Donor pretreatment using the aerosolized prostacyclin analogue iloprost optimizes post-ischemic function of non-heart beating donor lungs

Review 2: Primary graft dysfunction after lung transplant-pathophysiology, clinical considerations and therapeutic targets

Primary graft dysfunction (PGD) is one of the most common complications in the early postoperative period and is the most common cause of death in the first postoperative month. The underlying pathophysiology is thought to be the ischaemia–reperfusion injury that occurs during the storage and reperfusion of the lung engraftment; this triggers a cascade of pathological changes, which result in pulmonary vascular dysfunction and loss of the normal alveolar architecture. There are a number of surgical and anaesthetic factors which may be related to the development of PGD. To date, although treatment options for PGD are limited, there are several promising experimental therapeutic targets. In this review, we will discuss the pathophysiology, clinical management and potential therapeutic targets of PGD.

Therapeutic iloprost for the treatment of acute respiratory distress syndrome (ARDS) (the ThIlo trial): a prospective, randomized, multicenter phase II study

Background

Acute respiratory distress syndrome (ARDS) is caused by rapid-onset (within hours) acute inflammatory processes in lung tissue, and it is a life-threatening condition with high mortality. The treatment of ARDS to date is focused on the prevention of further iatrogenic damage of the lung rather than the treatment of the initial inflammatory process. Several preclinical studies have revealed a beneficial effect of iloprost on the control of pulmonary inflammation, and in a small number of patients with ARDS, iloprost treatment resulted in improved oxygenation. Therefore, we plan to conduct a large multicenter trial to evaluate the effect of iloprost on ARDS.

Methods

The Therapeutic Iloprost during ARDS trial (ThIlo trial) is a multicenter, randomized, single blinded, clinical phase II trial assessing the efficacy of inhaled iloprost for the prevention of the development and progression of ARDS in critically ill patients. One hundred fifty critically ill patients suffering from acute ARDS will be treated either by nebulized iloprost or NaCl 0.9% for 5 days. Blood samples will be drawn at defined time points to elucidate the serum levels of iloprost and inflammatory markers during treatment. Mechanical ventilation will be standardized. In follow-up visits at days 28 and 90 as well as 6 months after enrollment, functional status according to the Barthel Index and a health care-related questionnaire, and frailty (Vulnerable Elders Survey) will be evaluated. The primary endpoint is the improvement of oxygenation, defined as the ratio of PaO₂/FiO₂. Secondary endpoints include 90-day all-cause mortality, Sequential Organ Failure Assessment scores during the study period up to day 90, the duration of mechanical ventilation, the length of intensive care unit (ICU) stay, ventilator-associated pneumonia, delirium, ICU-acquired weakness, and discharge localization. The study will be conducted in three university ARDS centers in Germany.

Discussion

The results of the ThIlo trial will highlight the anti-inflammatory effect of iloprost on early inflammatory processes during ARDS, resulting in the improvement of outcome parameters in patients with ARDS.

Trial registration

EUDRA-CT: 2016-003168-37. Registered on 12 April 2017. ClinicalTrials.gov: NCT03111212. Registered on 4 June 2017.

Donor pretreatment with nebulized complement C3a receptor antagonist mitigates brain-death induced immunological injury post-lung transplant

Donor brain death (BD) is an inherent part of lung transplantation (LTx) and a key contributor to ischemia-reperfusion injury (IRI). Complement activation occurs as a consequence of BD in other solid organ Tx and exacerbates IRI, but the role of complement in LTx has not been investigated. Here, we investigate the utility of delivering nebulized C3a receptor antagonist (C3aRA) pretransplant to BD donor lungs in order to reduce post-LTx IRI. BD was induced in Balb/c donors, and lungs nebulized with C3aRA or vehicle 30 minutes prior to lung procurement. Lungs were then cold stored for 18 hours before transplantation into C57Bl/6 recipients. Donor lungs from living donors (LD) were removed and similarly stored. At 6 hours and 5 days post-LTx, recipients of BD donor lungs had exacerbated IRI and acute rejection (AR), respectively, compared to recipients receiving LD lungs, as determined by increased histopathological injury, immune cells, and cytokine levels. A single pretransplant nebulized dose of C3aRA to the donor significantly reduced IRI as compared to vehicle-treated BD donors, and returned IRI and AR grades to that seen following LD LTx. These data demonstrate a role for complement inhibition in the amelioration of IRI post-LTx in the context of donor BD.

