Eosinophils restrain humoral alloimmunity after lung transplantation.

While the function of many leukocytes in transplant biology has been well defined, the role of eosinophils is controversial and remains poorly explored. Conflicting data exist regarding eosinophils' role in alloimmunity. Due to their prevalence in the lung, and their defined role in other pulmonary pathologies such as asthma, we set out to explore the role of eosinophils in the long-term maintenance of the lung allograft. We noted that depletion of eosinophils results in the generation of donor-specific antibodies. Eosinophil depletion increased memory B cell, plasma cell, and antibody-secreting cell differentiation and resulted in de novo generation of follicular germinal centers. Germinal center formation depended on the expansion of CD4+Foxp3-Bcl6+CXCR5+PD-1+ T follicular helper (Tfh) cells, which increase in number after eosinophil depletion. Mechanistically, we demonstrate that eosinophils prevent Tfh cell generation by acting as the dominant source of IFN-γ in an established lung allograft, thus facilitating Th1 rather than Tfh polarization of naive CD4+ T cells. Our data thus describe what we believe is a unique and previously unknown role for eosinophils in maintaining allograft tolerance and suggest that indiscriminate administration of eosinophil-lytic corticosteroids for treatment of acute cellular rejection may inadvertently promote humoral alloimmunity.

Pulmonary thromboendarterectomy in hospitalized versus elective patients with chronic thromboembolic pulmonary hypertension.

OBJECTIVE: We sought to characterize outcomes in patients undergoing pulmonary thromboendarterectomy electively versus after acute presentation. METHODS: This is a retrospective analysis of patients who underwent pulmonary thromboendarterectomy from October 2015 to April 2022. Patients were divided into 2 groups depending on elective surgery or surgery during the same hospitalization as their presentation. RESULTS: In total, 69 patients were included: 45 in the hospitalized group and 24 in the elective group. Patients in the hospitalized group were less likely to have chronic lung disease, history of pulmonary embolism and hypertension, be on anticoagulation and medication for pulmonary hypertension, and present with >1 month of respiratory symptoms. They were more likely to have worse preoperative right ventricular function. Among other demographics, risk factors for venous thromboembolism were similar between both groups. Thirteen patients in the hospitalized group required preoperative extracorporeal membrane oxygenation. There was no difference in disease classification and operative, cardiopulmonary bypass, and hypothermic circulatory arrest durations between both groups. Postoperative complications were similar between both groups, except for greater frequency of deep vein thrombosis in the hospitalized group (26.7% vs 4.2%, P = .03). In-hospital and intensive care unit length of stay were similar between both groups. Overall, in-hospital mortality was 4.3% and was similar between both groups; P = .28. CONCLUSIONS: Our series shows that pulmonary thromboendarterectomy can be safely performed in patients presenting acutely, with comparable postoperative complications and in-hospital mortality to an elective setting. Such patients present with worse right ventricular function, sometimes requiring temporary mechanical support.

Monitoring regulatory T cells as a prognostic marker in lung transplantation.

Lung transplantation is the major surgical procedure, which restores normal lung functioning and provides years of life for patients suffering from major lung diseases. Lung transplant recipients are at high risk of primary graft dysfunction, and chronic lung allograft dysfunction (CLAD) in the form of bronchiolitis obliterative syndrome (BOS). Regulatory T cell (Treg) suppresses effector cells and clinical studies have demonstrated that Treg levels are altered in transplanted lung during BOS progression as compared to normal lung. Here, we discuss levels of Tregs/FOXP3 gene expression as a crucial prognostic biomarker of lung functions during CLAD progression in clinical lung transplant recipients. The review will also discuss Treg mediated immune tolerance, tissue repair, and therapeutic strategies for achieving in-vivo Treg expansion, which will be a potential therapeutic option to reduce inflammation-mediated graft injuries, taper the toxic side effects of ongoing immunosuppressants, and improve lung transplant survival rates.

