Problem In Lung Transplantation Research Articles

Aging exacerbates murine lung ischemia-reperfusion injury by excessive inflammation and impaired tissue repair response

Donor shortage is a major problem in lung transplantation (LTx), and the use of lungs from elderly donors is one of the possible solutions in a rapidly aging population. However, the utilization of organs from donors aged >65 years has remained infrequent and may be related to a poor outcome. To investigate the molecular events in grafts from elderly donors early after LTx, the left lungs of young and old mice were subjected to 1 hour of ischemia and subsequent reperfusion. The left lungs were collected at 1 hour, 1 day, and 3 days after reperfusion and subjected to wet-to-dry weight ratio measurement, histological analysis, and molecular biological analysis, including RNA sequencing. The lungs in old mice exhibited more severe and prolonged pulmonary edema than those in young mice after ischemia reperfusion, which was accompanied by upregulation of the genes associated with inflammation and impaired expression of cell cycle-related genes. Apoptotic cells increased and proliferating type 2 alveolar epithelial cells decreased in the lungs of old mice compared with young mice. These factors could become conceptual targets for developing interventions to ameliorate lung ischemia-reperfusion injury after LTx from elderly donors, which may serve to expand the old donor pool.

Bioengineering and Clinical Translation of Human Lung and its Components.

Clinical lung transplantation has rapidly established itself as the gold standard of treatment for end-stage lung diseases in a restricted group of patients since the first successful lung transplant occurred. Although significant progress has been made in lung transplantation, there are still numerous obstacles on the path to clinical success. The development of bioartificial lung grafts using patient-derived cells may serve as an alternative treatment modality; however, challenges include developing appropriate scaffold materials, advanced culture strategies for lung-specific multiple cell populations, and fully matured constructs to ensure increased transplant lifetime following implantation. This review highlights the development of tissue-engineered tracheal and lung equivalents over the past two decades, key problems in lung transplantation in a clinical environment, the advancements made in scaffolds, bioprinting technologies, bioreactors, organoids, and organ-on-a-chip technologies. The review aims to fill the lacuna in existing literature toward a holistic bioartificial lung tissue, including trachea, capillaries, airways, bifurcating bronchioles, lung disease models, and their clinical translation. Herein, the efforts are on bridging the application of lung tissue engineering methods in a clinical environment as it is thought that tissue engineering holds enormous promise for overcoming the challenges associated with the clinical translation of bioengineered human lung and its components.

Fetal Lung Tissue Engineering.

Lung transplantation may be considered as a final treatment option for diseases such as chronic lung disease, pulmonary hypertension, bronchopulmonary dysplasia, pulmonary fibrosis, and end-stage lung disease. The five-year survival rate of lung transplants is nearly 50%. Unfortunately, many patients will die before a suitable lung donor can be found. Importantly, the shortage of donor organs has been a significant problem in lung transplantation. The tissue engineering approach uses de- and recellularization of lung tissue to create functional lung substitutes to overcome donor lung limitations. Decellularization is hope for generating an intact ECM in the development of the engineered lung. The goal of decellularizationis to prepare a suitable scaffold of lung tissue that contains an appropriate framework for the functionality of regenerated lung tissue. In this chapter, we aim to describe the decellularization protocols for lung tissue regenerative purposes.

Assessment of expressions of Bcl-XL, b-FGF, Bmp-2, Caspase-3, PDGFR-α, Smad1 and TGF-β1 genes in a rat model of lung ischemia/reperfusion.

