The effect of reflux and bile acid aspiration on the lung allograft and its surfactant and innate immunity molecules SP-A and SP-D

Concurrent abnormal non-acid reflux is associated with additional chronic rejection risk in lung transplant patients with increased acid exposure

Acid reflux has been associated with allograft injury and rejection in lung transplant patients; however, the pathogenic role of non-acid reflux remains debated. We aimed to evaluate the impact of concurrent abnormal non-acid reflux with acid reflux on chronic rejection in lung transplant patients with acid reflux. This was a retrospective cohort study of lung transplant recipients who underwent pre-transplant combined impedance-pH study off acid suppression. Only subjects with acid exposure >4% were included. Non-acid reflux (pH > 4) episodes >27 was considered abnormal per prior normative studies. Chronic rejection was defined as chronic lung allograft dysfunction (CLAD) per International Society for Heart and Lung Transplantation criteria. Time-to-event analyses were performed using Cox proportional hazards and Kaplan-Maier methods, with censoring at death, anti-reflux surgery, or last follow-up. In total, 68 subjects (28 abnormal/40 normal non-acid reflux) met inclusion criteria for the study. Baseline demographic/clinical characteristics were similar between groups. Among this cohort of patients with increased acid exposure, subjects with concurrent abnormal non-acid reflux had significantly higher risk of CLAD than those without on Kaplan-Meier analysis (log-ranked P = 0.0269). On Cox multivariable regression analysis controlling for body mass index, age at transplantation, and proton pump inhibitor use, concurrent abnormal non-acid reflux remained independently predictive of increased CLAD risk (hazard ratio 2.31, confidence interval: 1.03-5.19, P = 0.04). Presence of concurrent abnormal non-acid reflux in lung transplant subjects with increased acid exposure is associated with additional risk of chronic rejection. Non-acid reflux may also contribute to pathogenicity in lung allograft injury/rejection, supporting a potential role for impedance-based testing in this population.

Optimizing the prelung transplant candidate

PURPOSE OF REVIEW

Lung transplant outcomes are impacted by multiple modifiable risk factors. Candidate deterioration on the wait list remains problematic. Innovative technology and strategies to identify and impact pretransplant morbidity have improved short- and long-term outcomes. We focus our review on recent advances in pretransplant recipient assessment and optimization.

RECENT FINDINGS

Advancements in recipient management have focused on risk factor identification for adverse outcomes and the development of a lung transplant specific frailty assessment. Early surgical correction of gastroesophageal reflux disease (GERD), including the use of partial fundoplication in the setting of esophageal dysmotility, leads to improvements in graft function/longevity. New evidence supports expanding criteria for extracorporeal life support as a bridge to transplant.

SUMMARY

Candidate optimization requires early intervention to limit functional deterioration potentially contributing to adverse outcomes. Frailty can be identified with a transplant specific frailty assessment, and positively impacted with dedicated rehabilitation. Pretransplant frailty is reversible following transplant and should be considered in the context of overall fitness at the time of candidate selection. Invasive support modes including extracorporeal membrane oxygenation (ECMO) are appropriate to preserve strength and mobility, with awake, ambulatory ECMO preferred. The deleterious effect of GERD on graft function can be managed with early fundoplication over medical management alone.

Ineffective esophageal motility is associated with acute rejection after lung transplantation independent of gastroesophageal reflux

BACKGROUND

Gastroesophageal reflux is associated with poorer outcomes after lung transplant, likely through recurrent aspiration and allograft injury. Although prior studies have demonstrated a relationship between impedance-pH results and transplant outcomes, the role of esophageal manometry in the assessment of lung transplant patients remains debated, and the impact of esophageal dysmotility on transplant outcomes is unclear. Of particular interest is ineffective esophageal motility (IEM) and its associated impact on esophageal clearance.

AIM

To assess the relationship between pre-transplant IEM diagnosis and acute rejection after lung transplantation.

METHODS

This was a retrospective cohort study of lung transplant recipients at a tertiary care center between 2007 and 2018. Patients with pre-transplant anti-reflux surgery were excluded. Manometric and reflux diagnoses were recorded from pre-transplant esophageal function testing. Time-to-event analysis using Cox proportional hazards model was applied to evaluate outcome of first episode of acute cellular rejection, defined histologically per International Society of Heart and Lung Transplantation guidelines. Subjects not meeting this endpoint were censored at time of post-transplant anti-reflux surgery, last clinic visit, or death. Fisher’s exact test for binary variables and student’s t-test for continuous variables were performed to assess for differences between groups.

RESULTS

Of 184 subjects (54% men, mean age: 58, follow-up: 443 person-years) met criteria for inclusion. Interstitial pulmonary fibrosis represented the predominant pulmonary diagnosis (41%). During the follow-up period, 60 subjects (33.5%) developed acute rejection. The all-cause mortality was 16.3%. Time-to-event univariate analyses demonstrated significant association between IEM and acute rejection [hazard ratio (HR): 1.984, 95%CI: 1.03-3.30, P = 0.04], confirmed on Kaplan-Meier curve. On multivariable analysis, IEM remained independently associated with acute rejection, even after controlling for potential confounders such as the presence of acid and nonacid reflux (HR: 2.20, 95%CI: 1.18-4.11, P = 0.01). Nonacid reflux was also independently associated with acute rejection on both univariate (HR: 2.16, 95%CI: 1.26-3.72, P = 0.005) and multivariable analyses (HR: 2.10, 95%CI: 1.21-3.64, P = 0.009), adjusting for the presence of IEM.

CONCLUSION

Pre-transplant IEM was associated with acute rejection after transplantation, even after controlling for acid and nonacid reflux. Esophageal motility testing may be considered in lung transplant to predict outcomes.

miR-27a-3p alleviates lung transplantation-induced bronchiolitis obliterans syndrome (BOS) via suppressing Smad-mediated myofibroblast differentiation and TLR4-induced dendritic cells maturation

BACKGROUND

Bronchiolitis obliterans syndrome (BOS), induced by a chronic rejection, remains a significant obstacle for end-stage lung diseases after lung transplantation. We have previously determined that the small non-coding mRNA (miRNA) miR-27a-3p maintained the immature state of dendritic cells (DCs) via the interleukin 10 (IL-10)-dependent regulatory pathway. Such status helped in preventing rejection and alleviating BOS. The present study explored mechanisms how miR-27a-3p may suppress the fibrosis as well as the maturation of DCs, ultimately attenuating BOS in vitro and in vivo.

METHODS/RESULTS

In our tracheal transplantation mouse model, the expression of Smad2, Smad4, and αSMA were significantly decreased in the miR-27a-3p-transfected DCs (p < 0.0001, p = 0.0006, and p = 0.0002 respectively). Moreover, the expression of fibrosis markers (α-SMA, collagen I, and Fn) were potently inhibited in the miR-27a-3p-transfected NIH-3 T3 cells (p < 0.0001, p = 0.00148, and p < 0.0001 respectively). At the same time, reversed results were observed in the inhibitor group (p = 0.0002, p < 0.0001, and p < 0.0001 respectively), indicating that miR-27a-3p could directly inhibit myofibroblast differentiation. Furthermore, in the tracheal transplanted mice, the population of Treg cells was significantly decreased (p < 0.0001). In contrast, Th17 cells were down-regulated in the miR-27a-3p-transfected DCs group (p < 0.0001), accompanied by the decreased IL-17 levels (p = 0.0007) and the induction of TGF-β1 and IL-10 (p < 0.0001 and p = 0.0016 respectively). Further mechanistic studies indicated that miR-27a-3p altered the maturation of DCs by targeting TLR4 and IRAK (p < 0.0001 and p = 0.0002 respectively).

CONCLUSIONS

Our study suggests that miR-27a-3p selectively blocked the TGF-β1/Smad pathways to suppress the myofibroblast differentiation and targeted the TRL4/IRAK4 pathway to restrain DCs maturation, thus attenuating BOS. Our findings suggest that miR-27a-3p is a potential active molecule on BOS management after lung transplantation.

