The success of lung transplantation is limited by the high rate of primary graft dysfunction due to ischemia-reperfusion injury (IRI). Lung IRI is characterized by a robust inflammatory response, ...lung dysfunction, endothelial barrier disruption, oxidative stress, vascular permeability, edema, and neutrophil infiltration. These events are dependent on the health of the endothelium, which is a primary target of IRI that results in pulmonary endothelial barrier dysfunction. Over the past 10 years, research has focused more on the endothelium, which is beginning to unravel the multi-factorial pathogenesis and immunologic mechanisms underlying IRI. Many important proteins, receptors, and signaling pathways that are involved in the pathogenesis of endothelial dysfunction after IR are starting to be identified and targeted as prospective therapies for lung IRI. In this review, we highlight the more significant mediators of IRI-induced endothelial dysfunction discovered over the past decade including the extracellular glycocalyx, endothelial ion channels, purinergic receptors, kinases, and integrins. While there are no definitive clinical therapies currently available to prevent lung IRI, we will discuss potential clinical strategies for targeting the endothelium for the treatment or prevention of IRI. The accruing evidence on the essential role the endothelium plays in lung IRI suggests that promising endothelial-directed treatments may be approaching the clinic soon. The application of therapies targeting the pulmonary endothelium may help to halt this rapid and potentially fatal injury.
National Institutes of Health (NIH) funding for academic (noncardiac) thoracic surgeons at the top-140 NIH-funded institutes in the United States was assessed. We hypothesized that thoracic surgeons ...have difficulty in obtaining NIH funding in a difficult funding climate.
The top-140 NIH-funded institutes' faculty pages were searched for noncardiac thoracic surgeons. Surgeon data, including gender, academic rank, and postfellowship training were recorded. These surgeons were then queried in NIH Research Portfolio Online Reporting Tools Expenditures and Results for their funding history. Analysis of the resulting grants (1980-2019) included grant type, funding amount, project start/end dates, publications, and a citation-based Grant Impact Metric to evaluate productivity.
A total of 395 general thoracic surgeons were evaluated with 63 (16%) receiving NIH funding. These 63 surgeons received 136 grants totaling $228 million, resulting in 1772 publications, and generating more than 50,000 citations. Thoracic surgeons have obtained NIH funding at an increasing rate (1980-2019); however, they have a low percentage of R01 renewal (17.3%). NIH-funded thoracic surgeons were more likely to have a higher professorship level. Thoracic surgeons perform similarly to other physician-scientists in converting K-Awards into R01 funding.
Contrary to our hypothesis, thoracic surgeons have received more NIH funding over time. Thoracic surgeons are able to fill the roles of modern surgeon-scientists by obtaining NIH funding during an era of increasing clinical demands. The NIH should continue to support this mission.
The COVID-19 pandemic has resulted in more than 72 million cases and 1.6 million deaths. End-stage lung disease from COVID-19 is a new and growing entity that may benefit from lung transplant, ...however there is limited data on the patient selection, perioperative management and expected outcomes of transplantation for this indication.
A systematic review of the literature was performed with searches of MEDLINE and Web of Science databases as well the gray literature. All manuscripts, editorials, commentaries and gray literature reports of lung transplantation for COVID related respiratory failure were included. A case from the University of Virginia is described and included in the review.
A total of 27 studies were included; 11 manuscripts, 5 commentaries, and 11 gray literature reports. The total number of transplantations for COVID related lung disease was 21. The mean age was 55 ± 12 years, 16 (76%) were male, and the acuity was high with 85% on extracorporeal membrane oxygenation preoperatively. There was a 95% early survival rate, with one additional late death. There is growing histopathologic evidence for permanent structural damage with no replicating virus at the time of transplantation.
Bilateral lung transplantation is an effective treatment option with reasonable short-term outcomes for patients suffering from end-stage lung failure secondary to COVID-19. However, specific considerations in this new population require a multidisciplinary approach. As we move into the second wave of the COVID-19 global pandemic, lung transplantation will likely have a growing role in management of these complex patients.
