Vibha N. Lama

Evidence for tissue-resident mesenchymal stem cells in human adult lung from studies of transplanted allografts

The origin and turnover of connective tissue cells in adult human organs, including the lung, are not well understood. Here, studies of cells derived from human lung allografts demonstrate the presence of a multipotent mesenchymal cell population, which is locally resident in the human adult lung and has extended life span in vivo. Examination of plastic-adherent cell populations in bronchoalveolar lavage samples obtained from 76 human lung transplant recipients revealed clonal proliferation of fibroblast-like cells in 62% (106 of 172) of samples. Immunophenotyping of these isolated cells demonstrated expression of vimentin and prolyl-4-hydroxylase, indicating a mesenchymal phenotype. Multiparametric flow cytometric analyses revealed expression of cell-surface proteins, CD73, CD90, and CD105, commonly found on mesenchymal stem cells (MSCs). Hematopoietic lineage markers CD14, CD34, and CD45 were absent. Multipotency of these cells was demonstrated by their capacity to differentiate into adipocytes, chondrocytes, and osteocytes. Cytogenetic analysis of cells from 7 sex-mismatched lung transplant recipients harvested up to 11 years after transplant revealed that 97.2% +/- 2.1% expressed the sex genotype of the donor. The presence of MSCs of donor sex identity in lung allografts even years after transplantation provides what we believe to be the first evidence for connective tissue cell progenitors that reside locally within a postnatal, nonhematopoietic organ.

An international ISHLT/ATS/ERS clinical practice guideline: diagnosis and management of bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome (BOS) is a major complication of lung transplantation that is associated with poor survival. The International Society for Heart and Lung Transplantation, American Thoracic Society, and European Respiratory Society convened a committee of international experts to describe and/or provide recommendations for 1) the definition of BOS, 2) the risk factors for developing BOS, 3) the diagnosis of BOS, and 4) the management and prevention of BOS. A pragmatic evidence synthesis was performed to identify all unique citations related to BOS published from 1980 through to March, 2013. The expert committee discussed the available research evidence upon which the updated definition of BOS, identified risk factors and recommendations are based. The committee followed the GRADE (Grading of Recommendation, Assessment, Development and Evaluation) approach to develop specific clinical recommendations. The term BOS should be used to describe a delayed allograft dysfunction with persistent decline in forced expiratory volume in 1 s that is not caused by other known and potentially reversible causes of post-transplant loss of lung function. The committee formulated specific recommendations about the use of systemic corticosteroids, cyclosporine, tacrolimus, azithromycin and about re-transplantation in patients with suspected and confirmed BOS. The diagnosis of BOS requires the careful exclusion of other post-transplant complications that can cause delayed lung allograft dysfunction, and several risk factors have been identified that have a significant association with the onset of BOS. Currently available therapies have not been proven to result in significant benefit in the prevention or treatment of BOS. Adequately designed and executed randomised controlled trials that properly measure and report all patient-important outcomes are needed to identify optimal therapies for established BOS and effective strategies for its prevention. Diagnosis of BOS requires careful exclusion of other complications that can cause delayed lung allograft dysfunction http://ow.ly/AZmbr

Lung Resident Mesenchymal Stem Cells Isolated From Human Lung Allografts Inhibit T Cell Proliferation via a Soluble Mediator

Development of allograft rejection continues to be the major determinant of morbidity and mortality postlung transplantation. We have recently demonstrated that a population of donor-derived mesenchymal stem cells is present in human lung allografts and can be isolated and expanded ex vivo. In this study, we investigated the impact of lung resident mesenchymal stem cells (LR-MSCs), derived from allografts of human lung transplant recipients, on T cell activation in vitro. Similar to bone marrow-derived MSCs, LR-MSCs did not express MHC II or the costimulatory molecules CD80 or CD86. In vitro, LR-MSCs profoundly suppressed the proliferative capacity of T cells in response to a mitogenic or an allogeneic stimulus. The immunosuppressive function of LR-MSCs was also noted in the absence of direct cell contact, indicating that LR-MSCs mediated their effect predominantly via a soluble mediator. LR-MSCs isolated from lung transplant recipients demonstrated PGE2 secretion at baseline (385 ± 375 pg/ml), which increased in response to IL-1β (1149 ± 1081 pg/ml). The addition of PG synthesis inhibitors (indomethacin and NS-398) substantially abrogated LR-MSC-mediated immunosuppression, indicating that PGE2 may be one of the major soluble mediators impacting T cell activity. This is the first report to demonstrate that human tissue-derived MSCs isolated from an allogeneic environment have the potential to mediate immunological responses in vitro.

