Bronchiolitis obliterans syndrome: the final frontier for lung transplantation

A review of the therapeutic potential of the cysteinyl leukotriene antagonist Montelukast in the treatment of bronchiolitis obliterans syndrome following lung and hematopoietic-stem cell transplantation and its possible mechanisms

Lung and hematopoietic stem cell transplantation are therapeutic modalities in chronic pulmonary and hematological diseases, respectively. One of the complications in these patients is the development of bronchiolitis obliterans syndrome (BOS). The efficacy and safety of available treatment strategies in BOS remain a challenge. A few mechanisms have been recognized for BOS in lung transplant and graft-versus-host disease (GVHD) patients involving the TH-1 and TH-2 cells, NF-kappa B, TGF-b, several cytokines and chemokines, and cysteinyl leukotrienes (CysLT). Montelukast is a highly selective CysLT receptor antagonist that has been demonstrated to exert anti-inflammatory and anti-fibrotic effects in abundant experiments. One area of interest for the use of montelukast is lung transplants or GVHD-associated BOS. Herein, we briefly review data regarding the mechanisms involved in BOS development and montelukast administration as a treatment modality for BOS, and finally, the possible relationship between CysLTs antagonism and BOS improvement will be discussed.

Donor IL-17 receptor A regulates LPS-potentiated acute and chronic murine lung allograft rejection

Chronic lung allograft dysfunction (CLAD) is a major complication after lung transplantation that results from a complex interplay of innate inflammatory and alloimmune factors, culminating in parenchymal and/or obliterative airway fibrosis. Excessive IL-17A signaling and chronic inflammation have been recognized as key factors in these pathological processes. Herein, we developed a model of repeated airway inflammation in mouse minor alloantigen-mismatched single-lung transplantation. Repeated intratracheal LPS instillations augmented pulmonary IL-17A expression. LPS also increased acute rejection, airway epithelial damage, and obliterative airway fibrosis, similar to human explanted lung allografts with antecedent episodes of airway infection. We then investigated the role of donor and recipient IL-17 receptor A (IL-17RA) in this context. Donor IL-17RA deficiency significantly attenuated acute rejection and CLAD features, whereas recipient IL-17RA deficiency only slightly reduced airway obliteration in LPS allografts. IL-17RA immunofluorescence positive staining was greater in human CLAD lungs compared with control human lung specimens, with localization to fibroblasts and myofibroblasts, which was also seen in mouse LPS allografts. Taken together, repeated airway inflammation after lung transplantation caused local airway epithelial damage, with persistent elevation of IL-17A and IL-17RA expression and particular involvement of IL-17RA on donor structural cells in development of fibrosis.

Ferroptosis in the post-transplantation inflammatory response

Transplantation is a life-saving therapy for patients with end-stage organ disease. Successful outcomes after transplantation require mitigation of the post-transplant inflammatory response, limiting alloreactivity, and prevention of organ rejection. Traditional immunosuppressive regimens aim to dampen the adaptive immune response; however, recent studies have shown the feasibility and efficacy of targeting the innate immune response. Necroinflammation initiated by donor organ cell death is implicated as a critical mediator of primary graft dysfunction, acute rejection, and chronic rejection. Ferroptosis is a form of regulated cell death that triggers post-transplantation inflammation and drives the activation of both innate and adaptive immune cells. There is a growing acceptance of the clinical relevance of ferroptosis to solid organ transplantation. Modulating ferroptosis may be a potentially promising strategy to reduce complications after organ transplantation.

Successful treatment of postinfectious bronchiolitis obliterans with gamma globulin in a tertiary center: 10 years of experience

INTRODUCTION

Bronchiolitis obliterans is characterized by partial or total occlusion of the bronchioles due to inflammation and fibrosis, and the most common form is postinfectious bronchiolitis obliterans (PIBO). This study aimed to retrospectively present our intravenous immunoglobulin (IVIG) treatment experience in PIBO patients with a clinically severe course despite receiving commonly used treatment protocols.

MATERIALS AND METHODS

The study included patients aged 0-18 with subtle immunological abnormalities who were followed up in our center for PIBO between 2010 and 2021. Clinical evaluation, body mass index (BMI), computerized tomography (CT) image scoring, and immunological parameters were recorded before and after IVIG treatment.

RESULTS

Of the 11 patients included in the study, 90% were male, the mean age at diagnosis was 27.1 months (range: 5-68 months) and the mean current age was 81.4 months (range: 15-188 months). The number of hospital visits due to infection and the frequency of hospitalizations decreased markedly in the patients who underwent IVIG therapy. Oxygen therapy was discontinued in all patients, and improvements in radiological severity scores were observed. BMI z-scores improved over the baseline values after IVIG therapy.

CONCLUSION

Corticosteroids are considered the best first-line treatment to control inflammation in PIBO. In our study group, PIBO patients showed favorable clinical and radiological responses to regular IVIG treatment, possibly due to minor immune deficiency secondary to steroids or as a result of undetected adaptive and innate immune defects involved in the etiology of severe PIBO.

IL-17A neutralization fails to attenuate airway remodeling and potentiates a proinflammatory lung microenvironment in diacetyl-exposed rats

Bronchiolitis obliterans (BO) is a devastating lung disease that can develop following inhalation exposure to certain chemicals. Diacetyl (DA) is one chemical commonly associated with BO development when inhaled at occupational levels. Previous studies in rats have shown that repetitive DA vapor exposures increased lung CD4+CD25+ T cells and bronchoalveolar (BAL) interleukin-17A (IL-17A) concentrations concurrent with the development of airway remodeling. We hypothesized that IL-17A neutralization would attenuate the severity of airway remodeling after repetitive DA vapor exposures. Sprague-Dawley rats were exposed to 200 parts-per-million DA vapor or filtered air (RA) for 6 h/day × 5 days and monitored for 2 wk postexposure. Treatment with IL-17A neutralization (αIL-17A) or IgG (control) began immediately following exposures and continued twice weekly until study's end. Lungs were harvested for histology, flow cytometry, and BAL analyses. Survival, oxygen saturations, and percent weight change decreased significantly in DA-exposed versus RA-exposed rats, but did not differ significantly between DA + αIL-17A versus DA + IgG. Similarly, the number nor severity of airway lesions did not differ significantly between DA + αIL-17A versus DA + IgG rats despite the percentage of lung regulatory T cells increasing with decreased BAL IL-17A concentrations. Ashcroft scoring of the distal lung parenchyma suggested worse parenchymal remodeling in DA + αIL-17A versus DA + IgG rats with increased expression of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and nuclear factor-kappa B (NF-κB). Collectively, IL-17A neutralization in DA-exposed rats failed to attenuate airway remodeling with increased expression of pro-inflammatory cytokines TNF-α, IL-1β, and NF-κB.NEW & NOTEWORTHY Interleukin-17A (IL-17A) neutralization has shown benefit previously in preclinical models of transplant-associated bronchiolitis obliterans (BO), yet it remains unknown whether IL-17A neutralization has similar benefit for other forms of BO. Here, IL-17A neutralization fails to prevent severe airway remodeling in rats exposed repetitively to the flavoring chemical diacetyl, and instead, promotes a proinflammatory microenvironment with increased expression of TNF-α, IL-1β, and NF-κB within the lung.