Acute respiratory distress syndrome represents the devastating result of acute lung injury, with high mortality. Limited methods are available for rehabilitation of lungs affected by acute ...respiratory distress syndrome. Our laboratory has demonstrated rehabilitation of sepsis-injured lungs via normothermic ex vivo and in vivo perfusion with Steen solution (Steen). However, mechanisms responsible for the protective effects of Steen remain unclear. This study tests the hypothesis that Steen directly attenuates pulmonary endothelial barrier dysfunction and inflammation induced by lipopolysaccharide.
Primary pulmonary microvascular endothelial cells were exposed to lipopolysaccharide for 4 hours and then recovered for 8 hours in complete media (Media), Steen, or Steen followed by complete media (Steen/Media). Oxidative stress, chemokines, permeability, interendothelial junction proteins, and toll-like receptor 4-mediated pathways were assessed in pulmonary microvascular endothelial cells using standard methods.
Lipopolysaccharide treatment of pulmonary microvascular endothelial cells and recovery in Media significantly induced reactive oxygen species, lipid peroxidation, expression of chemokines (eg, chemokine C-X-C motif ligand 1 and C-C motif chemokine ligand 2) and cell adhesion molecules (P-selectin, E-selectin, and vascular cell adhesion molecule 1), permeability, neutrophil transmigration, p38 mitogen-activated protein kinase and nuclear factor kappa B signaling, and decreased expression of tight and adherens junction proteins (zonula occludens-1, zonula occludens-2, and vascular endothelial-cadherin). All of these inflammatory pathways were significantly attenuated after recovery of pulmonary microvascular endothelial cells in Steen or Steen/Media.
Steen solution preserves pulmonary endothelial barrier function after lipopolysaccharide exposure by promoting an anti-inflammatory environment via attenuation of oxidative stress, toll-like receptor 4-mediated signaling, and conservation of interendothelial junctions. These protective mechanisms offer insight into the advancement of methods for in vivo lung perfusion with Steen for the treatment of severe acute respiratory distress syndrome.
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Abstract Objective Critical organ shortages have resulted in ex vivo lung perfusion gaining clinical acceptance for lung evaluation and rehabilitation to expand the use of donation after circulatory ...death organs for lung transplantation. We hypothesized that an innovative use of airway pressure release ventilation during ex vivo lung perfusion improves lung function after transplantation. Methods Two groups (n = 4 animals/group) of porcine donation after circulatory death donor lungs were procured after hypoxic cardiac arrest and a 2-hour period of warm ischemia, followed by a 4-hour period of ex vivo lung perfusion rehabilitation with standard conventional volume-based ventilation or pressure-based airway pressure release ventilation. Left lungs were subsequently transplanted into recipient animals and reperfused for 4 hours. Blood gases for partial pressure of oxygen/inspired oxygen fraction ratios, airway pressures for calculation of compliance, and percent wet weight gain during ex vivo lung perfusion and reperfusion were measured. Results Airway pressure release ventilation during ex vivo lung perfusion significantly improved left lung oxygenation at 2 hours (561.5 ± 83.9 mm Hg vs 341.1 ± 136.1 mm Hg) and 4 hours (569.1 ± 18.3 mm Hg vs 463.5 ± 78.4 mm Hg). Likewise, compliance was significantly higher at 2 hours (26.0 ± 5.2 mL/cm H2 O vs 15.0 ± 4.6 mL/cm H2 O) and 4 hours (30.6 ± 1.3 mL/cm H2 O vs 17.7 ± 5.9 mL/cm H2 O) after transplantation. Finally, airway pressure release ventilation significantly reduced lung edema development on ex vivo lung perfusion on the basis of percentage of weight gain (36.9% ± 14.6% vs 73.9% ± 4.9%). There was no difference in additional edema accumulation 4 hours after reperfusion. Conclusions Pressure-directed airway pressure release ventilation strategy during ex vivo lung perfusion improves the rehabilitation of severely injured donation after circulatory death lungs. After transplant, these lungs demonstrate superior lung-specific oxygenation and dynamic compliance compared with lungs ventilated with standard conventional ventilation. This strategy, if implemented into clinical ex vivo lung perfusion protocols, could advance the field of donation after circulatory death lung rehabilitation to expand the lung donor pool.