Lung microbiome and disease progression in idiopathic pulmonary fibrosis: an analysis of the COMET study

BACKGROUND The role of the lung microbiome in the pathogenesis of idiopathic pulmonary fibrosis is unknown. We investigated whether unique microbial signatures were associated with progression of idiopathic pulmonary fibrosis. METHODS Patients (aged 35-80 years) with idiopathic pulmonary fibrosis within 4 years of diagnosis from the Correlating Outcomes with biochemical Markers to Estimate Time-progression (COMET) in idiopathic pulmonary fibrosis study were followed up for a maximum of 80 weeks. Progression-free survival was defined as time to death, acute exacerbation, lung transplant, or decrease in forced vital capacity (FVC) of 10% or greater or decrease in diffusion capacity of the lung (DLCO) of 15% or greater. DNA was isolated from 55 samples of bronchoscopic alveolar lavage. 454 pyrosequencing was used to assign operational taxonomic units (OTUs) to bacteria based on a 3% sequence divergence. Adjusted Cox models were used to identify OTUs that were significantly associated with progression-free survival at a p<0.10. These OTUs were then used in the analysis of the principal components. The association between principal components and microbes with high factor loadings and progression-free survival were assessed with Cox regression analyses. The COMET study is registered with ClinicalTrials.gov, number NCT01071707. FINDINGS Mean FVC was 70.1% (SD 17.0) and DLCO 42.3% (14.0) of predicted. Disease progression was significantly associated with increased relative abundance of two OTUs-Streptococcus OTU 1345 (relative risk 1.11, 95% CI 1.04-1.18; p=0.0009) and Staphylococcus OTU 1348 (1.16, 1.03-1.31, p=0.012). Thresholds for relative abundance of each OTU associated with progression-free survival were more than 3.9% for Streptococcus OTU 1345 (10.19, 2.94-35.35; p=0.0002) and more than 1.8% for Staphylococcus OTU 1348 (5.06, 1.71-14.93; p=0.003). INTERPRETATION These preliminary data suggest progression of idiopathic pulmonary fibrosis is associated with the presence of specific members within the Staphylococcus and Streptococcus genera. Additional research will be needed to identify the specific bacterial species and to ascertain whether this is a causal association. FUNDING National Institutes of Health.

Lung microbiome and disease progression in idiopathic pulmonary fibrosis

BACKGROUND The role of the lung microbiome in the pathogenesis of idiopathic pulmonary fibrosis is unknown. We investigated whether unique microbial signatures were associated with progression of idiopathic pulmonary fibrosis. METHODS Patients (aged 35-80 years) with idiopathic pulmonary fibrosis within 4 years of diagnosis from the Correlating Outcomes with biochemical Markers to Estimate Time-progression (COMET) in idiopathic pulmonary fibrosis study were followed up for a maximum of 80 weeks. Progression-free survival was defined as time to death, acute exacerbation, lung transplant, or decrease in forced vital capacity (FVC) of 10% or greater or decrease in diffusion capacity of the lung (DLCO) of 15% or greater. DNA was isolated from 55 samples of bronchoscopic alveolar lavage. 454 pyrosequencing was used to assign operational taxonomic units (OTUs) to bacteria based on a 3% sequence divergence. Adjusted Cox models were used to identify OTUs that were significantly associated with progression-free survival at a p<0.10. These OTUs were then used in the analysis of the principal components. The association between principal components and microbes with high factor loadings and progression-free survival were assessed with Cox regression analyses. The COMET study is registered with ClinicalTrials.gov, number NCT01071707. FINDINGS Mean FVC was 70.1% (SD 17.0) and DLCO 42.3% (14.0) of predicted. Disease progression was significantly associated with increased relative abundance of two OTUs-Streptococcus OTU 1345 (relative risk 1.11, 95% CI 1.04-1.18; p=0.0009) and Staphylococcus OTU 1348 (1.16, 1.03-1.31, p=0.012). Thresholds for relative abundance of each OTU associated with progression-free survival were more than 3.9% for Streptococcus OTU 1345 (10.19, 2.94-35.35; p=0.0002) and more than 1.8% for Staphylococcus OTU 1348 (5.06, 1.71-14.93; p=0.003). INTERPRETATION These preliminary data suggest progression of idiopathic pulmonary fibrosis is associated with the presence of specific members within the Staphylococcus and Streptococcus genera. Additional research will be needed to identify the specific bacterial species and to ascertain whether this is a causal association. FUNDING National Institutes of Health.