JAK-STAT activation contributes to cytotoxic T cell-mediated basal cell death in human chronic lung allograft dysfunction

Chronic lung allograft dysfunction (CLAD) is the leading cause of death in lung transplant recipients. CLAD is characterized clinically by a persistent decline in pulmonary function and histologically by the development of airway-centered fibrosis known as bronchiolitis obliterans. There are no approved therapies to treat CLAD, and the mechanisms underlying its development remain poorly understood. We performed single-cell RNA-Seq and spatial transcriptomic analysis of explanted tissues from human lung recipients with CLAD, and we performed independent validation studies to identify an important role of Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling in airway epithelial cells that contributes to airway-specific alloimmune injury. Specifically, we established that activation of JAK-STAT signaling leads to upregulation of major histocompatibility complex 1 (MHC-I) in airway basal cells, an important airway epithelial progenitor population, which leads to cytotoxic T cell-mediated basal cell death. This study provides mechanistic insight into the cell-to-cell interactions driving airway-centric alloimmune injury in CLAD, suggesting a potentially novel therapeutic strategy for CLAD prevention or treatment.

Donor Batf3 inhibits murine lung allograft rejection and airway fibrosis

Chronic lung allograft dysfunction (CLAD) limits survival after lung transplantation. Noxious stimuli entering the airways foster CLAD development. Classical dendritic cells (cDCs) link innate and adaptive immunity and exhibit regional and functional specialization in the lung. The transcription factor basic leucine zipper ATF-like 3 (BATF3) is absolutely required for the development of type 1 cDCs (cDC1s), which reside in the airway epithelium and have variable responses depending on the context. We studied the role of BATF3 in a mouse minor alloantigen-mismatched orthotopic lung transplant model of CLAD with and without airway inflammation triggered by repeated administration of intratracheal lipopolysaccharide (LPS). We found that cDC1s accumulated in allografts compared with isografts and that donor cDC1s were gradually replaced by recipient cDC1s. LPS administration increased the number of cDC1s and enhanced their state of activation. We found that Batf3^-/- recipient mice experienced reduced acute rejection in response to LPS; in contrast, Batf3^-/- donor grafts underwent enhanced lung and skin allograft rejection and drove augmented recipient cluster of differentiation 8⁺ T-cell expansion in the absence of LPS. Our findings suggest that donor and recipient cDC1s have differing and context-dependent roles and may represent a therapeutic target in lung transplantation.

Markers of Bronchiolitis Obliterans Syndrome after Lung Transplant: Between Old Knowledge and Future Perspective

Bronchiolitis obliterans syndrome (BOS) is the most common form of CLAD and is characterized by airflow limitation and an obstructive spirometric pattern without high-resolution computed tomography (HRCT) evidence of parenchymal opacities. Computed tomography and microCT analysis show abundant small airway obstruction, starting from the fifth generation of airway branching and affecting up to 40-70% of airways. The pathogenesis of BOS remains unclear. It is a multifactorial syndrome that leads to pathological tissue changes and clinical manifestations. Because BOS is associated with the worst long-term survival in LTx patients, many studies are focused on the early identification of BOS. Markers may be useful for diagnosis and for understanding the molecular and immunological mechanisms involved in the onset of BOS. Diagnostic and predictive markers of BOS have also been investigated in various biological materials, such as blood, BAL, lung tissue and extracellular vesicles. The aim of this review was to evaluate the scientific literature on markers of BOS after lung transplant. We performed a systematic review to find all available data on potential prognostic and diagnostic markers of BOS.

Corticotropin releasing hormone as an identifier of bronchiolitis obliterans syndrome

Lung transplantion (LTx) recipients have low long-term survival and a high incidence of bronchiolitis obliterans syndrome (BOS), an inflammation of the small airways in chronic rejection of a lung allograft. There is great clinical need for a minimally invasive biomarker of BOS. Here, 644 different proteins were analyzed to detect biomarkers that distinguish BOS grade 0 from grades 1–3. The plasma of 46 double lung transplant patients was analyzed for proteins using a high-component, multiplex immunoassay that enables analysis of protein biomarkers. Proximity Extension Assay (PEA) consists of antibody probe pairs which bind to targets. The resulting polymerase chain reaction (PCR) reporter sequence can be quantified by real-time PCR. Samples were collected at baseline and 1-year post transplantation. Enzyme-linked immunosorbent assay (ELISA) was used to validate the findings of the PEA analysis across both time points and microarray datasets from other lung transplantation centers demonstrated the same findings. Significant decreases in the plasma protein levels of CRH, FERC2, IL-20RA, TNFB, and IGSF3 and an increase in MMP-9 and CTSL1 were seen in patients who developed BOS compared to those who did not. In this study, CRH is presented as a novel potential biomarker in the progression of disease because of its decreased levels in patients across all BOS grades. Additionally, biomarkers involving the remodeling of the extracellular matrix (ECM), such as MMP-9 and CTSL1, were increased in BOS patients.

Human distal airways contain a multipotent secretory cell that can regenerate alveoli

The human lung differs substantially from its mouse counterpart, resulting in a distinct distal airway architecture affected by disease pathology in chronic obstructive pulmonary disease. In humans, the distal branches of the airway interweave with the alveolar gas-exchange niche, forming an anatomical structure known as the respiratory bronchioles. Owing to the lack of a counterpart in mouse, the cellular and molecular mechanisms that govern respiratory bronchioles in the human lung remain uncharacterized. Here we show that human respiratory bronchioles contain a unique secretory cell population that is distinct from cells in larger proximal airways. Organoid modelling reveals that these respiratory airway secretory (RAS) cells act as unidirectional progenitors for alveolar type 2 cells, which are essential for maintaining and regenerating the alveolar niche. RAS cell lineage differentiation into alveolar type 2 cells is regulated by Notch and Wnt signalling. In chronic obstructive pulmonary disease, RAS cells are altered transcriptionally, corresponding to abnormal alveolar type 2 cell states, which are associated with smoking exposure in both humans and ferrets. These data identify a distinct progenitor in a region of the human lung that is not found in mouse that has a critical role in maintaining the gas-exchange compartment and is altered in chronic lung disease.

Graft dysfunction and rejection of lung transplant, a review on diagnosis and management

Introduction

Lung transplantation has proven to be an effective treatment option for end‐stage lung disease. However, early and late complications following transplantation remain significant causes of high mortality.

Objectives

In this review, we focus on the time of onset in primary graft dysfunction and rejection complications, as well as emphasize the role of imaging manifestations and pathological features in early diagnosis, thus assisting clinicians in the early detection and treatment of posttransplant complications and improving patient quality of life and survival.

Data source

We searched electronic databases such as PubMed, Web of Science, and EMBASE. We used the following search terms: lung transplantation complications, primary graft dysfunction, acute rejection, chronic lung allograft dysfunction, radiological findings, and diagnosis and treatment.

Conclusion

Primary graft dysfunction, surgical complications, immune rejection, infections, and neoplasms represent major posttransplant complications. As the main posttransplant survival limitation, chronic lung allograft dysfunction has a characteristic imaging presentation; nevertheless, the clinical and imaging manifestations are often complex and overlap, so it is essential to understand the temporal evolution of these complications to narrow the differential diagnosis for early treatment to improve prognosis.

Early and late complications after lung transplantation remain essential causes of high mortality. In this review, we focus on the timing of the onset of primary graft dysfunction and rejection complications and highlight the role of imaging manifestations and clinicopathologic features in early diagnosis, thus assisting clinicians in the early detection and treatment of posttransplant complications and improving patient quality of life and survival.

Pulmonary hypertension associated with busulfan

Busulfan is widely used to treat malignant diseases, particularly for therapeutic intensification prior to an autologous stem cell graft. Numerous side effects consecutive to busulfan are described, but few descriptions of pulmonary hypertension exist, while bronchiolitis obliterans remains a rare complication. We report the clinical observations of four patients from the French Pulmonary Hypertension Registry who experienced subacute pulmonary hypertension after receiving busulfan as preparation regimen before an autologous stem cell graft for malignancies (Hodgkin's disease, Ewing's sarcoma and primary large B cell lymphoma of the brain). Patients experienced severe pulmonary arterial hypertension 2 to 4.5 months after busulfan administration. Pulmonary hypertension improved after treatment with approved drugs for pulmonary arterial hypertension and/or corticosteroids. During the follow-up period, two patients developed chronic respiratory insufficiency due to interstitial lung disease, leading to double lung transplantation. The pathological assessment of explanted lungs revealed interstitial lung fibrosis with advanced bronchiolar lesions and severe pulmonary vascular damage. Three of the four patients were still alive after 36 to 80 months and the fourth died unexpectedly and suddenly after 5 months. In conclusion, PAH is a rare but severe complication associated with busulfan chemotherapy in adults. Histological examinations provide evidence for diffuse pulmonary vascular damage combined with interstitial lung injury in most cases.

