Reperfusion-induced gene expression profiles in rat lung transplantation

Applications of transcriptomics in ischemia reperfusion research in lung transplantation

Ischemia-reperfusion (IR) injury contributes to primary graft dysfunction, a major cause of early mortality after lung transplantation. Transcriptomics uses high-throughput techniques to profile the RNA transcripts within a sample and provides a unique view of the mechanisms underlying various biological processes. This review aims to highlight the applications of transcriptomics in lung IR injury studies, which have thus far revealed inflammatory responses to be the major event activated by IR, identified potential biomarkers and therapeutic targets, and investigated the mechanisms of therapeutic interventions. Ex vivo lung perfusion, together with advanced bioinformatic and transcriptomic techniques, including single-cell RNA-sequencing, microRNA profiling, and multi-omics, continue to expand the capabilities of transcriptomics. In the future, the construction of biospecimen banks and the promotion of international collaborations among clinicians and researchers have the potential to advance our understanding of IR injury and improve the management of lung transplant recipients.

Cellular and molecular mechanisms of cell damage and cell death in ischemia-reperfusion injury in organ transplantation

Ischemia-reperfusion injury (IRI) is a critical pathological condition in which cell death plays a major contributory role, and negatively impacts post-transplant outcomes. At the cellular level, hypoxia due to ischemia disturbs cellular metabolism and decreases cellular bioenergetics through dysfunction of mitochondrial electron transport chain, causing a switch from cellular respiration to anaerobic metabolism, and subsequent cascades of events that lead to increased intracellular concentrations of Na+, H+ and Ca2+ and consequently cellular edema. Restoration of blood supply after ischemia provides oxygen to the ischemic tissue in excess of its requirement, resulting in over-production of reactive oxygen species (ROS), which overwhelms the cells' antioxidant defence system, and thereby causing oxidative damage in addition to activating pro-inflammatory pathways to cause cell death. Moderate ischemia and reperfusion may result in cell dysfunction, which may not lead to cell death due to activation of recovery systems to control ROS production and to ensure cell survival. However, prolonged and severe ischemia and reperfusion induce cell death by apoptosis, mitoptosis, necrosis, necroptosis, autophagy, mitophagy, mitochondrial permeability transition (MPT)-driven necrosis, ferroptosis, pyroptosis, cuproptosis and parthanoptosis. This review discusses cellular and molecular mechanisms of these various forms of cell death in the context of organ transplantation, and their inhibition, which holds clinical promise in the quest to prevent IRI and improve allograft quality and function for a long-term success of organ transplantation.

Early Growth Response-1: Friend or Foe in the Heart?

Cardiovascular disease is a major cause of mortality and morbidity worldwide. Early growth response-1 (Egr-1) plays a critical regulatory role in a range of experimental models of cardiovascular diseases. Egr-1 is an immediate-early gene and is upregulated by various stimuli including shear stress, oxygen deprivation, oxidative stress and nutrient deprivation. However, recent research suggests a new, underexplored cardioprotective side of Egr-1. The main purpose of this review is to explore and summarise the dual nature of Egr-1 in cardiovascular pathobiology.

Ex vivo perfusion induces a time- and perfusate-dependent molecular repair response in explanted porcine lungs

Ex vivo lung perfusion (EVLP) shows promise in ameliorating pretransplant acute lung injury (ALI) and expanding the donor organ pool, but the mechanisms of ex vivo repair remain poorly understood. We aimed to assess the utility of gene expression for characterizing ALI during EVLP. One hundred sixty-nine porcine lung samples were collected in vivo (n = 25), after 0 (n = 11) and 12 (n = 11) hours of cold static preservation (CSP), and after 0 (n = 57), 6 (n = 8), and 12 (n = 57) hours of EVLP, utilizing various ventilation and perfusate strategies. The expression of 53 previously described ALI-related genes was measured and correlated with function and histology. Twenty-eight genes were significantly upregulated and 6 genes downregulated after 12 hours of EVLP. Aggregate gene sets demonstrated differential expression with EVLP (P < .001) but not CSP. Upregulated 28-gene set expression peaked after 6 hours of EVLP, whereas downregulated 6-gene set expression continued to decline after 12 hours. Cellular perfusates demonstrated a greater reduction in downregulated 6-gene set expression vs acellular perfusate (P < .038). Gene set expression correlated with relevant functional and histologic parameters, including P/F ratio (P < .001) and interstitial inflammation (P < .005). Further studies with posttransplant results are warranted to evaluate the clinical significance of this novel molecular approach for assessing organ quality during EVLP.

