Adenovirus-mediated interleukin-10 gene transfer inhibits post-transplant fibrous airway obliteration in an animal model of bronchiolitis obliterans

Creating superior lungs for transplantation with next-generation gene therapy during ex vivo lung perfusion

Engineering donor organs to better tolerate the harmful non-immunological and immunological responses inherently related to solid organ transplantation would improve transplant outcomes. Our enhanced knowledge of ischemia-reperfusion injury, alloimmune responses and pathological fibroproliferation after organ transplantation, and the advanced toolkit available for gene therapies, have brought this goal closer to clinical reality. Ex vivo organ perfusion has evolved rapidly especially in the field of lung transplantation, where clinicians routinely use ex vivo lung perfusion (EVLP) to confirm the quality of marginal donor lungs before transplantation, enabling safe transplantation of organs originally considered unusable. EVLP would also be an attractive platform to deliver gene therapies, as treatments could be administered to an isolated organ before transplantation, thereby providing a window for sophisticated organ engineering while minimizing off-target effects to the recipient. Here, we review the status of lung transplant first-generation gene therapies that focus on inducing transgene expression in the target cells. We also highlight recent advances in next-generation gene therapies, that enable gene editing and epigenetic engineering, that could be used to permanently change the donor organ genome and to induce widespread transcriptional gene expression modulation in the donor lung. In a future vision, dedicated organ repair and engineering centers will use gene editing and epigenetic engineering, to not only increase the donor organ pool, but to create superior organs that will function better and longer in the recipient.

Gene Therapy: Will the Promise of Optimizing Lung Allografts Become Reality?

Lung transplantation is the definitive therapy for patients living with end-stage lung disease. Despite significant progress made in the field, graft survival remains the lowest of all solid organ transplants. Additionally, the lung has among the lowest of organ utilization rates-among eligible donors, only 22% of lungs from multi-organ donors were transplanted in 2019. Novel strategies are needed to rehabilitate marginal organs and improve graft survival. Gene therapy is one promising strategy in optimizing donor allografts. Over-expression or inhibition of specific genes can be achieved to target various pathways of graft injury, including ischemic-reperfusion injuries, humoral or cellular rejection, and chronic lung allograft dysfunction. Experiments in animal models have historically utilized adenovirus-based vectors and the majority of literature in lung transplantation has focused on overexpression of IL-10. Although several strategies were shown to prevent rejection and prolong graft survival in preclinical models, none have led to clinical translation. The past decade has seen a renaissance in the field of gene therapy and two AAV-based in vivo gene therapies are now FDA-approved for clinical use. Concurrently, normothermic ex vivo machine perfusion technology has emerged as an alternative to traditional static cold storage. This preservation method keeps organs physiologically active during storage and thus potentially offers a platform for gene therapy. This review will explore the advantages and disadvantages of various gene therapy modalities, review various candidate genes implicated in various stages of allograft injury and summarize the recent efforts in optimizing donor lungs using gene therapy.

T Helper Cell Subsets in Experimental Lung Allograft Rejection

BACKGROUND

Human lung transplantation has evolved to an established treatment for pulmonary diseases in their end stages; however, the long-term outcome is worse when compared to all other solid transplantable organs. The major reason for this unfavorable outcome is rejection, either in its acute or chronic form, the latter termed as chronic lung allograft dysfunction.

METHODS

A systematic review search was performed.

RESULTS

One of the most important immune cells responsible for rejection are T cells. Beside alloreactive CD8+ T cells, CD4+ T cells play a key role during the evolvement of allograft rejection. Certain subsets of these allograft CD4+ T cells have been identified which have been shown to exert either transplant-protective or transplant-injuring properties. These effects have been proven in various experimental models, mainly in rats and mice, and allowed for the gain of important insights into these proinflammatory and anti-inflammatory characteristics including their targetability: while the subsets Th1, Th17, Th22, and Tfh cells have been shown to act in a rather proinflammatory way, Tregs, Th2, and Th9 subsets exert anti-inflammatory effects. Chronic airway obstruction is mainly induced by IL17 as shown across models.

CONCLUSIONS

This review shall summarize and provide an overview of the current evidence about the role and effects of proinflammatory and anti-inflammatory CD4-+ T helper cell subsets during lung allograft rejection in experimental rodent models.

Reepithelialization of Orthotopic Tracheal Allografts Prevents Rejection after Withdrawal of Immunosuppression

Prior work has demonstrated that immunosuppressed orthotopic tracheal allografts undergo progressive reepithelialization over a 48-day period with recipient-derived tracheal epithelium. We hypothesized that reepithelialization of tracheal allografts would prevent rejection after withdrawal of immunosuppression. BALB/c murine tracheal grafts were transplanted orthotopically into either syngeneic or allogeneic C57/BL6 recipients. The recipients were either not immunosuppressed, immunosuppressed with cyclosporine A (10 mg/kg per day) continuously, or immunosuppressed for 48 days and then withdrawn from immunosuppression. The grafts were assessed for acute and chronic rejection 10 days and 50 days after immunosuppression withdrawal. The immunosuppressed allograft recipients maintained a ciliated epithelium acutely and chronically after immunosuppression withdrawal. Ten days after immunosuppression withdrawal, there was a mild cellular infiltrate, which resolved 50 days after withdrawal. Electron microscopy, lymphocyte subpopulation assays, and lamina propria analysis demonstrated that immunosuppression withdrawal did not result in tracheal allograft rejection. In vitro and in vivo assessments did not demonstrate evidence of systemic or local immune tolerance. We conclude that reepithelialization of orthotopic tracheal allografts with recipient-derived mucosa prevents rejection of allograft segments. Tracheal transplantation may require only transient immunosuppression, which can be withdrawn after tracheal reepithelialization.

A new heterotopic transplant animal model of intestinal fibrosis

BACKGROUND

Severe mucosal tissue damage requiring efficient wound healing is a main feature of inflammatory bowel disease but excessive tissue repair promotes fibrosis. The clinical investigation of fibrosis is confined to the limited amount of biological material available from patients. This makes the establishment of a new animal model, a highly desirable goal. We investigated whether intestinal fibrosis occurs after heterotopic transplantation of small bowel resections in rats.

METHODS

Donor (Brown Norway or Lewis rats) small bowel resections were transplanted subcutaneously into the neck of recipients (Lewis rats). Grafts were explanted 2, 7, 14, and 21 days after transplantation.