Factors affecting complications development and mortality after single lung transplant

Lung transplantation (LT) is a life-saving therapeutic procedure that prolongs survival in patients with end-stage lung disease. Furthermore, as a therapeutic option for high-risk candidates, single LT (SLT) can be feasible because the immediate morbidity and mortality after transplantation are lower compared to sequential single (double) LT (SSLTx). Still, the long-term overall survival is, in general, better for SSLTx. Despite the great success over the years, the early post-SLT period remains a perilous time for these patients. Patients who undergo SLT are predisposed to evolving early or late postoperative complications. This review emphasizes factors leading to post-SLT complications in the early and late periods including primary graft dysfunction and chronic lung allograft dysfunction, native lung complications, anastomosis complications, infections, cardiovascular, gastrointestinal, renal, and metabolite complications, and their association with morbidity and mortality in these patients. Furthermore, we discuss the incidence of malignancy after SLT and their correlation with immunosuppression therapy.

Dysphagia and medicine regimes in patients following lung transplant surgery: A retrospective review

PURPOSE

Dysphagia is reported following lung transplantation. Characteristics and trajectory for dysphagia are poorly understood. This retrospective study explored dysphagia and medicine regimes in patients following lung transplant.

METHOD

Medical records and endoscopic recordings of 101 patients (M:50yrs, range 20-67yrs, SD 13yrs) were reviewed. Standardised endoscopic swallowing measures were reported. Discharge reports were analysed for medicines known to cause dysphagia.

RESULT

All patients received bilateral sequential single-lung transplant. Prevalence of referral to speech pathology was 65% with 37 requiring more than one instrumental assessment. Twenty-nine patients were referred to otorhinolaryngology with suspected laryngeal abnormalities. Seventy-five percent of patients (n = 49/65) who received an instrumental assessment aspirated; of whom 63% aspirated silently (31/49). Diet on first day transferred from Intensive Care Unit (ICU) was significantly associated with intubation duration, ICU and hospital length of stay, tracheostomy and vocal fold paralysis (p < 0.001). In contrast, pre-operative reflux was significantly associated with diet on discharge (p < 0.05). Only three patients remained enterally fed on discharge. Polypharmacy (concurrent use of 5+ medicines) was prevalent.

CONCLUSION

Endoscopic, radiographic and/or manometric assessment of dysphagia in patients prior to, and following, lung transplant may allow for early management and prevention of secondary complications. Teams must consider pre-surgical reflux, length of stay in ICU and current medicine regimes when managing patients.

Protein Signatures of Remodeled Airways in Transplanted Lungs with Bronchiolitis Obliterans Syndrome Obtained Using Laser-Capture Microdissection

Bronchiolitis obliterans syndrome, a common form of chronic lung allograft dysfunction, is the major limitation to long-term survival after lung transplantation. The histologic correlate is progressive, fibrotic occlusion of small airways, obliterative bronchiolitis lesions, which ultimately lead to organ failure. The molecular composition of these lesions is unknown. In this sutdy, the protein composition of the lesions in explanted lungs from four end-stage bronchiolitis obliterans syndrome patients was analyzed using laser-capture microdissection and optimized sample preparation protocols for mass spectrometry. Immunohistochemistry and immunofluorescence were used to determine the spatial distribution of commonly identified proteins on the tissue level, and protein signatures for 14 obliterative bronchiolitis lesions were established. A set of 39 proteins, identified in >75% of lesions, included distinct structural proteins (collagen types IV and VI) and cellular components (actins, vimentin, and tryptase). Each respective lesion exhibited a unique composition of proteins (on average, n = 66 proteins), thereby mirroring the morphologic variation of the lesions. Antibody-based staining confirmed these mass spectrometry-based findings. The 14 analyzed obliterative bronchiolitis lesions showed variations in their protein content, but also common features. This study provides molecular and morphologic insights into the development of chronic rejection after lung transplantation. The protein patterns in the lesions were correlated to pathways of extracellular matrix organization, tissue development, and wound healing processes.

siRNA: Mechanism of action, challenges, and therapeutic approaches

Owing to specific and compelling gene silencing, RNA interference (RNAi) is expected to become an essential approach in treating a variety of infectious, hemato-oncological, cardiovascular, and neurodegenerative conditions. The mechanism of action of small interfering RNA (siRNA) is based on post-transcriptional gene silencing. siRNA molecules are usually specific and efficient in the knockdown of disease-related genes. However, they are characterized by low cellular uptake and are susceptible to nuclease-mediated degradation. Therefore, siRNAs require a carrier for their protection and efficient delivery into target cells. The current review highlights the siRNA-based mechanism of action, challanges, and recent advances in clinical applications.

Esophageal Motility Disorders Associated With Death or Allograft Dysfunction After Lung Transplantation? Results of a Retrospective Monocentric Study

OBJECTIVES

Pathological gastroesophageal reflux (GER) is a known risk factor for bronchiolitis obliterans syndrome (BOS) after lung transplantation. This study aimed at determining whether functional esophageal evaluation might predict BOS occurrence and survival in this setting.

METHODS

Ninety-three patients who underwent esophageal high-resolution manometry and 24-hour pH-impedance monitoring within the first year after lung transplantation were retrospectively included. A univariable analysis was performed to evaluate the parameters associated with GER disease and BOS occurrence. The Cox regression model was used to identify the prognostic factors of death or retransplantation.

RESULTS

Thirteen percent of patients exhibited major esophageal motility disorders and 20% pathological GER. GER occurrence was associated with younger age, cystic fibrosis, and hypotensive esophagogastric junction. Within a median follow-up of 62 months, 10 patients (11%) developed BOS, and no predictive factors were identified. At the end of the follow-up, 10 patients died and 1 underwent retransplantation. The 5-year cumulative survival rate without retransplantation was lower in patients with major esophageal motility disorders compared with that in those without (75% vs 90%, P = 0.01) and in patients who developed BOS compared with that in those without (66% vs 91%; P = 0.005). However, in multivariable analysis, major esophageal motility disorders and BOS were no longer significant predictors of survival without retransplantation.

DISCUSSION

Major esophageal motility disorders and BOS were associated with allograft survival in lung transplantation in the univariable analysis. Although the causes of this association remain to be determined, this observation confirms that esophageal motor dysfunction should be evaluated in the context of lung transplantation.

