Pathogenesis Of Primary Graft Dysfunction Research Articles

Temporal correlation between postreperfusion complement deposition and severe primary graft dysfunction in lung allografts

Growing evidence implicates complement in the pathogenesis of primary graft dysfunction (PGD). We hypothesized that early complement activation postreperfusion could predispose to severe PGD grade 3 (PGD-3) at 72 hours, which is associated with worst posttransplant outcomes. Consecutive lung transplant patients (n = 253) from January 2018 through June 2023 underwent timed open allograft biopsies at the end of cold ischemia (internal control) and 30 minutes postreperfusion. PGD-3 at 72 hours occurred in 14% (35/253) of patients; 17% (44/253) revealed positive C4d staining on postreperfusion allograft biopsy, and no biopsy-related complications were encountered. Significantly more patients with PGD-3 at 72 hours had positive C4d staining at 30 minutes postreperfusion compared with those without (51% vs 12%, P < .001). Conversely, patients with positive C4d staining were significantly more likely to develop PGD-3 at 72 hours (41% vs 8%, P < .001) and experienced worse long-term outcomes. In multivariate logistic regression, positive C4d staining remained highly predictive of PGD-3 (odds ratio 7.92, 95% confidence interval 2.97-21.1, P < .001). Hence, early complement deposition in allografts is highly predictive of PGD-3 at 72 hours. Our data support future studies to evaluate the role of complement inhibition in patients with early postreperfusion complement activation to mitigate PGD and improve transplant outcomes.

Management of primary graft dysfunction after lung transplantation with extracorporeal life support: an evidence-based review.

Primary graft dysfunction (PGD) is a complex inflammatory syndrome that can lead to respiratory failure after lung transplantation (LTx). The pathogenesis of PGD is multifactorial and can be driven by attributes of both the donor and recipient, perioperative characteristics, and technical handling of the graft. Despite significant advancements in patient and donor selection, perioperative management and surgical technique, PGD is still a major contributor to morbidity and mortality after lung transplant. Although there are no known durable treatment options for PGD after LTx, an increasing body of evidence and experience in high-volume lung transplant centers show that extracorporeal life support (ECLS) is a reliable option for both preventing PGD and supporting critically ill patients with PGD. Both veno-venous (V-V) ECLS and veno-arterial (V-A) ECLS are proven and feasible strategies for mitigating the morbidity and mortality associated with post-LTx PGD. In this evidence-based review, we provide an overview of the epidemiology and physiology of PGD as well as a growing body of data that supports ECLS as a major tool to manage PGD. We describe the role of ECMO in PGD prevention and management, worldwide outcomes of LTx with ECLS support, and outline our step-wise approach to managing this complex respiratory syndrome leading up to institution of ECLS.

Spontaneous Donor Hypothermia is Independently Associated with Increased Risk of Primary Graft Dysfunction After Heart Transplant

<h3>Purpose</h3> Multiple donor and recipient characteristics contribute to the pathogenesis of primary graft dysfunction (PGD) after heart transplantation (HT). The purpose of this study was to determine the association between spontaneous donor hypothermia and PGD. <h3>Methods</h3> Consecutive adult HT recipients (n=1106) from 3/2012 to 12/2019 at two high-volume centers were included. Severe PGD was defined using the ISHLT consensus statement. Donor physiologic parameters were collected from the United Network for Organ Sharing Donor Management Goals registry. Univariable and multivariable logistic modeling were performed. <h3>Results</h3> Donors were predominantly male (66.6%), with a mean donor age of 34.9±13.0 years. Severe PGD occurred in 66 (6.0%) patients. Patients with severe PGD were more likely to receive organs from older donors (38.0±13.0 vs. 34.7±12.7 years, p=0.04) and lower donor to recipient heart mass ratio (1.00±0.15 vs. 1.05±0.20, p=0.048). Single variable modeling showed predicted heart mass ratio, donor age, and spontaneous donor hypothermia defined as less than 36 degrees Celsius at time of procurement to be significant predictors of severe PGD. Multivariable modeling showed that spontaneous donor hypothermia (OR 2.21, 95% CI: [1.21-4.03], p=0.01) was significantly associated with severe PGD after adjusting for donor age and predicted heart mass ratio. There was no increased incidence of severe PGD with spontaneous donor hypothermia either at time of referral (OR: 1.35, 95% CI: [0.78-2.35], p=0.28) or 12 to 18 hours later (OR: 1.16, 95% CI: [0.51-2.66], p=0.71). Spontaneous donor hyperthermia defined as greater than 37.5 degrees Celsius at time of procurement was not associated with severe PGD (OR: 1.69, 95% CI: [0.64-4.45], p=0.29). <h3>Conclusion</h3> Spontaneous donor hypothermia at time of organ procurement is associated with an increased risk of severe PGD.

