Ramiro Fernandez

Ureaplasma Transmitted From Donor Lungs Is Pathogenic After Lung Transplantation

Hyperammonemia is a highly fatal syndrome in lung recipients that is usually refractory to medical therapy. We recently reported that infection by a Mollicute, Ureaplasma, is causative for hyperammonemia and can be successfully treated with antimicrobial agents. However, it remains unknown whether the pathogenic strain of Ureaplasma is donor or recipient derived. Here we provide evidence that donor-derived Ureaplasma infection can be pathogenic. As such, we uncover a previously unknown lethal donor-derived opportunistic infection in lung recipients. Given the high mortality associated with hyperammonemia, strategies for routine donor screening or prophylaxis should be further evaluated in prospective studies.

Donor pulmonary intravascular nonclassical monocytes recruit recipient neutrophils and mediate primary lung allograft dysfunction

Donor nonclassical monocytes mediate primary lung allograft dysfunction by recruiting neutrophils via MyD88-dependent production of CXCL2. Nonclassical monocytes prompt primary graft dysfunction Despite concerted efforts, primary graft dysfunction is a major cause of graft failure after organ transplantation. In lung transplantation, primary graft dysfunction is known to be mediated by early neutrophil infiltration. Zheng et al. used syngeneic and allogeneic mouse models of lung transplantation to show that nonclassical monocytes were the key cell population recruiting these destructive neutrophils. These intravascular cells were donor-derived and were also detectable in human lung grafts being used for transplant. Because depletion of nonclassical monocytes prevented primary graft dysfunction in the mouse models, targeting this cell population during human transplant could lead to improved rates of graft success. Primary graft dysfunction is the predominant driver of mortality and graft loss after lung transplantation. Recruitment of neutrophils as a result of ischemia-reperfusion injury is thought to cause primary graft dysfunction; however, the mechanisms that regulate neutrophil influx into the injured lung are incompletely understood. We found that donor-derived intravascular nonclassical monocytes (NCMs) are retained in human and murine donor lungs used in transplantation and can be visualized at sites of endothelial injury after reperfusion. When NCMs in the donor lungs were depleted, either pharmacologically or genetically, neutrophil influx and lung graft injury were attenuated in both allogeneic and syngeneic models. Similar protection was observed when the patrolling function of donor NCMs was impaired by deletion of the fractalkine receptor CX3CR1. Unbiased transcriptomic profiling revealed up-regulation of MyD88 pathway genes and a key neutrophil chemoattractant, CXCL2, in donor-derived NCMs after reperfusion. Reconstitution of NCM-depleted donor lungs with wild-type but not MyD88-deficient NCMs rescued neutrophil migration. Donor NCMs, through MyD88 signaling, were responsible for CXCL2 production in the allograft and neutralization of CXCL2 attenuated neutrophil influx. These findings suggest that therapies to deplete or inhibit NCMs in donor lung might ameliorate primary graft dysfunction with minimal toxicity to the recipient.

Humoral Human Lung Allograft Rejection by Tissue-Restricted Non-HLA Antibodies

A third of lung recipients have preexisting antibodies against nonhuman leukocyte self-antigens (nHAbs) present in the lung tissue. These nHAbs also form de novo in about 70% of patients within 3 years after transplantation. Both preexisting and de novo nHAbs can cause murine lung allograft dysfunction. However, their role in human transplantation remains unclear. We report hyperacute rejection after right lung transplant in a recipient with preexisting nHAbs. The recipient of the left lung from the same donor had an uneventful initial course, but de novo nHAbs developed at 3 weeks, leading to acute humoral rejection. Both patients were successfully treated with antibody-directed therapies.