Ischemia is described as organs and tissues are destitute of oxygen due to decreased arterial or venous blood flow. Many mechanisms play role in cell death happened as a consequence of a new blood flow is needed for both cell regeneration and to clean toxic metabolites during ischemia and later. Lung damage induced by ischemia/reperfusion (I/R) is a frequent problem in lung transplantation. Apoptosis (programmed cell death) is known as cell suicide, and plays a key role in embryonic developmental and in maintain adult tissue's life. It is investigated expressions of Smad1, Bmp-2, Bcl-XL, b-FGF, Caspase-3, TGF-β1, PDGFR-α genes for molecular changes in lung tissues, after I/R is formed, in this study. For this, we included 40 Wistar albino rats to this study and divided 4 groups (n=10). The Groups were determined as Control (C), Group 1= 1 hr ischemia (I), Group 2= 1 hr ischemia+2 hr reperfusion (I+2R), Group 3= 1 hr ischemia+4 hr reperfusion (I+4R). Besides, molecular analysis and histopathologic examinations of tissues were performed, and the results were evaluated by normalization and statistics analysis. We have found a significant increase in expression of Bcl-XL (P=0.046) and Caspase-3 (P=0.026) genes of group 1, and it was not monitored any significant difference in Group 2 and Group 3. In all groups, the changes in b-FGF (P=0.087), Bmp-2 (P=0.457), TGF-β1 (P=0.201) and PDGFR-α (P=0.116) were not significant compared to control group. We did not see any mRNA expression of Smad1 gene in all groups include control. These findings suggest that I/R injury may trigger apoptotic mechanism in lung.

Up to Six Years Experience of Lobar Lung Transplantation

Objectives: The shortage of suitable donor organs is a problem in lung transplantation. This dilemma is even worse in recipients with small chest cavities. To exploit a larger donor pool, we electively accepted bigger organs for small patients and performed lobar lung transplants. We further compared this patient group with patients receiving regular bilateral lung transplantation concerning survival and lung function.

Elective Lobar Lung Transplantation - A Single Center Experience

Objectives: The shortage of suitable donor organs is a major problem in lung transplantation and has led to an increased gap between the number of donors and the number of recipients on the waiting list. This dilemma is even worse in recipients with small chest cavities, which markedly prolongs their waiting times. To exploit a larger donor pool, we electively accepted bigger organs for small patients and performed lobar lung transplants. Methods: In this case series, we present 11 patients (9 women and 2 men, 45 ± 11.8 years old) that underwent elective lobar lung transplantation between March 2009 and August 2014 with a mean waiting time of 227 ± 163 days. The underlying diseases were IPF (n = 7), CF (n = 3) and PHT (n = 1). The mean recipient height was 164 ± 8 cm and their calculated total lung capacity (TLC) was 5.2 ± 0.9 L. Results: We accepted lungs from 9 male and 2 female donors with a calculated TLC of 7.7 ± 0.3 L and 5.2 ± 0.1 L and a donor height of 185 ± 4 cm and 165 ± 0 cm, respectively. The mean donor age was 45.5 ± 7.1 years. Two lungs were transplanted using the Organ Care System (TransMedicsTM). All recipients were successfully transplanted via antero-lateral or clamshell incisions using intraoperative ECMO support. In 5 cases, we transplanted a right upper (RUL) + right middle lobe (RML) and a left upper lobe (LUL). The remaining patients received RUL and LUL (n = 2), RLL and LLL (n = 2), and complete right lung and LUL (n = 2). There were no postoperative air leaks requiring further intervention. The 30-day survival was 90.9%. Two patients died during the first year from graft failure (at day 11) and SIRS (at day 77), respectively. All other patients are still alive at 44.4 ± 14.3 months. One patient developed BOS stage III and 7 recipients were hospitalized for infections at some point. All survivors are followed as outpatients and have little activity limitations. Their FVC and FEV1 is 52.2 ± 20.2% and 51.6 ± 18.8%, respectively. Conclusion: Although lobar lung transplantation has been used as a bailout strategy in cases of unexpected size mismatches or in very urgent patients, we show here that elective lobar lung transplantation can be performed safely with similar overall results as regular lung transplants. It is a valuable option for patients, mainly female with small thoraces.

Antibody-mediated rejection in a lung transplant recipient after acute stroke

Antibody-mediated rejection (AMR) is becoming a more recognized problem in lung transplantation. We present a case of late onset AMR in a lung transplant recipient after an acute embolic stroke requiring thrombolytic therapy, who previously had a completely unremarkable course for over 3years.