Pro-inflammatory IgG1 N-glycan signature correlates with primary graft dysfunction onset in COPD patients

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide. The pathogenesis of COPD is complex; however, recent studies suggest autoimmune changes, characterized by the presence of autoantibodies to elastin and collagen, may contribute to disease status. COPD patients make up approximately 30% of all lung transplants (LTx) annually, however, little is known regarding the relationship between COPD-related autoantibodies and LTx outcomes. We hypothesized that COPD patients that undergo LTx and develop primary graft dysfunction (PGD) have altered circulating autoantibody levels and phenotypic changes as compared those COPD-LTx recipients that do not develop PGD. We measured total immunoglobulin and circulating elastin and collagen autoantibody levels in a cohort of COPD lung transplant recipients pre- and post-LTx. No significant differences were seen in total, elastin, or collagen IgM, IgG, IgG1, IgG2, IgG3, and IgG4 antibodies between PGD+ and PGD- recipients. Antibody function can be greatly altered by glycosylation changes to the antibody Fc region and recent studies have reported altered IgG glycosylation profiles in COPD patients. We therefore utilized a novel mass spectrometry-based multiplexed N-glycoprotein imaging approach and measured changes in IgG-specific antibody N-glycan structures. COPD-LTx recipients who developed PGD had significantly increased IgG1 N-glycan signatures as compared PGD- recipients. In conclusion, we show that immunoglobulin and autoreactive antibody levels are not significantly different in COPD LTx recipients that develop PGD. However, using a novel IgG glycomic analysis we were able to demonstrate multiple significant increases in IgG1 specific N-glycan signatures that were predictive of PGD development. Taken together, these data represent a potential novel method for identifying COPD patients at risk for PGD development and may provide clues to mechanisms by which antibody N-glycan signatures could contribute to antibody-mediated PGD pathogenesis.

Obesity-related IL-18 Impairs T-Regulatory Cell Function and Promotes Lung Ischemia-Reperfusion Injury.

Rationale: Primary graft dysfunction (PGD) is a severe form of acute lung injury, leading to increased early morbidity and mortality after lung transplant. Obesity is a major health problem, and recipient obesity is one of the most significant risk factors for developing PGD. Objectives: We hypothesized that T-regulatory cells (Tregs) are able to dampen early ischemia-reperfusion events and thereby decrease the risk of PGD, whereas that action is impaired in obese recipients. Methods: We evaluated Tregs, T cells, and inflammatory markers, plus clinical data, in 79 lung transplant recipients and 41 liver or kidney transplant recipients and studied two groups of mice on a high-fat diet (HFD), which did ("inflammatory" HFD) or did not ("healthy" HFD) develop low-grade inflammation with decreased Treg function. Measurements and Main Results: We identified increased levels of IL-18 as a previously unrecognized mechanism that impairs Tregs' suppressive function in obese individuals. IL-18 decreases levels of FOXP3, the key Treg transcription factor, decreases FOXP3 di- and oligomerization, and increases the ubiquitination and proteasomal degradation of FOXP3. IL-18-treated Tregs or Tregs from obese mice fail to control PGD, whereas IL-18 inhibition ameliorates lung inflammation. The IL-18-driven impairment in Tregs' suppressive function before transplant was associated with an increased risk and severity of PGD in clinical lung transplant recipients. Conclusions: Obesity-related IL-18 induces Treg dysfunction that may contribute to the pathogenesis of PGD. Evaluation of Tregs' suppressive function together with evaluation of IL-18 levels may serve as a screening tool to identify obese individuals with an increased risk of PGD before transplant.