RESULTS

Heterotopic intestinal transplants remained viable for 21 days. Rapid loss of crypt structures at day 2 after intestinal transplantation was followed by lymphocyte infiltration and obliteration of the intestinal lumen by fibrous tissue at day 21. Loss of the intestinal epithelium was confirmed by the lack of cytokeratin staining in immunohistochemistry. Collagen expression was increased with time after transplantation as confirmed by real-time PCRs, Elastica van Gieson, and Sirius Red staining. Lumen obliteration was connected with increased expression of potent mediators of fibrosis such as α5β6 integrin, interleukin (IL)-13, and transforming growth factor β. Myofibroblast phenotype was demonstrated by the presence of both α-smooth muscle actin and vimentin in the obliterated lumen.

CONCLUSIONS

We established a method for heterotopic transplantation of small bowel resections. A variety of histologic and molecular features of fibrosis were observed in the heterotopic intestinal grafts which suggests, that this new in vivo model will be instrumental in studying pathogenesis and treatment of intestinal fibrosis.

Cryopreservation of the tracheal grafts: Review and perspective

Transplantation of the trachea may become the preferred method for the reconstruction of extensive tracheal defects, however, several unresolved problems must be addressed, such as immunosuppression, preservation and donor shortage. In this manuscript, the cryopreservation of tracheal grafts is reviewed, which potentially is associated with a lessened immunological response. Cryopreservation may be used clinically for long-term preservation and may solve the donor shortage. It is very important to confirm the immunomodulatory effect of cryopreservation on tracheal allografts in order to expand the potential clinical application of tracheal transplantation in the future. The cartilage as well as the epithelium and lamina propria serve as targets for rejection. However, the effect of cryopreservation on chondrocytes could be associated with reduced allogenicity of the trachea. The long-term cryopreservation of cartilage must be investigated in basic research models of chondrocyte viability. Growth of cryopreserved tracheal allografts is less well understood. Further studies are needed to elucidate the mechanism of synergistic effects of both cryopreservation and adequate immunosuppression for tracheal xenografts.

Transbronchial human interleukin-10 gene transfer reduces acute inflammation associated with allograft rejection and intragraft interleukin-2 and tumor necrosis factor-alpha gene expression in a rat model of lung transplantation

BACKGROUND

The ability to express genes with potential immunoregulatory capacity could reduce allograft rejection (AR). This study examined the effect of ex vivo lipid-mediated transbronchial human interleukin-10 (hIL-10) gene transfer on AR and the intragraft cytokine profile in a rat model of lung transplantation.

METHODS

Left single lung transplants were performed between a highly histoincompatible combination of inbred rats. The donor left lung was extracted and intrabronchially instilled with a plasmid encoding hIL-10 (IL-10 group) or Escherichia coli beta-galactosidase (control group), mixed with a cationic lipid. At 3 and 6 days after transplantation, the degree of AR was graded histologically (stage 1-4) and several pathologic categories of inflammation were scored on a scale of 0 to 4 according to the percentage of involvement. Intragraft cytokine profile was examined by real-time reverse transcription polymerase chain reaction.

RESULTS

The stage of AR (3.1 +/- 0.4 vs 3.8 +/- 0.4) and the pathologic scores for edema (2.3 +/- 0.8 vs 3.2 +/- 0.4), intraalveolar hemorrhage (0.3 +/- 0.5 vs 2.2 +/- 0.8), and necrosis (0.3 +/- 0.5 vs 1.2 +/- 0.4) in the IL-10 group were significantly decreased compared with the control group at Day 6. IL-2 and tumor necrosis factor-alpha messenger RNA expression levels on Day 3 were significantly decreased in the IL-10 group.

CONCLUSIONS

Ex vivo lipid-mediated transbronchial hIL-10 gene transfer attenuated acute inflammation associated with AR, which was related to decreased levels of proinflammatory cytokine gene expression in a rat model of lung transplantation.

Animal models for bronchiolitis obliterans syndrome following human lung transplantation

Lung transplantation is the only viable treatment option that can improve survival and enhance the quality of life of patients with end-stage lung diseases such as emphysema, cystic fibrosis, idiopathic pulmonary fibrosis, and primary pulmonary hypertension. However, the long-term survival of lung allografts is still limited by the development of bronchiolitis obliterans syndrome (BOS), an irreversible condition unresponsive to therapy. BOS is the most significant cause of long-term morbidity and mortality after lung transplantation. Over the past decade, several animal models have been developed to investigate BOS. These are valuable to elucidate the immunologic and pathologic mechanisms that lead to BOS and to test treatment options for BOS. In this review, we discuss the advantages and disadvantages of different animal models and highlight work that has been done with each model.

Perfluorochemical (PFC) liquid enhances recombinant adenovirus vector-mediated viral interleukin-10 (AdvIL-10) expression in rodent lung

Adenovirus and cationic liposome mediated transfer of Interleukin-10 (IL-10), a potent anti-inflammatory cytokine, has been shown to decrease pro-inflammatory cytokine levels and overall lung inflammation in models of lung transplantation and injury. Limitations to current approaches of IL-10 gene therapy include poor vector delivery methods and pro-inflammatory properties of human IL-10 under certain conditions. We hypothesize that using perfluorochemical (PFC) liquid to deliver the highly homologous viral IL-10 (vIL-10), which is predominantly anti-inflammatory with minimal pro-inflammatory activities, can potentially be a more effective strategy to combat inflammatory lung diseases. In this study, we compare the use of PFC liquid versus aerosolized method to deliver adenovirus encoding the vIL-10 gene (AdvIL-10) in C57Bl6 mice. Detectable vIL-10 levels were measured from bronchoalveolar lavage fluid and lung homogenates at one, four, ten and thirty days after AdvIL-10. Furthermore, we determined if use of PFC liquid could allow for the use of a lower dose of AdvIL-10 by comparing the levels of detectable vIL-10 at different doses of AdvIL-10 delivered +/- PFC liquid. Results showed that PFC liquid enhanced detectable vIL-10 by up to ten fold and that PFC liquid allowed the use of ten-fold less vector. PFC liquid increased detectable vIL-10 in lung homogenates at all time points; however, the increase in detectable vIL-10 in BAL fluid peaked at four days and was no longer evident by thirty days after intratracheal instillation. In summary, this is the first report utilizing PFC liquid to enhance the delivery of a potentially therapeutic molecule, vIL-10. We believe this strategy can be used to perform future studies on the use of the predominantly anti-inflammatory vIL-10 to treat inflammatory lung diseases.

Impact of TGFβ1 Gene Polymorphisms on Acute and Chronic Rejection in Pediatric Heart Transplant Allografts

BACKGROUND

The aim of this study was to assess the influence of IL-10 and TGFbeta1 gene polymorphisms on the development of acute rejection and coronary disease in pediatric heart transplant recipients.

METHODS

Patients were classified as either Rejectors or Nonrejectors. Coronary artery disease (CAD) was diagnosed by angiography or on macroscopic examination. Genotyping PCR-SSP were performed for IL-10 and TGFbeta1 (codon 10 and 25) in 111 patients. Thirty-nine were Rejectors and 31 developed CAD.