Immediate post-operative broncho-alveolar lavage IL-6 and IL-8 are associated with early outcomes after lung transplantation

INTRODUCTION

Previous studies demonstrated that increased cytokine and chemokine levels, either shortly before or after lung transplantation, were associated with post-transplant outcome. However, small patient cohorts were mostly used, focusing on 1 molecule and 1 outcome. In a large single-center cohort, we investigated the predictive value of immediate post-operative broncho-alveolar lavage (BAL) expression of IL-6 and IL-8 on multiple key outcomes, including PGD, CLAD, graft survival, as well as several secondary outcomes.

MATERIAL AND METHODS

All patients undergoing a first lung transplant in whom routine bronchoscopy with BAL was performed during the first 48 hours post-transplantation were included. IL-6 and IL-8 protein levels were measured in BAL via ELISA.

RESULTS

A total of 336 patients were included. High IL-6 levels measured within 24 hours of transplantation were associated with longer time on ICU and time to hospital discharge; and increased prevalence of PGD grade 3. Increased IL-8 levels, measured within 24 hours, were associated with PGD3, more ECMO use, higher donor paO₂ , younger donor age, but not with other short-or long-term outcome. IL-6 and IL-8 measured between 24 and 48 hours of transplantation were not associated with any outcome parameters.

CONCLUSION

Recipient BAL IL-6 and IL-8 within 24 hours post-transplant were associated with an increased incidence of PGD3.

Early Growth Response-1 Plays an Important Role in Ischemia-Reperfusion Injury in Lung Transplants by Regulating Polymorphonuclear Neutrophil Infiltration

BACKGROUND

Early growth response-1 (Egr-1) has been shown to be a trigger-switch transcription factor that is involved in lung ischemia-reperfusion injury (IRI).

METHODS

Mouse lung transplants were performed in wild-type (WT) C57BL/6 and Egr1-knockout (KO) mice in the following donor → recipient combinations: WT → WT, KO → WT, WT → KO, and KO → KO to determine whether the presence of Egr-1 in the donor or recipient is the most critical factor for IRI. Pulmonary grafts were retrieved after 18 hours of ischemia after 4 hours of reperfusion. We analyzed graft function by analyzing arterial blood gas and histology in each combination and assessed the effects of Egr1 depletion on inflammatory cytokines that are regulated by Egr-1 as well on polymorphonuclear neutrophil (PMN) infiltration.

RESULTS

Deletion of Egr1 improved pulmonary graft function in the following order of donor → recipient combinations: WT → WT < WT → KO < KO → WT < KO → KO. Polymerase chain reaction assays for Il1B, Il6, Mcp1, Mip2, Icam1, and Cox2 showed significantly lower expression levels in the KO → KO group than in the other groups. Immunohistochemistry demonstrated clear Egr-1 expression in the nuclei of pulmonary artery endothelial cells and PMN cytoplasm in the WT grafts. Flow cytometry analysis showed that Egr1 deletion reduced PMN infiltration and that the extent of reduction correlated with graft function.

CONCLUSIONS

Both graft and recipient Egr-1 played a role in lung IRI, but the graft side contributed more to this phenomenon through regulation of PMN infiltration. Donor Egr-1 expression in pulmonary artery endothelial cells may play an important role in PMN infiltration, which results in IRI after lung transplantation.

δV1-1 Reduces Pulmonary Ischemia Reperfusion-Induced Lung Injury by Inhibiting Necrosis and Mitochondrial Localization of PKCδ and p53

Ischemia-reperfusion (IR)-induced lung injury is one of the major contributing factors of morbidity and mortality after lung transplantation. To determine the IR-induced molecular changes in lung epithelial cells, we developed a cell-culture model that simulates lung preservation and transplantation. Six hours of cold ischemic time (CIT) and reperfusion elicited production of multiple inflammatory cytokines and chemokines and increased expression of endoplasmic reticulum (ER) proteins. Prolonged hypothermic condition (18 h CIT) reduced ER stress protein levels, and induced apoptosis and necrosis (via mechanisms related to mitochondrial permeability transition pore opening). Protein kinase C (PKCδ) was activated during CIT, and its downregulation via small interference (si) (in siRNA) RNA reduced IR-induced cytokine production and apoptotic cell death. δV1-1, a PKCδ peptide inhibitor, reduced translocation of PKCδ and p53 to the mitochondria after 18 h CIT, rescued ER stress protein expression, and converted the major mode of cell death from necrosis to apoptosis. Administration of δV1-1 effectively reduced lung transplantation and IR-induced pulmonary injury in rats. Therefore, inhibition of PKCδ by δV1-1 could be an effective strategy to ameliorate IR-induced lung injury by inhibiting the signaling pathways leading to necrosis.

