone marrow mesenchymal stromal cells (BM-MSCs). These cells, designated as MEi (mesenchymal stem cell-like mucoepidermoid tumor) cells, could be differentiated towards mesenchymal lineages both with and without induction, and formed spheroids in vitro. The MEi cells shared several multipotent characteristics with BM-MSCs. However, they displayed differences to BM-MSCs in growth kinectics and gene expression profiles relating to cancer pathways and tube development. Despite this, the MEi cells did not possess in vivo tumor-initiating capacity, as proven by the absence of growth in situ after localized injection in immunocompromised mice. Our results provide an initial characterization of benign tracheal cancer-derived niche cells. We believe that this report could be of importance to further understand tracheal cancer initiation and progression as well as therapeutic development.