Lung Transplantation: CT Assessment of Chronic Lung Allograft Dysfunction (CLAD)

Chronic lung allograft rejection remains one of the major causes of morbi-mortality after lung transplantation. The term Chronic Lung Allograft Dysfunction (CLAD) has been proposed to describe the different processes that lead to a significant and persistent deterioration in lung function without identifiable causes. The two main phenotypes of CLAD are Bronchiolitis Obliterans Syndrome (BOS) and Restrictive Allograft Syndrome (RAS), each of them characterized by particular functional and imaging features. These entities can be associated (mixed phenotype) or switched from one to the other. If CLAD remains a clinical diagnosis based on spirometry, computed tomography (CT) scan plays an important role in the diagnosis and follow-up of CLAD patients, to exclude identifiable causes of functional decline when CLAD is first suspected, to detect early abnormalities that can precede the diagnosis of CLAD (particularly RAS), to differentiate between the obstructive and restrictive phenotypes, and to detect exacerbations and evolution from one phenotype to the other. Recognition of early signs of rejection is crucial for better understanding of physiopathologic pathways and optimal management of patients.

miRNAs Potentially Involved in Post Lung Transplant-Obliterative Bronchiolitis: The Role of miR-21-5p

Epigenetic changes, including miRNAs deregulation, have been suggested to play a significant role in development of obliterative bronchiolitis (OB) in transplanted lungs. Many studies have tried to identify ideal candidate miRNAs and the downstream pathways implicated in the bronchiolar fibro-obliterative process. Several candidate miRNAs, previously indicated as possibly being associated with OB, were analyzed by combining the quantitative real time-polymerase chain reaction (qRT-PCR) and in situ hybridization (ISH) of lung tissues of OB affected patients. Disease and OB-lesion-specific expression of miR-21-5p was confirmed and by computational analysis we were able to identify the network of genes most probably associated miR-21-5p in the context of OB fibrogenesis. Among all potentially associated genes, STAT3 had a very high probability score. Immunohistochemistry showed that STAT3/miR-21-5p were co-over expressed in OB lesions, thus, suggesting miR-21-5p could regulate STAT3 expression. However, miR-21-5p inhibition in cultures of bronchiolitis obliterans syndrome (BOS) derived myofibroblasts did not significantly affect STAT3 mRNA and protein expression levels. This study demonstrates the specificity of miR-21-5p over-expression in OB lesions and contributes to existing knowledge on the miR-21-5p downstream pathway. Activation of STAT3 is associated with miR-21-5p upregulation, however, STAT-3 network activation is most likely complex and miR-21-5p is not the sole regulator of STAT3.

Chronic Lung Allograft Dysfunction: Review of CT and Pathologic Findings

Chronic lung allograft dysfunction (CLAD) is the most common cause of mortality in lung transplant recipients after the 1st year of transplantation. CLAD has traditionally been classified into two distinct obstructive and restrictive forms: bronchiolitis obliterans syndrome and restrictive allograft syndrome. However, CLAD may manifest with a spectrum of imaging and pathologic findings and a combination of obstructive and restrictive physiologic abnormalities. Although the initial CT manifestations of CLAD may be nonspecific, the progression of findings at follow-up should signal the possibility of CLAD and may be present on imaging studies prior to the development of functional abnormalities of the lung allograft. This review encompasses the evolution of CT findings in CLAD, with emphasis on the underlying pathogenesis and pathologic condition, to enhance understanding of imaging findings. The purpose of this article is to familiarize the radiologist with the initial and follow-up CT findings of the obstructive, restrictive, and mixed forms of CLAD, for which early diagnosis and treatment may result in improved survival. Supplemental material is available for this article. © RSNA, 2021.

Exploring the Developmental Impact of Cystic Fibrosis on Lung Transplant Candidacy: Considerations for Adulthood

The average life expectancy for cystic fibrosis (CF) has increased over the past four decades resulting in a higher rate of adult CF patients. Adults seeking lung transplant to address CF-related advanced lung disease (ALD) represent a small, yet growing, subset of lung transplant recipients. Psychosocial factors such as adherence to medical recommendations, self-management of medical care, and caregiver support have been identified as positive prognostic factors in lung transplant outcomes. These factors are also implicated in the pediatric chronic illness literature and are crucial as patients begin to transition to a more autonomous and independent role in their own health management. Adults with CF facing ALD must navigate through another transitional phase as lung transplant requires additional supports and new expectations. A case series is used to highlight specific psychosocial considerations in this population and to explore the seemingly dichotomous relationship between independent self-management and caregiver support.

A case of bronchiolitis obliterans after living-donor renal transplantation

We herein report the case of a 20 year-old-man who developed bronchiolitis obliterans after living-donor renal transplantation. The patient presented with dyspnea on exertion and wheezing two years after renal transplantation, and spirometry showed an obstructive pattern. Surgical lung biopsy revealed subepithelial fibrosis that constricted and obstructed the intrabronchiolar space. Based on these findings, the patient was diagnosed with bronchiolitis obliterans. He was prescribed bronchodilators and azithromycin, and he achieved stable respiratory function for two years. The differential diagnosis of respiratory symptoms after renal transplantation includes opportunistic infection and drug-induced lung injury; however, bronchiolitis obliterans should also be considered.

[Predictors for the Bronchiolitis Obliterans Syndrome in Lung Transplant Patient]

肺移植是治疗终末期肺病的有效方法。目前，肺移植术后1年生存率已达到80%，由于闭塞性细支气管炎综合症（bronchiolitis obliterans syndrome, BOS）的发生，5年生存率维持在50%左右。BOS是一个纤维化的过程，最终导致不可逆的气道闭塞。缺血-再灌注损伤、感染、氧化应激以及急性排斥反应等多个因素参与了BOS的发生。研究证实BOS的早期诊断与预后良好相关。因此，寻找灵敏、特异的BOS预测标记物对于提高肺移植患者长期生存具有重要的科学和临床意义。本文就与BOS发生发展相关的免疫调节细胞、分泌性蛋白质、细胞膜蛋白等指标的变化在BOS早期诊断中的作用进行综述。

Occupational exposures in constrictive bronchiolitis

Bronchiolitis obliterans is a clinical entity which results from a variety of etiologies and has a detrimental impact on patients' quality of life when it remains undiagnosed and untreated. Due to its non-pathognomic clinical symptoms and signs, physicians often proceed to radiological examination, especially with high resolution chest tomography. Histological examination reveals constrictive bronchiolitis, the pathological definition of bronchiolitis obliterans. Due to an almost normal aspect of the lung parenchyma this condition can be missed. However, its recognition and the identification of a possible exposure are important for removing the patient from the incriminating agent. We present a case of constrictive bronchiolitis in a metal-cutting worker, highlighting the principal findings of this disease.

Successful Pseudomonas aeruginosa eradication improves outcomes after lung transplantation: a retrospective cohort analysis

Long-term survival after lung transplantation (LTx) is hampered by development of chronic lung allograft dysfunction (CLAD). Pseudomonas aeruginosa is an established risk factor for CLAD. Therefore, we investigated the effect of P. aeruginosa eradication on CLAD-free and graft survival.

Patients who underwent first LTx between July, 1991, and February, 2016, and were free from CLAD, were retrospectively classified according to P. aeruginosa presence in respiratory samples between September, 2011, and September, 2016. P. aeruginosa-positive patients were subsequently stratified according to success of P. aeruginosa eradication following targeted antibiotic treatment. CLAD-free and graft survival were compared between P. aeruginosa-positive and P. aeruginosa-negative patients; and between patients with or without successful P. aeruginosa eradication. In addition, pulmonary function was assessed during the first year following P. aeruginosa isolation in both groups.

CLAD-free survival of P. aeruginosa-negative patients (n=443) was longer compared with P. aeruginosa-positive patients (n=95) (p=0.045). Graft survival of P. aeruginosa-negative patients (n=443, 82%) was better compared with P. aeruginosa-positive patients (n=95, 18%) (p<0.0001). Similarly, P. aeruginosa-eradicated patients demonstrated longer CLAD-free and graft survival compared with patients with persistent P. aeruginosa. Pulmonary function was higher in successfully P. aeruginosa-eradicated patients compared with unsuccessfully eradicated patients (p=0.035).

P. aeruginosa eradication after LTx improves CLAD-free and graft survival and maintains pulmonary function. Therefore, early P. aeruginosa detection and eradication should be pursued.