A new preservation solution for lung transplantation: Evaluation in a porcine transplantation model

Lung preservation injury is still a major problem in lung transplantation. The aim of the current study was to evaluate the effects of a new preservation solution (Custodiol-N) for lung preservation. Using an in vivo pig model, 7 lungs each were preserved for 24 hours after perfusion with: low-potassium dextran (LPD) solution as control (Group I); base solution of Custodiol-N without iron chelators (Group II); Custodiol-N (Group III); or Custodiol-N supplemented with dextran 40 (Group IV). Four animals received a sham operation. After left lung transplantation and contralateral lung exclusion, hemodynamics and blood gases were monitored for 6 hours; tissue samples were taken at the end of the experiments. All animals survived the transplantation procedure. Base solution- and Custodiol-N-preserved lungs (Groups II and III) showed graft function similar to that of LPD-preserved lungs (Group I), showing a trend toward improved values. Custodiol-N with dextran (Group IV) led to a significant reduction of mean pulmonary arterial pressure (20 ± 2 vs 28 ± 3 mm Hg, p < 0.01) and pulmonary vascular resistance (410 ± 51 vs 588 ± 83 dyne/s/cm(5), p < 0.01), and oxygenation ratio was significantly higher (536 ± 52 vs 313 ± 107 mm Hg at 6 hours, p < 0.01) and PCO(2) values were significantly lower (51 ± 9 vs 77 ± 5 mm Hg at 6 hours, p < 0.01) at 6 hours compared with LPD (Group I). Custodiol-N (Groups II to IV) showed a trend toward a lower wet/dry ratio and reduced oxidative stress; in the presence of dextran (Group IV), the difference was again statistically significant, when compared with LPD (Group I). Custodiol-N solution is a new alternative preservation solution for lung transplantation that offers significantly superior protection compared with LPD when dextran 40 is added.

Challenges in lung transplantation

Lung transplantation is an established therapy for end-stage pulmonary disorders in selected patients without significant comorbidities. The particular constraints associated with organ transplantation from deceased donors involve specific allocation rules in order to optimise the medical efficacy of the procedure. Comparison of different policies adopted by national transplant agencies reveals that an optimal and unique allocation system is an elusive goal, and that practical, geographical and logistic parameters must be taken into account. A solution to attenuate the imbalance between the number of lung transplant candidates and the limited availability of organs is to consider marginal donors. In particular, assessment and restoration of gas exchange capacity ex vivo in explanted lungs is a new and promising approach that some lung transplant programmes have started to apply in clinical practice. Chronic lung allograft dysfunction, and especially bronchiolitis obliterans, remains the major medium- and long-term problem in lung transplantation with a major impact on survival. Although there is to date no cure for established bronchiolitis obliterans, new preventive strategies have the potential to limit the burden of this feared complication. Unfortunately, randomised prospective studies are infrequent in the field of lung transplantation, and data obtained from larger studies involving kidney or liver recipients are not always relevant for this purpose.

Targeted Endothelial Delivery of Nanosized Catalase Immunoconjugates Protects Lung Grafts Donated After Cardiac Death

Donor organ shortage represents a major problem in lung transplantation. Donation after cardiac death could help to expand the pool of organs, but the additional period of warm ischemia after cardiac arrest aggravates primary graft dysfunction. The pulmonary endothelium of the graft constitutes an important source and target of reactive oxygen species generated during ischemia and reperfusion. Targeted protection of graft pulmonary endothelial cells by the antioxidant enzyme catalase, conjugated with a platelet/endothelial cell adhesion molecule-1 (PECAM-1) antibody to nanosized particles (anti-PECAM/catalase conjugates), might improve outcome in lung transplantation using donors after cardiac death and prolonged hypothermic preservation. Left lung transplantation was performed in 18 pigs. Before cardiac arrest, donors received anti-PECAM/catalase, unconjugated component mixture or vehicle solution. After 90-min warm and 18-hr hypothermic ischemia, lungs were transplanted, and function was assessed during 6 hr after reperfusion. Samples of bronchoalveolar lavage fluid and lung tissue were taken thereafter. Six sham-operated animals served as controls. During 6-hr reperfusion, anti-PECAM/catalase significantly ameliorated graft function, evidenced by major improvements of gas exchange and reduced intrapulmonary shunt fraction. Furthermore, lipid peroxidation, alveolar leakage, and edema formation were reduced in protected grafts. Similarly moderate lung pathology was seen after transplantation. Augmentation of the antioxidant capacity of graft pulmonary endothelial cells with anti-PECAM/catalase nanoparticles represents a straightforward approach to enable a safe transplantation of prolonged preserved donation after cardiac death lungs. Anti-PECAM/catalase protection alleviated oxidative stress and allowed immediate reconstitution of normal gas exchange and pulmonary microcirculation, a prerequisite for improved graft and patient outcome.