Regadenoson for the treatment of COVID-19: A five case clinical series and mouse studies.

BACKGROUND: Adenosine inhibits the activation of most immune cells and platelets. Selective adenosine A2A receptor (A2AR) agonists such as regadenoson (RA) reduce inflammation in most tissues, including lungs injured by hypoxia, ischemia, transplantation, or sickle cell anemia, principally by suppressing the activation of invariant natural killer T (iNKT) cells. The anti-inflammatory effects of RA are magnified in injured tissues due to induction in immune cells of A2ARs and ecto-enzymes CD39 and CD73 that convert ATP to adenosine in the extracellular space. Here we describe the results of a five patient study designed to evaluate RA safety and to seek evidence of reduced cytokine storm in hospitalized COVID-19 patients. METHODS AND FINDINGS: Five COVID-19 patients requiring supplemental oxygen but not intubation (WHO stages 4-5) were infused IV with a loading RA dose of 5 µg/kg/h for 0.5 h followed by a maintenance dose of 1.44 µg/kg/h for 6 hours, Vital signs and arterial oxygen saturation were recorded, and blood samples were collected before, during and after RA infusion for analysis of CRP, D-dimer, circulating iNKT cell activation state and plasma levels of 13 proinflammatory cytokines. RA was devoid of serious side effects, and within 24 hours from the start of infusion was associated with increased oxygen saturation (93.8 ± 0.58 vs 96.6 ± 1.08%, P<0.05), decreased D-dimer (754 ± 17 vs 518 ± 98 ng/ml, P<0.05), and a trend toward decreased CRP (3.80 ± 1.40 vs 1.98 ± 0.74 mg/dL, P = 0.075). Circulating iNKT cells, but not conventional T cells, were highly activated in COVID-19 patients (65% vs 5% CD69+). RA infusion for 30 minutes reduced iNKT cell activation by 50% (P<0.01). RA infusion for 30 minutes did not influence plasma cytokines, but infusion for 4.5 or 24 hours reduced levels of 11 of 13 proinflammatory cytokines. In separate mouse studies, subcutaneous RA infusion from Alzet minipumps at 1.44 µg/kg/h increased 10-day survival of SARS-CoV-2-infected K18-hACE2 mice from 10 to 40% (P<0.001). CONCLUSIONS: Infused RA is safe and produces rapid anti-inflammatory effects mediated by A2A adenosine receptors on iNKT cells and possibly in part by A2ARs on other immune cells and platelets. We speculate that iNKT cells are activated by release of injury-induced glycolipid antigens and/or alarmins such as IL-33 derived from virally infected type II epithelial cells which in turn activate iNKT cells and secondarily other immune cells. Adenosine released from hypoxic tissues, or RA infused as an anti-inflammatory agent decrease proinflammatory cytokines and may be useful for treating cytokine storm in patients with Covid-19 or other inflammatory lung diseases or trauma.

Regadenoson Reduces Soluble Receptor for Advanced Glycation End-Products in Lung Recipients.

BACKGROUND: The selective adenosine A2A receptor (A2AR) agonist regadenoson reduces inflammation due to lung ischemia-reperfusion injury (IRI). The objective of this study was to investigate molecular and cellular mechanisms by which regadenoson reduces IRI in lung transplant recipients. METHODS: Fourteen human lung transplant recipients were infused for 12 hours with regadenoson and 7 more served as untreated controls. Plasma levels of high mobility group box 1 and its soluble receptor for advanced glycation end-products (sRAGE) were measured by Luminex. Matrix metalloproteinase (MMP) 2 and 9 were measured by gelatin zymography. Tissue inhibitor of metalloproteinase 1 was measured by mass spectroscopy. A2AR expression on leukocytes was analyzed by flow cytometry. MMP-9-mediated cleavage of RAGE was evaluated using cultured macrophages in vitro. RESULTS: Regadenoson treatment during lung transplantation significantly reduced levels of MMP-9 (P < .05), but not MMP-2, and elevated levels of tissue inhibitor of metalloproteinase 1 (P < .05), an endogenous selective inhibitor of MMP-9. Regadenoson infusion significantly reduced plasma levels of sRAGE (P < .05) during lung reperfusion compared with control subjects. A2AR expression was highest on invariant natural killer T cells and higher on monocytes than other circulating immune cells (P < .05). The shedding of RAGE from cultured monocytes/macrophages was increased by MMP-9 stimulation and reduced by an MMP inhibitor or by A2AR agonists, regadenoson or ATL146e. CONCLUSIONS: In vivo and in vitro studies suggest that A2AR activation reduces sRAGE in part by inhibiting MMP-9 production by monocytes/macrophages. These results suggest a novel molecular mechanism by which A2AR agonists reduce primary graft dysfunction.