Amphiregulin contributes to airway remodeling in chronic allograft dysfunction after lung transplantation

Chronic lung allograft dysfunction (CLAD), a condition of excess matrix deposition and airways fibrosis, limits survival after lung transplantation. Amphiregulin (Areg) is an epidermal growth factor receptor (EGFR) ligand suggested to regulate airway injury and repair. We sought to determine whether Areg expression increases in CLAD, localize the cellular source of Areg induction in CLAD, and assess its effects on airway matrix deposition. Lung fluid Areg protein was quantified in patients with or without CLAD. In situ hybridization was performed to localize Areg and EGFR transcript in CLAD and normal lung tissue. Expression of hyaluronan, a matrix constituent that accumulates in CLAD, was measured in Areg-exposed bronchial epithelial cells in the presence or absence of an EGFR inhibitor. We demonstrated that lung fluid Areg protein was significantly increased in CLAD in a discovery and replication cohort. Areg and EGFR transcripts were abundantly expressed within CLAD tissue, localized to basally distributed airway epithelial cells overlying fibrotic regions. Areg-exposed bronchial epithelial cells increased hyaluronan and hyaluronan synthase expression in an EGFR-dependent manner. Collectively, these novel observations suggest that Areg contributes to airway remodeling and CLAD. Moreover these data implicate a role for EGFR signaling in CLAD pathogenesis, suggesting novel therapeutic targets.

Mitigation of Primary Graft Dysfunction in Lung Transplantation: Current Understanding and Hopes for the Future

Primary graft dysfunction (PGD) is a form of acute lung injury that develops within the first 72 hours after lung transplantation. The overall incidence of PGD is estimated to be around 30%, and the 30-day mortality for grade 3 PGD around 36%. PGD is also associated with the development of bronchiolitis obliterans syndrome, a specific form of chronic lung allograft dysfunction. In this article, we will discuss perioperative strategies for PGD prevention as well as possible future avenues for prevention and treatment.

Optimization of Transbronchial Cryobiopsy in Lung Transplant Recipients

BACKGROUND

Previous studies suggest that transbronchial lung biopsy using a cryoprobe is superior to transbronchial lung biopsy using forceps for evaluating lung grafts, although the technique can be associated an increase in complications. Because cryoprobe experience is limited, assessment of a greater number of cases is warranted. This prospective study evaluates the diagnostic yield, complications, and risk factors associated with the cryoprobe technique.

METHODS

From April 2013 to April 2016, 321 consecutive cryoprobe transbronchial biopsies were indicated in single or bilateral lung transplant patients with acute or chronic clinical lung injury or in asymptomatic patients before hospital discharge after lung transplantation.

RESULTS

With a mean of 4.32 lung parenchyma specimens per procedure, adequate alveolar lung parenchyma was obtained in 96.6% (84.27 ± 44.14 mm²) of cases. Obtaining at least 4 samples increased the histological diagnostic certainty (P < .001). Moderate to severe bleeding was observed in 7.48% of patients and was significantly more frequent in patients with unilateral transplantation (odds ratio, 0.10; 95% confidence interval, 0.02-0.30; P < .001) and in those with high blood pressure during scanning (odds ratio, 0.31; 95% confidence interval, 0.12-0.86; P = .019). Pneumothorax was observed in 7.7% of the patients, but only 3.7% of these patients required pleural drainage.

CONCLUSIONS

Obtaining 4 or more cryobiopsy samples is valuable and safe for lung allograft monitoring. Being a recipient of a unilateral lung transplant or having arterial hypertension during bronchoscopy seem to be risk factors associated with increased bleeding.

Lack of association of Aspergillus colonization with the development of bronchiolitis obliterans syndrome in lung transplant recipients: An international cohort study

BACKGROUND

Bronchiolitis obliterans syndrome (BOS) is a major limitation in the long-term survival of lung transplant recipients (LTRs). However, the risk factors in the development of BOS remain undetermined. We conducted an international cohort study of LTRs to assess whether Aspergillus colonization with large or small conidia is a risk factor for the development of BOS.

METHODS

Consecutive LTRs from January 2005 to December 2008 were evaluated. Rates of BOS and associated risk factors were recorded at 4 years. International Society of Heart and Lung Transplantation criteria were used to define fungal and other infections. A Cox proportional-hazards-model was constructed to assess the association between Aspergillus colonization and the development of BOS controlling for confounders.

RESULTS

A total of 747 LTRs were included. The cumulative incidence of BOS at 4 years after transplant was 33% (250 of 747). Additionally, 22% of LTRs experienced Aspergillus colonization after transplantation. Aspergillus colonization with either large (hazard ratio [HR] = 0.6, 95% confidence interval [CI] = 0.3-1.2, p = 0.12) or small conidia (HR = 0.9, 95% CI = 0.6-1.4, p = 0.74) was not associated with the development of BOS. Factors associated with increased risk of development of BOS were the male gender (HR = 1.4, 95% CI = 1.1-1.8, p = 0.02) and episodes of acute rejection (1-2 episodes, HR = 1.5, 95% CI = 1.1-2.1, p = 0.014; 3-4 episodes, HR = 1.6, 95% CI = 1.0-2.6, p = 0.036; >4 episodes, HR = 2.2, 95% CI = 1.1-4.3, p = 0.02), whereas tacrolimus use was associated with reduced risk of BOS (HR = 0.6, 95% CI = 0.5-0.9, p = 0.007).

CONCLUSIONS

We conclude from this large multicenter cohort of lung transplant patients, that Aspergillus colonization with large or small conidia did not show an association with the development of BOS.

MRI-derived regional flow-volume loop parameters detect early-stage chronic lung allograft dysfunction

BACKGROUND

Chronic lung allograft dysfunction (CLAD) is a major cause for the low long-term survival rates after lung transplantation (LTx). Early detection of CLAD may enable providing medical treatment before a nonreversible graft dysfunction has occurred. MRI is advantageous to pulmonary function testing (PFT) in the ability to assess regional function changes, and thus have the potential in detecting very early stages of CLAD before changes in global forced expiratory volume during the first second (FEV1%) occur.

PURPOSE

To examine whether early stages of CLAD (diagnosed based on PFT values) could also be detected using MRI-derived parameters of regional flow-volume dynamics.

STUDY TYPE

Retrospective.

POPULATION

62 lung transplantation recipients were included in the study, 29 of which had been diagnosed with CLAD at various stages.

FIELD STRENGTH/SEQUENCE

MRI datasets were acquired with a 1.5T Siemens scanner using a spoiled gradient echo sequence.

ASSESSMENT

MRI datasets were retrospectively preprocessed and analyzed by a blinded radiologist according to the phase resolved functional lung MRI (PREFUL-MRI) approach, resulting in fractional ventilation (FV) maps and regional flow-volume loops (rFVL). FV- and rFVL-based parameters of regional lung ventilation were estimated.

STATISTICAL TESTS

Differences between groups were compared by Mann-Whitney U-test with a Bonferroni correction for multiple comparisons (n = 2).

RESULTS

rFVL-CC-based parameters discriminated significantly between the presence or absence of CLAD (P < 0.003).

DATA CONCLUSION

Using the contrast media-free PREFUL-MRI technique, parameters of ventilation dynamics and its regional heterogeneity were shown to be sensitive for the detection of early CLAD stages.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY: Stage 3 J. Magn. Reson. Imaging 2019;50:1873-1882.

Antibody-Mediated Rejection in a Multiple Lung Transplant Patient: A Case Report

Lung transplant is an effective way to treat many end-stage lung diseases. However, one of the main barriers of allograft organ transplant is still the immunologic rejection of transplanted tissue, which is a response of the HLA molecules. Rejection is a complex process involving both T-cell-mediated delayed-type hypersensitivity reactions and antibody-mediated hypersensitivity reactions to histocompatibility molecules on foreign grafts. We report the case of a 25-year-old female patient with cystic fibrosis who underwent 2 lung transplants because of her initial diagnosis and appearance of bronchiolitis obliterans syndrome after the first transplant. Only 13 months after the second transplant, despite the therapies applied, a new rejection occurred associated with high mean fluorescent intensity donor-specific antibody levels, which resulted later in the death of the patient. The present case draws attention to the importance of matching HLA molecules between donor and recipient in addition to immunosuppressive therapy.