Mixed Chimerism Achieved by a Nonlethal Conditioning Regimen Induces Donor-Specific Tolerance to Lung Allografts

Graft rejection and toxicity associated with chronic immunosuppressive therapy remain a major problem in lung transplantation (Tx). Mixed hematopoietic chimerism has been shown to produce long-lasting donor-specific transplant tolerance without immunosuppressive drugs in animal models; however, most conditioning regimens required to achieve mixed chimerism are too toxic for clinical use. The aim of this study was to develop a nonlethal conditioning regimen to induce tolerance to lung allografts. Four to 6-wk old ACI (RT1.A(a)) and Wistar Furth (RT1.A(u)) rats were used as organ donors and recipients, respectively. The recipient conditioning regimen included: 10 mg/animal antilymphocyte globulin (on day-5), 1 mg/kg/d tacrolimus (days 1 to 10), total body irradiation (500 cGy; day 0), and donor bone marrow (DBM) Tx (100 x 10(6) T-cell depleted cells on day 0 following irradiation). Six weeks after DBM Tx, chimeric animals received orthotopic left lung Tx. Graft survival was monitored by chest X-ray and histology. Long-term DBM engraftment was observed: hematopoietic chimerism in the peripheral blood was 12.4 +/- 3.4%, 36.7 +/- 14.1%, and 31.9 +/- 14.1% at 30 d, 6 mo, and 16 mo following DBM Tx, respectively. There was no graft versus host disease. Chimeric recipients (RT1.A(u)) permanently accepted (>400 d) donor-specific lungs (RT1.A(a); n = 8), yet rapidly rejected (<8 d) third party hearts (RT1.A(l); n = 5). Graft (lung) tolerant (>150 d) chimeric recipients accepted secondary donor-specific heart grafts (>150 d; n = 4) but rejected third party heart grafts (<7 d; n = 3). Graft tolerant recipients demonstrated reduced (P < 0.05) in vitro donor-specific lymphoproliferative response and cytotoxicity, and no evidence of acute or chronic graft rejection. Mixed chimerism achieved by a nonlethal conditioning regimen induced long-term donor-specific tolerance to lung allografts.

A new murine model for bronchiolitis obliterans post-bone marrow transplant.

Bronchiolitis obliterans (BO) is a major problem in lung transplantation and is also part of the spectrum of late-onset pulmonary complications that can occur after hematopoietic stem cell transplant. Better mouse models are needed to study the onset of this disease so that therapeutic interventions can be developed. Our goal was to develop a BO mouse model. Recipients were lethally conditioned and given a rescue dose of T-cell-depleted, allogeneic bone marrow (BM) supplemented with a sublethal dose of allogeneic T cells. At 2 months post-BM transplant, the lungs had extensive perivascular and peribronchiolar inflammation consisting of CD4(+) T cells, CD8(+) T cells, B cells, macrophages, neutrophils, and fibroblasts. In contrast to the acute model, histology showed airway obstruction consistent with BO. Epithelial cells of airways in the early stages of occlusion exhibited changes in expression of cytokeratins. Although the lung had severe allogeneic BM transplant-mediated disease, there was only mild to moderate graft-versus-host disease in liver, colon, skin, and spleen. High wet/dry weight ratios and elevated hydroxyproline were seen, consistent with pulmonary edema and fibrosis. Mice with BO exhibited high airway resistance and low compliance. Increases in many inflammatory mediators in the lungs of mice that develop BO were seen early post-transplant and not later at the time of BO. This new mouse model will be useful for the study of BO associated with late post-hematopoietic stem cell transplant onset and chronic graft-versus-host disease, which also leads to poor outcome in the lung transplant setting.