Extracorporeal life support as a bridge to lung transplantation: Where are we now?

The number of lung transplant procedures performed internationally is increasing but the donor organ pool is insufficient to meet demand and waiting list mortality is unacceptably high. As survival rates for patients with acute respiratory distress syndrome managed on extracorporeal life support (ECLS) have steadily improved, a potential role for ECLS to support critically ill patients awaiting a donor organ match has emerged. We explore the rapidly evolving landscape of ECLS as a bridge to lung transplantation with review of the patient selection criteria, predictors of survival, modes of pre and peri-transplant support, and the importance of a holistic multidisciplinary approach to care. Finally, we consider innovations that are envisaged to increase the accessibility, safety, and effectiveness of ECLS delivery for future lung transplant candidates.

Genetically Modified Porcine-to-Human Cardiac Xenotransplantation.

A 57-year-old man with nonischemic cardiomyopathy who was dependent on venoarterial extracorporeal membrane oxygenation (ECMO) and was not a candidate for standard therapeutics, including a traditional allograft, received a heart from a genetically modified pig source animal that had 10 individual gene edits. Immunosuppression was based on CD40 blockade. The patient was weaned from ECMO, and the xenograft functioned normally without apparent rejection. Sudden diastolic thickening and failure of the xenograft occurred on day 49 after transplantation, and life support was withdrawn on day 60. On autopsy, the xenograft was found to be edematous, having nearly doubled in weight. Histologic examination revealed scattered myocyte necrosis, interstitial edema, and red-cell extravasation, without evidence of microvascular thrombosis - findings that were not consistent with typical rejection. Studies are under way to identify the mechanisms responsible for these changes. (Funded by the University of Maryland Medical Center and School of Medicine.).

Ischemia-reperfusion Injury in the Transplanted Lung: A Literature Review.

Lung ischemia-reperfusion injury (LIRI) and primary graft dysfunction are leading causes of morbidity and mortality among lung transplant recipients. Although extensive research endeavors have been undertaken, few preventative and therapeutic treatments have emerged for clinical use. Novel strategies are still needed to improve outcomes after lung transplantation. In this review, we discuss the underlying mechanisms of transplanted LIRI, potential modifiable targets, current practices, and areas of ongoing investigation to reduce LIRI and primary graft dysfunction in lung transplant recipients.

Ex Vivo Lung Perfusion: Current Achievements and Future Directions.

There is a severe shortage in the availability of donor organs for lung transplantation. Novel strategies are needed to optimize usage of available organs to address the growing global needs. Ex vivo lung perfusion has emerged as a powerful tool for the assessment, rehabilitation, and optimization of donor lungs before transplantation. In this review, we discuss the history of ex vivo lung perfusion, current evidence on its use for standard and extended criteria donors, and consider the exciting future opportunities that this technology provides for lung transplantation.

Adenosine A2A receptor agonist (regadenoson) in human lung transplantation.