RESULTS

The proportion of IL-10 low-producers was higher in Rejectors than in Nonrejectors (respectively 46% versus 22%, P=0.009). IL-10 gene polymorphism was not associated with CAD. TGFbeta1-codon10-25 high-producers were 92.3% in Rejectors and 75% in Nonrejectors (P=0.026), 93.5% in patients with CAD and 76.2% in patients free from CAD (P=0.037). TGFbeta1-codon25 high-production separately analyzed correlated with CAD (31/31 high-producers in CAD=100% versus 69/80 in noCAD patients=86.2%, P=0.03). TGFbeta1-codon10 gene polymorphisms were not associated with CAD.

CONCLUSION

IL-10 low-producers have an increased risk of acute rejection. High-expressors of TGFbeta1-codon10-25 have an increased risk of acute rejection and CAD, while TGFbeta1-codon25 high-production is associated with coronary disease. Genetic polymorphism may reveal patients at high-risk in whom therapies and monitoring should be adjusted.

Pulmonary dendritic cells

Dendritic cells (DCs) are leukocytes that are emerging as chief orchestrators of immune responses. The crucial task of DCs is the continuous surveillance of antigen-exposed sites throughout the body, and their unique responsibility is to decide whether to present sampled antigen in an immunogenic or tolerogenic way. Any misstep can either lead to a flawed immune defense or to allergy, even autoimmunity. It comes as no surprise that the lungs become increasingly the subject of DC-related investigations, as they represent a vast interface between the body and the outer world. This constitutes an enormous challenge for the immune system: "firing up" immune responses inappropriately could have devastating results for the fragile gas exchange structures. Evidence accumulates that DCs play a pivotal role in maintaining the delicate balance between tolerance and active immune response in our respiratory system. The exponentially growing body of DC-related publications is a big challenge. This article aims to provide researchers and clinicians with an up-to-date view on DC biology and its relevance to pulmonary medicine. A developing trend in the field of DCs is the shift from fundamental immunologic research toward exciting clinical insights and applications. For the pulmonary clinician, this heralds the dawn of promising therapies in various domains such as infections, allergy, and cancer.

A novel model for post-transplant obliterative airway disease reveals angiogenesis from the pulmonary circulation

We present a novel animal model for post-transplant obliterative airway disease in which the donor trachea is implanted into the recipient's lung parenchyma. Although this procedure is technically more challenging than the heterotopic model of implantation into a subcutaneous pouch, it has several important advantages some of which are the appropriate local environment and the possibility of local immunosuppressive therapy after transtracheal gene, cell or drug delivery. This model has revealed new insights into angiogenic potential of the pulmonary circulation.

Adenoviral transfer of human interleukin-10 gene in lethal pancreatitis

AIM: To evaluate the therapeutic effect of adenoviral-vector-delivered human interleukin-10 (hIL-10) gene on severe acute pancreatitis (SAP) rats.

METHODS: Healthy Sprague-Dawley (SD) rats were intraperitoneally injected with adenoviral IL-10 gene (AdvhIL-10), empty vector (Adv0) or PBS solution. Blood, liver, pancreas and lung were harvested on the second day to examine hIL-10 level by ELISA and serum amylase by enzymatic assay. A SAP model was induced by retrograde injection of sodium taurocholate through pancreatic duct. SAP rats were then administered with AdvhIL-10, Adv0 and PBS solution by a single intraperitoneal injection 20 min after SAP induction. In addition to serum amylase assay, levels of hIL-10 and tumor necrosis factor-α (TNF-α ) were detected by RT-PCR, ELISA and histological study. The mortality rate was studied and analyzed by Kaplan–Meier and log rank analysis.

RESULTS: The levels of hIL-10 in the pancreas, liver and lung of healthy rats increased significantly after AdvhIL-10 injection (1.42 ng/g in liver, 0.91 ng/g in pancreas); while there was no significant change of hIL-10 in the other two control groups. The concentration of hIL-10 was increased significantly in the SAP rats after AdvhIL-10 injection (1.68 ng/g in liver, 1.12 ng/g in pancreas) compared to the other two SAP groups with blank vector or PBS treatment (P < 0.05). The serum amylase levels remained normal in the AdvhIL-10 transfected healthy rats. However, the serum amylase level was significantly elevated in the other two control SAP rats. In contrast, serum amylase was down-regulated in the AdvhIL-10 treated SAP groups. The TNF-α expression in the AdvhIL-10 treated SAP rats was significantly lower compared to the other two control SAP groups. The pathohistological changes in the AdvhIL-10 treated group were better than those in the other two control groups. Furthermore, the mortality of the AdvhIL-10 treated group was significantly reduced compared to the other two control groups (P < 0.05).

CONCLUSION: Adenoviral hIL-10 gene can significantly attenuate the severity of SAP rats, and can be used in the treatment of acute inflammation process.

Bronchiolitis obliterans in chronic graft-versus-host disease: analysis of risk factors and treatment outcomes

Bronchiolitis obliterans (BrOb), a late complication of bone marrow transplantation (BMT), is associated with chronic graft-versus-host disease (GVHD) and is frequently fatal. To identify the risk factors associated with BrOb, the factors affecting survival, treatment outcomes, and causes of death of patients with BrOb, we retrospectively analyzed 2859 BMT recipients. No cases of BrOb occurred among 1070 autologous BMT recipients. Among 1789 allogeneic BMT recipients, we identified 47 patients with BrOb. In multivariate analysis, older recipients or donors and acute GVHD were significantly associated with the development of BrOb. Among patients with BrOb, 5-year survival from the time of transplantation was only 10%, versus 40% among allogeneic BMT recipients without BrOb. The clinical course of BrOb had a significant effect on survival: 79% survived 5 years from the time of BrOb diagnosis if BrOb improved versus 13% if there was no improvement after the first-line therapy. Predictors of response included older donors and recipients, a previous diagnosis of chronic GVHD, and diagnosis of BrOb 6 months after transplantation; each of these significantly increased the likelihood of a favorable response to treatment. BrOb had high mortality rate of 55%, and pulmonary failure was the leading cause of death. More effective BrOb therapy is needed, especially for patients with unfavorable presentation.