A Peptide to Reduce Pulmonary Edema in a Rat Model of Lung Transplantation

BACKGROUND

Despite significant advances in organ preservation, surgical techniques and perioperative care, primary graft dysfunction is a serious medical problem in transplantation medicine in general and a specific problem in patients undergoing lung transplantation. As a result, patients develop lung edema, causing reduced tissue oxygenation capacity, reduced lung compliance and increased requirements for mechanical ventilatory support. Yet, there is no effective strategy available to protect the grafted organ from stress reactions induced by ischemia/reperfusion and by the surgical procedure itself.

METHODS

We assessed the effect of a cingulin-derived peptide, XIB13 or a random peptide in an established rat model of allogeneic lung transplantation. Donor lungs and recipients received therapeutic peptide at the time of transplantation and outcome was analyzed 100min and 28 days post grafting.

RESULTS

XIB13 improved blood oxygenation and reduced vascular leak 100min post grafting. Even after 28 days, lung edema was significantly reduced by XIB13 and lungs had reduced fibrotic or necrotic zones. Moreover, the induction of an allogeneic T cell response was delayed indicating a reduced antigen exchange between the donor and the host.

CONCLUSIONS

In summary, we provide a new tool to strengthen endothelial barrier function thereby improving outcomes in lung transplantation.

Netrin-1 pretreatment protects rat kidney against ischemia/reperfusion injury via suppression of oxidative stress and neuropeptide Y expression

Netrin-1 has been found to protect kidneys from ischemia/reperfusion injury. In this study, we aimed to address whether the protective effects were mediated through suppression of oxidative stress and neuropeptide Y. Compared to sham-operated animals, animals after ischemia/reperfusion showed marked kidney damage and significantly increased levels of serum creatinine, blood urea nitrogen, malondialdehyde, and neuropeptide Y. Renal myeloperoxidase activity was elevated in animals with ischemia/reperfusion relative to sham-operated animals, whereas renal superoxide dismutase activity was reduced. Netrin-1 pretreatment attenuated ischemia/reperfusion-induced functional and pathological changes in the kidney. Moreover, the ischemia/reperfusion-induced changes in the oxidative stress biomarkers and neuropeptide Y were significantly counteracted by prior administration of netrin-1. Taken together, our data showed that netrin-1 pretreatment prevented renal ischemia/reperfusion injury, at least partially through reduction of oxidative stress and neuropeptide Y expression.

Impact of prolonged cold preservation on the graft function and gene expression levels in an experimental lung transplantation model

PURPOSE

Ischemia reperfusion injury (IRI) remains a significant cause of morbidity and mortality after lung transplantation. Early growth response-1 (EGR1) drives the expression of inflammatory mediators and has an important role in IRI. We hypothesized that the severe IRI caused by a long preservation induces a specific expression pattern of EGR1 and its target genes which would correlate with the lung graft function.

METHODS

SD rat lungs were preserved at 4 °C for 3 or 18 h, then transplanted and reperfused. Pulmonary grafts were evaluated for the blood gas oxygenation and pathological findings. The intra-graft mRNA levels of EGR1 and its downstream target genes were measured by real-time PCR. A Western blotting analysis of the EGR1 expression was used to validate the changes in the protein level.

RESULTS

There was upregulation of EGR1, MIP-2 and PAI-1 when there was prolonged hypothermic preservation. The expression levels of MIP-2 and PAI-1 were observed to increase for up to 4 h in the 18 h preserved lungs. There were no differences in the expression levels of IL-1β and ICAM-1 between the lungs subjected to short and long periods of ischemia.

CONCLUSIONS

Our data showed that prolonged hypothermic graft preservation deteriorates the pulmonary graft function, which was associated with the induction of EGR1 and its downstream target genes, which may aggravate IRI following lung transplantation.