BACKGROUND: Currently, there are no clinically approved treatments for ischemia-reperfusion injury after lung transplantation. Pre-clinical animal models have demonstrated a promising efficacy of adenosine 2A receptor (A2AR) agonists as a treatment option for reducing ischemia-reperfusion injury. The purpose of this human study, is to conduct a Phase I clinical trial for evaluating the safety of continuous infusion of an A2AR agonist in lung transplant recipients. METHODS: An adaptive, two-stage continual reassessment trial was designed to evaluate the safety of regadenoson (A2AR agonist) in the setting of lung transplantation. Continuous infusion of regadenoson was administered to lung transplant recipients that was started at the time of skin incision. Adverse events and dose-limiting toxicities, as pre-determined by a study team and assessed by a clinical team and an independent safety monitor, were the primary end-points for safety in this trial. RESULTS: Between January 2018 and March 2019, 14 recipients were enrolled in the trial. Of these, 10 received the maximum infused dose of 1.44 µg/kg/min for 12 hours. No dose-limiting toxicities were observed. The steady-state plasma regadenoson levels sampled before the reperfusion of the first lung were 0.98 ± 0.46 ng/ml. There were no mortalities within 30 days. CONCLUSIONS: Regadenoson, an A2AR agonist, can be safely infused in the setting of lung transplantation with no dose-limiting toxicities or drug-related mortality. Although not powered for the evaluation of secondary end-points, the results of this trial and the outcome of pre-clinical studies warrant further investigation with a Phase II randomized controlled trial.

The Surge After the Surge: Cardiac Surgery Post-COVID-19.

Background: The coronavirus disease 2019 (COVID-19) pandemic has dramatically reduced adult cardiac surgery case volumes as institutions and surgeons curtail nonurgent operations. There will be a progressive increase in deferred cases during the pandemic that will require completion within a limited time frame once restrictions ease. We investigated the impact of various levels of increased postpandemic hospital operating capacity on the time to clear the backlog of deferred cases. Methods: We collected data from 4 cardiac surgery programs across 2 health systems. We recorded case rates at baseline and during the COVID-19 pandemic and created a mathematical model to quantify the cumulative surgical backlog based on the projected pandemic duration. We then used the model to predict the time required to clear the backlog depending on the level of increased operating capacity. Results: Cardiac surgery volumes fell to 54% of baseline after restrictions were implemented. Assuming a service restoration date of either June 1 or July 1, we calculated the need to perform 216% or 263% of monthly baseline volume, respectively, to clear the backlog in 1 month. The actual duration required to clear the backlog highly depends on hospital capacity in the post-COVID period, and ranges from 1 to 8 months, depending on when services are restored and the degree of increased capacity. Conclusions: Cardiac surgical operating capacity during the COVID-19 recovery period will have a dramatic impact on the time to clear the deferred cases backlog. Inadequate operating capacity may cause substantial delays and increase morbidity and mortality. If only prepandemic capacity is available, the backlog will never clear.

Is less really more? Reexamining video-assisted thoracoscopic versus open lobectomy in the setting of an enhanced recovery protocol.