Indirect Minor Histocompatibility Antigen Presentation by Allograft Recipient Cells in the Draining Lymph Node Leads to the Activation and Clonal Expansion of CD4+T Cells That Cause Obliterative Airways Disease

Ag recognition by OVA-reactive OT-II (I-Ab restricted) and DO11.10 (I-Ad restricted) TCR-Tg CD4+ T cells after heterotopic transplantation of OVA transgene-expressing tracheal grafts was examined as a model of minor histocompatibility Ag (mHAg)-induced chronic allograft rejection. In response to airway allotransplantation with grafts expressing the OVA transgene, these TCR-Tg CD4+ T cells expressed the activation markers CD69 and CD44, demonstrated evidence of blastogenesis, underwent multiple rounds of cell division leading to their clonal expansion in the draining lymph node, and proceeded to differentiate to a effector/memory T cell phenotype based on a reduction in the expression of CD45RB. These mHAg-specific TCR-Tg CD4+ T cells responded equally well to fully MHC-mismatched tracheas and to class II-deficient allografts, demonstrating that donor mHAg recognition by recipient CD4+ T cells does not rely on Ag presentation by donor-derived APC. The activation of mHAg-specific TCR-Tg CD4+ T cells after their adoptive transfer into recipient mice given MHC-matched, but mHAg-disparate, airway allografts was associated with their movement into the allograft and the near uniform destruction of the transplanted airway tissue secondary to the development of obliterative airways disease. These results demonstrate that an activation of mHAg-reactive CD4+ T cells in the draining lymph node by recipient APC that indirectly express graft mHAg-derived peptide/class II MHC complexes precedes responder T cell proliferation and differentiation, and leads to the eventual migration of these alloreactive T cells to the transplanted airway tissue and the promotion of chronic graft rejection.

Role of CXCL9/CXCR3 chemokine biology during pathogenesis of acute lung allograft rejection

Acute allograft rejection is a major complication postlung transplantation and is the main risk factor for the development of bronchiolitis obliterans syndrome. Acute rejection is characterized by intragraft infiltration of activated mononuclear cells. The ELR-negative CXC chemokines CXCL9, CXCL10, and CXCL11) are potent chemoattractants for mononuclear cells and act through their shared receptor, CXCR3. Elevated levels of these chemokines in bronchoalveolar lavage fluid have been associated with human acute lung allograft rejection. This led to the hypothesis that the expression of these chemokines during an allogeneic response promotes the recruitment of mononuclear cells, leading to acute lung allograft rejection. We performed studies in a rat orthotopic lung transplantation model of acute rejection, and demonstrated increased expression of CXCL9 and CXCL10 paralleling the recruitment of mononuclear cells and cells expressing CXCR3 to the allograft. However, CXCL9 levels were 15-fold greater than CXCL10 during maximal rejection. Inhibition of CXCL9 decreased intragraft recruitment of mononuclear cells and cellular expression of CXCR3, resulting in lower acute lung allograft rejection scores. Furthermore, the combination of low dose cyclosporin A with anti-CXCL9 therapy had more profound effects on intragraft leukocyte infiltration and in reducing acute allograft rejection scores. This supports the notion that CXCL9 interaction with cells expressing CXCR3 has an important role in the recruitment of mononuclear cells, a pivotal event in the pathogenesis of acute lung allograft rejection.

Optimal modes and targets of gene therapy in transplantation

Genetic modification strategies have the potential to improve outcome following cell/organ transplantation. A unique opportunity in transplantation is that gene therapies need not be restricted to in vivo approaches and that ex vivo genetic modification of cell and/or organs can be of value. Improvements in vector design, production, and delivery should enhance transfection efficiency and optimize gene expression. Herein, we discuss potential modes of gene therapy, focusing on viral, liposome, or naked DNA-based systems for gene delivery. We suggest gene therapy targets taking into consideration the essential constituents of anti-allograft repertory. In addition to strategies that may have salutary effects in mitigating the threat of acute rejection, we suggest genetic strategies for minimizing ischemia/reperfusion injury as well as for the perennial problem of progressive functional loss of the transplanted organ. Data from pre-clinical transplant models support the idea that gene therapy may improve allograft function and survival. We are optimistic that gene therapy will be of clinical value in the near future in the management of recipients of allografts; we believe that genetic strategies would be essential for successful breaching of the formidable challenge of xenotransplantation.

Graft protective effects of heme oxygenase 1 in mouse tracheal transplant-related obliterative bronchiolitis

BACKGROUND

Heme oxygenase (HO)-1, long believed to be a cytoprotective protein, has recently been identified as a graft survival gene. This study evaluates the role of HO-1 in a murine heterotopic tracheal allograft model for obliterative bronchiolitis.

METHODS

Mice with deficient or experimentally enhanced HO-1 expression underwent subcutaneous implantation of murine tracheal isografts and allografts. Grafts were excised after 9, 16, or 21 days and evaluated by histologic examination, immunohistochemistry for HO-1 and interleukin (IL)-10 proteins, and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling. To evaluate the relationships between IL-10 and HO-1, the effects of modulation of HO-1 expression on IL-10 expression were evaluated and HO-1 expression was examined in tracheal transplants from IL-10 null mice.

RESULTS

Isografts demonstrated normal histology with minimal HO-1 staining, whereas allografts showed features of human airway rejection (loss of respiratory epithelium, luminal granulation tissue, lymphocytic tracheitis) with increased HO-1 staining in macrophages and mesenchymal cells. HO-1-deficient mice demonstrated a more rapid progression of the tracheal allograft injury as compared with control allografts, and this was associated with a decrease in the anti-inflammatory cytokine, IL-10. Tracheal transplants using IL-10-deficient mice also resulted in a more severe injury, and this was accompanied by a decrease in HO-1 staining.

CONCLUSIONS

HO-1 protein expression is increased in murine heterotopic airway rejection, and deficiency of HO-1 accelerates the development of the obliterative bronchiolitis-like lesion. IL-10 protein expression parallels expression of HO-1, suggesting that IL-10 may participate in the genesis of HO-1's effects on the inflammatory processes triggered by allotransplantation.

The kinetics and pattern of tracheal allograft re-epithelialization

Extensive tracheal defects may pose a life-threatening dilemma. Although tracheal transplantation may represent a reconstructive solution, very little is known regarding the immunobiology and behavior of tracheal allografts. The objective of this study was to assess the pattern and kinetics of re-epithelialization of orthotopic tracheal allografts in immunosuppressed recipients. Thirty-eight age-matched mice were randomly assigned to five experimental groups. BALB/c donor tracheal segments were orthotopically transplanted into either syngeneic BALB/c or MHC mismatched allogeneic C57BL/6 recipients with and without immunosuppression. On post-transplant days 7, 14, 28, 48, and 62, animals from each group were evaluated by serial histology, electron microscopy, and serial immunohistochemical analysis for mucosal phenotype, re-epithelialization pattern, and lymphocyte subpopulations. Nonimmunosuppressed recipients underwent recipient-derived basal cell re-epithelialization by Day 48, with differentiation into a sparse population of ciliated columnar epithelium by Day 62, whereas immunosuppressed recipients underwent basal cell re-epithelialization 28 d after transplantation and differentiation into a dense population of ciliated columnar epithelium by Day 48. The re-epithelialization process occurred in a definable pattern that was significantly enhanced with the addition of immunosuppression. Orthotopic tracheal transplants undergo progressive re-epithelialization with recipient-derived basal cells that differentiate into ciliated columnar epithelium in a definable pattern that is enhanced with the addition of immunosuppression.