Inhaled hydrogen sulfide improves graft function in an experimental model of lung transplantation

OBJECTIVES

Ischemia/reperfusion injury (IRI) is a common complication of lung transplantation (LTx). Hydrogen sulfide (H(2)S) is a novel agent previously shown to slow metabolism and scavenge reactive oxygen species, potentially mitigating IRI. We hypothesized that pretreatment with inhaled H(2)S would improve graft function in an ex vivo model of LTx.

METHODS

Rabbits (n = 10) were ventilated for 2 h prior to heart-lung bloc procurement. The treatment group (n = 5) inhaled room air (21% O(2)) supplemented with 150 ppm H(2)S while the control group (n = 5) inhaled room air alone. Both groups were gradually cooled to 34°C. All heart-lung blocs were then recovered and cold-stored in low-potassium dextran solution for 18 h. Following storage, the blocs were reperfused with donor rabbit blood in an ex vivo apparatus. Serial clinical parameters were assessed and serial tissue biochemistry was examined.

RESULTS

Prior to heart-lung bloc procurement, rabbits pretreated with H(2)S exhibited similar oxygenation (P = 0.1), ventilation (P = 0.7), and heart rate (P = 0.5); however, treated rabbits exhibited consistently higher mean arterial blood pressures (P = 0.01). During reperfusion, lungs pretreated with H(2)S had better oxygenation (P < 0.01) and ventilation (P = 0.02), as well as lower pulmonary artery pressures (P < 0.01). Reactive oxygen species levels were lower in treated lungs during reperfusion (P = 0.01). Additionally, prior to reperfusion, treated lungs demonstrated more preserved mitochondrial cytochrome c oxidase activity (P = 0.01).

CONCLUSIONS

To our knowledge, this study represents the first reported therapeutic use of inhaled H(2)S in an experimental model of LTx. After prolonged ischemia, lungs pretreated with inhaled H(2)S exhibited improved graft function during reperfusion. Donor pretreatment with inhaled H(2)S represents a potentially novel adjunct to conventional preservation techniques and merits further exploration.

Activations of mitogen-activated protein kinases and regulation of their downstream molecules after rat lung transplantation from donors after cardiac death

OBJECTIVES

Accepting organs donated after cardiac death (DCD) is an effective approach to the donor shortage. However, lung transplantations from DCD donors show severe rapid pulmonary graft dysfunction (PGD) followed by warm ischemia-reperfusion injury (IRI). This study sought to clarify the molecular mediators in warm IRI, including activation of mitogen-activated protein kinase (MAPK) and the downstream cascades.

METHODS

We performed single left lung transplantation using organs from male Sprague-Dawley rats after 0 (CIT group), 30 (30WIT group), or 180 (180WIT group) minutes of warm ischemia time. Pulmonary graft functions were estimated by blood gas analysis. At 1 hour after reperfusion, the phosphorylation status of MAPKs (ERK, p38, and JNK) and the gene expression levels of transcription factors (Egr-1 and ATF-3) and immune mediators (MCP-1, MIP-2, PAI-1, ICAM-1, TNF-α, IL-1β, IL-6, and COX-2) in the grafts were examined using Western blotting and real-time polymerase chain reaction assays.

RESULTS

Severe PGD was observed in the 180WIT group compared with transplanted lungs in the other groups, which exhibited good pulmonary graft function. ERK and JNK activations, as well as mRNA levels of transcription factors (Egr-1 and ATF3) significantly increased with greater warm ischemic times. The pattern of JNK activation correlated with the severity of PGD. MCP-1, ICAM-1, IL-1β, IL-6, and COX-2 were also up-regulated among the 180WIT group, although MIP-2 and PAI-1 showed no significant differences among the groups.

CONCLUSIONS

We suggest that the ERK and JNK pathways may play important roles to induce the injury caused by prolonged warm ischemia followed by reperfusion in the setting of lung transplantation from DCD donors.

Src tyrosine kinase inhibition prevents pulmonary ischemia-reperfusion-induced acute lung injury

PURPOSE

Pulmonary ischemia-reperfusion is a pathological process seen in several clinical conditions, including lung transplantation, cardiopulmonary bypass, resuscitation for circulatory arrest, atherosclerosis, and pulmonary embolism. A better understanding of its molecular mechanisms is very important.