202: A double-blind randomized trial comparing basiliximab to placebo in lung transplantation

Acute rejection (AR) remains a common problem in lung transplantation (LTx) with AR rates generally being in the range of 40%. Induction therapy however is not uniformly applied due to lack of definitively proven efficacy and concern for infectious complications of over–immunosuppression in these patients. No fully reported trials have compared any form of induction therapy to placebo in a double-blind fashion in LTx. This study explored the tolerability and cumulative benefit of combining basiliximab with triple-drug therapy-cyclosporine (Neoral), azathioprine, and steroids.

Effective application of ET-Kyoto solution for clinical lung transplantation

The shortage of lung donors and ischemia-reperfusion injury following transplantation have been grave problems in lung transplantation (LTx). One of the most important strategies to solve these problems is the development of effective and highly reliable methods for lung preservation. Therefore, we developed a new organ preservation solution, namely, the extracellular-type trehalose-containing Kyoto (ET-Kyoto) solution. Here we report the first experience of clinical application of ET-Kyoto solution for cadaveric LTx. The recipient was a 38-year-old man with pulmonary emphysema. The donor was a 51-year-old male current smoker with a smoking history of 62 pack-years. The ventilated donor's PaO 2 was 340 Torr (FiO 2 = 1.0). The pulmonary vasculature was flushed with ET-Kyoto solution supplemented with nitroglycerine and dibutyryl cAMP. The recipient underwent bilateral sequential LTx on cardiopulmonary bypass. The ischemic time was 544 and 613 minutes for the left and right lung, respectively. PaO 2 (FiO 2 = 1.0) was 385 Torr immediately after reperfusion. The donor lung was so large that bilateral partial resections were performed at 413 minutes (right) and 348 minutes (left) after reperfusion. On histopathologic examination of the resected transplanted lungs the structure was almost normal. Postoperatively, PaO 2 (FiO 2 = 1.0) was over 400 Torr with or maximum of 526 Torr. The clinical course was almost uneventful. In conclusion, ET-Kyoto solution may be safely applied in clinical cadaveric LTx with extended donor lungs and relatively long ischemic times. Functional and histopathological efficiency of ET-Kyoto solution was confirmed. Longer preservation times with preserved quality using ET-Kyoto solution would increase the donor pool and enable semielective LTx.

The effects of a specific neutrophil elastase inhibitor (ONO-5046) in pulmonary ischemia-reperfusion injury.

Ischemia-reperfusion injury is a significant problem in lung transplantation. Polymorphonuclear elastase derived from neutrophils plays a major mechanistic role in this process. Hence, we have investigated the effects of ONO-5046, a neutrophil elastase inhibitor, on ischemia-reperfusion injury. Fifteen rabbits were divided into three groups: 2 h of single left-lung perfusion (control group, n=3); 2 h of ischemia followed by 2 h of reperfusion (ischemic group, n=6); and drip intravenous administration of ONO-5046 during the 2 h of ischemia and 2 h of reperfusion (ONO-5046 group, n=6). Hemodynamic parameters were determined and a histopathological examination of the lung was performed. In the ONO-5046 group, arterial oxygen pressure, cardiac output, and tissue blood perfusion were higher and pulmonary vascular resistance was lower than in the ischemic group. The ONO-5046 group also showed large decreases in neutrophil infiltration, pulmonary edema, and intra-alveolar hemorrhage. Treatment with ONO-5046 improves lung function in a rabbit-lung ischemia-reperfusion model.