Primary Graft Dysfunction.

Primary graft dysfunction (PGD) is a form of acute lung injury after transplantation characterized by hypoxemia and the development of alveolar infiltrates on chest radiograph that occurs within 72 hours of reperfusion. PGD is among the most common early complications following lung transplantation and significantly contributes to increased short-term morbidity and mortality. In addition, severe PGD has been associated with higher 90-day and 1-year mortality rates compared with absent or less severe PGD and is a significant risk factor for the subsequent development of chronic lung allograft dysfunction. The International Society for Heart and Lung Transplantation released updated consensus guidelines in 2017, defining grade 3 PGD, the most severe form, by the presence of alveolar infiltrates and a ratio of PaO2:FiO2 less than 200. Multiple donor-related, recipient-related, and perioperative risk factors for PGD have been identified, many of which are potentially modifiable. Consistently identified risk factors include donor tobacco and alcohol use; increased recipient body mass index; recipient history of pulmonary hypertension, sarcoidosis, or pulmonary fibrosis; single lung transplantation; and use of cardiopulmonary bypass, among others. Several cellular pathways have been implicated in the pathogenesis of PGD, thus presenting several possible therapeutic targets for preventing and treating PGD. Notably, use of ex vivo lung perfusion (EVLP) has become more widespread and offers a potential platform to safely investigate novel PGD treatments while expanding the lung donor pool. Even in the presence of significantly prolonged ischemic times, EVLP has not been associated with an increased risk for PGD.

Characterization of Extracellular Vesicles from Ex Vivo Perfused Human Lungs and Their Relationship with Allograft Injury

<h3>Purpose</h3> Primary graft dysfunction (PGD) is an important cause of morbidity and mortality following lung transplantation and results in part from injuries sustained in the donor. Extracellular vesicles (EVs), membrane-bound sacs released by cells, are increasingly being recognized as key modulators of inflammation. EVs have been implicated in the anti-donor response to the lung allograft and may play a role in the pathogenesis of PGD. Perfusate from ex-vivo lung perfusion (EVLP) allows interrogation of donor EVs which may serve as predictive biomarkers for lung injury. In this study, we aim to identify and characterize EVs derived from EVLP perfusates of marginal donor lungs. <h3>Methods</h3> Hourly perfusate samples of lungs undergoing EVLP were collected, precleared and ultracentrifuged at 100,000x<i>g</i> for 90mins to isolate small EVs. The presence of EVs was validated by Nanoparticle tracking analysis (NTA), Western blot (WB), and flow cytometry (FACS). Next, EV protein arrays were used to investigate differences in protein content between lungs accepted for transplant (n=20), and injured lungs declined for transplant (n=20). <h3>Results</h3> Our analyses show the presence of EV-sized particles (≤300nm) positive for canonical EV markers. CD9 and CD81 were identified by both WB(Fig1) and FACS, while CD63 was only detectable by FACS(Fig2). Using EV arrays, CD63 and CD31, an endothelial adhesion marker, were found to be elevated in EVs from damaged lungs declined for transplantation (p=0.0183; p=0.0167). There was no difference observed in levels of EV-associated CD9(Fig3). <h3>Conclusion</h3> Our findings show that EVLP perfusates contain donor EVs. CD63+ and CD31+ EVs may reflect damage in lungs declined for transplantation. Next, we aim to characterize and compare the RNA cargo of EVs acquired from the same cohort of donor samples, to determine whether differences can be observed at the transcript level. Together, these findings will provide an insight to the potential role of EVs as biomarkers for lung injury.