Effects of intraoperative inhaled iloprost on primary graft dysfunction after lung transplantation: A retrospective single center study

DESIGN

Inhaled iloprost was known to alleviate ischemic-reperfusion lung injury. We investigated whether intraoperative inhaled iloprost can prevent the development of primary graft dysfunction after lung transplantation. Data for a consecutive series of patients who underwent lung transplantation with extracorporeal membrane oxygenation were retrieved. By propensity score matching, 2 comparable groups of 30 patients were obtained: patients who inhaled iloprost immediately after reperfusion of the grafted lung (ILO group); patients who did not receive iloprost (non-ILO group).

RESULTS

The severity of pulmonary infiltration on postoperative days (PODs) 1 to 3 was significantly lower in the ILO group compared to the non-ILO group. The PaO2/FiO2 ratio was significantly higher in the ILO group compared to the non-ILO group (318.2 ± 74.2 vs 275.9 ± 65.3 mm Hg, P = 0.022 on POD 1; 351.4 ± 58.2 vs 295.8 ± 53.7 mm Hg, P = 0.017 on POD 2; and 378.8 ± 51.9 vs 320.2 ± 66.2 mm Hg, P = 0.013 on POD 3, respectively). The prevalence of the primary graft dysfunction grade 3 was lower in the ILO group compared to the non-ILO group (P = 0.042 on POD 1; P = 0.026 on POD 2; P = 0.024 on POD 3, respectively). The duration of ventilator use and intensive care unit were significantly reduced in the ILO group (P = 0.041 and 0.038).

CONCLUSIONS

Intraoperative inhaled iloprost could prevent primary graft dysfunction and preserve allograft function, thus reducing the length of ventilator care and intensive care unit stay, and improving the overall early post-transplant morbidity in patients undergoing lung transplantation.

Mesenchymal stem cell pretreatment of non-heart-beating-donors in experimental lung transplantation

Background

Lung transplantation (LTx) is still limited by organ shortage. To expand the donor pool, lung retrieval from non-heart-beating donors (NHBD) was introduced into clinical practice recently. However, primary graft dysfunction with inactivation of endogenous surfactant due to ischemia/reperfusion-injury is a major cause of early mortality. Furthermore, donor-derived human mesenchymal stem cell (hMSC) expansion and fibrotic differentiation in the allograft results in bronchiolitis obliterans syndrome (BOS), a leading cause of post-LTx long-term mortality. Therefore, pretreatment of NHBD with recipient-specific bone-marrow-(BM)-derived hMSC might have the potential to both improve the postischemic allograft function and influence the long-term development of BOS by the numerous paracrine, immunomodulating and tissue-remodeling properties especially on type-II-pneumocytes of hMSC.

Methods

Asystolic pigs (n = 5/group) were ventilated for 3 h of warm ischemia (groups 2–4). 50x106 mesenchymal-stem-cells (MSC) were administered in the pulmonary artery (group 3) or nebulized endobronchially (group 4) before lung preservation. Following left-lung-transplantation, grafts were reperfused, pulmonary-vascular-resistance (PVR), oxygenation and dynamic-lung-compliance (DLC) were monitored and compared to control-lungs (group 2) and sham-controls (group 1). To prove and localize hMSC in the lung, cryosections were counter-stained. Intra-alveolar edema was determined stereologically. Statistics comprised ANOVA with repeated measurements.

Results

Oxygenation (p = 0.001) and PVR (p = 0.009) following endovascular application of hMSC were significantly inferior compared to Sham controls, whereas DLC was significantly higher in endobronchially pretreated lungs (p = 0.045) with overall sham-comparable outcome regarding oxygenation and PVR. Stereology revealed low intrapulmonary edema in all groups (p > 0.05). In cryosections of both unreperfused and reperfused grafts, hMSC were localized in vessels of alveolar septa (endovascular application) and alveolar lumen (endobronchial application), respectively.