A potential mechanism by which aspiration of duodenogastric fluid augments the risk for bronchiolitis obliterans syndrome after lung transplantation

OBJECTIVE

Aspiration of duodenogastric refluxate may damage the respiratory epithelium of lung allografts in transplant recipients. We sought to define a mechanism by which aspiration of duodenogastric fluid augments the risk of bronchiolitis obliterans syndrome after lung transplant in a murine model.

METHODS

We analyzed the immunological effects of acute aspiration of duodenogastric fluid (0.5 mL/kg) on transplant naive (strain DBA/2J) and transplanted mice (strain B6D2F1/J to strain DBA/2J). Serum antibodies to the lung self-antigens (SAgs) K-alpha1 tubulin and collagen-V were determined by enzyme-linked immunosorbent assay. Exosomes were isolated from serum, and immunoblot membranes were probed for antibodies to lung SAgs. Lung sections were assessed for fibrotic burden and obliterative bronchiolitis lesions by histologic and immunohistochemical analyses, including trichrome staining.

RESULTS

Transplanted mice that received duodenogastric fluid developed higher levels of antibodies to the lung SAgs K-alpha1 tubulin and collagen-V and exosomes with lung SAgs on posttransplant days 14 and 28 than transplanted mice with sham aspiration or transplant naive mice (with and without aspiration). All lung allografts demonstrated severe grade A4 rejection on posttransplant day 14, with the highest mean fibrotic burden and mean number of obliterative bronchiolitis-like lesions per microscopic field on day 28 in recipients with aspiration.

CONCLUSIONS

This study links aspiration of duodenogastric fluid after lung transplant to higher autoimmune responses to lung SAgs and the release of circulating exosomes with lung SAgs, which together promote sustained immune responses leading to extensive lung parenchymal damage and, ultimately, severe obliterative bronchiolitis-the histologic hallmark of bronchiolitis obliterans syndrome.

Association Between Antibodies Against Lung Self-Antigens and Gastroesophageal Reflux in Lung Transplant Candidates

Gastroesophageal reflux (GER) and pretransplant antibodies against lung self-antigens (SAbs) collagen-V and/or k-alpha 1 tubulin are both independently associated with allograft dysfunction after lung transplantation (LTx). The role of GER in inducing lung injury and SAbs is unknown. We aimed to study the association between pre-LTx GER and SAbs. After IRB approval, we retrieved SAb assays conducted between 2015 and 2019 and collected 24 hour GER data for these patients. Patients were divided into 2 groups: no reflux (GER-) and pathologic reflux (GER+) to compare the prevalence of SAbs. Multivariate analysis was used to study the association between GER and SAbs in the whole cohort and in restrictive lung disease (RLD) and obstructive lung disease (OLD) subsets. Proximal esophageal reflux (PER) events ≥5 was considered abnormal. Patients (n = 134; 73 men) were divided into groups: GER- (54.5%, n = 73) and GER+ (45.5%, n = 61). The prevalence of GER was higher in the RLD than in the OLD subset (p < 0.001). The overall prevalence of SAbs was 53.7% (n = 72), higher in the GER+ than the GER- group (65.6% vs 43.8%, p = 0.012), but comparable between RLD and OLD subsets. Overall, SAbs were associated with GER (p = 0.012) and abnormal PER (p = 0.017). GER and abnormal PER increased the odds of SAbs in the RLD subset (OR [95% CI]: 2.825 [1.033-7.725], p = 0.040 and OR [95% CI]: 3.551 [1.271-9.925], p = 0.014, respectively) but not in the OLD subset. LTx candidates have a high prevalence of SAbs, which are significantly associated with GER and abnormal PER in patients with RLD.

Utilization of Oil Red O staining for assessing aspiration risk in lung transplant patients: A multidisciplinary prospective study with clinical practice insights

BACKGROUND

Gastroesophageal reflux disease with microaspiration has been associated with graft dysfunction in lung transplant patients. Identifying patients with aspiration is clinically important because it enables implementation of appropriate interventions like antireflux therapy. Oil Red O (ORO) staining with determination of the lipid-laden macrophage index (LLMI) has been proposed as a noninvasive surrogate marker in the detection of aspiration. The aim of this study was to prospectively evaluate clinical utilization of ORO staining in the assessment of aspiration risk.

METHODS

All transbronchial surgical pathology biopsies obtained in lung transplant patients undergoing routine surveillance from August 2020 through November 2021 were included in this study. Clinical team members prospectively ascertained the aspiration risk category (ARC) of each patient both before and after biopsy findings and recorded reasons for change in ARC.

RESULTS

A total of 132 transbronchial biopsies with concurrent LLMI were included in the study. LLMI was low in 51 cases (38.6%), including 21 of the 54 cases (38.9%) where aspiration was suggested based on the transbronchial biopsy findings. In total, 19 cases (14.4%) underwent a change in ARC post-biopsy including 10 that were upgraded and nine cases that were downgraded. Transbronchial biopsy findings were noted as the reason for change in ARC in the majority (15/19; 79%) of cases; only a minority (2/19; 10.5%) were due to the LLMI. Notably, 16 cases (12.1%) had a low LLMI with high-risk post-biopsy ARC and nine cases (6.8%) had a high LLMI with low-risk post-biopsy ARC.

CONCLUSIONS

This study observed that clinical evaluation for aspiration relied more heavily on transbronchial biopsy findings. Although LLMI may retain clinical utility in some scenarios, reevaluation of the clinical value of ORO testing would be prudent.

Utility of bile acids in large airway bronchial wash versus bronchoalveolar lavage as biomarkers of microaspiration in lung transplant recipients: a retrospective cohort study

Background

Bronchoalveolar lavage (BAL) is a key tool in respiratory medicine for sampling the distal airways. BAL bile acids are putative biomarkers of pulmonary microaspiration, which is associated with poor outcomes after lung transplantation. Compared to BAL, large airway bronchial wash (LABW) samples the tracheobronchial space where bile acids may be measurable at more clinically relevant levels. We assessed whether LABW bile acids, compared to BAL bile acids, are more strongly associated with poor clinical outcomes in lung transplant recipients.

Methods

Concurrently obtained BAL and LABW at 3 months post-transplant from a retrospective cohort of 61 lung transplant recipients were analyzed for taurocholic acid (TCA), glycocholic acid (GCA), and cholic acid by mass spectrometry and 10 inflammatory proteins by multiplex immunoassay. Associations between bile acids with inflammatory proteins and acute lung allograft dysfunction were assessed using Spearman correlation and logistic regression, respectively. Time to chronic lung allograft dysfunction and death were evaluated using multivariable Cox proportional hazards and Kaplan–Meier methods.

Results

Most bile acids and inflammatory proteins were higher in LABW than in BAL. LABW bile acids correlated with inflammatory proteins within and between sample type. LABW TCA and GCA were associated with acute lung allograft dysfunction (OR = 1.368; 95%CI = 1.036–1.806; P = 0.027, OR = 1.064; 95%CI = 1.009–1.122; P = 0.022, respectively). No bile acids were associated with chronic lung allograft dysfunction. Adjusted for risk factors, LABW TCA and GCA predicted death (HR = 1.513; 95%CI = 1.014–2.256; P = 0.042, HR = 1.597; 95%CI = 1.078–2.366; P = 0.020, respectively). Patients with LABW TCA in the highest tertile had worse survival compared to all others.

Conclusions

LABW bile acids are more strongly associated than BAL bile acids with inflammation, acute lung allograft dysfunction, and death in lung transplant recipients. Collection of LABW may be useful in the evaluation of microaspiration in lung transplantation and other respiratory diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02131-5.

Esophageal Dysfunction in Post-lung Transplant: An Enigma

The prevalence of lung transplants has increased over the years, albeit with a low survival rate amongst all solid organ transplants, including liver and heart transplantation. Microaspiration is one of the primary mechanisms that has been implicated in the pathogenesis of lung injury following lung transplants. Of late, esophageal dysfunction such as gastroesophageal reflux and esophageal hypercontractility is often noted post-lung transplant. However, reflux is associated with chronic allograft lung injury such as bronchiolitis obliterans syndrome, which is one of the predictors for long-term survival in this specialized population. Its role in acute lung injury post-lung transplant is still being explored. This review critically examines the salient points which provide the current understanding of the characteristics, pathophysiology, and implications of esophageal dysfunction following lung transplant.