Plasma Levels of Receptor for Advanced Glycation End Products, Blood Transfusion, and Risk of Primary Graft Dysfunction

RATIONALE The receptor for advanced glycation end products (RAGE) is an important marker of lung epithelial injury and may be associated with impaired alveolar fluid clearance. We hypothesized that patients with primary graft dysfunction (PGD) after lung transplantation would have higher RAGE levels in plasma than patients without PGD. OBJECTIVES To test the association of soluble RAGE (sRAGE) levels with PGD in a prospective, multicenter cohort study. METHODS We measured plasma levels of sRAGE at 6 and 24 hours after allograft reperfusion in 317 lung transplant recipients at seven centers. The primary outcome was grade 3 PGD (Pa(O(2))/Fi(O(2)) < 200 with alveolar infiltrates) within the first 72 hours after transplantation. MEASUREMENTS AND MAIN RESULTS Patients who developed PGD had higher levels of sRAGE than patients without PGD at both 6 hours (median 9.3 ng/ml vs. 7.5 ng/ml, respectively; P = 0.028) and at 24 hours post-transplantation (median 4.3 ng/ml vs. 1.9 ng/ml, respectively; P < 0.001). Multivariable logistic regression analyses indicated that the relationship between levels of sRAGE and PGD was attenuated by elevated right heart pressures and by the use of cardiopulmonary bypass. Median sRAGE levels were higher in subjects with cardiopulmonary bypass at both 6 hours (P = 0.003) and 24 hours (P < 0.001). sRAGE levels at 6 hours were significantly associated with intraoperative red cell transfusion (Spearmans rho = 0.39, P = 0.002 in those with PGD), and in multivariable linear regression analyses this association was independent of confounding variables (P = 0.02). CONCLUSIONS Elevated plasma levels of sRAGE are associated with PGD after lung transplantation. Furthermore, plasma sRAGE levels are associated with blood product transfusion and use of cardiopulmonary bypass.

Obesity and Primary Graft Dysfunction after Lung Transplantation: The Lung Transplant Outcomes Group Obesity Study

RATIONALE Obesity has been linked to acute lung injury and is a risk factor for early mortality after lung transplantation. OBJECTIVES To examine the associations of obesity and plasma adipokines with the risk of primary graft dysfunction after lung transplantation. METHODS We performed a prospective cohort study of 512 adult lung transplant recipients with chronic obstructive pulmonary disease or interstitial lung disease enrolled in the Lung Transplant Outcomes Group Study. In a nested case-control study, we measured plasma leptin, adiponectin, and resistin before lung transplantation and 6 and 24 hours after lung transplantation in 40 cases of primary graft dysfunction and 80 control subjects. Generalized linear mixed models and logistic regression were used to estimate risk ratios and odds ratios. MEASUREMENTS AND MAIN RESULTS Grade 3 primary graft dysfunction developed within 72 hours of transplantation in 29% participants. Obesity was associated with a twofold increased risk of primary graft dysfunction (adjusted risk ratio 2.1; 95% confidence interval, 1.7-2.6). The risk of primary graft dysfunction increased by 40% (confidence interval, 30–50%) for each 5 kg/m(2) increase in body mass index after accounting for center, diagnosis, cardiopulmonary bypass, and transplant procedure. Higher plasma leptin levels were associated with a greater risk of primary graft dysfunction (sex-adjusted P = 0.02). The associations of both obesity and leptin with primary graft dysfunction tended to be stronger among those who did not undergo cardiopulmonary bypass. CONCLUSIONS Obesity is an independent risk factor for primary graft dysfunction after lung transplantation.