METHODS

Rat left lung underwent in situ ischemia for 60 min, followed by 2 h of reperfusion. The gene expression profiles and Src protein tyrosine kinase (PTK) phosphorylation were studied over time, and PP2, an Src PTK inhibitor, was intravenously administered 10 min before lung ischemia to determine the role of Src PTK in lung injury.

RESULTS

Reperfusion following ischemia significantly changed the expression of 169 genes, with Mmp8, Mmp9, S100a9, and S100a8 being the most upregulated genes. Ischemia alone only affected expression of 9 genes in the lung. However, Src PTK phosphorylation (activation) was increased in the ischemic lung, mainly on the alveolar wall. Src PTK inhibitor pretreatment decreased phosphorylation of Src PTKs, total protein tyrosine phosphorylation, and STAT3 phosphorylation. It increased phosphorylation of the p85α subunit of PI3 kinase, a signal pathway that can inhibit coagulation and inflammation. PP2 reduced leukocyte infiltration in the lung, apoptotic cell death, fibrin deposition, and severity of acute lung injury after reperfusion. Src inhibition also significantly reduced CXCL1 (GRO/KI) and CCL2 (MCP-1) chemokine levels in the serum.

CONCLUSION

During pulmonary ischemia, Src PTK activation, rather than alteration in gene expression, may play a critical role in reperfusion-induced lung injury. Src PTK inhibition presents a new prophylactic treatment for pulmonary ischemia-reperfusion-induced acute lung injury.

Maintenance of IKKβ activity is necessary to protect lung grafts from acute injury

BACKGROUND

Signaling pathways that target I-κB kinase β (IKKβ) activation stimulate the expression of nuclear factor (NF)-κB-dependent genes and are thus believed to primarily promote inflammation and injury in solid organ grafts.

METHODS

We examined the role of IKKβ in a mouse model of lung transplantation-mediated ischemia-reperfusion injury using NF-κB essential modulator (NEMO)-binding domain (NBD) peptide to pharmacologically inhibit IKK activation. As myeloid cells are primarily responsible for the production of acute inflammatory mediators after lung transplantation, we also investigated the effects of myeloid cell-specific IKKβ gene deletion on acute lung graft injury by transplanting mutant mice.

RESULTS

When NBD was administered at a dose that partially inhibits IKKβ activation, we observed attenuated lung graft injury and blunted expression of intragraft proinflammatory mediators. Surprisingly, when the dose of NBD was increased to a level that ablates intragraft IKKβ activation, graft inflammation, and injury were significantly worse compared with recipients treated with control peptide. Similar to lung recipients with pharmacologically ablated IKKβ activity, donor-recipient transplant combinations with a myeloid cell-specific IKKβ gene deletion had marked intragraft inflammation and poor lung function.

CONCLUSIONS

Our data show maintenance of IKKβ activity is critical for promoting graft homeostasis with important implications for targeting NF-κB-dependent signaling pathways for treating acute lung injury.

Anti-IL-23 antibody blockade of IL-23/IL-17 pathway attenuates airway obliteration in rat orthotopic tracheal transplantation

Obliterative bronchiolitis (OB) has been a major obstacle to long-term allograft survival after lung transplantation, and the underlying mechanism is not well understood. As IL-23/IL-17 pathway has been shown to play important roles in airway inflammation, in this study we have investigated the role of IL-23/IL-17 pathway in acute and chronic airway allograft rejection. We used a rat OB model in orthotopic tracheal transplantation, and investigated the effects of anti-IL-23 blockade antibody on acute and chronic airway allograft rejection. Anti-IL-23 antibody impaired the function of IL-23 in inducing IL-17 production. The rats that received allografts and treated with anti-IL-23 antibody showed significantly less symptom of airway obliteration and chronic transplant rejection compared with control rats which received physiological saline or IgG antibody. Taken together, our results suggest that anti-IL-23 antibody is effective in protecting allograft rejection and the development of chronic OB in allo-tracheal transplantation. These findings may have implications for new therapies to prevent OB and allograft rejection in human lung transplantation.