Correlation between cytology Oil Red O staining and lung biopsy specimens: utility of the lipid-laden macrophage index

INTRODUCTION

Oil Red O staining is used for enumeration of the lipid-laden macrophage index (LLMI) as a surrogate for aspiration. As part of quality improvement efforts aimed at optimizing resource utilization, the utility of this stain in current cytopathology practice was re-evaluated. The objective of this study was to explore the clinical utility of Oil Red O staining in bronchoalveolar lavage (BAL) samples by correlating the LLMI with findings in concurrent histologic tissue samples.

MATERIALS AND METHODS

Lung transbronchial biopsy specimens that suggested aspiration that were submitted with concurrent BAL cytology samples were retrieved. Lung tissue biopsies were reviewed for the presence of foamy alveolar macrophages (graded as 0, 1+, and 2+), foreign material, and giant cells. The concurrent BAL was reviewed with consensus determination of the LLMI.

RESULTS

A total of 53 cases were identified. On histology, 13 cases (24.5%) were found to have no foamy alveolar macrophages, 23 cases (43.4%) were found to have 1+ foamy alveolar macrophages, and 17 cases (32.1%) were found to have 2+ foamy alveolar macrophages. Six cases (11.3%) were found to have foreign material, and 10 cases (18.9%) were found to have multinucleated giant cells. The average LLMI score was 16, with 44 (83.0%) in the low range (LLMI &lt;40) and 9 (17.0%) in the intermediate range (LLMI of 40-90).

CONCLUSIONS

None of the cases in our study had an LLMI that exceeded the cutoff value for which aspiration would be suspected. We found no correlation of the LLMI with lung biopsies that suggested aspiration.

Prevalence of Micro-Aspiration of Bile Acids in Patients with Primary Lung Cancer: A Cross-Sectional Study

Background

Lung cancer remains a serious public health problem and is the first cause of cancer-related death worldwide. There is some evidence suggests that bile acid micro-aspiration may contribute to the development of lung diseases. This study aimed to assess the prevalence of micro-aspiration of bile acids in patients with primary lung cancer.

Methods

In a cross-sectional study, 52 patients with primary lung cancer referred to a teaching hospital affiliated with Kerman University of Medical Sciences, Kerman, Iran were enrolled. Patients with pathology-confirmed lung cancer who did not receive specific treatment were included in the present study. All patients underwent bronchoscopy and the levels of bile acid was assessed in their Broncho-Alveolar Lavage (BAL) samples.

Results

According to the results, 53.85% of patients were in the age group of 40 to 59 years. Of the participants, 88.46% were male, 82.69% were smokers, and 69.23% were opium addicted. The most common presenting clinical symptoms of patients were heartburn (61.55%), hoarseness (17.31%), and epigastric pain (9.61%), respectively. Ninety-two point thirty-two percent of patients had endobronchial lesions in bronchoscopy. Squamous cell carcinoma, small-cell lung carcinoma and adenocarcinoma accounts for 48.08%, 34.61% and 17.31% of all cases of lung cancer, respectively. Bile acids were found in the BAL sample of all patients with primary lung cancer. The mean Bile acids levels in patients were 63.42 (SD=7.03) µmol/Lit.

Conclusion

According to the results of present study, there was a micro-aspiration of bile acids in all patients with primary lung cancer that may participate in shaping early events in the etiology of primary lung cancer. It seems that developing clinical strategies preventing the micro-aspiration of bile acids into the lungs could remove a key potential trigger in this process.

Role of gastric per-oral endoscopic myotomy (G-POEM) in post-lung transplant patients: a multicenter experience

Background and study aims  Gastroparesis post-lung transplant (LTx) can lead to increased risk of gastroesophageal reflux (GER) and accelerated graft dysfunction. We aimed to evaluate the efficacy and safety of gastric per-oral endoscopic myotomy (G-POEM), a promising tool in patients with refractory gastroparesis, for managing refractory gastroparesis and GER in post-LTx patients. Patents and methods  This was a multicenter retrospective study on post-LTx patients who underwent G-POEM for management of gastroparesis and GER that were refractory to standard medical therapy. The primary outcome was clinical success post-G-POEM. Secondary outcomes included the rate of post-G-POEM objective esophageal pH exam normalization, rate of gastric emptying scintigraphy (GES) normalization, technical success, and adverse events. Results  A total of 20 patients (mean age 54.7 ± 14.1 years, Female 50 %) underwent G-POEM at a median time of 13 months (interquartile range 6.5-13.5) post-LTx. All G-POEM procedures were technically successful. Clinical success was achieved in 17 (85 %) patients during a median follow-up time of 8.9 (IQR: 3-17) months post-G-POEM. Overall GCSI and two of its subscales (bloating and postprandial fullness/early satiety) improved significantly following G-POEM. Two patients (10 %) developed post-procedural AEs (delayed bleeding 1, pyloric stenosis 1, both moderate in severity). Post-G-POEM GES improvement was achieved in 12 of 16 patients (75 %). All 20 patients were on proton pump inhibitors pre-G-POEM, as opposed to five post-G-POEM. Post-G-POEM PH study normalization was noted in nine of 10 patients (90 %) who underwent both pre- and post-G-poem pH testing. Conclusions  G-POEM is a promising noninvasive therapeutic tool for management of refractory gastroparesis and GER post-LTx.

Bile acids-induced lung injury: update of reverse translational biology

The presence of bile acids in lung tissue is associated with some clinical features observed in various medical specialties, but it took time to understand that these are due to a "bile acid-induced lung injury" since specific translational studies and cross-disciplinary awareness were lacking. We used a reverse translational approach to update and summarize the current knowledge about the mechanisms of bile acid-induced lung injury. This has been done in a cross-disciplinary fashion since these conditions may occur in patients of various age and in different medical fields. We here define these clinical conditions, then we review the physiopathology of these conditions and the animal models used to mimic them and, finally, their pathobiology. Mechanisms of bile acid-induced lung injury have been partially clarified overtime and are represented by: 1) the interaction with secretory phospholipase A2 pathway, 2) the effect on surfactant function and structure, 3) the biological effects on inflammation and local immunity, 4) the direct cellular toxicity. These mechanisms are schematically illustrated and histological comparisons between ARDS induced by bile acids and other triggers are also provided. Based on these mechanisms we propose possible direct therapeutic applications and, finally, we discuss further research steps to improve the understanding of processes that generate pathological clinical conditions.

Risk Factors and Outcomes for Gastroparesis After Lung Transplantation

BACKGROUND

Gastroparesis is common after lung transplantation and is associated with worse transplant outcomes, including the development of chronic lung allograft dysfunction (CLAD). This study sought to identify the prevalence, risk factors, and outcomes associated with a new diagnosis of gastroparesis after lung transplantation.

METHODS

This was a single-center retrospective study of patients who underwent lung transplantation in 2008-2018. The primary outcome was a new diagnosis of gastroparesis within 3 years of transplant. Secondary outcomes included a new diagnosis of gastroesophageal reflux and the association between gastroparesis and both post-transplant survival and CLAD-free survival. Multivariable logistic regression was used to compare diagnosis of gastroparesis and gastroesophageal reflux, while multivariable Cox proportional hazards models were used to analyze gastroparesis and post-transplant outcomes.

RESULTS

Of 616 patients with no prior history of gastroparesis, 107 (17.4%) were diagnosed with delayed gastric emptying within 3 years of transplant. On multivariable logistic regression, black race (OR 2.16, 95% CI 1.18-3.98, p = 0.013) was significantly associated with a new diagnosis of gastroparesis. Age, sex, history of diabetes, connective tissue disease, type of transplant, diagnosis group, renal function, and body mass index were not predictive of gastroparesis post-transplant. Gastroparesis was significantly associated with CLAD (HR 1.76, 95% CI 1.20-2.59, p = 0.004), but not with overall mortality (HR 1.16, p = 0.43).