Transient receptor potential vanilloid 4 (TRPV4) is a nonselective cation channel important in many physiological and pathophysiological processes, including pulmonary disease. Using a murine model, ...we previously demonstrated that TRPV4 mediates lung ischemia-reperfusion injury, the major cause of primary graft dysfunction after transplant. The current study tests the hypothesis that treatment with a TRPV4 inhibitor will attenuate lung ischemia-reperfusion injury in a clinically relevant porcine lung transplant model.
A porcine left-lung transplant model was used. Animals were randomized to 2 treatment groups (n = 5/group): vehicle or GSK2193874 (selective TRPV4 inhibitor). Donor lungs underwent 30 minutes of warm ischemia and 24 hours of cold preservation before left lung allotransplantation and 4 hours of reperfusion. Vehicle or GSK2193874 (1 mg/kg) was administered to the recipient as a systemic infusion after recipient lung explant. Lung function, injury, and inflammatory biomarkers were compared.
After transplant, left lung oxygenation was significantly improved in the TRPV4 inhibitor group after 3 and 4 hours of reperfusion. Lung histology scores and edema were significantly improved, and neutrophil infiltration was significantly reduced in the TRPV4 inhibitor group. TRPV4 inhibitor-treated recipients had significantly reduced expression of interleukin-8, high mobility group box 1, P-selectin, and tight junction proteins (occludin, claudin-5, and zonula occludens-1) in bronchoalveolar lavage fluid as well as reduced angiopoietin-2 in plasma, all indicative of preservation of endothelial barrier function.
Treatment of lung transplant recipients with TRPV4 inhibitor significantly improves lung function and attenuates ischemia-reperfusion injury. Thus, selective TRPV4 inhibition may be a promising therapeutic strategy to prevent primary graft dysfunction after transplant.
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To determine trends in National Institutes of Health (NIH) funding for cardiac surgeons, hypothesizing they are at a disadvantage in obtaining funding owing to intensive clinical demands.
Cardiac ...surgeons (adult/congenital) currently at the top 141 NIH-funded institutions were identified using institutional websites. The NIH funding history for each cardiac surgeon was queried using the NIH Research Portfolio Online Reporting Tools Expenditures and Results (RePORTER). Total grant funding, publications, and type was collected. Academic rank, secondary degrees, and fellowship information was collected from faculty pages. Grant productivity was calculated using a validated grant impact metric.
A total of 818 academic cardiac surgeons were identified, of whom 144 obtained 293 NIH grants totaling $458 million and resulting in 6694 publications. We identified strong associations between an institution's overall NIH funding rank and the number of cardiac surgeons, NIH grants to cardiac surgeons, and amount of NIH funding to cardiac surgeons (P < .0001 for all). The majority of NIH funding to cardiac surgeons is concentrated in the top quartile of institutions. Cardiac surgeons had a high conversion rates from K awards (mentored development awards) to R01s (6 of 14; 42.9%). Finally, we demonstrate that the rate of all NIH grants awarded to cardiac surgeons has increased, driven primarily by P and U (collaborative project) grants.
NIH-funded cardiac surgical research has had a significant impact over the last 3 decades. Aspiring cardiac surgeon-scientists may be more successful at top quartile institutions owing to better infrastructure and mentorship.