Resident Tissue-Specific Mesenchymal Progenitor Cells Contribute to Fibrogenesis in Human Lung Allografts

Fibrotic obliteration of the small airways leading to progressive airflow obstruction, termed bronchiolitis obliterans syndrome (BOS), is the major cause of poor outcomes after lung transplantation. We recently demonstrated that a donor-derived population of multipotent mesenchymal stem cells (MSCs) can be isolated from the bronchoalveolar lavage (BAL) fluid of human lung transplant recipients. Herein, we study the organ specificity of these cells and investigate the role of local mesenchymal progenitors in fibrogenesis after lung transplantation. We demonstrate that human lung allograft-derived MSCs uniquely express embryonic lung mesenchyme-associated transcription factors with a 35,000-fold higher expression of forkhead/winged helix transcription factor forkhead box (FOXF1) noted in lung compared with bone marrow MSCs. Fibrotic differentiation of MSCs isolated from normal lung allografts was noted in the presence of profibrotic mediators associated with BOS, including transforming growth factor-β and IL-13. MSCs isolated from patients with BOS demonstrated increased expression of α-SMA and collagen I when compared with non-BOS controls, consistent with a stable in vivo fibrotic phenotype. FOXF1 mRNA expression in the BAL cell pellet correlated with the number of MSCs in the BAL fluid, and myofibroblasts present in the fibrotic lesions expressed FOXF1 by in situ hybridization. These data suggest a key role for local tissue-specific, organ-resident, mesenchymal precursors in the fibrogenic processes in human adult lungs.

Construct validity of the definition of primary graft dysfunction after lung transplantation

BACKGROUND This study tested the discriminant validity of International Society for Heart and Lung Transplantation (ISHLT) primary graft dysfunction (PGD) grades with lung injury biomarker profiles and survival. METHODS The study samples consisted of a multicenter prospective cohort study for the biomarker analysis and a cohort study of 450 patients for the mortality analyses. PGD was defined according to ISHLT consensus at 24, 48, and 72 hours after transplantation. We compared the changes in plasma markers of acute lung injury between PGD grades using longitudinal data models. To test predictive validity, we compared differences in the 30-day mortality and long-term survival according to PGD grade. RESULTS PGD Grade 3 demonstrated greater differences between plasma intercellular adhesion molecule 1 (ICAM-1), protein C, and plasminogen activator inhibitor type 1 (PAI-1) levels than did PGD Grades 0 to 2 at 24, 48, and 72 hours after lung transplantation (p < 0.05 for each). Grade 3 had the highest 30-day (test for trend p < 0.001) and overall mortality (log rank p < 0.001), with PGD Grades 1 and 2 demonstrating intermediate risks of mortality. The ability to discriminate both 30-day and overall mortality improved as the time of grading moved away from the time of transplantation (test for trend p < 0.001). CONCLUSIONS The ISHLT grading system has good discriminant validity, based on plasma markers of lung injury and mortality. Grade 3 PGD was associated with the most severely altered plasma biomarker profile and the worst outcomes, regardless of the time point of grading. PGD grade at 48 and 72 hours discriminated mortality better than PGD grade at 24 hours.

Changes in the Lung Microbiome following Lung Transplantation Include the Emergence of Two Distinct Pseudomonas Species with Distinct Clinical Associations

Background Multiple independent culture-based studies have identified the presence of Pseudomonas aeruginosa in respiratory samples as a positive risk factor for bronchiolitis obliterans syndrome (BOS). Yet, culture-independent microbiological techniques have identified a negative association between Pseudomonas species and BOS. Our objective was to investigate whether there may be a unifying explanation for these apparently dichotomous results. Methods We performed bronchoscopies with bronchoalveolar lavage (BAL) on lung transplant recipients (46 procedures in 33 patients) and 26 non-transplant control subjects. We analyzed bacterial communities in the BAL fluid using qPCR and pyrosequencing of 16S rRNA gene amplicons and compared the culture-independent data with the clinical metadata and culture results from these subjects. Findings Route of bronchoscopy (via nose or via mouth) was not associated with changes in BAL microbiota (p = 0.90). Among the subjects with positive Pseudomonas bacterial culture, P. aeruginosa was also identified by culture-independent methods. In contrast, a distinct Pseudomonas species, P. fluorescens, was often identified in asymptomatic transplant subjects by pyrosequencing but not detected via standard bacterial culture. The subject populations harboring these two distinct pseudomonads differed significantly with respect to associated symptoms, BAL neutrophilia, bacterial DNA burden and microbial diversity. Despite notable differences in culturability, a global database search of UM Hospital Clinical Microbiology Laboratory records indicated that P. fluorescens is commonly isolated from respiratory specimens. Interpretation We have reported for the first time that two prominent and distinct Pseudomonas species (P. fluorescens and P. aeruginosa) exist within the post-transplant lung microbiome, each with unique genomic and microbiologic features and widely divergent clinical associations, including presence during acute infection.