CONCLUSION

While gastroparesis is common after lung transplantation, it remains difficult to predict which patients will develop these complications post-transplant. Black patients were more likely to be diagnosed with gastroparesis after adjusting for relevant confounders. Gastroparesis is associated with increased risk of CLAD, and further studies are needed to assess whether early detection and treatment can reduce the incidence of CLAD.

Delayed Gastric Emptying in Prelung Transplant Patients Is Associated With Posttransplant Acute Cellular Rejection Independent of Reflux

GOAL

The goal of this study was to evaluate the relationship between pretransplant delayed gastric emptying (DGE) and posttransplant acute cellular rejection (ACR) in lung transplant recipients.

BACKGROUND

DGE is very prevalent (23% to 91%) after lung transplantation but pretransplant prevalence has not been well studied. DGE may lead to poor posttransplant outcomes by predisposing to microaspiration. Pretransplant testing for DGE may help identify patients at risk for negative posttransplant outcomes including ACR.

MATERIALS AND METHODS

A retrospective review of a prospectively collected database of consecutive patients undergoing prelung transplant evaluation at a tertiary referral center from 2010 to 2015 was performed. Patients with pretransplant gastric emptying scintigraphy were included in the study. ACR diagnosis was made using International Society for Heart and Lung Transplantation (ISHLT) histologic criteria. Typical gastroparesis symptoms at the time of gastric emptying scintigraphy and pretransplant 24-hour pH impedance monitoring (MII-pH) data was collected. Logistic regression was used for multivariate analysis. Subgroup analyses were performed to account for gastroesophageal reflux (GER).

RESULTS

A total of 83 subjects (18 with DGE, 51.8% male, mean age: 53.6 y) met the criteria for inclusion. Patients with DGE were more likely to have typical symptoms of gastroparesis, though 61.1% of DGE patients were asymptomatic. ACR was more prevalent in patients with DGE (33.3% vs. 12.3%, P=0.04). This correlation was independent of GER as measured by MII-pH on subgroup analysis (75% vs. 14.3%, n=0.02).

DISCUSSION

Lung transplant recipients with pretransplant DGE have a higher incidence of ACR, independent of GER. Routine pretransplant testing for DGE may help identify patients at greater risk for adverse posttransplant outcomes as the majority of patients with DGE are asymptomatic.

Fundoplication after lung transplantation in patients with systemic sclerosis-related end-stage lung disease

INTRODUCTION

Gastroesophageal reflux and aspiration are risk factors for chronic lung allograft dysfunction in lung transplant recipients. Patients with systemic sclerosis are at an increased risk of aspiration due to esophageal dysmotility and an ineffective lower esophageal sphincter. The aim of this study is to understand the effect of fundoplication on outcomes in systemic sclerosis recipients.

METHODS

Between 2001 and 2019, 168 systemic sclerosis patients were referred for lung transplantation-51 (30.3%) were listed and 36 (21.4%) were transplanted. Recipients were stratified whether they underwent a fundoplication (n = 10, 27.8%) or not (n = 26, 72.2%). Freedom from chronic lung allograft dysfunction and survival were analyzed using log-rank test. Multivariable analysis for known risk factors was performed using a Cox-proportional hazards model.

RESULTS

Median time to fundoplication after transplantation was 16.4 months (interquartile range: 9.6-25.1) and all were laparoscopic (Dor 50%, Nissen 40%, Toupet 10%). There were no differences in acute rejection ⩾ A1 (26.9% vs 30%), or primary graft dysfunction grades 2-3 at 72 h (42.3% vs 40%) between groups. Recipients with fundoplication had an increased freedom from chronic lung allograft dysfunction (p = 0.035) and overall survival (p = 0.01). Fundoplication was associated with a reduced risk of mortality adjusting for other comorbidities (hazard ratio = 0.13; 95% confidence interval = 0.02-0.65; p = 0.014). Double and single lung transplant did not have different post-transplant survival.

CONCLUSION

Fundoplication in systemic sclerosis lung transplant recipients is associated with greater freedom from chronic lung allograft dysfunction and overall survival. Screening for reflux and aspiration followed by early fundoplication may delay graft deterioration in this population.

Strategies to protect surfactant and enhance its activity

The knowledge about surfactant biology is now deeper and recent research has allowed to clarify its role in several human lung disorders. The balance between surfactant production and consumption is better known and the same applies to their regulatory mechanisms. This has allowed to hypothesize and investigate several new and original strategies to protect surfactant and enhance its activity. These interventions are potentially useful for several disorders and particularly for acute respiratory distress syndrome. We here highlight the mechanisms regulating surfactant consumption, encompassing surfactant catabolism but also surfactant injury due to other mechanisms, in a physiopathology-driven fashion. We then analyze each corresponding strategy to protect surfactant and enhance its activity. Some of these strategies are more advanced in terms of research & development pathway, some others are still investigational, but all are promising and deserve a joint effort from clinical-academic researchers and the industry.

Identification of Lung Transplant Recipients with a Survival Benefit after Fundoplication

BACKGROUND

Gastroesophageal reflux disease (GERD) and aspiration of enteric contents is associated with worse outcomes after lung transplant. The purpose of this study is to elucidate populations that benefit the most from fundoplication after lung transplant.

METHODS

Lung transplants from 2001-2019 (n=971) were retrospectively reviewed and stratified by a fundoplication before (n=128) or after (n=24) chronic lung allograft dysfunction (CLAD) development vs those who didn't. Patients with a fundoplication prior to CLAD were propensity-matched to those without a fundoplication. The primary outcome of interest was post-transplant survival. Time-to-event rates were calculated using a multivariable Cox proportional hazards model and Kaplan-Meier functions.

RESULTS

A fundoplication prior to CLAD improved post-transplant survival before and after propensity-matching, and remained a significant predictor after adjusting for baseline characteristics (HR:0.57, 95% CI:0.4-0.8, P=0.001). Recipients with a restrictive disorder (HR: 0.46, 95% CI:0.3-0.73, P=0.001), age <65 (HR:0.48, 95% CI:0.32-0.71, P<0.001), and both single (HR:0.47, 95% CI:0.28-0.79, P=0.005) or double (HR:0.55, 95% CI:0.32-0.93, P=0.027) lung transplants had a significant decrease in mortality after fundoplication. The effect was present after excluding early deaths and/or CLAD diagnoses. GERD diagnosed by pH, impedance or EGD was not associated with worse outcomes. Among patients with CLAD, a fundoplication was an independent predictor of post-CLAD survival (HR:0.27, 95% CI:0.12-0.61, P=0.002).

CONCLUSIONS

A fundoplication before or after CLAD development is an independent predictor of survival. Younger patients with restrictive disease, independent of the type of transplant, have a survival benefit. GERD diagnosed by conventional methods was not associated with worse survival.

Systems Biology and Bile Acid Signalling in Microbiome-Host Interactions in the Cystic Fibrosis Lung

The study of the respiratory microbiota has revealed that the lungs of healthy and diseased individuals harbour distinct microbial communities. Imbalances in these communities can contribute to the pathogenesis of lung disease. How these imbalances occur and establish is largely unknown. This review is focused on the genetically inherited condition of Cystic Fibrosis (CF). Understanding the microbial and host-related factors that govern the establishment of chronic CF lung inflammation and pathogen colonisation is essential. Specifically, dissecting the interplay in the inflammation–pathogen–host axis. Bile acids are important host derived and microbially modified signal molecules that have been detected in CF lungs. These bile acids are associated with inflammation and restructuring of the lung microbiota linked to chronicity. This community remodelling involves a switch in the lung microbiota from a high biodiversity/low pathogen state to a low biodiversity/pathogen-dominated state. Bile acids are particularly associated with the dominance of Proteobacterial pathogens. The ability of bile acids to impact directly on both the lung microbiota and the host response offers a unifying principle underpinning the pathogenesis of CF. The modulating role of bile acids in lung microbiota dysbiosis and inflammation could offer new potential targets for designing innovative therapeutic approaches for respiratory disease.