Despite resuscitation advances including extracorporeal cardiopulmonary resuscitation (ECPR), freedom from neurologic and myocardial insult after cardiac arrest remains unlikely. We hypothesized that ...adenosine 2A receptor (A2AR) agonism, which attenuates reperfusion injury, would improve outcomes in a porcine model of ECPR.
Adult swine underwent 20 min of circulatory arrest followed by defibrillation and 6 h of ECPR. Animals were randomized to receive saline vehicle or A2AR agonist (ATL1223 or Regadenoson) infusion during extracorporeal membrane oxygenation. Animals were weaned off extracorporeal membrane oxygenation and monitored for 24 h. Clinical and biochemical end points were compared.
The administration of A2AR agonists increased survival (P = 0.01) after cardiac arrest compared to vehicle. Markers of neurologic damage including S100 calcium binding protein B and glial fibrillary acidic protein were significantly lower with A2AR agonist treatment.
In a model of cardiac arrest treated with ECPR, A2AR agonism increased survival at 24 h and reduced neurologic damage suggesting A2AR activation may be a promising therapeutic target after cardiac arrest.
Background Sepsis is the number one cause of lung injury in adults. Ex vivo lung perfusion (EVLP) is gaining clinical acceptance for donor lung evaluation and rehabilitation and may expand the use of ...marginal organs for transplantation. We hypothesized that 4 hours of normothermic EVLP would improve compliance and oxygenation in a porcine model of sepsis-induced lung injury. Methods We used intravenous lipopolysaccharide (LPS) to induce a systemic inflammatory response in a porcine model of lung injury. Two groups of 4 animals each received a 2-hour infusion of LPS through the external jugular vein. Serial measurements of blood gases were performed every 30 minutes until the partial pressure of oxygen/fraction of inspired oxygen ratio dropped below 150 on two consecutive readings. Lungs were then randomized to treatment with 4 hours of normothermic EVLP with STEEN Solution (XVIVO Perfusion Inc, Englewood, CO) or 4 additional hours of in vivo perfusion (control). Airway pressures and blood gases were recorded for calculation of dynamic lung compliance and partial pressure of oxygen/fraction of inspired oxygen ratios. EVLP was performed with hourly recruitment maneuvers and oxygen challenge. Results All animals reached a partial pressure of oxygen/fraction of inspired oxygen ratio of less than 150 mm Hg within 3 hours after start of the LPS infusion. Oxygenation and compliance in the control animals continued to decline during the 4-hour in vivo perfusion period, and 3 of the 4 animals died of severe hypoxia within 4 hours. The EVLP group demonstrated significant improvements hour 1 to hour 4 in oxygenation (365.8 ± 53.0 vs 584.4 ± 21.0 mm Hg, p = 0.02) and dynamic compliance (9.0 ± 2.8 vs 15.0 ± 3.6, p = 0.02 mL/cm H2 O). Conclusions EVLP successfully rehabilitated LPS-induced lung injury in this preclinical porcine model and may thus provide a means to rehabilitate many types of acute lung injury.
Acute respiratory distress syndrome (ARDS) is associated with high morbidity and mortality, and current management has a dramatic impact on healthcare resource utilization. While our understanding of ...this disease has improved, the majority of treatment strategies remain supportive in nature and are associated with continued poor outcomes. There is a dramatic need for the development and breakthrough of new methods for the treatment of ARDS. Isolated machine lung perfusion is a promising surgical platform that has been associated with the rehabilitation of injured lungs and the induction of molecular and cellular changes in the lung, including upregulation of anti-inflammatory and regenerative pathways. Initially implemented in an ex vivo fashion to evaluate marginal donor lungs prior to transplantation, recent investigations of isolated lung perfusion have shifted in vivo and are focused on the management of ARDS. This review presents current tenants of ARDS management and isolated lung perfusion, with a focus on how ex vivo lung perfusion (EVLP) has paved the way for current investigations utilizing in vivo lung perfusion (IVLP) in the treatment of severe ARDS.
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