Conclusions

Preischemic deposition of hMSC in donor lungs is feasible and effective, and endobronchial application is associated with significantly better DLC as compared to sham controls. In contrast, transvascular hMSC delivery results in inferior oxygenation and PVR. In the long term perspective, due to immunomodulatory, paracrine and tissue-remodeling effects on epithelial and endothelial restitution, an endobronchial NHBD allograft-pretreatment with autologous mesenchymal-stem-cells to attenuate limiting bronchiolitis-obliterans-syndrome in the long-term perspective might be promising in clinical lung transplantation. Subsequent work with chronic experiments is initiated to further elucidate this important field.

Electronic supplementary material

The online version of this article (doi:10.1186/s13019-014-0151-3) contains supplementary material, which is available to authorized users.

Effects of exogenous surfactant on the non-heart-beating donor lung graft in experimental lung transplantation - a stereological study

The use of non-heart-beating donor (NHBD) lungs may help to overcome the shortage of lung grafts in clinical lung transplantation, but warm ischaemia and ischaemia/reperfusion injury (I/R injury) resulting in primary graft dysfunction represent a considerable threat. Thus, better strategies for optimized preservation of lung grafts are urgently needed. Surfactant dysfunction has been shown to contribute to I/R injury, and surfactant replacement therapy is effective in enhancing lung function and structural integrity in related rat models. In the present study we hypothesize that surfactant replacement therapy reduces oedema formation in a pig model of NHBD lung transplantation. Oedema formation was quantified with (SF) and without (non-SF) surfactant replacement therapy in interstitial and alveolar compartments by means of design-based stereology in NHBD lungs 7 h after cardiac arrest, reperfusion and transplantation. A sham-operated group served as control. In both NHBD groups, nearly all animals died within the first hours after transplantation due to right heart failure. Both SF and non-SF developed an interstitial oedema of similar degree, as shown by an increase in septal wall volume and arithmetic mean thickness as well as an increase in the volume of peribron-chovascular connective tissue. Regarding intra-alveolar oedema, no statistically significant difference could be found between SF and non-SF. In conclusion, surfactant replacement therapy cannot prevent poor outcome after prolonged warm ischaemia of 7 h in this model. While the beneficial effects of surfactant replacement therapy have been observed in several experimental and clinical studies related to heart-beating donor lungs and cold ischaemia, it is unlikely that surfactant replacement therapy will overcome the shortage of organs in the context of prolonged warm ischaemia, for example, 7 h. Moreover, our data demonstrate that right heart function and dysfunctions of the pulmonary vascular bed are limiting factors that need to be addressed in NHBD.

Iloprost reduces myocardial edema in a rat model of myocardial ischemia reperfusion

OBJECTIVE

Myocardial ischemia severely reduces myocyte longevity and function. Extensive interstitial edema and cell damage occur as a result of myocardial reperfusion injury. Current therapies are directed at prevention of ischemia-induced damage to cardiac tissue. Iloprost is a novel pharmaceutical agent for the treatment of ischemia.

METHODS

Twenty rats were segregated into four experimental groups. The procedure control group consisted of four rats undergoing a sham operation. The remaining 16 rats were divided into two equal groups. The first group (control group) received a continuous intravenous infusion of physiological serum immediately prior to the procedure. Iloprost was administered by a continuous intravenous infusion into the right jugular vein at an infusion rate of 100 ng/kg/min for 30 minutes prior to reperfusion in the experimental group (study group). Following the infusion treatments, ligation of the left coronary artery was conducted for 30 minutes to induce myocardial ischemia. The rats were euthanized 24 hours after reperfusion and cardiac tissue was harvested from all specimens for analysis.

RESULTS

Histological examination revealed three myocardial tissue specimens with grade II damage and five myocardial tissue specimens with grade III reperfusion injury in the control group. However, the study group consisted of two grade III myocardial tissue specimens, five grade II myocardial tissue specimens and one grade I myocardial tissue specimen. Moreover, a statistically significant reduction in myocardial edema was observed in the study group (p=0.022).

CONCLUSION

Our results support the hypothesis that iloprost enhances protection against cardiac ischemia reperfusion injury. This protective effect may be associated with vasodilation, antioxidant or anti-edema mechanisms.