OBJECTIVES: Video-assisted thoracoscopic surgery lobectomy has been associated with improved pain, length of stay, and outcomes compared with open lobectomy. However, enhanced recovery protocols improve outcomes after both procedures. We aimed to compare video-assisted thoracoscopic surgery and open lobectomy in the setting of a comprehensive enhanced recovery protocol. METHODS: All patients undergoing lobectomy for lung cancer at a single institution since the adoption of an enhanced recovery protocol (May 2016 to December 2018) were stratified by video-assisted thoracoscopic surgery versus open status and compared. Demographics and outcomes, including length of stay, daily pain scores, and short-term operative complications, were compared using standard univariate statistics and multivariable models. RESULTS: A total of 130 patients underwent lobectomy, including 71 (54.6%) undergoing video-assisted thoracoscopic surgery and 59 (45.4%) undergoing open surgery. Video-assisted thoracoscopic surgery versus open cases exhibited similar length of stay (median 4 days for both, P = .07), opioid requirement (33.2 vs 30.8 mg morphine equivalents, P = .86), and pain scores at 0, 1, 2, and 3 days after surgery (4.3 vs 2.8, P = .12; 4.4 vs 3.7, P = .27; 3.9 vs 3.5, P = .83; and 3.4 vs 3.5, P = .98, respectively). Patients undergoing video-assisted thoracoscopic surgery lobectomy exhibited lower rates of readmission (1.4% vs 17.0%, P < .01), postoperative transfusion requirement (0% vs 10.2%, P < .01), and pneumonia (1.4% vs 10.2%, P = .05). After risk adjustment, an open procedure (vs video-assisted thoracoscopic surgery status) did not significantly affect the length of stay (effect 0.18; P = .10) or overall complication rate (odds ratio, 1.9; P = .12). CONCLUSIONS: In the setting of a comprehensive enhanced recovery protocol, patients undergoing video-assisted thoracoscopic surgery versus open lobectomy exhibited similar short-term outcomes. Surgical incision may have less impact on outcomes in the setting of a comprehensive thoracic enhanced recovery protocol.

Poor Performance Flagging Is Associated With Fewer Transplantations at Centers Flagged Multiple Times.

BACKGROUND: Lung transplantation outcomes are heavily scrutinized, given the high stakes of these operations, yet the Center for Medicare and Medicaid Services (CMS) method of using Scientific Registry of Transplant Recipients (SRTR) risk-adjusted outcomes to identify underperforming centers is controversial. We hypothesized that CMS flagging results in conservative behavior for recipient and organ selection, resulting in fewer patients added to the waitlist and fewer transplantations performed. METHODS: SRTR reports from July 2012 through July 2017 were included. Center characteristics were compared, stratified by number of flagging events. The impact of flagging for underperformance on risk aversion outcomes was analyzed using a mixed-effects regression model. RESULTS: A total of 72 centers had reported SRTR data during the study period. Of these, 21 centers (29%) met flagging criteria a median of 2 times (interquartile range, 1 to 4 times) for a total of 53 events. Flagging had no statistically significant impact on waitlist or transplantation volume and patient selection by mixed-effects modeling. Despite similar average expected 1-year survival (86.6% versus 87.7%, p = 0.27), centers that were flagged only once added more patients per year to the waitlist (16.3 patients versus 7.8 patients, p = 0.01) and performed more transplantations per year (28.4 transplantations versus 11.1 transplantations, p = 0.01). CONCLUSIONS: This analysis defines center-level trends in lung transplantation after CMS flagging. Contrary to our primary hypothesis, flagging did not result in temporal center-level changes. However, programs on prolonged probation demonstrated reduced activity, which likely indicates a shift to higher performing centers.

Implementing a Thoracic Enhanced Recovery Program: Lessons Learned in the First Year.

BACKGROUND: To minimize the stress of operations, improve the patient experience, reduce variability, and optimize resource utilization, we implemented a thoracic enhanced recovery after surgery (ERAS) protocol and evaluated progress after 1 year. METHODS: Two protocols were developed: video-assisted thoracic surgery (ERAS-VATS) and thoracotomy (ERAS-T). Each incorporated preoperative patient education, carbohydrate loading, opioid-sparing analgesia, conservative fluid management, and early ambulation. Patient outcomes, length of stay, pain scores, opioid use, fluid administration, and cost for ERAS patients were compared with historic controls from the year before program initiation. RESULTS: Historic VATS (n = 162) were compared with 81 ERAS-VATS patients. Median postoperative morphine equivalents (86 versus 22 mg, p < 0.0001), total fluid balance (1279 versus 227 mL, p < 0.0001), and mean inflation adjusted hospital costs ($20,169 versus $14,870, p = 0.0003) all decreased significantly. Historic thoracotomy patients (n = 62) were compared with 58 ERAS-T patients. Median postoperative morphine equivalents (130 versus 54 mg, p < 0.0001), total fluid balance (788 versus -489 mL, p = 0.012), length of stay (6.0 versus 4.0 days, p = 0.009), and mean inflation adjusted hospital costs ($41,950 versus $26,089, p < 0.00001) all decreased significantly. CONCLUSIONS: Implementation of thoracic ERAS is a dynamic process with potential to improve outcomes in thoracic surgical procedures. In the first year we shortened length of stay, decreased opioid usage, minimized fluid overload, and decreased hospital costs.