Metabolomic profiling of extraesophageal reflux disease in children

Although respiratory symptoms in children are often attributed to gastroesophageal reflux disease, establishing a clear diagnosis of extraesophageal reflux disease (EERD) can be challenging, as there are no sensitive or specific EERD biomarkers. The aim of this study was to evaluate the metabolite profile in bronchoalveolar (BAL) fluid from children with suspected EERD and assess the impact of reflux treatment on these metabolites. In this prospective pilot study, we performed nontargeted global metabolomic profiling on BAL fluid from 43 children undergoing testing with bronchoscopy, upper endoscopy, and multichannel intraluminal impedance with pH (pH-MII) for evaluation of chronic respiratory symptoms. Twenty-three (54%) patients had an abnormal pH-MII study. Seventeen (40%) patients were on proton pump inhibitors (PPIs) for testing. Levels of histamine, malate, adenosine 5'-monophosphate, and ascorbate were significantly lower in subjects with abnormal pH-MII studies compared to those normal studies. Furthermore, in children off PPI therapy, those with abnormal pH-MII studies had robust increases in a number of glycerophospholipids within phospholipid metabolic pathways, including derivatives of glycerophosphorylcholine, glycerophosphoglycerol, and glycerophosphoinositol, compared to those with normal pH-MII studies. These findings offer insight into the impact of reflux and PPIs on the lungs and provide a foundation for future studies using targeted metabolomic analysis to identify potential biomarkers of EERD.

Aspiration of conjugated bile acids predicts adverse lung transplant outcomes and correlates with airway lipid and cytokine dysregulation

INTRODUCTION

Duodeno-gastroesophageal reflux aspiration is associated with chronic lung allograft dysfunction (CLAD). Reflux aspirate can contain bile acids (BA), functional molecules in the gastro-intestinal tract with emulsifying properties. We sought to determine and quantify the various BA species in airways of the lung transplant recipients to better understand the various effects of aspirated BA that contribute to post-transplantation outcomes.

METHODS

Bronchial washings (BW) were prospectively collected from lung transplant recipients and subsequently assayed by liquid chromatography-mass spectrometry for 13 BA and 25 lipid families. Patients were monitored for CLAD, rejection, inflammation and airway infections.

RESULTS

Detectable BA were present in 45/50 patients (90%) at 3 months after transplant. Elevated BA and predominance of conjugated species were independent predictors of CLAD (hazard ratio 7.9; 95% confidence interval 2.7-23.6; p < 0.001 and 7.3; 2.4-22; p < 0.001, respectively) and mortality (hazard ratio 4.4; 1.5-12.7; p = 0.007 and 4.8; 1.4-15.8; p = 0.01, respectively). High BA associated with increased positive bacterial cultures (60% vs 25%, p = 0.02). Primary conjugated species independently correlated with the rate of bacterial cultures during the first-year post-transplant (Beta coefficient: 0.77; 0.28-1.26; p = 0.003) and changes in airway lipidome and cytokines.

CONCLUSIONS

Higher BA levels and predominance of conjugated BA are independent predictors of chronic lung allograft dysfunction, mortality and bacterial infections. Primary conjugated BA are related to distinct changes in airway lipidome and inflammatory cytokines. This elucidates novel evidence into the mechanism following BA aspiration and proposes novel markers for prediction of adverse post-transplant outcomes.

Safety and efficacy of an implantable device for management of gastroesophageal reflux in lung transplant recipients

Background

Magnetic sphincter augmentation (MSA) is a promising minimally invasive surgical technique for management of gastroesophageal reflux disease (GERD); however, device implantation after transplantation has not been studied and may be concerning in these immunosuppressed patients. We explored the safety of the LINX Reflux Management System (MSA device) for management of GERD following lung transplantation (LTx).

Methods

Lung transplant recipients who underwent LINX implantation at our institution between 2017 and 2019 were followed prospectively in the Reflux Following Lung Transplantation and Associated Treatment Registry. Ambulatory pH testing and acid-suppressing medication use were compared before and after LINX implantation. One-year outcomes and change in pulmonary function were compared between matched LINX and fundoplication groups.

Results

Of 17 patients who underwent post-lung transplant LINX implantation, 8 (47.1%) agreed to undergo post-LINX pH testing. Three/eight (37.5%) patients achieved normal esophageal acid exposure time; 14 (82.4%) remained on acid-suppressing medication at one-year under the direction of their transplant teams. One-year patient survival and change in pulmonary function were similar between groups. LINX patients experienced more early side effects.

Conclusions

Use of the LINX MSA device in a cohort of lung transplant recipients at our institution was associated with similar short-term safety compared to traditional fundoplication, however assessment of efficacy was limited. Further investigation is needed to characterize the long-term efficacy of LINX implantation after LTx.

High-fiber diets attenuate emphysema development via modulation of gut microbiota and metabolism

Dietary fiber functions as a prebiotic to determine the gut microbe composition. The gut microbiota influences the metabolic functions and immune responses in human health. The gut microbiota and metabolites produced by various dietary components not only modulate immunity but also impact various organs. Although recent findings have suggested that microbial dysbiosis is associated with several respiratory diseases, including asthma, cystic fibrosis, and allergy, the role of microbiota and metabolites produced by dietary nutrients with respect to pulmonary disease remains unclear. Therefore, we explored whether the gut microbiota and metabolites produced by dietary fiber components could influence a cigarette smoking (CS)-exposed emphysema model. In this study, it was demonstrated that a high-fiber diet including non-fermentable cellulose and fermentable pectin attenuated the pathological changes associated with emphysema progression and the inflammatory response in CS-exposed emphysema mice. Moreover, we observed that different types of dietary fiber could modulate the diversity of gut microbiota and differentially impacted anabolism including the generation of short-chain fatty acids, bile acids, and sphingolipids. Overall, the results of this study indicate that high-fiber diets play a beneficial role in the gut microbiota-metabolite modulation and substantially affect CS-exposed emphysema mice. Furthermore, this study suggests the therapeutic potential of gut microbiota and metabolites from a high-fiber diet in emphysema via local and systemic inflammation inhibition, which may be useful in the development of a new COPD treatment plan.

LPS-induced Airway-centered Inflammation Leading to BOS-like Airway Remodeling Distinct From RAS-like Fibrosis in Rat Lung Transplantation

BACKGROUND

Localization of inflammatory stimuli may direct lung allografts to different phenotypes of chronic dysfunction, such as bronchiolitis obliterans syndrome (BOS) or restrictive allograft syndrome (RAS). We hypothesized that airway stimulation with lipopolysaccharide (LPS) in rats leads to airway-centered inflammation similar to human BOS.

METHODS

Rat left lung transplantation was conducted (donor: Brown Norway, recipient: Lewis). Allotransplant recipients received cyclosporine A (CsA) until postoperative day 56 with airway instillation of LPS (Allo-LPS, n = 8), phosphate buffered saline (Allo-PBS, n = 5) from days 35 to 46 (3 times a wk), or no further treatment (n = 4). Some allotransplant recipients received CsA until day 14 and were immunosuppression free after day 15 until day 56. Bronchial and pleural fibrosis were semiquantified; alveolar fibrosis was evaluated with a histological scale.

RESULTS

The Allo-LPS group had significantly increased International Society for Heart and Lung Transplantation rejection grades (grade A, P = 0.005; grade B, P = 0.004), bronchial obstructive proportion (0.34 ± 0.04% [Allo-LPS] versus 0.11 ± 0.04% [Allo-PBS], P = 0.006), and airway resistance (3.05 ± 1.78 cm H2O·s/mL [Allo-LPS] versus 0.83 ± 0.58 cm H2O·s/mL [Allo-PBS], P = 0.007) compared with other groups. Allotransplant recipients that underwent a short course of CsA developed RAS-like fibrosis involving the airways, alveoli, and pleura.

CONCLUSIONS

Airway instillation of LPS in allografts under immunosuppression resulted in BOS-like airway-centered inflammation and fibrosis distinct from RAS-like diffuse fibrosis, which was induced by a shortened course of immunosuppression. We propose novel animal models for BOS and RAS after lung transplantation.