Pulmonary vasodilators--treating the right ventricle

Pulmonary hypertension remains a significant complication of several systemic and cardiothoracic diseases. It is important to emphasize that the hemodynamic relevance relates to the effect of pulmonary hypertension on right ventricular function and right-left ventricular interaction. The goal of pulmonary vasodilation should focus on optimizing right ventricular function and improving systemic perfusion. The properties of an optimum vasodilator include selective pulmonary vasodilation (avoiding systemic vasodilation), rapid onset of action, short half-life, and ease of administration. Inhaled nitric oxide or nebulization of traditional systemically administered agents offers the greatest clinical promise. An additional merit of selective pulmonary vasodilation consists of augmenting oxygenation by improving ventilation perfusion matching.

Donor heart preservation with iloprost supplemented St. Thomas Hospital cardioplegic solution in isolated rat hearts

This study was designed to assess the influence of St. Thomas Hospital cardioplegic solution (St. Th.) on heart preservation in rat hearts subjected to 6h ischemia when supplemented with iloprost. In the control group (n=8), nothing was added to St. Th., whereas 10 or 1000 nmol L(-1) iloprost was added in the second (n=7) and third (n=8) groups, respectively. Mechanical contraction parameters, cardiac tissue damage and oxidative stress markers were evaluated. The 10 nmol/L iloprost group peak systolic pressure (71.0+/-30.9 versus 41.0+/-9.4 mm Hg) and -dp/dtmax (1103.8+/-94.3 versus 678.6+/-156.8 mm Hg s(-1)) were significantly higher than control group at 30 min of reperfusion (p<0.05). Iloprost supplemented groups had higher GSH and catalase levels of coronary perfusate at reperfusion, in comparison with initial values (p<0.05). AST, CK, CK-MB values increased at 0 min of reperfusion and cTnI values at 45 min of reperfusion (p<0.05) in all groups with no difference between groups. According to our results, iloprost supplementation had mild but significant improvement in postischemic values in mechanical and oxidative stress parameters, resulting in better heart preservation.

Preischemic iloprost application for improvement of graft preservation: which route is superior in experimental pig lung transplantation: inhaled or intravenous?

BACKGROUND

Optimal allograft protection is essential in lung transplantation to reduce postoperative organ dysfunction. Although intravenous prostanoids are routinely used to ameliorate reperfusion injury, the latest evidence suggests a similar efficacy of inhaled prostacyclin. Therefore, we compared donor lung-pretreatment using inhaled lioprost (Ventavis) with the commonly used intravenous technique.

METHODS

Five pig lungs were each preserved with Perfadex and stored for 27 hours without (group 1) or with (group-2, 100 prior aerosolized of iloprost were (group 3) or iloprost (IV). Following left lung transplantation, hemodynamics, Po(2)/F(i)o(2), compliance, and wet-to-dry ratio were monitored for 6 hours and compared to sham controls using ANOVA analysis with repeated measures.

RESULTS

The mortality was 100% in group 3. All other animals survived (P < .001). Dynamic compliance and PVR were superior in the endobronchially pretreated iloprost group as compared with untreated organs (P < .05), whereas oxygenation was comparable overall W/D-ratio revealed significantly lower lung water in group 2 (P = .027) compared with group 3.

CONCLUSION

Preischemic alveolar deposition of iloprost is superior to IV pretreatment as reflected by significantly improved allograft function. This strategy offers technique to optimize pulmonary preservation.

Inhaled iloprost in eight heart transplant recipients presenting with post-bypass acute right ventricular dysfunction

BACKGROUND

During heart transplantation, weaning from cardiopulmonary bypass may be particularly laborious as a result of superimposed acute right ventricular dysfunction in the setting of pre-existing pulmonary hypertension. Research in recent years has focused on inhaled vasodilatory treatment modalities which selectively target the pulmonary circulation.

METHODS

We present a series of eight patients in whom inhaled iloprost, a synthetic prostacyclin analog, was used to treat pulmonary hypertension and right ventricular dysfunction detected by transesophageal echocardiography during a heart transplant procedure. In addition to conventional inotropic support, 20 mug of inhaled iloprost was administered via nebulized aerosol for a 20-min period. Complete sets of hemodynamic measurements were obtained before inhalation and during and after cessation of the inhalation period.