Prospective study of giant paraesophageal hernia repair with 1-year follow-up.

OBJECTIVE: Evaluating giant paraesophageal hernia (GPEH) repair requires long-term follow-up. GPEH repair can have associated high recurrence rates, yet this incidence depends on how recurrence is defined. Our objective was to prospectively evaluate patients undergoing GPEH repair with 1-year follow-up. METHODS: Patients undergoing elective GPEH repair between 2011 and 2014 were enrolled prospectively. Postoperatively, patients were evaluated at 1 month and 1 year. Radiographic recurrence was evaluated by barium swallow and defined as a gastroesophageal junction located above the hiatus. Quality of life was evaluated pre- and postoperatively with the use of a validated questionnaire. RESULTS: One-hundred six patients were enrolled. The majority of GPEH repairs were performed laparoscopically (80.2%), and 7.5% were redo repairs. At 1-year follow-up, 63.4% of patients were symptom free, and radiographic recurrence was 32.7%. Recurrence rate was 18.8% with standard definition (>2 cm of stomach above the diaphragm). Quality of life scores at 1 year were significantly better after operative repair, even in patients with radiographic recurrence (7.0 vs 22.5 all patients, 13.0 vs 22.5 with recurrence; P < .001). Patients with small radiographic recurrences have similar satisfaction and symptom severity to patients with >2 cm recurrences. CONCLUSIONS: GPEH repair can be performed with low operative mortality and morbidity. The rate of recurrence at 1 year depends on the definition used. Patient satisfaction and symptom severity are similar between patients with radiographic and greater than 2 cm hernia recurrences. Longer follow-up and critical assessment of our results are needed to understand the true impact of this procedure and better inform perioperative decision making.

Perioperative statin use is associated with decreased incidence of primary graft dysfunction after lung transplantation.

BACKGROUND: Primary graft dysfunction (PGD) is a major cause of early morbidity and mortality after lung transplantation. Statins reduce the risk of chronic rejection after lung transplantation, but their effects on PGD are unknown. We hypothesized that perioperative statin therapy decreases the risk for PGD after lung transplantation. METHODS: We retrospectively reviewed records of all patients undergoing lung transplantation between January 1999 and December 2014 at the University of Virginia Health System. The primary outcome was PGD (grades 1-3). Secondary outcomes included grade 3 PGD, length of intensive care unit and hospital stay, and mortality. RESULTS: Of 266 patients who met final inclusion criteria, 138 (52%) were diagnosed with PGD. In-hospital mortality among patients with PGD was 6.5%. There were no deaths in patients without PGD (p < 0.001). PGD was diagnosed in 24 patients taking statins (34.8%) and in 114 patients (57.9%) who did not take statins (p = 0.001). After propensity score adjustments, perioperative statin use was independently associated with a reduced risk for PGD (odds ratio [OR] 0.41, 95% confidence interval [CI] 0.20-0.84, p = 0.015) and reduced risk to develop grade 3 PGD (OR 0.42, 95% CI 0.18-0.94, p = 0.036). Other risk factors associated with PGD included intraoperative use of cardiopulmonary bypass (OR 3.74, 95% CI 1.75-8.02, p = 0.001) and positive donor smoking status (OR 2.27, 95% CI 1.18-4.35, p = 0.014). CONCLUSIONS: The results demonstrate that perioperative use of statins is independently associated with reduced risk for PGD after lung transplantation.