The Great ESKAPE: Exploring the Crossroads of Bile and Antibiotic Resistance in Bacterial Pathogens

Throughout the course of infection, many pathogens encounter bactericidal conditions that threaten the viability of the bacteria and impede the establishment of infection. Bile is one of the most innately bactericidal compounds present in humans, functioning to reduce the bacterial burden in the gastrointestinal tract while also aiding in digestion. It is becoming increasingly apparent that pathogens successfully resist the bactericidal conditions of bile, including bacteria that do not normally cause gastrointestinal infections. This review highlights the ability of Enterococcus, Staphylococcus, Klebsiella, Acinetobacter, Pseudomonas, Enterobacter (ESKAPE), and other enteric pathogens to resist bile and how these interactions can impact the sensitivity of bacteria to various antimicrobial agents. Given that pathogen exposure to bile is an essential component to gastrointestinal transit that cannot be avoided, understanding how bile resistance mechanisms align with antimicrobial resistance is vital to our ability to develop new, successful therapeutics in an age of widespread and increasing antimicrobial resistance.

Esophageal Evaluation for Patients Undergoing Lung Transplant Evaluation: What Should We Do for Evaluation and Management

Lung transplantation is a high-risk, but lifesaving, procedure for patients with end-stage lung disease. Although 1-year survival is high, long-term survival is not nearly as high, due mainly to acute and chronic rejection. Bronchiolitis obliterans syndrome is the most common type of chronic rejection and often leads to poor outcomes. For this reason, esophageal testing in the lung transplant population has become a major issue, and this article discusses the evidence behind esophageal testing, the importance of esophageal dysmotility gastroesophageal reflux disease, both acidic and nonacidic reflux, and aspiration and the treatment of these findings.

Chronic lung allograft dysfunction post-lung transplantation: The era of bronchiolitis obliterans syndrome and restrictive allograft syndrome

Chronic lung allograft dysfunction (CLAD) following lung transplantation limits long-term survival considerably. The main reason for this is a lack of knowledge regarding the pathological condition and the establishment of treatment. The consensus statement from the International Society for Heart and Lung Transplantation on CLAD in 2019 classified CLAD into two main phenotypes: Bronchiolitis obliterans syndrome and restrictive allograft syndrome. Along with this clear classification, further exploration of the mechanisms and the development of appropriate prevention and treatment strategies for each phenotype are desired. In this review, we summarize the new definition of CLAD and update and summarize the existing knowledge on the underlying mechanisms of bronchiolitis obliterans syndrome and restrictive allograft syndrome, which have been elucidated from clinicopathological observations and animal experiments worldwide.

Bronchoalveolar bile acid and inflammatory markers to identify high-risk lung transplant recipients with reflux and microaspiration

BACKGROUND

Gastroesophageal reflux disease (GERD) is a risk factor for chronic lung allograft dysfunction. Bile acids-putative markers of gastric microaspiration-and inflammatory proteins in the bronchoalveolar lavage (BAL) have been associated with chronic lung allograft dysfunction, but their relationship with GERD remains unclear. Although GERD is thought to drive chronic microaspiration, the selection of patients for anti-reflux surgery lacks precision. This multicenter study aimed to test the association of BAL bile acids with GERD, lung inflammation, allograft function, and anti-reflux surgery.

METHODS

We analyzed BAL obtained during the first post-transplant year from a retrospective cohort of patients with and without GERD, as well as BAL obtained before and after Nissen fundoplication anti-reflux surgery from a separate cohort. Levels of taurocholic acid (TCA), glycocholic acid, and cholic acid were measured using mass spectrometry. Protein markers of inflammation and injury were measured using multiplex assay and enzyme-linked immunosorbent assay.

RESULTS

At 3 months after transplantation, TCA, IL-1β, IL-12p70, and CCL5 were higher in the BAL of patients with GERD than in that of no-GERD controls. Elevated TCA and glycocholic acid were associated with concurrent acute lung allograft dysfunction and inflammatory proteins. The BAL obtained after anti-reflux surgery contained reduced TCA and inflammatory proteins compared with that obtained before anti-reflux surgery.

CONCLUSIONS

Targeted monitoring of TCA and selected inflammatory proteins may be useful in lung transplant recipients with suspected reflux and microaspiration to support diagnosis and guide therapy. Patients with elevated biomarker levels may benefit most from anti-reflux surgery to reduce microaspiration and allograft inflammation.

Esophageal Function Tests are Not Associated with Barium Swallow Findings in Advanced Lung Disease

Gastroesophageal reflux disease and esophageal dysmotility are common in patients with advanced lung disease (ALD) and are associated with worse outcomes. Assessing esophageal function in these patients is relevant for determining pulmonary transplant eligibility and prognosticating post-transplant outcomes. Barium Swallow (BaS) is a non-invasive testing modality often performed as a complement to formal esophageal function tests (EFTs), but its role and clinical utility in this context is unknown. Therefore, we aimed to determine the relationship between BaS and EFTs with high-resolution manometry (HRM) and 24-h ambulatory pH-metry in patients with ALD. We performed a retrospective study of 226 consecutive patients undergoing evaluation for lung transplantation at a single center. All patients underwent EFTs and BaS independent of clinical history or symptoms per institutional protocol. Appropriate statistical tests were performed to evaluate the relationship between EFTs and BaS. Mucosal, reflux and motility findings were categorized. Abnormal motility was reported in 133 (59%) patients by BaS and 99 (44%) by HRM, with a significant difference in the proportions of patients with abnormal studies (p < 0.01). There were 7 (26%) patients with abnormal barium tablet passage who had normal HRM. The sensitivity (35%) and specificity (77%) for detecting pathologic reflux with BaS was poor. Inducibility of reflux and barium column height were not associated with pH-metry results. No clinically significant luminal irregularities were identified. In conclusion, while BaS can non-invasively assess esophageal mucosa, its findings are not associated with EFTs in patients with ALD.

Gastroesophageal Reflux and Microaspiration in Lung Transplant Recipients: The Utility of a Single Esophageal Manometry and pH Probe Monitoring Study

BACKGROUND

Gastroesophageal reflux (GER) in recipients of lung transplant (LTX) is associated with chronic allograft rejection, presumably via microaspiration that damages airway epithelium. Most LTX programs perform a single post-LTX esophageal study to evaluate for GER; the efficacy of this test is unclear.

METHODS

Patients with 1 year of post-LTX follow-up, including routine bronchoscopies with bronchoalveolar lavage fluid (BALF) samples as well as high-resolution esophageal manometry and pH probe monitoring (HREMpH), were evaluated. BALF samples were analyzed with competitive enzyme-linked immunosorbent assay to detect bile salts, which are indicative of aspiration. These results were compared to results of HREMpH studies post LTX.

RESULTS

Ninety BALF samples were analyzed for bile salts and acted as disease positive for this evaluation. Of the 13 HREMpH cases, 8 were positive for GER, but only 3 were positive for bile salts via assay. Of the 5 HREMpH-negative cases, 2 experienced aspiration. A solitary HREMpH study had 60.0% sensitivity and 37.5% specificity with positive and negative likelihood ratios: 0.96 and 1.07, respectively.

CONCLUSION

Microaspiration appears to be an intermittent phenomenon, and HREMpH screening poorly correlates with BALF evidence of aspiration; which may not be adequate. As aspiration detection is crucial in this population, further analysis is warranted.

Bronchiolitis obliterans syndrome and restrictive allograft syndrome after lung transplantation: why are there two distinct forms of chronic lung allograft dysfunction?

Bronchiolitis obliterans syndrome (BOS) had been considered to be the representative form of chronic rejection or chronic lung allograft dysfunction (CLAD) after lung transplantation. In BOS, small airways are affected by chronic inflammation and obliterative fibrosis, whereas peripheral lung tissue remains relatively intact. However, recognition of another form of CLAD involving multiple tissue compartments in the lung, termed restrictive allograft syndrome (RAS), raised a fundamental question: why there are two phenotypes of CLAD? Increasing clinical and experimental data suggest that RAS may be a prototype of chronic rejection after lung transplantation involving both cellular and antibody-mediated alloimmune responses. Some cases of RAS are also induced by fulminant general inflammation in lung allografts. However, BOS involves alloimmune responses and the airway-centered disease process can be explained by multiple mechanisms such as external alloimmune-independent stimuli (such as infection, aspiration and air pollution), exposure of airway-specific autoantigens and airway ischemia. Localization of immune responses in different anatomical compartments in different phenotypes of CLAD might be associated with lymphoid neogenesis or the de novo formation of lymphoid tissue in lung allografts. Better understanding of distinct mechanisms of BOS and RAS will facilitate the development of effective preventive and therapeutic strategies of CLAD.