Progressive increase of CD4+/CD45RC− lymphocytes after allograft rat lung transplantation: A marker of acute rejection

Background: Acute rejection remains one the most serious problems in lung transplantation. Although biopsy has been used for assessing the dysfunction of grafts, it is difficult to determine rejection at an early stage. Lymphocyte infiltration and activation play an important role in acute rejection of transplanted organs, and the dynamic change of lymphocyte subpopulations might be a marker to determine graft rejection after lung transplantation. Methods: A rat lung transplant model was used. Graft-infiltrating lymphocytes in lung tissues were examined by means of histology, and isolated cells were analyzed by means of flow cytometry. Phenotypes of lymphocytes in the regional and remote lymph nodes, spleen, peripheral blood, and bronchoalveolar lavage fluid were also measured by means of flow cytometry. Results: After allograft transplantation, increased lymphocytes were seen in allografts but not in isografts. In allografts the percentage of T cells increased from day 1 to day 5, whereas that of B cells was decreased. The CD4+/CD8+ ratio decreased in allografts. The proportion of CD4+/CD45RC− cells increased in the allografts, which was mainly due to the increase of CD45RC− cells in the total CD4+ cells. Similar changes were found in regional mediastinal lymph nodes but not in the mesenteric lymph nodes, spleen, or peripheral blood. Thus this is a specific response to lung allografts. Importantly, CD45RC− cells were significantly increased in the bronchoalveolar lavage fluid. Conclusion: Significant change of lymphocyte subpopulations is a sign of lymphocyte activation. Increased CD4+/CD45RC− cells in lung allografts could be an early marker of acute rejection, which can be examined by means of lung lavage and flow cytometry.J Thorac Cardiovasc Surg 2002;124:675-83

Cardiac and pulmonary replacement Inhaled nitric oxide improves lung allograft function after prolonged storage

Morbidity caused by early allograft dysfunction, manifested by a progressive increase in pulmonary vascular resistance and a decrease in oxygenation, remains a serious problem in lung transplantation. Inhalation of nitric oxide, an essential homeostatic molecule, has been shown to have beneficial effects on a variety of acute lung injuries. The purpose of the present study was to investigate the effect of inhaled nitric oxide on posttransplant function of canine left lung allografts. Fourteen dogs underwent left lung allotransplantation. Donors received systemic heparin and prostaglandin E 1 followed by pulmonary artery flush with modified Euro-Collins solution. Donor left lungs were stored for 18 hours at 1º C and subsequently implanted. Immediately after reperfusion, the contralateral right main pulmonary artery and bronchus were ligated. The chest was closed and recipients turned to the supine position for the 6-hour assessment period. Hemodynamic and arterial and venous blood gas analyses were made at 15-minute intervals at an inspired oxygen fraction of 1.0 and 5 cm of water positive end-expiratory pressure. Animals were killed at the end of the assessment. Allograft myeloperoxidase activity assays and wet/dry weight ratios were done. In group I ( n = 5), nitric oxide gas was administered continuously at concentrations of 60 to 70 ppm before reperfusion and throughout the 6-hour assessment period. In group II ( n = 5), nitric oxide administration was initiated at the same concentration after reperfusion injury had developed. Group III animals ( n = 4) received no nitric oxide. Significant improvement in gas exchange was apparent in group I. At the end of the 6-hour assessment period, mean arterial oxygen <abs2>tension was 253.8 ± 44.7 mm Hg and 114.9 ± 25.5 mm Hg in groups I and III, respectively ( p < 0.05). Group II animals had no improvement in oxygenation with nitric oxide. Systemic hemodynamics were unaffected by nitric oxide. However, an immediate decrease in pulmonary vascular resistance was noted. Group I myeloperoxidase activity was significantly lower than that in control group III (0.24 ± 0.06 versus 0.36 ± 0.04 units, respectively; p < 0.05). (J T horac C ardiovasc S urg 1996;112:293-9)

Results of single and bilateral lung transplantation in 131 consecutive recipients