Characterization of Plasma-Derived Exosomes from Patient with Primary Graft Dysfunction after Lung Transplantation

Purpose Recipient responses to primary graft dysfunction (PGD) after lung transplantation (LTx) have important implications for the fate of the allograft. Exosomes, small circulating vesicles, are considered critical mediators of intercellular information and play a role in injury-induced tissue repair processes in multiple physiological systems. Identifying the potential molecular components that contribute to patient-specific responses may lead to new strategies for LTx. Therefore, we seek to elucidate differences in plasma-derived exosomes gene expression in subjects who develop PGD after LTx. Methods Plasma-derived exosomes RNA expression was measured before and 72h after LTx in 6 consented age, sex, commodities, and primary diagnosis matched subjects (PGD n=3; Non-PGD n=3). RNA seq was normalized with the TMM normalization algorithm, and differential expression was performed by edgeR. Differential expressed genes with a p-value 1.5 were considered significant. Gene set enrichment analysis (GSEA) was applied by g: Profiler and genome.jp. PGD was defined as PGD3 at 48-72 hours after reperfusion. Results Compared to the baseline, the PGD group at 72h presented 251 genes with increased relative expression and 27 with decreased relative expression. The same comparison showed 86/16 genes with increased/decreased relative expression respectively in the non-PGD group (Table 1). GSEA in the PGD group identified 327 gene ontology (GO) terms associated with the upregulated gene set, some of these GO associations, such as morphogenesis of epithelium, epithelium development, TNF signaling pathway, MAPK signaling pathway, cytokine-cytokine receptor interaction, Th1 and Th2 cell differentiation, leukocyte transendothelial migration were exclusively found in the PGD group. In the non-PGD group, 237 GO terms were significantly associated with the upregulated gene set, such as HIF-1, tight junction, GO was not observed in the PGD. Conclusion We demonstrated that the RNA content from plasma-derived exosomes and preliminary investigation using GSEA associated with the differentially expressed genes in PGD patients is different from non-PGD patients. Our findings suggest a potential role of exosome-carried RNA in the pathogenesis of PGD. Future investigations are needed to confirm the findings.

Plasma Levels of Histidine-Rich Glycoprotein are Associated with the Development of Primary Graft Dysfunction after Lung Transplantation

<h3>Purpose</h3> Histidine-rich glycoprotein (HRG) is a 75 kDa plasma glycoprotein produced in and secreted from the liver. Recently, supplementary HRG treatment has been shown to inhibit acute respiratory distress syndrome (ARDS) and prevent septic lethality. The pathogenesis of primary graft dysfunction (PGD) after lung transplantation (LT) could be similar to that of ARDS. However, the relationship between plasma levels of HRG and PGD after LT remains unknown. <h3>Methods</h3> Blood samples were collected from a total of 68 patients who underwent LT, including the patients with PGD grade 0-1 (the non-PGD group, n = 43), those with PGD grade 2 (the moderate PGD group, n = 18) and those with PGD grade 3 (the severe PGD group, n = 7) at 72 hours after LT. Plasma levels of HRG were quantified using ELISA and compared among the three groups. Appropriate cut-off values of HRG levels were set for overall survival (OS) after LT. <h3>Results</h3> The median follow-up period was 1208 (286-2982) days. Plasma levels of HRG at 72 hours after LT in the severe PGD group were significantly lower than those of the other groups (the non-PGD group vs. the severe PGD group, P = 0.042; the moderate PGD group vs. the severe PGD group, P = 0.040) (Fig. 1). An ROC analysis of the performance of plasma levels of HRG as a marker of overall survival yielded an AUC of 0.61 at a threshold level of 34.4 µg/mL. Patients with plasma levels of HRG ≥ 34.4 µg/mL showed significantly better OS and chronic lung allograft dysfunction (CLAD) free survival than those with plasma levels of HRG < 34.4 µg/mL (OS, P = 0.037; CLAD-free survival, P = 0.046) (Fig. 2). <h3>Conclusion</h3> Plasma level of HRG at 72 hours after LT was associated with the development of PGD, suggesting its usefulness as a predictor of the development of CLAD and survival after LT.