Nitric oxide ventilation of rat lungs from non-heart-beating donors improves posttransplant function

Lungs from non-heart-beating donors (NHBDs) would enhance the donor pool. Ex vivo perfusion and ventilation of NHBD lungs allows functional assessment and treatment. Ventilation of rat NHBD lungs with nitric oxide (NO) during ischemia, ex vivo perfusion and after transplant reduced ischemia-reperfusion injury (IRI) and improved lung function posttransplant. One hour after death, Sprague-Dawley rats were ventilated for another hour with either 60% O2 or 60% O2/40 ppm NO. Lungs were then flushed with 20-mL cold Perfadex, stored cold for 1 h, perfused in an ex vivo circuit with Steen solution and warmed to 37 degrees C, ventilated 15 min, perfusion-cooled to 20 degrees C, then flushed with cold Perfadex and stored cold. The left lung was transplanted and ventilated separately. Recipients were sacrificed after 1 h. NO-ventilation was associated with significantly reduced wet:dry weight ratio in the ex vivo circuit, better oxygenation, reduced pulmonary vascular resistance, increased lung tissue levels of cGMP, maintained endothelial NOS eNOS, and reduced increases in tumor necrosis factor alpha (TNF-alpha) and inducible nitric oxide synthase (iNOS). NO-ventilation had no effect on MAP kinases or NF-kappaB activation. NO administration to NHBDs before and after lung retrieval may improve function of lungs from NHBDs.

Impact of human donor lung gene expression profiles on survival after lung transplantation: a case-control study

Primary graft dysfunction (PGD) continues to be a major cause of early death after lung transplantation. Moreover, there remains a lack of accurate pretransplant molecular markers for predicting PGD. To identify distinctive donor lung gene expression signatures associated with PGD, we profiled human donor lungs using microarray technology prior to implantation. The genomic profiles of 10 donor lung samples from patients who subsequently developed clinically defined severe PGD were compared with 16 case-matched donor lung samples from those who had a favorable outcome without PGD (development set, n = 26). Selected PCR validated predictive genes were tested by quantitative reverse transcription-polymerase chain reaction in an independent test set (n = 81). Our microarray analyses of the development set identified four significantly upregulated genes (ATP11B, FGFR2, EGLN1 and MCPH1) in the PGD samples. These genes were also significantly upregulated in donor samples of the test set of patients with poor outcomes when compared to those of patients with good outcomes after lung transplantation. This type of biological donor lung assessment shows significant promise for development of a more accurate diagnostic strategy to assess donor lungs prior to implantation.

Alterations in the proteome of pulmonary alveolar type II cells in the rat after hepatic ischemia-reperfusion

OBJECTIVE

Hepatic ischemia-reperfusion can be associated with acute lung injury. Alveolar epithelial type II cells (ATII) play an important role in maintaining lung homeostasis in acute lung injury.

DESIGN

To study potentially new mechanisms of hepatic ischemia-reperfusion-induced lung injury, we examined how liver ischemia-reperfusion altered the proteome of ATII.

SETTING

Laboratory investigation.

SUBJECTS

Spontaneously breathing male Zucker rats.

INTERVENTIONS

Rats were anesthetized with isoflurane. The vascular supply to the left and medial lobe of the liver was clamped for 75 mins and then reperfused. Sham-operated rats were used as controls. After 8 hrs, rats were killed.

MEASUREMENTS AND MAIN RESULTS

Bronchoalveolar lavage and differential cell counts were performed, and tumor necrosis factor-alpha and cytokine-induced neutrophil chemotactic factor-1 in plasma were determined by enzyme-linked immunosorbent assay. ATII were isolated, lysed, tryptically digested, and labeled using isobaric tags (iTRAQ). The samples were fractionated by cation exchange chromatography, separated by high-performance liquid-chromatography, and identified using electrospray tandem mass spectrometry. Spectra were interrogated and quantified using ProteinProspector. Quantitative proteomics provided quantitative data for 94 and 97 proteins in the two groups. Significant changes in ATII protein content included 30% to 40% increases in adenosine triphosphate synthases, adenosine triphosphate/adenosine diphosphate translocase, and catalase (all p < .001). Following liver ischemia-reperfusion, there was also a significant increase in the percentage of neutrophils in bronchoalveolar lavage (48% +/- 26%) compared with sham-operated controls (5% +/- 3%) (p < .01), and plasma tumor necrosis factor-alpha levels were also significantly increased.

CONCLUSIONS

The proteins identified by quantitative proteomics indicated significant changes in moderators of cell metabolism and host defense in ATII. These findings provide new insights into possible mechanisms responsible for hepatic ischemia-reperfusion-related acute lung injury and suggest that ATII cells in the lung sense and respond to hepatic injury.