Airway-directed gene transfer of interleukin-10 using recombinant Sendai virus effectively prevents post-transplant fibrous airway obliteration in mice

Bronchiolitis obliterans (BO) after lung transplantation prevents a satisfactory prognosis, and recent studies suggested that interleukin-10 (IL-10) gene transfer to distant organs could inhibit BO in rodent models. Although delivery of the therapeutic gene to a local airway would be favored to minimize systemic effects, current limitations include lower gene transfer efficiency to airway epithelium. As recombinant Sendai virus (SeV) can produce dramatically efficient gene transfer to airway epithelium, we determined if SeV-mediated IL-10 gene transfer to the local airway would inhibit bronchial fibrous obliteration in murine tracheal allografts. Administration of cyclosporine A (CsA) significantly promoted not only recovery of the injured airway epithelium but also SeV-mediated IL-10 expression (CsA- versus CsA+ =228+/-78 versus 3627+/-1372 pg/graft with 5 x 10(7) pfu), thereby suggesting the requirement of epithelia for efficient gene transfer. Even at the highest expression, no significant leakage of IL-10 was evident in the systemic circulation, and the induction of interferon-gamma was completely diminished on day 7 by IL-10 gene transfer. As a result, luminal loss was significantly prevented in allografts treated with SeV-IL-10 (luminal opening, all control groups: 0% respectively, and SeV-IL-10 5 x 10(7) pfu: 25.7+/-10.5%), an effect that was enhanced by short-term CsA treatment (SeV-IL-10 5 x 10(7) pfu with CsA: 63.7+/-12.7%). We propose that SeV is a useful vector that can target airway epithelium to prevent BO avoiding putative systemic effect.

Regulatory role of IL-10 in experimental obliterative bronchiolitis in rats

Obliterative bronchiolitis (OB) affects over half of all chronic human survivors following lung or heart-lung transplantation. Respiratory epithelial cell injury, peribronchial inflammation, and proliferation of fibrovascular connective tissue causing airway occlusion characterize this lesion. Using a rat model of experimental OB, tracheas and mainstem bronchi from Brown-Norway or Lewis (LEW) rats were transplanted subcutaneously into LEW recipients. At 7 days, airway lumens of allografts showed minimal luminal obstruction but significant respiratory epithelial loss. By 14 days, allografts demonstrated marked peribronchial inflammation, nearly complete loss of respiratory epithelium, and extensive intraluminal proliferation of fibrovascular connective tissue, with a mean 58% reduction in airway cross-sectional diameter. However, isografts showed only limited peribronchial inflammation and no loss of airway lumen. When recipients of allotransplants were treated with anti-IL-10, OB developed more rapidly. As early as 7 days, there was marked histologic evidence of OB and a 43% reduction in mean cross-sectional area. Allograft animals that received 5 microg/day of recombinant IL-10 as a constant infusion on day 14 showed almost complete preservation of respiratory epithelium and only mild peribronchial inflammation with only a 15% reduction in airway cross-sectional area. These findings suggest that endogenous IL-10 plays a regulatory role in the development of experimental OB.

The role of interleukin-10 in lung transplantation

Interleukin-10 (IL-10) is a pleiotropic cytokine and its main function is to limit and terminate inflammatory responses. Lung transplantation is a relatively young clinical field compared to the transplantation of other solid organs and long-term survival is still limited. Complications after lung transplantation include ischemia-reperfusion injury immediately after transplantation, acute rejection and infection within the first year after transplantation and chronic allograft dysfunction in form of bronchiolitis obliterans thereafter. In the setting of lung transplantation two key functions of IL-10 might be of interest: (1) the inhibition of inflammatory immune responses; and (2) the inhibition of T-cell mediated immune responses. In animal models, it has been shown that exogenous IL-10 is able to prevent posttransplant ischemia-reperfusion injury as well as to decrease acute rejection. It was also effective in preventing airway obliteration in an animal model of posttransplant bronchiolitis obliterans. Beneficial effects of IL-10 may be found early and late after lung transplantation. Location of IL-10 expression as well as the timing of administration seems to be important for the desired effects.

Transplant immunosuppression enhances efficiency of adenoviral-mediated gene retransfection: inhibition of interferon-gamma and immunoglobin G

BACKGROUND

Transplant immunosuppression regimen facilitates successful adenovirus-mediated gene transfection and retransfection in the rat lung. Herein, we investigated the effect of this strategy on circulating cytokines and antiadenoviral immunoglobin G antibody.

METHODS

Male Lewis rats were transfected with 1 x 10(9) pfu/mL of E1-deleted Ad5CMVLacZ vector transtracheally. Rats were randomly assigned to receive daily intraperitoneal triple immunosuppression regimen consisting of cyclosporine (15 mg/kg per day), azathioprine (6 mg/kg per day), and methylprednisolone (2.5 mg/kg per day), or normal saline solution. Retransfection was performed 35 days later to all nonimmunosuppressed animals, whereas immunosuppressed rats were further randomized to receive retransfection or phosphate-buffered saline. Animals were sacrificed on days 1, 2, 7, 35, 42, and 49 after the initial transfection. Beta-galactosidase activity was measured on lung homogenates. Interferon-gamma, tumor necrosis factor-alpha, and antiadenoviral immunoglobin G were measured from the serum.

RESULTS

Enhanced and prolonged transgene expression was observed in immunosuppressed animals, especially after retransfection. Concentrations of serum tumor necrosis factor-alpha in both groups were less than 12 pg/mL throughout the study. A significant increase in serum interferon-gamma levels was observed in nonimmunosuppressed animals after retransfection; this was not seen in the immunosuppressed animals. Serum antiadenoviral immunoglobin G titers in both groups were sharply elevated on day 1, and declined to basal levels by day 7, reflecting a preexisting level of humoral immunity to adenovirus. The titer in nonimmunosuppressed rats was significantly increased after retransfection, but remained at very low level in immunosuppressed animals.

CONCLUSIONS

Inhibition of interferon-gamma and antiadenoviral immunoglobin G production by triple immunosuppressants may be part of the mechanisms that lead to enhanced and prolonged transgene expression after retransfection.