Donor Neutrophils and B Cells in EVLP Perfusate are Associated with Severe Primary Graft Dysfunction

<h3>Purpose</h3> Primary graft dysfunction (PGD) remains a major obstacle to lung transplantation (LT) success and is classified as severe (PGD3) in 10-15% of all LT recipients. Ex vivo lung perfusion (EVLP) allows for evaluation of donor lungs prior to LT and measurement of circulating cells and soluble factors in the perfusate. The contributions of donor cells to PGD are unknown, and whether specific cells might confer a risk of PGD is unclear. We hypothesized that larger quantities of donor myeloid cells in EVLP perfusate might predict PGD3. <h3>Methods</h3> In this retrospective study, we selected consecutive clinical EVLP cases and grouped them based on Pa_O2/F_IO2 (P/F) ratio at 72h post-LT, resulting in two groups: PGD3 (n = 33, P/F = 183 ± 48mmHg) and PGD0/1 (n = 25, P/F = 395 ± 71mmHg). Cryopreserved perfusate cells from the first and last hour of EVLP were subjected to multiparameter flow cytometry to identify major leukocyte populations. Time and PGD-dependent differences were assessed by two-way ANOVA with post-hoc testing adjusted for multiple comparisons. <h3>Results</h3> In the first hour of EVLP, the total cells/mL was higher in the PGD3 group compared to PGD0/1 (12.1 × 10⁵ versus 8.4 × 10⁵ cells/ml, p = 0.0573) - the cell/ml decreased in both groups to similar densities by the end of EVLP (Fig A). In the PGD3 group, neutrophils (Fig B) and B cells (Fig C) were significantly higher than in the PGD0/1 group in the first hour and significantly decreased over time. Macrophages (Fig D) and classical monocytes (Fig E) were also elevated in PGD3 group in the first hour, although this observation did not reach statistical significance. <h3>Conclusion</h3> Neutrophils and B cells in the 1-hour perfusate are associated with PGD3 development at 72h post-LT. While these findings suggest that higher numbers of these donor cells may play a role in PGD pathogenesis, PGD3 developed even though these populations were reduced by the end of EVLP. Studies of cellular activation states will be conducted to validate these findings and explore donor cellular contributions to PGD.

Risk Factors for Primary Graft Dysfunction in Patients with Cystic Fibrosis Receiving Lung Transplants

Purpose The primary driver of poor outcomes in the early stages of lung transplantation is primary graft dysfunction (PGD). Patients with cystic fibrosis (CF) have unique physiology and demographics compared to other lung transplant recipients. Therefore, we sought to identify risk factors for PGD in the CF patient population undergoing lung transplantation. Methods We utilized clinical data on lung transplant recipients with CF and their donors from the Lung Transplant Outcomes Group cohort, a multi-center prospective cohort study of PGD pathogenesis. The primary outcome was grade 3 PGD within the first 72 hours after transplantation. Potential covariates were identified in univariate analysis and assessed for collinearity. Independent PGD risk factors were identified using multivariate logistic regression. A sensitivity analysis was performed using grade 3 PGD 48 to 72 hours after transplantation. Results We identified 195 patients with CF who received lung transplants between August 2014 and June 2018 across ten centers. Grade 3 PGD developed in 80 subjects (41%). Risk factors for PGD in CF patients based on the multivariable model were white donor race (odds ratio [OR]: 2.6, 95% confidence interval [CI]: 1.4-5.1), any positive panel reactive antibodies (PRA) (OR: 2.2, 95% CI: 1.0-4.7), recipient female gender (OR: 2.1, 95% CI: 1.1-3.9), intraoperative cardiopulmonary bypass use (OR: 2.2, 95% CI: 1.2-4.2), increasing lung allocation score (LAS) (OR: 1.2 per 10 point increase in LAS, 95% CI: 1.0-1.4), and ECMO (extracorporeal membrane oxygenation) bridge to transplant (OR: 2.7, 95% CI: 1.1-6.7). LAS and ECMO were assessed in separate models due to their collinearity. Mean pulmonary artery pressure at the time of transplant was included as a potential confounder. Similar findings were seen in a more severe phenotype of PGD that developed 48 to 72 hours after transplant. Conclusion The CF population is often considered to be at low risk of PGD, however we observed a relatively high rate of PGD in this study. Any positive PRA, female recipient gender, intraoperative bypass, increasing LAS, and ECMO are PGD risk factors that have been identified non-CF transplant populations. We validated these risk factors in recipients with CF. White donor race is a novel risk factor that has not been previously identified in lung transplant recipients with another primary diagnosis.