Expression profiling of human donor lungs to understand primary graft dysfunction after lung transplantation

Lung transplantation is the treatment of choice for end-stage pulmonary diseases. A limited donor supply has resulted in 4,000 patients on the waiting list. Currently, 10-20% of donor organs offered for transplantation are deemed suitable under the selection criteria, of which 15-25% fail due to primary graft dysfunction (PGD). This has spawned efforts to re-examine the current selection criteria as well as search for alternative donor lungs selection criteria. In this study, we attempt to further our understanding of PGD by observing the changes in gene expression across donor lungs that developed PGD versus those that did not. From our analysis, we have obtained differentially expressed transcripts that were involved in signaling, apoptosis and stress-activated pathways. Results also indicate that metallothionein 3 was over expressed in lungs that didn't develop PGD. This is the first such attempt to perform expression profiling of actual human lungs used for transplantation, for the identification of a molecular signature for PGD.

Techniques for experimental heterotopic and orthotopic tracheal transplantations — When to use which model?

BACKGROUND

Different animal models have been developed to study the pathogenesis and treatment of obliterative airway disease (OAD). Here we describe the techniques of heterotopic and orthotopic tracheal transplantations in the rat, comparing the kinetics of systemic host immune response and of histopathologic OAD development.

METHODS

Heterotopic and orthotopic tracheal transplantations were performed in both allogeneic (Brown Norway-to-Lewis) and syngeneic (Lewis-to-Lewis) models. Grafts were harvested after 7, 30, and 60 days post-transplant for histologic evaluation and analysis of host cellular and humoral response.

RESULTS

Syngeneic tracheal grafts did not develop luminal obliteration and were morphologically indistinguishable from native tracheas. In heterotopic allografts, airway epithelium was rapidly destroyed and OAD progressed with complete luminal occlusion by 30 days. Orthotopic allografts showed enhanced early infiltration (1298+/-45 vs. 674+/-75 cells/high power field, p<0.001) with concomitant greater day 7 luminal narrowing (45+/-6% vs. 14+/-3%, p<0.001). In this model, donor-type BN epithelium (62+/-17%, 21+/-19%, and 1+/-1% on days 7, 30, and 60) was gradually replaced by recipient-type epithelial cells (2+/-4%, 70+/-22%, and 98+/-2%). OAD developed with circular orientation of cells and connective tissue fibers to 45+/-6% obliteration by day 60. Cellular host response, as determined by IFN-gamma-ELISPOT assay (548+/-132 vs. 402+/-197 spots, p=0.046) and anti-donor alloreactive IgM antibody production (2827+/-148 vs. 1565+/-393 mean channel fluorescence, p<0.001) were significantly stronger in rats bearing orthotopic vs. heterotopic allografts.

CONCLUSIONS

The orthotopic tracheal transplantation model may be more representative of OAD found in human lung transplant recipients and we therefore encourage the wider use of this model.

A mouse model of orthotopic vascularized aerated lung transplantation

Outcomes after lung transplantation are markedly inferior to those after other solid organ transplants. A better understanding of cellular and molecular mechanisms contributing to lung graft injury will be critical to improve outcomes. Advances in this field have been hampered by the lack of a mouse model of lung transplantation. Here, we report a mouse model of vascularized aerated single lung transplantation utilizing cuff techniques. We show that syngeneic grafts have normal histological appearance with minimal infiltration of T lymphocytes. Allogeneic grafts show acute cellular rejection with infiltration of T lymphocytes and recipient-type antigen presenting cells. Our data show that we have developed a physiological model of lung transplantation in the mouse, which provides ample opportunity for the study of nonimmune and immune mechanisms that contribute to lung allograft injury.

Hypothermic preservation of lung allograft inhibits cytokine-induced chemoattractant-1, endothelial leucocyte adhesion molecule, vascular cell adhesion molecule-1 and intracellular adhesion molecule-1 expression