Interleukin-1 receptor antagonist as a biomarker for bronchiolitis obliterans syndrome in lung transplant recipients

BACKGROUND

The major limitation to survival after lung transplantation is bronchiolitis obliterative syndrome (BOS). BOS is a chronic inflammatory/immunologic process characterized by fibroproliferation, matrix deposition, and obliteration of the airways. The mechanism(s) that lead to fibro-obliteration of allograft airways have not been fully elucidated. Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring antagonist of the pro-inflammatory cytokine IL-1 and has been associated with a number of fibroproliferative diseases.

METHODS

We determined whether IL-1Ra, as compared to IL-1beta, IL-10, transforming growth factor (TGF)-beta, and tumor necrosis factor (TNF)-alpha, in the bronchoalveolar lavage fluid (BALF) from lung transplant recipients was associated with BOS. BALF was collected from three groups of patients: BOS (n=22), acute rejection (n=33), and healthy transplant recipients (n=30).

RESULTS

IL-1Ra levels were significantly elevated in patients with BOS compared to healthy lung transplant recipients and patients with acute rejection (P<0.001 and P<0.05, respectively). Furthermore, when patients with BOS had their BALF analyzed from their last bronchoscopy before the development of BOS (Future BOS [FBOS] group) (n=20), their levels of IL-1Ra were also significantly elevated compared to healthy lung transplant recipients and patients with acute rejection (P<0.001 and P<0.05, respectively). Importantly, the elevated levels of IL-1Ra in the BOS and FBOS groups were not accompanied by any significant increases in IL-1beta, IL-10, TGF-beta, or TNF-alpha.

CONCLUSION

These findings suggest that elevated levels of IL-1Ra may be attenuating IL-1 bioactivity during the pathogenesis of BOS and creating a local environment that favors fibroproliferation and matrix deposition.

Soluble transforming growth factor-beta type III receptor gene transfection inhibits fibrous airway obliteration in a rat model of Bronchiolitis obliterans

Post-transplant bronchiolitis obliterans (BO) is characterized by fibroproliferation and fibrous obliteration of distal airways in chronically rejected lungs. In this study, using a rat heterotopic allogeneic tracheal transplant model of BO, we evaluated the expression of transforming growth factor-beta (TGFbeta) during the development of airway fibrous obliteration. Immunohistochemical analysis revealed TGFbeta staining in infiltrating mononuclear cells at Days 2 and 7, and in the fibrous tissues until Day 21. Soluble TGFbeta receptor type III (TGFBIIIR), by blocking TGFbeta binding to its membrane receptors, functions as a TGFbeta antagonist. To study the role of TGFbeta in the development of BO, adenoviral-mediated soluble TGFBIIIR gene transfection (5 x 10(9) particles) was performed topically at the site of transplant on Day 5 after transplantation, which leads to inhibition of fibrous airway obliteration. In contrast, empty vector gene delivered through intramuscular injection, or given locally at Days 0 or 10 after tracheal transplantation had no significant effect. These results suggest that TGFbeta expressed in the allografts plays a pivotal role in the pathogenesis of BO. Soluble TGFBIIIR may competitively inhibit TGFbeta activity locally. Adenoviral-mediated soluble TGFBIIIR gene transfection should be further explored as a potential therapeutic modality for BO and other conditions involving chronic fibrosis.

The nasal epithelium as a factory for systemic protein delivery

We have previously shown that recombinant Sendai virus (SeV) produces efficient in vivo airway epithelial gene transfer. The ability to produce therapeutic levels of circulating proteins following noninvasive gene transfer would have widespread clinical application. Here, we compared nose, lung, and skeletal muscle for the ability to produce circulating levels of the secreted mouse antiinflammatory cytokine interleukin-10 (IL10) following SeV-mediated gene transfer. High levels of serum IL10 were obtained from each site with a potency order of lung > nose > muscle for a given viral titer. Serum levels from each site were within the likely required range for anti-inflammatory effects. The combination of a high-efficiency gene transfer agent (SeV) and sites that can be assessed noninvasively (nose or lung) may circumvent several current challenges to gene therapy.

Critical role for the chemokine MCP-1/CCR2 in the pathogenesis of bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome (BOS) is the major limitation to survival after lung transplantation. Acute rejection, its main risk factor, is characterized by perivascular/bronchiolar leukocyte infiltration. BOS is characterized by persistent peribronchiolar leukocyte recruitment leading to airway fibrosis and obliteration. The specific mechanism(s) by which these leukocytes are recruited are unknown. Because MCP-1, acting through its receptor CCR2, is a potent mononuclear cell chemoattractant, we hypothesized that expression of this chemokine during an allogeneic-response promotes persistent recruitment of leukocytes and, ultimately, rejection. We found that elevated levels of biologically active MCP-1 in human bronchial lavage fluid (BALF) were associated with the continuum from acute to chronic allograft rejection. Translational studies in a murine model of BOS demonstrated increased MCP-1 expression paralleling mononuclear cell recruitment and CCR2 expression. Loss of MCP-1/CCR2 signaling, as seen in CCR2(-/-) mice or in WT mice treated with neutralizing antibodies to MCP-1, significantly reduced recruitment of mononuclear phagocytes following tracheal transplantation and led to attenuation of BOS. Lymphocyte infiltration was not reduced under these conditions. We suggest that MCP-1/CCR2 signaling plays an important role in recruitment of mononuclear phagocytes, a pivotal event in the pathogenesis of BOS.

In vivo transtracheal adenovirus-mediated transfer of human interleukin-10 gene to donor lungs ameliorates ischemia-reperfusion injury and improves early posttransplant graft function in the rat

We examined the effect of adenovirus-mediated transtracheal transfer of the human interleukin 10 (hIL-10) gene on lung ischemia-reperfusion (IR) injury, which is the insult due to hypothermic preservation plus graft reperfusion, and posttransplant lung function in Lewis rat lungs. Thirty rats were divided into 6 groups (n = 5). Groups 1 and 4 received 5 x 10(9) PFU of Ad5E1RSVhIL-10, groups 2 and 5 received 5 x 10(9) PFU of Ad5BGL2 ("empty" vector), and groups 3 and 6 received 3% sucrose (diluent). After 24 hr of in vivo transfection, lungs were stored at 4 degrees C (cold ischemic time, CIT) for 6 hr (groups 1-3) or 24 hr (groups 4-6) before transplantation. After 2 hr of reperfusion, lung function was assessed by oxygenation (FIO2, 1.0), airway pressure (AwP), and wet-to-dry (W/D) weight ratios. Rat tumor necrosis factor alpha (rTNF-alpha), interferon gamma (IFN-gamma), IL-10, and hIL-10 were measured in graft tissue and recipient plasma by ELISA and detected by immunohistochemistry (IHC). Partial pressure of oxygen (PaO2) levels in the hIL-10 group (6 hr of CIT) were higher than in empty vector and diluent groups (PaO2, 530 +/- 23 vs. 387 +/- 31 and 439 +/- 27 mmHg, respectively, p < 0.05). IL-10 rats after 24 hr of CIT showed higher PaO2 levels (260 +/- 29 mmHg) than empty vector (96 +/- 24 mmHg) or diluent (133 +/- 10 mmHg) lungs (p < 0.05). AwP and W/D ratios were reduced in hIL10 lungs (p < 0.05) compared with the other groups. rTNF-alpha and INF-gamma were reduced in tissue and plasma in groups 1 and 4 (p < 0.05). rIL-10 was reduced in the tissue of hIL-10 lungs (p < 0.05). IHC showed equal distribution of cytokines in tissue and abundant transgene expression in large and small airway epithelium in hIL-10 lungs.