Diagnosis, Pathophysiology and Experimental Models of Chronic Lung Allograft Rejection

Chronic rejection is the Achilles heel of modern lung transplantation, characterized by a slow, progressive decline in allograft function. Clinically, this manifests as obstructive disease, restrictive disease, or a mixture of the 2 depending on the underlying pathology. The 2 major phenotypes of chronic rejection include bronchiolitis obliterans syndrome and restrictive allograft syndrome. The last decade of research has revealed that each of these phenotypes has a unique underlying pathophysiology which may require a distinct treatment regimen for optimal control. Insights into the intricate alloimmune pathways contributing to chronic rejection have been gained from both large and small animal models, suggesting directions for future research. In this review, we explore the pathological hallmarks of chronic rejection, recent insights gained from both clinical and basic science research, and the current state of animal models of chronic lung rejection.

Transplant arteriosclerosis in humanized mice reflects chronic lung allograft dysfunction and is controlled by regulatory T cells

OBJECTIVE

Chronic lung allograft dysfunction (CLAD) is a severe complication of lung transplantation limiting long-term survival. We studied correlations between CLAD after clinical lung transplantation and leukocyte-mediated development of transplant arteriosclerosis (TA) in a humanized mouse model. The pericardiophrenic artery was procured from surplus tissue of donor lungs (n = 22) transplanted in our clinical program and was implanted into the abdominal aorta of immune-deficient mice.

METHODS

Allogeneic human peripheral blood mononuclear cells (PBMCs) had been procured 1 day after lung transplantation from the respective recipients with or without enriching for CD4⁺CD25^high T cells were used. TA was assessed in mice 28 days later by histology. The respective clinical lung recipients were later divided into 2 groups. Eight patients (36.3%) had developed CLAD 23 ± 5 months after lung transplantation, whereas the remaining 14 (63.6%) did not develop CLAD within 25 ± 5 months.

RESULTS

In the PBMC CLAD+ group of mouse experiments, TA was significantly more severe than in the PBMC CLAD- group (39.9% ± 13% vs 14.9% ± 4% intimal thickening; P = .0081). Then, intimal thickening was significantly inhibited in the PBMC+ regulatory T cells CLAD+ group compared with the PBMC CLAD+ group (0.4% ± 4% vs 39.9% ± 13%; P = .003). In the experiments using PBMCs from lung recipients without CLAD, enriching regulatory T cells also suppressed the development of TA (0.9% ± 3% PBMC CLAD- vs 14.9% ± 4% PBMC+ regulatory T cells CLAD-; P = .001).

CONCLUSIONS

Lung transplant recipients who later develop CLAD have peripheral leukocytes already at the time of transplant that transfer proinflammatory properties leading to TA in a humanized mouse model. TA remains sensitive to inhibition by autologous regulatory T cells, suggesting a cell therapy-based approach for the prevention of CLAD after lung transplantation.

Prevalence of antibodies to lung self-antigens (Kα1 tubulin and collagen V) and donor specific antibodies to HLA in lung transplant recipients and implications for lung transplant outcomes: Single center experience

PURPOSE

For patients with end stage lung disease, lung transplantation (LT) remains the only definitive treatment option. Long term survival post LT is limited by acute and chronic allograft dysfunction. Antibodies to lung self-antigens Kα1Tubulin and collagen V (autoantibodies) have been implicated in adverse outcomes post LT. The aim of our study was to determine the prevalence of autoantibodies in pre- and post-transplant sera, evaluate the impact on post-transplant outcomes.

METHODS

In a prospective observational cohort analysis, 44 patients were enrolled who received LT between 09/01/2014 and 10/31/2015. Pre- and post-transplant sera were analyzed using enzyme-linked immunosorbent assay (ELISA) for the presence of antibodies to collagen I, collagen V, and K-alpha 1 tubulin. The outcome variables are presence of primary graft dysfunction (PGD), cumulative acute cellular rejection (ACR), treatment with pulse steroids for clinical rejection, association with DSA, and onset of Bronchiolitis Obliterans Syndrome (BOS).

RESULTS

In our cohort, 33 patients (75%) tested positive for the presence of autoantibodies. Pre-transplant autoantibodies were present in 23 patients (70%). Only a small percentage (26%) cleared these antibodies with standard immunosuppression. Some developed de novo post-transplant (n = 10). PGD was observed in 34% of our cohort, however the presence of autoantibodies did not correlate with increase in the incidence or severity of PGD. The prevalence of donor specific antibodies (DSA) in the entire cohort was 73%, with an increased prevalence of DSA noted in the autoantibody positive group (78.7% vs. 54.5%) than in the autoantibody negative group. BOS was observed in 20% of the cohort, with a median time to onset of 291 days' post-transplant. Patients with pre-transplant autoantibodies had a statistically significant decrease in BOS-free survival (p = 0.029 by log-rank test).

CONCLUSIONS

In our cohort, we observed a high prevalence of autoantibodies and DSA in lung transplant recipients. Pre-transplant autoantibodies were associated with de novo development of DSA along with a decrease in BOS-free survival. Limitations to our study include the small sample size and single center enrollment, along with limited time for follow-up.

Inhibition of B cell-dependent lymphoid follicle formation prevents lymphocytic bronchiolitis after lung transplantation

Lung transplantation (LTx) is the only therapeutic option for many patients with chronic lung disease. However, long-term survival after LTx is severely compromised by chronic rejection (chronic lung allograft dysfunction [CLAD]), which affects 50% of recipients after 5 years. The underlying mechanisms for CLAD are poorly understood, largely due to a lack of clinically relevant animal models, but lymphocytic bronchiolitis is an early sign of CLAD. Here, we report that lymphocytic bronchiolitis occurs early in a long-term murine orthotopic LTx model, based on a single mismatch (grafts from HLA-A2:B6-knockin donors transplanted into B6 recipients). Lymphocytic bronchiolitis is followed by formation of B cell-dependent lymphoid follicles that induce adjacent bronchial epithelial cell dysfunction in a spatiotemporal fashion. B cell deficiency using recipient μMT-/- mice prevented intrapulmonary lymphoid follicle formation and lymphocytic bronchiolitis. Importantly, selective inhibition of the follicle-organizing receptor EBI2, using genetic deletion or pharmacologic inhibition, prevented functional and histological deterioration of mismatched lung grafts. In sum, we provided what we believe to be a mouse model of chronic rejection and lymphocytic bronchiolitis after LTx and identified intrapulmonary lymphoid follicle formation as a target for pharmacological intervention of long-term allograft dysfunction after LTx.

Complement factor and T-cell interactions during alloimmune inflammation in transplantation

Complement factor and T-cell signaling during an effective alloimmune response plays a key role in transplant-associated injury, which leads to the progression of chronic rejection (CR). During an alloimmune response, activated complement factors (C3a and C5a) bind to their corresponding receptors (C3aR and C5aR) on a number of lymphocytes, including T-regulatory cells (Tregs), and these cell-molecular interactions have been vital to modulate an effective immune response to/from Th1-effector cell and Treg activities, which result in massive inflammation, microvascular impairments, and fibrotic remodeling. Involvement of the complement-mediated cell signaling during transplantation signifies a crucial role of complement components as a key therapeutic switch to regulate ongoing inflammatory state, and further to avoid the progression of CR of the transplanted organ. This review highlights the role of complement-T cell interactions, and how these interactions shunt the effector immune response during alloimmune inflammation in transplantation, which could be a novel therapeutic tool to protect a transplanted organ and avoid progression of CR.

Tissue-Resident Lymphocytes in Solid Organ Transplantation: Innocent Passengers or the Key to Organ Transplant Survival?