RESULTS

Inhaled iloprost decreased the transpulmonary gradient at the end of the inhalation period relative to baseline (8.2 +/- 1.6 mmHg vs. 11.2 +/- 0.9 mmHg, P < 0.05). The mean pulmonary artery pressure to systemic artery pressure ratio decreased over this period (0.24 +/- 0.07 vs. 0.44 +/- 0.09, P < 0.05). A statistically significant decrease in the pulmonary vascular resistance to systemic vascular resistance ratio was also observed (0.10 +/- 0.02 vs. 0.19 +/- 0.02, P < 0.05). Improved indices of right ventricular function were observed in echocardiographic monitoring.

CONCLUSION

During heart transplantation procedures, episodes of pulmonary hypertension can be successfully treated with inhaled iloprost administration, without untoward side-effects or significant systemic impact.

Endobronchial donor pre-treatment with ventavis: is a second administration during reperfusion beneficial to optimize post-ischemic function of non-heart beating donor lungs?

BACKGROUND

Lung retrieval from non-heart-beating donors (NHBD) has been introduced into clinical practice successfully. However, because of potentially deleterious effects of warm ischemia on microvascular integrity, use of NHBD lungs is limited by short tolerable time periods before preservation. Recently, improvement of NHBD graft function was demonstrated by donor pre-treatment using aerosolized Ventavis (Schering Inc., Berlin, Germany). Currently, there is no information whether additional application of this approach in reperfusion can further optimize immediate graft function.

MATERIAL AND METHODS

Asystolic pigs (n = 5/group) were ventilated for 180-min of warm ischemia (groups 1-3). In groups 2 and 3, 100 microg Ventavis were aerosolized over 30-min using an ultrasonic nebulizer (Optineb). Lungs were then retrogradely preserved with Perfadex and stored for 3-h. After left lung transplantation and contralateral lung exclusion, grafts were reperfused for 6-h. Only in group 3, another dose of 100 microg Ventavis was aerosolized during the first 30-min of reperfusion. Hemodynamics, pO2/FiO2 and dynamic compliance were monitored continuously and compared to controls. Intraalveolar edema was quantified stereologically, and extravascular-lung-water-index (EVLWI) was measured. Statistics comprised ANOVA analysis with repeated measurements.

RESULTS

Dynamic compliance was significantly lower in both Ventavis groups, but additional administration did not result in further improvement. Oxygenation, pulmonary hemodynamics, EVLWI and intraalveolar edema formation were comparable between groups.

CONCLUSIONS

Alveolar deposition of Ventavis in NHBD lungs before preservation significantly improves dynamic lung compliance and represents an important strategy for improvement of preservation quality and expansion of warm ischemic intervals. However, additional application of this method in early reperfusion is of no benefit.

High-flow endobronchial cooled humidified air protects non-heart-beating donor rat lungs against warm ischemia

OBJECTIVE

Lungs from non-heart-beating donors for transplantation require protection against warm ischemic damage. Minimally invasive techniques are required to reduce organ damage during the warm ischemic period because invasive surgical procedures are often not feasible at this time. This study investigated the preservative effect of high-flow endobronchial cooled humidified air during warm ischemia in non-heart-beating donor rat lungs.

METHODS

Fourteen animals were divided into a Cooling group (n = 7), which received cooled air/saline spray during a 2-hour warm ischemic period, and a Control group (n = 7), which received no cooling. After ischemia the lungs were reperfused on an isolated lung perfusion apparatus.

RESULTS

Endobronchial temperatures in the Cooling and Control groups were 8 degrees C and 36 degrees C at 10 minutes, and 5 degrees C and 35 degrees C at 20 minutes, respectively (P < .0001). Lung core and surface temperatures in the Cooling group were also lower than those in the corresponding Control group (P < .0001). After reperfusion, pulmonary arterial pressure (P = .003) and peak airway pressure (P = .002) were lower in the Cooling group than in the Control group. Higher pulmonary venous PO2 (P = .02), higher adenosine triphosphate levels (P = .01), and lower wet/dry lung weight ratio (P = .003) were seen in the Cooling group compared with the Control group.

CONCLUSIONS

High-flow endobronchial cooled humidified air can decrease lung temperature and improve post-ischemic pulmonary function and adenosine triphosphate levels in non-heart-beating donor lungs.