MiRNA's Profiling and Primary Graft Dysfunction: Novel Non-invasive Biomarkes

Lung transplantation is a clinical reality but survival rates are still improving. in this scenario, primary graft dysfunction (PGD) is the major cause of mortality in the first 30 days after lung transplantation and its pathogenesis remains poorly understood. MicroRNAs are ubiquitous regulators of human biology and emerging evidence indicates microRNA expression modulates disease processes. We aimed to identify microRNAs biomarker of PGD and their contribution in the PGD pathogenesis.

Significant role for microRNA-21 affecting toll-like receptor pathway in primary graft dysfunction after human lung transplantation

MicroRNAs (miRNAs) were recently identified as modulators of immune responses after human lung transplantation (LTx). This study was undertaken to assess the contribution of miRNAs to the pathogenesis of primary graft dysfunction (PGD) after LTx. Of the 39 recipients, 14 (35.9%) developed Grade 3 PGD (i.e., severe PGD) within the first 72 hours of LTx. The remaining 25 recipients (64.1%) had Grade 2 or less PGD, and served as the control group. miRNAs were isolated from cells purified by bronchoalveolar lavage (BAL). Bioinformatic prediction and validation by luciferase reporter assays were performed to identify targets regulated by miR-21. Transfection of human monocytic cell line (THP-1) was conducted to determine miR-21's cellular function. Pilot miRNA profiling of donor BAL samples before implantation in PGD (n = 6) revealed significant upregulation in 44 miRNAs and downregulation in 80 miRNAs compared with control (n = 6). Validation using a separate cohort demonstrated significant underexpression of miR-21 in patients with severe PGD. Furthermore, underexpression of miR-21 levels was negatively correlated with clinical PGD grades (Grade 2 PGD vs Grade 0 PGD: p = 0.042; Grade 3 PGD vs Grade 0 PGD: p = 0.004). Molecular analysis demonstrated that miR-21 targeted key components in the toll-like receptor (TLR) signaling pathway, including TLR4, IRAK3 and CXCL10. Further, incubation of THP-1 cells with cell-free BAL from severe PGD resulted in transactivation of inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). In contrast, increased expression of miR-21 resulted in marked suppression of IL-1-β and TNF-α production. Underexpression of miR-21 may lead to the development of severe PGD by activating key components of the TLR pathway.

Diastolic Dysfunction Increases the Risk of Primary Graft Dysfunction after Lung Transplant.

Primary graft dysfunction (PGD) is a significant cause of early morbidity and mortality after lung transplant and is characterized by severe hypoxemia and infiltrates in the allograft. The pathogenesis of PGD involves ischemia-reperfusion injury. However, subclinical increases in pulmonary venous pressure due to left ventricular diastolic dysfunction may contribute by exacerbating capillary leak. To determine whether a higher ratio of early mitral inflow velocity (E) to early diastolic mitral annular velocity (é), indicative of worse left ventricular diastolic function, is associated with a higher risk of PGD. We performed a retrospective cohort study of patients in the Lung Transplant Outcomes Group who underwent bilateral lung transplant at our institution between 2004 and 2014 for interstitial lung disease, chronic obstructive pulmonary disease, or pulmonary arterial hypertension. Transthoracic echocardiograms obtained during evaluation for transplant listing were analyzed for E/é and other measures of diastolic function. PGD was defined as PaO2/FiO2 less than or equal to 200 with allograft infiltrates at 48 or 72 hours after reperfusion. The association between E/é and PGD was assessed with multivariable logistic regression. After adjustment for recipient age, body mass index, mean pulmonary arterial pressure, and pretransplant diagnosis, higher E/é and E/é greater than 8 were associated with an increased risk of PGD (E/é odds ratio, 1.93; 95% confidence interval, 1.02-3.64; P = 0.04; E/é >8 odds ratio, 5.29; 95% confidence interval, 1.40-20.01; P = 0.01). Differences in left ventricular diastolic function may contribute to the development of PGD. Future trials are needed to determine whether optimization of left ventricular diastolic function reduces the risk of PGD.