Prolongation of sheep corneal allograft survival by ex vivo transfer of the gene encoding interleukin-10

BACKGROUND

Modification of a donor cornea by gene therapy ex vivo has potential to modulate irreversible rejection, the major cause of corneal graft failure. Our aim was to transfer the gene encoding mammalian IL-10 to ovine donor corneas and to determine subsequent orthotopic corneal allograft survival in an outbred sheep model.

METHODS

The replicative capacity of ovine corneal endothelium was determined by autoradiography after deliberate injury. A replication-defective adenovirus was used to deliver the lacZ reporter gene to ovine corneas and transfected corneas were organ-cultured in vitro to allow transfection efficiency, duration of reporter gene expression, and toxicity attributable to the vector to be determined. A cDNA encoding full-length ovine IL-10 was cloned into an adenoviral vector that was used to transfect donor corneas ex vivo before transplantation. Orthotopic penetrating corneal transplantation was performed in outbred sheep.

RESULTS

Sheep corneal endothelium was found to be essentially amitotic. Transfection of > 70% corneal endothelial cells was achieved with the viral vector and expression was maintained for 28 days in vitro. IL-10 mRNA was detectable in transfected, organ-cultured corneas for 21 days in vitro. Donor corneas transfected with cDNA encoding IL-10 showed significantly prolonged survival after penetrating keratoplasty (median 55 days, range 19 > or =300 days) compared with control corneas (median 20.5 days, range 18-32 days, P=0.011).

CONCLUSION

Local gene therapy-mediated expression of the immunomodulatory cytokine IL-10 has the potential to reduce the incidence of corneal graft rejection and to prolong corneal allograft survival.

Recipient intramuscular gene transfer of active transforming growth factor-beta1 attenuates acute lung rejection

BACKGROUND

Gene transfer into the donor graft has been demonstrated to be feasible in reducing ischemia-reperfusion injury and rejection in lung transplantation. This study was undertaken to determine whether intramuscular gene transfer into the recipient can also reduce subsequent lung graft rejection.

METHODS

Brown Norway rats served as donors and F344 rats as recipients. Recipient animals were injected with 10(10) plaque-forming units of adenovirus encoding active transforming growth factor beta1 (group I, n = 6), beta-galactosidase as adenoviral controls (group II, n = 6), or normal saline without adenovirus (group III, n = 6) into both gluteus muscles 2 days before transplantation. Gene expression was confirmed by enzyme-linked immunosorbent assay. Graft function was assessed on postoperative day 5.

RESULTS

Successful gene transfection and expression were confirmed by the presence of active transforming growth factor beta1 protein in muscle and plasma. Oxygenation was significantly improved in group I (group I vs II and III, 353.6 +/- 63.0 mm Hg vs 165.7 +/- 39.9 and 119.1 +/- 41.5 mm Hg; p = 0.02 and 0.004). The muscle transfected with the transforming growth factor beta1 showed granulation tissue with fibroblast accumulation.

CONCLUSIONS

Intramuscular adenovirus-mediated gene transfer of active transforming growth factor beta1 into the recipients attenuates acute lung rejection as manifested by significantly improved oxygenation in transplanted lung allografts. This intramuscular transfection approach as a cytokine therapy is feasible in transplantation and may be useful in reducing rejection as well as reperfusion injury.

Extended lung expression and increased tissue localization of viral IL-10 with adenoviral gene therapy

IL-10 is a pleiotropic cytokine that acts as an important regulator of macrophage, T cell, and natural killer cell functions. Human IL-10 (hIL-10) has both stimulatory and inhibitory effects on a wide variety of cell types. Viral IL-10 (vIL-10) possesses only a subset of hIL-10's activities, predominantly its suppression of cytokine synthesis by T helper type 1 clones. In the present report, we evaluated tissue accumulation and biological activity of hIL-10 and vIL-10 in vivo in individual organs by using a first-generation adenoviral (Ad) vector administered intratracheally and intravenously. We report the observation that Ad vectors delivering vIL-10, but not hIL-10, are associated with prolonged expression in the lung (>42 days) when delivered intratracheally. In contrast, there was no prolongation in vIL-10 expression when Ad vectors were intravenously administered, although vIL-10 levels in the tissue, but not serum, were markedly increased relative to hIL-10. Moreover, we report an augmented capacity of expressed vIL-10 versus hIL-10 to suppress the acute inflammatory responses in the lung to intratracheal administration of Ad. These findings confirm fundamental differences in Ad-induced expression of vIL-10 and hIL-10 when administered to the lungs. The results further suggest that Ad vectors expressing vIL-10 may have a role as anti-inflammatory agents in the treatment of acute and chronic lung inflammation.

Closed-circuit organ perfusion technique for gene transfer into the lungs. An experimental trial on farm pigs

In an attempt to develop gene therapy for lung diseases, we have explored a closed-circuit surgical perfusion method for gene transfer into the lung. For gene transfer we used a replication defective type 5 adenovirus carrying the E. coli beta-galactosidase gene as a reporter gene. The middle lobe of the right lung of eight young farm pigs was perfused in vivo via thoracotomy for up to 60 min with the viral solution. The gene transfer was performed using a closed-circuit organ perfusion method in vivo. The efficiency of gene transfer was assessed visually by analysis of histologic sections after X-gal, PAS and immunohistochemical stainings. The lung perfusion resulted in transgene expression in the alveolar epithelial cells, capillary endothelial cells, airway epithelial cells and alveolar macrophages of the lung examined seven days after perfusion. The present results suggest that operatively performed closed-circuit warm lung perfusion method may be used for gene transfer in treatment of diseases that have pulmonary manifestations.