We reviewed results of the first 131 recipients who received a single or bilateral sequential lung transplant at Barnes Hospital between July 1, 1988, and July 31, 1992. Follow-up data were complete as of January 1, 1993, for a minimum of 5 months' follow-up for all surviving recipients. There were 11 hospital deaths for an overall 92 % hospital survival. Thirteen late deaths occurred and 107 (81%) recipients remain alive with a median follow-up period of 19 months. One hundred nineteen recipients survived at least 3 months after transplantation, and for this group factors that might influence long-term results were evaluated. The prevalence of pathologically proved bronchiolitis obliterans was 18.5%. Functional deterioration, which may not correlate with pathologic findings, was evaluated with a recently developed bronchiolitis obliterans syndrome staging system. Factors not influencing longterm outcome included the number of early rejection episodes, matching donor and recipient cytomegalovirus antibody status, or underlying diagnosis. Patients undergoing single lung transplantation for primary pulmonary hypertension or Eisenmenger's syndrome had results similar to those of other diagnostic groups. Furthermore, the hemodynamic improvement previously reported for this group of patients after single lung transplantation has been maintained at long-term follow-up. The shortage of donor organs and the need for improved methods for diagnosis and management of chronic rejection remain the most challenging problems in lung transplantation.

The effect of transforming growth factor-α on airway angiogenesis

A problem in lung transplantation is tracheal or bronchial dehiscence from ischemia. To determine if an angiogenic factor applied to the airway would improve capillary regrowth, a three-ring segment of trachea was completely severed and sutured in rats. In one group of animals the ischemic segment was wrapped with Gelfoam soaked in an angiogenic factor, transforming growth factor-alpha. In a second group the ischemic area was wrapped with Gelfoam soaked with only the vehicle. In a third group the devascularized area received no additional treatment. One animal from each group was killed daily for 7 days after operation. The tracheal vasculature was cast and viewed by light and scanning electron microscopy. None of the four animals that died early were in the transforming growth factor-alpha group. All animals lost weight between the day of operation and death, but this was least in the transforming growth factor-alpha group (p = 0.05). The light microscopy showed ischemic changes and the development of granulation tissue. The scanning electron microscopy of the vascular casts showed extensive loss of the vessels in the cut area. On day 1 the vessels of all animals dilated and their walls became rough. By day 3 a few corkscrew vessels penetrated the ischemic zone. By day 4 the animal that received transforming growth factor-alpha had more capillaries than the others. By day 6 revascularization in the transforming growth factor-alpha animal was abundant. Besides budding, new capillaries appeared to develop by lateral growth. After the fifth day vessels about 30 to 50 microns in diameter bulged focally. On the bulges, ridges the size, shape, and pattern of capillaries formed. Capillary formation in this manner has not been reported previously. Revascularization emerged sooner and more extensively with transforming growth factor-alpha. No adverse effect of transforming growth factor-alpha was found.

Effect of donor bronchial length on healing: A canine model to evaluate bronchial anastomotic problems in lung transplantation

Bronchial anastomotic complications in lung transplantation in man remain a major cause of failure. To study this problem in a canine model, we varied the length of the distal bronchial component in three groups of dogs that underwent hilar stripping, bronchial transection, and reanastomosis, The distal bronchial component was thus analogous to the donor in a transplanted lung. Anastomoses were performed, respectively, at the level of the main carina (long single anastomosis), at the midpoint between the main carina and the bifurcation of the left main-stem bronchus (short single anastomosis), and just distal to the bifurcation of the left main-stem bronchus (lobar anastomosis). Bronchial anastomotic damage and necrosis were evaluated by periodic examination with a fiberoptic bronchoscope and by gross and microscopic examination at sacrifice on the seventh postoperative day. The long single anastomoses demonstrated the most necrosis, and the labor anastomoses showed the least. The short single anastomoses showed an intermediate degree of damage. These findings support the hypothesis that shortening the distal or donor bronchial component reduces anastomotic damage, probably because of better pulmonary-to-bronchial collateral blood supply. This study provides a canine model by which to examine bronchial anastomotic complicatons and demonstrates the feasibility of performing labor anastomoses as a means for decreasing bronchial anastomotic problems in lung transplantation.