Biomarkers of cellular apoptosis and necrosis in donor myocardium are not predictive of primary graft dysfunction.

Primary graft dysfunction (PGD) is a life-threatening complication among heart transplant recipients and a major cause of early mortality. Although the pathogenesis of PGD is still unclear, ischemia/reperfusion injury has been identified as a predominant factor. Both necrosis and apoptosis contribute to the loss of cardiomyocytes during ischemia/reperfusion injury, and this loss of cells can ultimately lead to PGD. The aim of our prospective study was to find out whether cell death, necrosis and apoptosis markers present in the donor myocardium can predict PGD. The prospective study involved 64 consecutive patients who underwent orthotopic heart transplantation at our institute between September 2010 and January 2013. High-sensitive cardiac troponin T (hs-cTnT) as a marker of minor myocardial necrosis was detected from arterial blood samples before the donor's pericardium was opened. Apoptosis (caspase-3, active + pro-caspase-3, bcl-2, TUNEL) was assessed from bioptic samples taken from the right ventricle prior graft harvesting. In our study, 14 % of transplant recipients developed PGD classified according to the standardized definition proposed by the ISHLT Working Group. We did not find differences between the groups in regard to hs-cTnT serum levels. The mean hs-cTnT value for the PGD group was 57.4+/-22.9 ng/l, compared to 68.4+/-10.8 ng/l in the group without PGD. The presence and severity of apoptosis in grafted hearts did not differ between grafts without PGD and hearts that subsequently developed PGD. In conclusion, our findings did not demonstrate any association between measured myocardial cell death, necrosis or apoptosis markers in donor myocardium and PGD in allograft recipients. More detailed investigations of cell death signaling pathways in transplanted hearts are required.

Protein Quantitative Trait Loci Analysis Identifies Genetic Variation in the Innate Immune Regulator TOLLIP in Post-Lung Transplant Primary Graft Dysfunction Risk.

The authors previously identified plasma plasminogen activator inhibitor-1 (PAI-1) level as a quantitative lung injury biomarker in primary graft dysfunction (PGD). They hypothesized that plasma levels of PAI-1 used as a quantitative trait could facilitate discovery of genetic loci important in PGD pathogenesis. A two-stage cohort study was performed. In stage 1, they tested associations of loci with PAI-1 plasma level using linear modeling. Genotyping was performed using the Illumina CVD Bead Chip v2. Loci meeting a p < 5 × 10(-4) cutoff were carried forward and tested in stage 2 for association with PGD. Two hundred ninety-seven enrollees were evaluated in stage 1. Six loci, associated with PAI-1, were carried forward to stage 2 and evaluated in 728 patients. rs3168046 (Toll interacting protein [TOLLIP]) was significantly associated with PGD (p = 0.006). The increased risk of PGD for carrying at least one copy of this variant was 11.7% (95% confidence interval 4.9-18.5%). The false-positive rate for individuals with this genotype who did not have PGD was 6.1%. Variants in the TOLLIP gene are associated with higher circulating PAI-1 plasma levels and validate for association with clinical PGD. A protein quantitative trait analysis for PGD risk prioritizes genetic variations in TOLLIP and supports a role for Toll-like receptors in PGD pathogenesis.

Primary graft dysfunction: lessons learned about the first 72 h after lung transplantation.

In 2005, the International Society for Heart and Lung Transplantation published a standardized definition of primary graft dysfunction (PGD), facilitating new knowledge on this form of acute lung injury that occurs within 72 h of lung transplantation. PGD continues to be associated with significant morbidity and mortality. This article will summarize the current literature on the epidemiology of PGD, pathogenesis, risk factors, and preventive and treatment strategies. Since 2011, several manuscripts have been published that provide insight into the clinical risk factors and pathogenesis of PGD. In addition, several transplant centers have explored preventive and treatment strategies for PGD, including the use of extracorporeal strategies. More recently, results from several trials assessing the role of extracorporeal lung perfusion may allow for much-needed expansion of the donor pool, without raising PGD rates. This article will highlight the current state of the science regarding PGD, focusing on recent advances, and set a framework for future preventive and treatment strategies.