The role of innate immunity in the long-term outcome of lung transplantation

Long-term survival after lung transplantation remains suboptimal due to chronic lung allograft dysfunction (CLAD), a progressive scarring process affecting the graft. Although anti-donor alloimmunity is central to the pathogenesis of CLAD, its underlying mechanisms are not fully elucidated and it is neither preventable nor treatable using currently available immunosuppression. Recent evidence has shown that innate immune stimuli are fundamental to the development of CLAD. Here, we examine long-standing assumptions and new concepts linking innate immune activation to late lung allograft fibrosis.

Esophageal contractility increases and gastroesophageal reflux does not worsen after lung transplantation

Gastroesophageal reflux and esophageal dysmotility are common in patients with advanced lung disease and are associated with allograft dysfunction after lung transplantation. The effect of transplantation on reflux and esophageal motility is unclear. The aim of this study was to describe the changes in esophageal function occurring after lung transplantation. A retrospective cohort study was performed on lung transplant candidates evaluated at a tertiary care center between 2015 and 2016. A total of 76 patients who underwent lung transplantation had high-resolution manometry and ambulatory pH-metry before and after transplant. Demographic data, esophageal function testing results, and clinical outcomes such as pulmonary function testing were collected and analyzed using appropriate statistical tests and multivariable regression. Of the 76 patients, 59 (78%) received a bilateral transplant. There was a significant increase in esophageal contractility posttransplant, with an increase in median distal contractile integral from 1470 to 2549 mmHg cm s (P < 0.01). There were 19 patients with Jackhammer esophagus posttransplant, including 15 patients with normal motility pretransplant. Nine patients with ineffective or fragmented peristalsis pretransplant had normal manometry posttransplant. Abnormal pH-metry was observed in 35 (46%) patients pretransplant and 29 (38%) patients posttransplant (P = 0.33). Patients with gastroesophageal reflux disease posttransplant had less improvement in pulmonary function at one year, as measured by forced expiratory volume (P = 0.04). These results demonstrate that esophageal contractility increases significantly after lung transplantation, with an associated change in motility classification. In comparison, gastroesophageal reflux does not worsen, but is associated with worse pulmonary function, posttransplant.

Bile acids inhibit cholinergic constriction in proximal and peripheral airways from humans and rodents

Duodenogastroesophageal reflux (DGER) is associated with chronic lung disease. Bile acids (BAs) are established markers of DGER aspiration and are important risk factors for reduced post-transplant lung allograft survival by disrupting the organ-specific innate immunity, facilitating airway infection and allograft failure. However, it is unknown whether BAs also affect airway reactivity. We investigated the acute effects of 13 BAs detected in post-lung-transplant surveillance bronchial washings (BW) on airway contraction. We exposed precision-cut slices from human and mouse lungs to BAs and monitored dynamic changes in the cross-sectional luminal area of peripheral airways using video phase-contrast microscopy. We also used guinea pig tracheal rings in organ baths to study BA effects in proximal airway contraction induced by electrical field stimulation. We found that most secondary BAs at low micromolar concentrations strongly and reversibly relaxed smooth muscle and inhibited peripheral airway constriction induced by acetylcholine but not by noncholinergic bronchoconstrictors. Similarly, secondary BAs strongly inhibited cholinergic constrictions in tracheal rings. In contrast, TC-G 1005, a specific agonist of the BA receptor Takeda G protein-coupled receptor 5 (TGR5), did not cause airway relaxation, and Tgr5 deletion in knockout mice did not affect BA-induced relaxation, suggesting that this receptor is not involved. BAs inhibited acetylcholine-induced inositol phosphate synthesis in human airway smooth muscle cells overexpressing the muscarinic M3 receptor. Our results demonstrate that select BAs found in BW of patients with lung transplantation can affect airway reactivity by inhibiting the cholinergic contractile responses of the proximal and peripheral airways, possibly by acting as antagonists of M3 muscarinic receptors.

Surfactant protein A and D polymorphisms and methylprednisolone pharmacogenetics in donor lungs

OBJECTIVE

Surfactant proteins A and D are important molecules involved in lung allograft innate immunity. Genetic polymorphisms of surfactant proteins A and D are associated with various lung diseases. In this study, surfactant protein A and D expression responses were investigated during pharmacogenetics upon methylprednisolone treatment as observed during lung transplantation.

METHODS

A human cell line (NCI-H441) and precision-cut lung slices from 16 human donors were incubated with methylprednisolone, and surfactant protein A1, surfactant protein A2, and surfactant protein D messenger RNA and surfactant protein A protein expression were assayed. Surfactant protein A1, A2, and D polymorphisms and surfactant protein A gene and protein expressions were determined.

RESULTS

In NCI-H441 cells, methylprednisolone treatment at 10^-5 M and 10^-6 M reduced surfactant protein A1 and surfactant protein A2 messenger RNA and surfactant protein A protein expression (P < .05). A pharmacogenetic relationship was observed in human donor precision-cut lung slices between the surfactant protein A2 (1A^x) variants: Surfactant protein A1, A2, and D messenger RNA expression were greater for 1A⁰ versus 1A¹ (P < .05); surfactant protein A1/surfactant protein A2 genotype 6A²6A²/1A⁰1A⁰ (n = 5) showed greater surfactant protein A1, A2, and D messenger RNA expression and surfactant protein A protein expression compared with the other surfactant protein A1/surfactant protein A2 genotypes (n = 11) (P < .05).

CONCLUSIONS

The surfactant protein A genotype and methylprednisolone stimuli influence donor lung surfactant protein A and D expression. Lungs carrying the surfactant protein A2 variant 1A⁰ have a greater expression of surfactant protein A when treated with methylprednisolone. Surfactant protein A polymorphisms could be used to personalize immunosuppressive regimens.

Guts and Gall: Bile Acids in Regulation of Intestinal Epithelial Function in Health and Disease

Epithelial cells line the entire surface of the gastrointestinal tract and its accessory organs where they primarily function in transporting digestive enzymes, nutrients, electrolytes, and fluid to and from the luminal contents. At the same time, epithelial cells are responsible for forming a physical and biochemical barrier that prevents the entry into the body of harmful agents, such as bacteria and their toxins. Dysregulation of epithelial transport and barrier function is associated with the pathogenesis of a number of conditions throughout the intestine, such as inflammatory bowel disease, chronic diarrhea, pancreatitis, reflux esophagitis, and cancer. Driven by discovery of specific receptors on intestinal epithelial cells, new insights into mechanisms that control their synthesis and enterohepatic circulation, and a growing appreciation of their roles as bioactive bacterial metabolites, bile acids are currently receiving a great deal of interest as critical regulators of epithelial function in health and disease. This review aims to summarize recent advances in this field and to highlight how bile acids are now emerging as exciting new targets for disease intervention.

Sequential broncho-alveolar lavages reflect distinct pulmonary compartments: clinical and research implications in lung transplantation

Background

Bronchoalveolar lavage (BAL) has proven to be very useful to monitor the lung allograft after transplantation. In addition to allowing detection of infections, multiple BAL analytes have been proposed as potential biomarkers of lung allograft rejection or dysfunction. However, BAL collection is not well standardized and differences in BAL collection represent an important source of variation. We hypothesized that there are systematic differences between sequential BALs that are relevant to BAL analysis.