Lung Injury Combined with Loss of Regulatory T Cells Leads to De Novo Lung-Restricted Autoimmunity

More than one third of patients with chronic lung disease undergoing lung transplantation have pre-existing Abs against lung-restricted self-Ags, collagen type V (ColV), and k-α1 tubulin (KAT). These Abs can also develop de novo after lung transplantation and mediate allograft rejection. However, the mechanisms leading to lung-restricted autoimmunity remain unknown. Because these self-Ags are normally sequestered, tissue injury is required to expose them to the immune system. We previously showed that respiratory viruses can induce apoptosis in CD4+CD25+Foxp3+ regulatory T cells (Tregs), the key mediators of self-tolerance. Therefore, we hypothesized that lung-tissue injury can lead to lung-restricted immunity if it occurs in a setting when Tregs are impaired. We found that human lung recipients who suffer respiratory viral infections experienced a decrease in peripheral Tregs. Pre-existing lung allograft injury from donor-directed Abs or gastroesophageal reflux led to new ColV and KAT Abs post respiratory viral infection. Similarly, murine parainfluenza (Sendai) respiratory viral infection caused a decrease in Tregs. Intratracheal instillation of anti-MHC class I Abs, but not isotype control, followed by murine Sendai virus infection led to development of Abs against ColV and KAT, but not collagen type II (ColII), a cartilaginous protein. This was associated with expansion of IFN-γ–producing CD4+ T cells specific to ColV and KAT, but not ColII. Intratracheal anti-MHC class I Abs or hydrochloric acid in Foxp3-DTR mice induced ColV and KAT, but not ColII, immunity, only if Tregs were depleted using diphtheria toxin. We conclude that tissue injury combined with loss of Tregs can lead to lung-tissue–restricted immunity.

Association of body mass index with lung transplantation survival in the United States following implementation of the lung allocation score

Background: The association of body mass index (BMI) with survival after lung transplantation remains controversial, owing to conflicting evidence in the literature. Previous reports have used traditional BMI categories, included patients who underwent transplantation before implementation of the lung allocation score (LAS), or were limited by single‐center experiences. Here we evaluated the association of individual BMI units with short‐term and long‐term mortality in a large national database following implementation of the LAS. Methods: The Scientific Registry of Transplant Recipients database was used to collect data for 17,233 adult lung transplantations performed between May 2005 and June 2016. The primary outcome was all‐cause mortality at 90 days and 1 year posttransplantation. Logistic regression modeling was used to independently predict mortality per BMI unit, adjusting for donor and recipient factors. Results: BMI was an independent predictor of mortality at both 90 days and 1 year. At 90 days, a BMI of 25 was associated with the lowest predicted probability of death (0.053; 95% confidence interval [CI], 0.047‐0.049), with increased odds of mortality at BMI ≤20 and ≥28. At 1 year, a BMI of 26 was associated with the lowest predicted probability of death (0.12; 95% CI, 0.11‐0.13), with increased odds of mortality at BMI ≤24 and ≥28. Conclusions: Each individual BMI unit has a quantifiable effect on posttransplantation survival, and the patterns of effect do not fit into the predefined BMI categories. The mortality risk associated with BMI should be considered by transplant centers when making listing decisions and by regulatory bodies for estimating expected outcomes.

Single-Cell Transcriptomic Analysis of Human Lung Reveals Complex Multicellular Changes During Pulmonary Fibrosis

Pulmonary fibrosis is a devastating disorder that results in the progressive replacement of normal lung tissue with fibrotic scar. Available therapies slow disease progression, but most patients go on to die or require lung transplantation. Single-cell RNA-seq is a powerful tool that can reveal cellular identity via analysis of the transcriptome, but its ability to provide biologically or clinically meaningful insights in a disease context is largely unexplored. Accordingly, we performed single-cell RNA-seq on lung tissue obtained from eight transplant donors and eight recipients with pulmonary fibrosis and one bronchoscopic cryobiospy sample. Integrated single-cell transcriptomic analysis of donors and patients with pulmonary fibrosis identified the emergence of distinct populations of epithelial cells and macrophages that were common to all patients with lung fibrosis. Analysis of transcripts in the Wnt pathway suggested that within the same cell type, Wnt secretion and response are restricted to distinct non-overlapping cells, which was confirmed using in situ RNA hybridization. Single-cell RNA-seq revealed heterogeneity within alveolar macrophages from individual patients, which was confirmed by immunohistochemistry. These results support the feasibility of discovery-based approaches applying next generation sequencing technologies to clinically obtained samples with a goal of developing personalized therapies. One Sentence Summary Single-cell RNA-seq applied to tissue from diseased and donor lungs and a living patient with pulmonary fibrosis identifies cell type-specific disease-associated molecular pathways.