(15) - Impact of Diastolic Dysfunction on Primary Graft Dysfunction (PGD) After Lung Transplantation

PGD is a significant cause of early morbidity and mortality after lung transplantation and is characterized by severe hypoxemia and infiltrates in the allograft. The pathogenesis of PGD is unclear, however subclinical increases in pulmonary venous pressure from left ventricular (LV) diastolic dysfunction may contribute by increasing capillary leak. We hypothesized that a higher ratio of early mitral inflow velocity (E) to early diastolic mitral annular velocity (é), indicative of worse diastolic function, would be associated with a higher risk of PGD.

Neutrophil extracellular traps are pathogenic in primary graft dysfunction after lung transplantation.

Primary graft dysfunction (PGD) causes early mortality after lung transplantation and may contribute to late graft failure. No effective treatments exist. The pathogenesis of PGD is unclear, although both neutrophils and activated platelets have been implicated. We hypothesized that neutrophil extracellular traps (NETs) contribute to lung injury in PGD in a platelet-dependent manner. To study NETs in experimental models of PGD and in lung transplant patients. Two experimental murine PGD models were studied: hilar clamp and orthotopic lung transplantation after prolonged cold ischemia (OLT-PCI). NETs were assessed by immunofluorescence microscopy and ELISA. Platelet activation was inhibited with aspirin, and NETs were disrupted with DNaseI. NETs were also measured in bronchoalveolar lavage fluid and plasma from lung transplant patients with and without PGD. NETs were increased after either hilar clamp or OLT-PCI compared with surgical control subjects. Activation and intrapulmonary accumulation of platelets were increased in OLT-PCI, and platelet inhibition reduced NETs and lung injury, and improved oxygenation. Disruption of NETs by intrabronchial administration of DNaseI also reduced lung injury and improved oxygenation. In bronchoalveolar lavage fluid from human lung transplant recipients, NETs were more abundant in patients with PGD. NETs accumulate in the lung in both experimental and clinical PGD. In experimental PGD, NET formation is platelet-dependent, and disruption of NETs with DNaseI reduces lung injury. These data are the first description of a pathogenic role for NETs in solid organ transplantation and suggest that NETs are a promising therapeutic target in PGD.

Oxidant stress regulatory genetic variation in recipients and donors contributes to risk of primary graft dysfunction after lung transplantation

Oxidant stress pathway activation during ischemia reperfusion injury may contribute to the development of primary graft dysfunction (PGD) after lung transplantation. We hypothesized that oxidant stress gene variation in recipients and donors is associated with PGD. Donors and recipients from the Lung Transplant Outcomes Group (LTOG) cohort were genotyped using the Illumina IBC chip filtered for oxidant stress pathway genes. Single nucleotide polymorphisms (SNPs) grouped into SNP sets based on haplotype blocks within 49 oxidant stress genes selected from gene ontology pathways and literature review were tested for PGD association using a sequencing kernel association test. Analyses were adjusted for clinical confounding variables and population stratification. Three hundred ninety-two donors and 1038 recipients met genetic quality control standards. Thirty percent of patients developed grade 3 PGD within 72 hours. Donor NADPH oxidase 3 (NOX3) was associated with PGD (P = .01) with 5 individual significant loci (P values between .006 and .03). In recipients, variation in glutathione peroxidase (GPX1) and NRF-2 (NFE2L2) was significantly associated with PGD (P = .01 for both). The GPX1 association included 3 individual loci (P values between .006 and .049) and the NFE2L2 association included 2 loci (P = .03 and .05). Significant epistatic effects influencing PGD susceptibility were evident between 3 different donor blocks of NOX3 and recipient NFE2L2 (P = .026, P = .017, and P = .031). Our study has prioritized GPX1, NOX3, and NFE2L2 genes for future research in PGD pathogenesis, and highlights a donor-recipient interaction of NOX3 and NFE2L2 that increases the risk of PGD.