Short-term outcomes of solid organ transplantation have improved dramatically over the past several decades; however, long-term survival has remained static over the same period, and chronic rejection remains a major cause of graft failure. The importance of donor, or "passenger," lymphocytes to the induction of tolerance to allografts was recognized in the 1990s, but their precise contribution to graft acceptance or rejection has not been elucidated. Recently, specialized populations of tissue-resident lymphocytes in nonlymphoid organs have been described. These lymphocytes include tissue-resident memory T cells, regulatory T cells, γδ T cells, invariant natural killer T cells, and innate lymphoid cells. These cells reside in commonly transplanted solid organs, including the liver, kidneys, heart, and lung; however, their contribution to graft acceptance or rejection has not been examined in detail. Similarly, it is unclear whether tissue-resident cells derived from the pool of recipient-derived lymphocytes play a specific role in transplantation biology. This review summarizes the evidence for the roles of tissue-resident lymphocytes in transplant immunology, focussing on their features, functions, and relevance for solid organ transplantation, with specific reference to liver, kidney, heart, and lung transplantation.

Machine Learning Algorithms Utilizing Quantitative CT Features May Predict Eventual Onset of Bronchiolitis Obliterans Syndrome After Lung Transplantation

RATIONALE AND OBJECTIVES

Long-term survival after lung transplantation (LTx) is limited by bronchiolitis obliterans syndrome (BOS), defined as a sustained decline in forced expiratory volume in the first second (FEV₁) not explained by other causes. We assessed whether machine learning (ML) utilizing quantitative computed tomography (qCT) metrics can predict eventual development of BOS.

MATERIALS AND METHODS

Paired inspiratory-expiratory CT scans of 71 patients who underwent LTx were analyzed retrospectively (BOS [n = 41] versus non-BOS [n = 30]), using at least two different time points. The BOS cohort experienced a reduction in FEV₁ of >10% compared to baseline FEV₁ post LTx. Multifactor analysis correlated declining FEV₁ with qCT features linked to acute inflammation or BOS onset. Student t test and ML were applied on baseline qCT features to identify lung transplant patients at baseline that eventually developed BOS.

RESULTS

The FEV₁ decline in the BOS cohort correlated with an increase in the lung volume (P = .027) and in the central airway volume at functional residual capacity (P = .018), not observed in non-BOS patients, whereas the non-BOS cohort experienced a decrease in the central airway volume at total lung capacity with declining FEV₁ (P = .039). Twenty-three baseline qCT parameters could significantly distinguish between non-BOS patients and eventual BOS developers (P < .05), whereas no pulmonary function testing parameters could. Using ML methods (support vector machine), we could identify BOS developers at baseline with an accuracy of 85%, using only three qCT parameters.

CONCLUSIONS

ML utilizing qCT could discern distinct mechanisms driving FEV₁ decline in BOS and non-BOS LTx patients and predict eventual onset of BOS. This approach may become useful to optimize management of LTx patients.

Airway injury in an in vitro human epithelium-fibroblast model of diacetyl vapor exposure: diacetyl-induced basal/suprabasal spongiosis

Inhalation exposure to diacetyl (DA) is associated with obliterative bronchiolitis (OB) in workers and induces OB-like fibrotic airway lesions in rats. The pathogenesis of OB is poorly understood in part due to complex interactions between airway epithelial, mesenchymal and blood-derived inflammatory cells. DA-induced airway toxicity in the absence of recruited-inflammatory/immune cells was characterized using an air-liquid interface (ALI) model consisting of human airway epithelium with (Epi/FT) and without (Epi) a mesenchymal component. ALI cultures were exposed to 25 mM DA-derived vapors (using vapor cups) for 1 h on day 0, 2 and 4. In some experiments, the tissues were exposed to 2,3-hexanedione (Hex) which is structurally-similar, but much less fibrogenic than DA. Lactate dehydrogenase activity and day 6 histopathologic changes associated with epithelial injury, including basal/suprabasal spongiosis, were increased following exposure of Epi/FT tissues to DA but not control or Hex vapors. IL-1a, IL-6, IL-8, sIL-1Ra, TGFa, MCP-3 and TNFa proteins were increased following DA exposure of Epi/FT tissues; only IL-1a, IL-8, sIL-1Ra and TGFa were increased following exposure of Epi tissues. MMP-1, MMP-3 and TIMP-1 proteins were increased following DA exposure of Epi/FT tissues; whereas MMP-2, MMP-7 and TIMP-2 were decreased, and production was largely dependent upon the presence of sub-epithelial stromal matrix/fibroblasts. Hex-induced protein changes were minimal. This in vitro study demonstrated that exposure of human airways to DA vapors induced epithelial injury (with the histopathologic feature of basal/suprabasal spongiosis) and increased release of pro-inflammatory and pro-fibrotic cytokines/chemokines as well as MMPs/TIMPs in the absence of recruited-inflammatory cells.

High-Resolution CT Findings of Obstructive and Restrictive Phenotypes of Chronic Lung Allograft Dysfunction: More Than Just Bronchiolitis Obliterans Syndrome

OBJECTIVE

The purpose of this article is to review the high-resolution CT characteristics of individual obstructive and restrictive chronic lung allograft dysfunction (CLAD) phenotypes to aid in making accurate diagnoses and guiding treatment.

CONCLUSION

Long-term survival and function after lung transplant are considerably worse compared with after other organ transplants. CLAD is implicated as a major limiting factor for long-term graft viability. Historically thought to be a single entity, bronchiolitis obliterans syndrome, CLAD is actually a heterogeneous group of disorders with distinct subtypes.

Depletion of Airway Submucosal Glands and TP63+KRT5+ Basal Cells in Obliterative Bronchiolitis

RATIONALE

Obliterative bronchiolitis (OB) is a major cause of mortality after lung transplantation. Depletion of airway stem cells (SCs) may lead to fibrosis in OB.

OBJECTIVES

Two major SC compartments in airways are submucosal glands (SMGs) and surface airway p63 (also known as TP63 [tumor protein 63])-positive/K5 (also known as KRT5 [keratin 5])-positive basal cells (BCs). We hypothesized that depletion of these SC compartments occurs in OB.

METHODS

Ferret orthotopic left lung transplants were used as an experimental model of OB, and findings were corroborated in human lung allografts. Morphometric analysis was performed in ferret and human lungs to evaluate the abundance of SMGs and changes in the expression of phenotypic BC markers in control, lymphocytic bronchiolitis, and OB airways. The abundance and proliferative capacity of proximal and distal airway SCs was assessed using a clonogenic colony-forming efficiency assay.

MEASUREMENTS AND MAIN RESULTS

Ferret allografts revealed significant loss of SMGs with development of OB. A progressive decline in p63+/K5+ and increase in K5+/K14+ and K14+ BC phenotypes correlated with the severity of allograft rejection in large and small ferret airways. The abundance and proliferative capacity of basal SCs in large allograft airways declined with severity of OB, and there was complete ablation of basal SCs in distal OB airways. Human allografts mirrored phenotypic BC changes observed in the ferret model.

CONCLUSIONS

SMGs and basal SC compartments are depleted in large and/or small airways of lung allografts, and basal SC proliferative capacity declines with progression of disease and phenotypic changes. Global airway SC depletion may be a mechanism for pulmonary allograft failure.