Methods

As part of 126 consecutive bronchoscopies in lung transplant recipients, two sequential BALs (BAL1 and BAL2) were performed in one location during each bronchoscopy by instilling and suctioning 50 ml of normal saline twice into separate containers. Cell concentration, viability and differentials, Surfactant Protein-D (SP-D), Club Cell Secretory Protein (CCSP), and levels of CXCL10, IL-10, CCL2, CCL5, VEGF-C, RAGE, CXCL9, CXCL1, IL-17A, IL-21, PDGF, and GCSF were compared between BAL1 and BAL2.

Results

Total cell concentration did not differ between BAL1 and BAL2; however, compared to BAL2, BAL1 had more dead cells, epithelial cells, neutrophils, and higher concentrations of airway epithelium-derived CCSP and inflammatory markers. BAL2 had a higher concentration of SP-D compared to BAL1.

Conclusion

In this study performed in lung transplant recipients, we show that sequential BALs represent different lung compartments and have distinct compositions. BAL1 represents the airway compartment with more epithelial cells, neutrophils, and epithelium-derived CCSP. Conversely, BAL2 samples preferentially the distal bronchoalveolar space with greater cell viability and higher SP-D. Our findings illustrate how the method of BAL collection can influence analyte concentrations and further emphasize the need for a standardized approach in translational research involving BAL samples.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0786-z) contains supplementary material, which is available to authorized users.

Lung Transplant Outcomes in Systemic Sclerosis with Significant Esophageal Dysfunction. A Comprehensive Single-Center Experience

RATIONALE

Consideration of lung transplantation in patients with systemic sclerosis (SSc) remains guarded, often due to the concern for esophageal dysfunction and the associated potential for allograft injury and suboptimal post-lung transplantation outcomes.

OBJECTIVES

The purpose of this study was to systematically report our single-center experience regarding lung transplantation in the setting of SSc, with a particular focus on esophageal dysfunction.

METHODS

We retrospectively reviewed all lung transplants at our center from January 1, 2000 through August 31, 2012 (n = 562), comparing the SSc group (n = 35) to the following lung transplant diagnostic subsets: all non-SSc (n = 527), non-SSc diffuse fibrotic lung disease (n = 264), and a non-SSc matched group (n = 109). We evaluated post-lung transplant outcomes, including survival, primary graft dysfunction, acute rejection, bronchiolitis obliterans syndrome, and microbiology of respiratory isolates. In addition, we defined severe esophageal dysfunction using esophageal manometry and esophageal morphometry criteria on the basis of chest computed tomography images. For patients with SSc referred for lung transplant but subsequently denied (n = 36), we queried the reason(s) for denial with respect to the concern for esophageal dysfunction.

MEASUREMENTS AND MAIN RESULTS

The 1-, 3-, and 5-year post-lung transplant survival for SSc was 94, 77, and 70%, respectively, and similar to the other groups. The remaining post-lung transplant outcomes evaluated were also similar between SSc and the other groups. Approximately 60% of the SSc group had severe esophageal dysfunction. Pre-lung transplant chest computed tomography imaging demonstrated significantly abnormal esophageal morphometry for SSc when compared with the matched group. Importantly, esophageal dysfunction was the sole reason for lung transplant denial in a single case.

CONCLUSIONS

Relative to other lung transplant indications, our SSc group experienced comparable survival, primary graft dysfunction, acute rejection, bronchiolitis obliterans syndrome, and microbiology of respiratory isolates, despite the high prevalence of severe esophageal dysfunction. Esophageal dysfunction rarely precluded active listing for lung transplantation.

Impaired Esophageal Motility and Clearance Post-Lung Transplant: Risk For Chronic Allograft Failure

OBJECTIVES

Gastroesophageal reflux is common in patients post-lung transplantation (LTx) and thus considered a risk factor for aspiration and consequently allograft rejection and the development of chronic allograft failure. However, evidence supporting this remains unclear and often contradictory. Our aim was to examine the role played by esophageal motility on gastroesophageal reflux exposure, along with its clearance and that of boluses swallowed, and the relationship to development of obstructive chronic lung allograft dysfunction (o-CLAD).

METHODS

Patients post-LTx (n=50, 26 female; mean age 55 years (range, 20-73 years)) completed high-resolution impedance manometry and 24-h pH/impedance. Esophageal motility abnormalities were classified based upon the Chicago Classification version 3.0.

RESULTS

Esophagogastric junction outflow obstruction alone (EGJOOa) (P=0.01), incomplete bolus transit (IBT) (P=0.006) and proximal reflux (P=0.042) increased the risk for o-CLAD. Patients with EGJOOa were most likely to present with o-CLAD (77%); despite being less likely to exhibit abnormal numbers of reflux events (10%) compared with those with normal motility (o-CLAD: 29%, P<0.05; abnormal reflux events: 64%, P<0.05). Patients with EGJOOa had lower total reflux bolus exposure time than those with normal motility (0.6 vs. 1.5%; P<0.05). In addition, poor esophageal clearance documented by abnormal post-reflux swallow-induced peristaltic wave index associated with o-CLAD; inversely correlating with the proportion of reflux events reaching the proximal esophagus (r=-0.251; P=0.052).

CONCLUSIONS

These observations support esophageal dysmotility, especially EGJOOa, and impaired clearance of swallowed bolus or refluxed contents, more so than just the presence of gastroesophageal reflux alone, as important risk factors in the development of o-CLAD.

Role of gastroesophageal reflux disease in lung transplantation

Lung transplantation is one of the highest risk solid organ transplant modalities. Recent studies have demonstrated a relationship between gastroesophageal reflux disease (GERD) and lung transplant outcomes, including acute and chronic rejection. The aim of this review is to discuss the pathophysiology, evaluation, and management of GERD in lung transplantation, as informed by the most recent publications in the field. The pathophysiology of reflux-induced lung injury includes the effects of aspiration and local immunomodulation in the development of pulmonary decline and histologic rejection, as reflective of allograft injury. Modalities of reflux and esophageal assessment, including ambulatory pH testing, impedance, and esophageal manometry, are discussed, as well as timing of these evaluations relative to transplantation. Finally, antireflux treatments are reviewed, including medical acid suppression and surgical fundoplication, as well as the safety, efficacy, and timing of such treatments relative to transplantation. Our review of the data supports an association between GERD and allograft injury, encouraging a strategy of early diagnosis and aggressive reflux management in lung transplant recipients to improve transplant outcomes. Further studies are needed to explore additional objective measures of reflux and aspiration, better compare medical and surgical antireflux treatment options, extend follow-up times to capture longer-term clinical outcomes, and investigate newer interventions including minimally invasive surgery and advanced endoscopic techniques.

Chronic microaspiration of bile acids induces lung fibrosis through multiple mechanisms in rats

Gastroesophageal reflux (GER) and microaspiration of duodenogastric refluxate have been recognized as a risk factor for pulmonary fibrosis. Recent evidence suggests that bile acid microaspiration may contribute to the development of lung fibrosis. However, the molecular evidence is scarce and the underlying mechanisms remain to be elucidated. We have recently demonstrated that bile acids induce activation of alveolar epithelial cells (AECs) and lung fibroblasts in vitro In the present study, a rat model of bile acid microaspiration was established by weekly intratracheal instillation of three major bile acids including chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), and lithocholic acid (LCA). Repeated microaspiration of CDCA, DCA, and LCA caused fibrotic changes, including alveolar wall thickening and extensive collagen deposition, in rat lungs. Bile acid microaspiration also induced alveolar epithelial-mesenchymal transition (EMT), as indicated by up-regulation of mesenchymal markers α-smooth muscle actin (α-SMA) and vimentin, as well as down-regulaton of epithelial markers E-cadherin and cytokeratin in alveolar epithelium of rat lungs. The expression of fibrogenic mediators, including transforming growth factor-β1 (TGF-β1), connective tissue growth factor (CTGF), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and periostin, was significantly elevated in rat lungs exposed to microaspiration of bile acids. Furthermore, microaspiration of bile acids also induced p-Smad3 and farnesoid X receptor (FXR) expression in rat lungs. Our findings suggest that microaspiration of bile acids could promote the development of pulmonary fibrosis in vivo, possibly via stimulating fibrogenic mediator expression and activating TGF-β1/Smad3 signaling and FXR.