Impact of Warm Ischemia on Different Leukocytes in Bronchoalveolar Lavage From Mouse Lung: Possible New Targets to Condition the Pulmonary Graft From the Non–Heart-Beating Donor

BACKGROUND

The use of non-heart-beating donors (NHBDs) for lung transplantation is a possible alternative for increasing the number of organs available. The warm ischemic period after circulatory arrest may contribute to a higher degree of primary graft dysfunction, resulting from ischemia-reperfusion injury (IRI). A better understanding of the role of inflammatory cells during the warm ischemic interval may be useful for developing new therapeutic strategies against IRI.

METHODS

Mice were divided in 7 groups (n = 6/group). In 3 groups, ischemia was induced by clamping the hilum of the left lung for 30, 60 or 90 minutes (Groups [30I], [60I] or [90I], respectively). In 3 more groups, the lung was reperfused for 4 hours after identical ischemic intervals (Groups [30I+R], [60I+R] or [90I+R], respectively). Surgical impact was evaluated in a sham group ([sham]). Total and differential cell counts and interleukin-1beta (IL-1beta) protein levels in bronchoalveolar lavage (BAL) were determined and their correlations were investigated.

RESULTS

Total cell, macrophage and lymphocyte numbers and IL-1beta protein levels increased progressively with longer ischemic intervals. A significant rise in BAL macrophages and lymphocytes was observed between [60I] and [90I] (p < 0.01 and p < 0.001, respectively). BAL neutrophils only increased after reperfusion with longer ischemic intervals. A positive correlation was found in the ischemic groups between IL-1beta levels and the number of macrophages (r = 0.62; p = 0.0012) and the number of lymphocytes (r = 0.68; p = 0.0002). A positive correlation was found in the reperfusion groups between IL-1beta levels and the number of neutrophils (r = 0.48; p = 0.044).

CONCLUSIONS

This study demonstrates for the first time that BAL macrophages and lymphocytes increase significantly during warm ischemia and correlate with IL-1beta levels.

S-nitroso human serum albumin attenuates ischemia/reperfusion injury after cardioplegic arrest in isolated rabbit hearts

BACKGROUND

Depletion of nitric oxide (NO) is associated with ischemia/reperfusion injury. The novel NO donor, S-nitroso human serum albumin (S-NO-HSA), could bridge NO depletion during reperfusion in cardiac transplantation and minimize ischemia/reperfusion injury.

METHODS

In an isolated erythrocyte-perfused working heart model, rabbit hearts were randomly assigned after assessment of hemodynamic baseline values to receive S-NO-HSA (0.2 micromol/100 ml, n = 8), L-arginine (10 mmol/100 ml, n = 8) or albumin (control) (0.2 micromol/100 ml, n = 8). After 20 minutes of infusion, the hearts were arrested and stored in Celsior (4 degrees C) enriched with respective drugs for 6 hours, followed by 75 minutes of reperfusion. Hemodynamic values were assessed and biopsy specimens were taken to determine calcium-ionophore stimulated release of NO and superoxide.

RESULTS

During early reperfusion, recovery of cardiac output (75% +/- 6% vs 49% +/- 5%, p < 0.05) and coronary flow (99% +/- 8% vs 70% +/- 5%, p < 0.05) were higher, and myocardial oxygen consumption was reduced in the S-NO-HSA Group compared with Control (4.08 +/- 0.46 ml/min/0.1 kg vs 6.78 +/- 0.38 ml/min/0.1 kg, p < 0.01). At the end of the experiment cardiac output (53% +/- 5% vs 27% +/- 5%, p < 0.01) was higher and left atrial pressure (115% +/- 9% vs 150% +/- 8%, p < 0.05) was lower in the S-NO-HSA Group compared with Control. NO release was increased (1,040 +/- 50 nmol/liter and 1,070 +/- 60 nmol/liter vs 860 +/- 10 nmol/liter, p < 0.01) and superoxide release diminished (31 +/- 5 nmol/liter and 38 +/- 5 nmol/liter vs 64 +/- 5 nmol/liter, p < .01) in the S-NO-HSA and L-arginine Groups compared with Control.

CONCLUSION

S-NO-HSA improved hemodynamic functions after prolonged hypothermic cardiac arrest by supplementing NO and thereby decreasing ischemia/reperfusion injury.