Extended lung expression and increased tissue localization of viral IL-10 with adenoviral gene therapy

IL-10 is a pleiotropic cytokine that acts as an important regulator of macrophage, T cell, and natural killer cell functions. Human IL-10 (hIL-10) has both stimulatory and inhibitory effects on a wide variety of cell types. Viral IL-10 (vIL-10) possesses only a subset of hIL-10's activities, predominantly its suppression of cytokine synthesis by T helper type 1 clones. In the present report, we evaluated tissue accumulation and biological activity of hIL-10 and vIL-10 in vivo in individual organs by using a first-generation adenoviral (Ad) vector administered intratracheally and intravenously. We report the observation that Ad vectors delivering vIL-10, but not hIL-10, are associated with prolonged expression in the lung (>42 days) when delivered intratracheally. In contrast, there was no prolongation in vIL-10 expression when Ad vectors were intravenously administered, although vIL-10 levels in the tissue, but not serum, were markedly increased relative to hIL-10. Moreover, we report an augmented capacity of expressed vIL-10 versus hIL-10 to suppress the acute inflammatory responses in the lung to intratracheal administration of Ad. These findings confirm fundamental differences in Ad-induced expression of vIL-10 and hIL-10 when administered to the lungs. The results further suggest that Ad vectors expressing vIL-10 may have a role as anti-inflammatory agents in the treatment of acute and chronic lung inflammation.

The heterotopic tracheal allograft as an animal model of obliterative bronchiolitis

Heterotopic tracheal allografts in small rodents have been shown to share many characteristics with the development of obliterative bronchiolitis (OB) in the clinic and therefore provide a suitable animal model for the study of OB. The model facilitates the examination of the pathogenesis of the disease and the elucidation of the cellular and molecular mechanisms involved in its development. The model provides a less technically demanding alternative to whole lung transplantation in small rodents and should lead to a speedier identification of new treatments that might prevent the development of post-transplantation OB in the clinic.

Transplant immunosuppression increases and prolongs transgene expression following adenoviral-mediated transfection of rat lungs

BACKGROUND

Gene therapy provides the potential to modify donor organs to better withstand transplantation, but this has yet to be realized. In vivo gene transfer using adenoviral vectors has had limited success because of host immune response that induces inflammation and limits the amount and duration of transgene expression. We hypothesize that transplantation immunosuppression can attenuate the post-transfection host-immune response to allow for improved gene transfer following adenoviral-mediated transfection.

METHODS

We intratracheally transfected with adenovirus containing the beta-galactosidase gene and randomized the rats to either the immunosuppression group, receiving daily cyclosporine, azathioprine, and methylprednisolone, or the control group, receiving no immunosuppression. We evaluated transgene expression and post-transfection inflammation at time points ranging from 1 day to 5 weeks.

RESULTS

Following transfection, control rats showed relatively low levels of transgene expression, which rapidly decreased to non-detectable levels. In contrast, immunosuppressed rats demonstrated significantly higher levels of transgene expression overall (p < 0.00005), peaking at almost 3 times that of the control group (p < 0.02), and showing prolonged and elevated transgene expression at 5 weeks (p < 0.02). On histologic sections of the lungs, immunosuppressed rats exhibited overall lesser grades of post-transfection inflammation.

CONCLUSIONS

Transplant immunosuppression provides the means to attenuate the severe immune response to adenoviral-mediated gene transfection and thereby increase and prolong transgene expression.

Elevated levels of interleukin-8 and transforming growth factor-beta in bronchoalveolar lavage fluid from patients with bronchiolitis obliterans syndrome: proinflammatory role of bronchial epithelial cells. Munich Lung Transplant Group

BACKGROUND

Obliterative bronchiolitis (OB), the most important long-term complication after lung transplantation, is thought to be a manifestation of chronic rejection within the airways, with the hallmarks inflammation and fibroproliferation.

METHODS

To characterize the inflammatory process in the context of OB we quantified tumor necrosis factor-alpha, interleukin (IL)-8, IL-10, and transforming growth factor (TGF)-beta on the protein and mRNA level in bronchoalveolar lavage fluid samples obtained from patients with bronchiolitis obliterans syndrome (BOS) and without BOS. In addition, bronchial cells sampled by bronchial brushing were analyzed for mRNA expression.

RESULTS

In respiratory epithelial lining fluid (ELF) from BOS patients the protein levels of IL-8 (52.4+/-22.2 vs. 4.4+/-0.9 pg/ml ELF, P<0.005) and TGF-beta (5.6+/-1.9 vs. 0.9+/-0.2 ng/ml ELF, P<0.005) were significantly elevated. In addition, bronchoalveolar lavage fluid cells of BOS patients showed increased expression of TGF-beta (1.13+/-0.44 vs. 0.45+/-0.16, optical density [O.D.]/O.D. glyceraldehyde-3-phosphate dehydrogenase [GAPDH], P=0.11) and IL-8 (0.25+/-0.13 vs. 0.09+/-0.03 O.D/O.D. GAPDH, P=0.53) without the differences reaching statistical significance. In contrast, IL-8 mRNA expression of bronchial cells was significantly higher in the BOS group (0.85+/-0.40 vs. 0.22+/-0.10 O.D./O.D. GAPDH, P<0.05).

CONCLUSIONS

We assume that IL-8 and TGF-beta may act as key mediators for airway inflammation and fibroproliferation in the pathogenesis of OB, with bronchial epithelial cells serving as a relevant source of IL-8.

Immunosuppressive therapies for the prevention and treatment of obliterative airway disease in heterotopic rat trachea allografts

BACKGROUND

Obliterative bronchiolitis remains a major long-term complication after lung transplantation. Using a reproducible model of heterotopically transplanted rat tracheas, this study examined the role of several novel immunosuppresive compounds to prevent and reverse obliterative airway disease in these animals.

METHODS

Brown Norway rat trachea were transplanted into the greater omentum of Lewis (allografts) or Brown Norway (isografts) animals. Recipient animals were treated with rapamycin, cyclosporine, 15-deoxyspergulin, mycophenolate mofetil, or leflunomide from day 0, 7, or 14 until day of graft removal, either day 28 or 50. Trachea segments were evaluated for degree of lumenal occlusion, as well as percent and type of lumen epithelial cell coverage.

RESULTS

All untreated allografted tracheas obliterated completely, although isografts appeared patent with normal respiratory epithelium when they were removed. Leflunomide, rapamycin, and cyclosporine effectively prevented obliteration when treatment was initiated at day 0, with rapamycin showing continued efficacy when initiated as late as day 7. 15-deoxyspergulin and mycophenolate mofetil failed to consistently inhibit obliteration with any treatment schedule. An inverse correlation was found between epithelial coverage and degree of obliteration, and was especially pronounced in grafts from cyclosporine-treated animals.

CONCLUSIONS

Immunosuppressive drug therapy will inhibit airway obliteration, but efficacy sharply diminishes if initiation of treatment is delayed. Efficacy also varies among immunosuppressive compounds, and results indicate those drugs that enable epithelial regrowth most effectively inhibit airway graft obliteration.