A novel strategy for cardiopulmonary support during lung transplantation

Contemporary modalities for cardiopulmonary support during lung transplantation include traditional cardiopulmonary bypass (CPB) and venoarterial extracorporeal membrane oxygenation (VA-ECMO). While highly effective, both are associated with morbidities such as arteriopathy and bleeding diathesis. In this report, we describe a novel approach for cardiopulmonary support during double lung transplantation in a patient with end-stage lung disease, pulmonary hypertension and moderate right ventricle (RV) dysfunction, using a percutaneous dual lumen cannula placed via the jugular vein which allowed us to achieve both RV bypass and membrane oxygenation. The cannula was left in place to provide ongoing RV support and the patient was successfully decannulated at bedside on post-operative day (POD) 2. Lack of arterial cannulation, percutaneous access, and bedside decannulation are benefits of this strategy, rendering this approach a useful addition to the armamentarium for CPB techniques in lung transplantation.

Spleen-derived classical monocytes mediate lung ischemia-reperfusion injury through IL-1β

&NA; Ischemia‐reperfusion injury, a form of sterile inflammation, is the leading risk factor for both short‐term mortality following pulmonary transplantation and chronic lung allograft dysfunction. While it is well recognized that neutrophils are critical mediators of acute lung injury, processes that guide their entry into pulmonary tissue are not well understood. Here, we found that CCR2+ classical monocytes are necessary and sufficient for mediating extravasation of neutrophils into pulmonary tissue during ischemia‐reperfusion injury following hilar clamping or lung transplantation. The classical monocytes were mobilized from the host spleen, and splenectomy attenuated the recruitment of classical monocytes as well as the entry of neutrophils into injured lung tissue, which was associated with improved graft function. Neutrophil extravasation was mediated by MyD88‐dependent IL‐1&bgr; production by graft‐infiltrating classical monocytes, which downregulated the expression of the tight junction‐associated protein ZO‐2 in pulmonary vascular endothelial cells. Thus, we have uncovered a crucial role for classical monocytes, mobilized from the spleen, in mediating neutrophil extravasation, with potential implications for targeting of recipient classical monocytes to ameliorate pulmonary ischemia‐reperfusion injury in the clinic.

Clinical Features of Metastatic Hepatic Malignancies

The liver is a common site for gastrointestinal tumor metastases as it is the first major organ reached by blood draining the portal venous system. With the development of more effective chemotherapeutic agents which may eradicate residual microscopic disease in the liver and help reduce known tumor burden, partial hepatectomy to remove gross metastatic disease will likely become increasingly utilized in the future. This chapter discusses the presentation and clinical factors in liver directed surgical resection.

Pleural gas analysis for the identification of alveolopleural fistulae

Purpose of review The method for identification of alveolopleural fistulae (APF) by visual inspection of air bubbles in the chest drainage system has several limitations and suffers from poor accuracy. Here we discuss the use of a novel technique of pleural gas analysis in the identification and management of APF. Recent findings We found that pleural gas analysis has higher sensitivity and specificity than visual inspection in identifying APF. Additionally, we demonstrated that intrapleural gas milieu impacts lung healing and reduction of intrapleural carbon dioxide can promote resolution of APF. Summary Pleural gas analysis is a novel technique to identify and manage APF. Integration of gas analysis in chest drainage systems would provide a more objective method for managing chest tubes and providing a favorable pleural gas environment for lung healing.