Zbtb7a induction in alveolar macrophages is implicated in anti-HLA-mediated lung allograft rejection

Chronic rejection significantly limits long-term success of solid organ transplantation. De novo donor-specific antibodies (DSAs) to mismatched donor human leukocyte antigen after human lung transplantation predispose lung grafts to chronic rejection. We sought to delineate mediators and mechanisms of DSA pathogenesis and to define early inflammatory events that trigger chronic rejection in lung transplant recipients and obliterative airway disease, a correlate of human chronic rejection, in mouse. Induction of transcription factor zinc finger and BTB domain containing protein 7a (Zbtb7a) was an early response critical in the DSA-induced chronic rejection. A cohort of human lung transplant recipients who developed DSA and chronic rejection demonstrated greater Zbtb7a expression long before clinical diagnosis of chronic rejection compared to nonrejecting lung transplant recipients with stable pulmonary function. Expression of DSA-induced Zbtb7a was restricted to alveolar macrophages (AMs), and selective disruption of Zbtb7a in AMs resulted in less bronchiolar occlusion, low immune responses to lung-restricted self-antigens, and high protection from chronic rejection in mice. Additionally, in an allogeneic cell transfer protocol, antigen presentation by AMs was Zbtb7a-dependent where AMs deficient in Zbtb7a failed to induce antibody and T cell responses. Collectively, we demonstrate that AMs play an essential role in antibody-induced pathogenesis of chronic rejection by regulating early inflammation and lung-restricted humoral and cellular autoimmunity.

Azithromycin Fails to Prevent Accelerated Airway Obliteration in T-bet-/- Mouse Lung Allograft Recipients

BACKGROUND

Cellular and molecular mechanisms of acute and chronic lung allograft rejection have yet to be clearly defined, and obliterative bronchiolitis (OB) remains the primary limitation to survival in lung transplant recipients (LTRs). We have previously shown that T-bet-deficient recipients of full major histocompatibility complex (MHC)-mismatched, orthotopic left lung transplants develop accelerated obliterative airway disease (OAD) in the setting of acute cellular rejection characterized by robust alloimmune CD8⁺ interleukin (IL)-17 and interferon (IFN)-γ responses that are attenuated with neutralization of IL-17. Azithromycin has been shown to be beneficial in some LTRs with bronchiolitis obliterans syndrome/OB. Here, we evaluated the effects of azithromycin on rejection pathology and T-cell effector responses in T-bet^-/- recipients of lung transplants.

METHODS

Orthotopic left lung transplantation was performed in BALB/c → B6 wild type or BALB/c → B6 T-bet^-/- strain combinations as previously described. Mice treated with azithromycin received 10 mg/kg or 50 mg/kg subcutaneously daily. Lung allograft histopathology was analyzed at day 10 or day 21 post-transplantation, and neutrophil staining for quantification was performed using anti-myeloperoxidase. Allograft mononuclear cells were isolated at day 10 for T-cell effector cytokine response assessment using flow cytometry.

RESULTS

We show that while azithromycin significantly decreases lung allograft neutrophilia and CXCL1 levels and attenuates allospecific CD8⁺ IL-17 responses early post-transplantation, OAD persists in T-bet-deficient mice.

CONCLUSIONS

Our results indicate that lung allograft neutrophilia is not essential for the development of OAD in this model and suggest allospecific T-cell responses that remain despite marked attenuation of CD8⁺ IL-17 are sufficient for obliterative airway inflammation and fibrosis.

Prevention of ischemia-reperfusion lung injury during static cold preservation by supplementation of standard preservation solution with HEMO2life® in pig lung transplantation model

We describe the results of adding a new biological agent HEMO₂life^® to a standard preservation solution for hypothermic static lung preservation aiming to improve early functional parameters after lung transplantation. HEMO₂life^® is a natural oxygen carrier extracted from Arenicola marina with high oxygen affinity developed as an additive to standard organ preservation solutions. Standard preservation solution (Perfadex^®) was compared with Perfadex^® associated with HEMO₂life^® and with sham animals after 24 h of hypothermic preservation followed by lung transplantation. During five hours of lung reperfusion, functional parameters and biomarkers expression in serum and in bronchoalveolar lavage fluid (BALF) were measured. After five hours of reperfusion, HEMO₂life^® group led to significant improvement in functional parameters: reduction of graft vascular resistance (p < .05) and increase in graft oxygenation ratio (p < .05). Several ischemia-reperfusion related biomarkers showed positive trends in the HEMO₂life^® group: expression of HMG B1 in serum tended to be lower in comparison (2.1 ± 0.8 vs. 4.6 ± 1.5) with Perfadex^® group, TNF-α and IL-8 in BALF were significantly higher in the two experimental groups compared to control (p < .05). During cold ischemia, expression of HIF1α and histology remained unchanged and similar to control. Supplementation of the Perfadex^® solution by an innovative oxygen carrier HEMO₂life^® during hypothermic static preservation improves early graft function after prolonged cold ischemia in lung transplantation.

The activity of nintedanib in an animal model of allogenic left lung transplantation resembling aspects of allograft rejection

AIM OF THE STUDY

The prevention and treatment of chronic lung allograft dysfunction (CLAD) after lung transplantation (LTx) remain unsatisfactory. Growth factors may play an important role in the development of CLAD. This study evaluated the effects of nintedanib, a receptor tyrosine kinase inhibitor, in the treatment of CLAD after experimental LTx.

MATERIALS AND METHODS

A rat model of left lung allo-transplantation (Fisher 344 to Wistar Kyoto) was used to evaluate the effect of nintedanib (50 mg/kg per day) on the development of CLAD. Therapy with nintedanib began 2 days before LTx and ended on postoperative day (POD) 20 (n = 6) or 60 (n = 6). Nontreated animals who underwent LTx (n = 12) were used as controls, whereas naïve lungs (n = 24) served as reference for physiological healthy organs without transplantation damage or medical effects. Acute and chronic rejection were evaluated on POD 20 and 60, respectively.

RESULTS

Immunohistologic analysis showed a decrease in growth factors/receptors on POD 60 (nintedanib-treated vs. nontreated controls: platelet-derived growth factor (PDGF) A: [P ≤ 0.001]; PDGF receptor-α: [P ≤ 0.001]; vascular endothelial growth factor (VEGF) A: [P ≤ 0.001]; VEGF receptor-2: [P ≤ 0.001]). However, no reductions in fibrotic changes were observed in nintedanib-treated allografts compared with nontreated allografts. Although nintedanib treatment started before LTx none of the animals showed impaired wound healing. No dehiscence of the sutures of the bronchus, vessels or skin, or stenosis of the bronchus was found.

CONCLUSION

In conclusion, while nintedanib reduced the expression of growth factors/receptors in a rat LTx model, a reduction in fibrotic alterations was not observed at POD 60.

Association between a Single Donor TARC/CCL17 Promotor Polymorphism and Obstructive Chronic Lung Allograft Dysfunction after Lung Transplantation

Lung transplantation (LTx) outcome is hampered by development of chronic rejection, often manifested as the bronchiolitis obliterans syndrome (BOS). Low serum levels of thymus and activation-regulated chemokine (TARC/CCL17), a chemoattractant, measured during the first month post-LTx are predictive for BOS development. Since TARC/CCL17 promotor polymorphisms correlate with serum TARC/CCL17 levels, we investigated seven single-nucleotide polymorphisms (SNPs) within this region and their potential association with LTx outcome. We analyzed donor and patient SNP configurations and haplotypes and observed a trend between a donor SNP (rs223899) configuration and patient TARC/CCL17 serum levels post-LTx (p = 0.066). Interestingly, this SNP configuration in patients did not show any correlation with pre-LTx TARC/CCL17 serum levels (p = 0.776). Survival analysis showed that receiving a graft from a donor heterozygous for rs223899 has a disadvantageous impact on transplantation outcome. When stratified per donor SNP genotype, patients receiving a transplant from a heterozygous donor showed a lower BOS-free survival (p = 0.023) and survival rate (p = 0.0079). Since rs223899 is located within a NFκB binding site, heterozygosity at this position could result in a reduced TARC/CCL17 expression. Our data indicate that a single TARC/CCL17 promotor SNP in the donor correlates with lower serum TARC/CCL17 levels measured 1 month after LTx and affects clinical outcome after LTx.