Organ dysfunction is a major clinical problem after lung transplantation. Prolonged cold ischaemia and reperfusion injury are believed to play a central role in this complication. The influence of cold preservation on subsequent warm reperfusion was studied in an isolated, ventilated and perfused rat lung. Rat lungs were flushed with cold Perfadex-solution and stored at 4 degrees C for different time periods. Thereafter lungs were perfused and ventilated for up to 3 h. Physiological parameters, production of inflammatory mediators and leucocyte infiltration were measured before and after perfusion. Lungs subjected to a cold ischaemia time of up to 6 h showed stable physiological conditions when perfused for 3 h. However, cold-ischaemia time beyond 6 h resulted in profound tissue oedema, thereby impairing ventilation and perfusion. Warm reperfusion and ventilation per se induced a strong inflammatory response, as demonstrated by a significant up-regulation of chemokines and adhesion molecules (cytokine-induced chemoattractant-1, intracellular adhesion molecule and endothelial leucocyte adhesion molecule), accompanied by enhanced leucocyte infiltration. Although the up-regulation of inflammatory mediators was blunted in lungs that were subjected to cold ischaemia, this did not influence leucocyte infiltration. In fact, cold ischaemia time correlated with leucocyte sequestration. Although cold preservation inhibits the expression of inflammatory mediators it does not affect leucocyte sequestration during warm reperfusion. Cold preservation might cause impairment of the endothelial barrier function, as evidenced by tissue oedema and profound leucocyte infiltration.

Microarrays: a monitoring tool for transplant patients?

Microarray technology holds a distinct advantage over traditional genomic methods, with the unique capability to rapidly generate multiple global gene expression profiles in parallel. This technology is quickly gaining widespread use in many areas of science and medicine because it can be easily adapted to study many experimental questions, particularly relating to disease heterogeneity. Microarray experiments have begun to advance our understanding of the underlying molecular processes in solid organ transplantation; however, several obstacles must be overcome before this technology is ready for application in the clinical setting. This article will review the current applications of microarray technology in the field of transplantation, and discuss the potential impact of this technology on monitoring of solid organ transplant recipients.

Wide gene expression profiling of ischemia-reperfusion injury in human liver transplantation

Ischemia-reperfusion injury (IRI) causes up to 10% of early liver failures in humans and can lead to a higher incidence of acute and chronic rejection. So far, very few studies have investigated wide gene expression profiles associated with the IRI process. The discovery of novel genes activated by IRI might lead to the identification of potential target genes for the prevention or treatment of the injury. In our study, we compared gene expression levels in reperfused livers (RL group) vs. the basal values before retrieval from the donor (basal liver [BL] group) using oligonucleotide array technology. We examined 10 biopsies from 5 livers, analyzing approximately 33,000 genes represented on the Affymetrix HG-U133APlus 2.0 oligonucleotide arrays (Affymetrix, Santa Clara, CA). About 13,000 individual genes were considered expressed in at least 1 condition. A total of 795 genes whose expression is significantly modified by ischemia-reperfusion in human liver transplantation were identified in this study. Some of them are likely to be completely activated by IRI, as they are not expressed in basal livers. The supervised gene expression analysis revealed that at least 12% of the genes involved in the apoptotic process, 12.5% of the genes involved in inflammatory processes, and 22.5% of the genes encoding for heat shock proteins are differentially expressed in RL samples vs. BL samples. Furthermore, IRI induces the upregulation of some genes' coding for adhesion molecules and integrins. In conclusion, we have identified a relevant amount of early genes regulated in the human liver after 7-9 hours of cold ischemia and 2 hours from reperfusion, many of them not having been described before in this process. Their analyses may help us to better understand the pathophysiology of IRI and to characterize potential target genes for the prevention or treatment of the liver injury in order to increase the number of patients that successfully undergo transplantation.

Gene expression profiling of target genes in ventilator-induced lung injury

In the lungs, high-pressure mechanical ventilation induces an inflammatory response similar to that observed in acute respiratory distress syndrome. To further characterize these responses and to compare them with classical inflammatory pathways, we performed gene expression profiling analysis of 20,000 mouse genes in isolated blood-free (to exclude genes from sequestered leukocytes) perfused mouse lungs exposed to low-pressure ventilation (10 cmH2O), high-pressure ventilation (25 cmH2O, overventilation), and LPS treatment. A large number of inflammatory and apoptotic genes were increased by both overventilation and LPS. However, certain growth factor-related genes, as well as genes related to development, cellular communication, and the cytoskeleton, were only regulated by overventilation. We validated and confirmed increased mRNA expression pattern of five genes (amphiregulin, gravin, Nur77, Cyr61, interleukin-11) by real-time PCR; furthermore, we confirmed increased protein expression of amphiregulin by immunohistochemistry and immunoblotting assays. These genes represent novel candidate genes in ventilator-induced lung injury.