Improvement of rat lung structure and function after preservation with celsior

Experimental Lung Transplantation: Impact of Preservation Solution and Route of Delivery

BACKGROUND

Optimal preservation of allograft integrity is essential to reduce post-ischemic organ dysfunction after lung transplantation. Retrograde organ preservation leads to homogeneous intrapulmonary distribution and eliminates intravascular thrombi. So far, no comparative studies exist with regard to preservation quality following retrograde preservation with Perfadex and Celsior after extended cold-ischemia intervals.

METHODS

In an in vivo pig model, 5 lungs each were preserved for 27 hours using antegrade or retrograde perfusion techniques with Celsior (Ce(ant)/CE(ret)) and Perfadex (PER(ant)/PER(ret)). After left lung transplantation and contralateral lung exclusion, hemodynamics, oxygenation and dynamic compliance were monitored for 6 hours and compared with sham-operated controls. Pulmonary edema was determined stereologically. Statistics consisted of analysis of variance (ANOVA) with repeated measures.

RESULTS

Mortality of all Celsior-protected lungs was 100% due to severe reperfusion injury with profound lung edema. In contrast, organ preservation with PER(ant) led to sufficient graft function without mortality. Preservation quality after retrograde administration of Perfadex resulted in optimized oxygenation capacity compared with PER(ant) (p = 0.046). Furthermore, intra-alveolar edema was reduced and generally comparable with sham controls. In general, retrograde preservation led to continuous washout of small blood and fibrin clots from the pulmonary capillary system.

CONCLUSIONS

Perfadex solution provided sufficient lung preservation for 27 hours of cold ischemia, and its retrograde application led to significant functional and histologic improvement compared with antegrade perfusion. In contrast, preservation with Celsior solution resulted in lethal post-ischemic outcome, regardless of the route of administration, and therefore must be considered unsuitable for extended lung procurement.

Impact of retrograde graft preservation in perfadex-based experimental lung transplantation

OBJECTIVE

Optimal preservation of postischemic organ function is a continuing challenge in clinical lung transplantation. Retrograde instillation of preservation solutions has theoretical advantages to achieve a homogeneous distribution in the lung due to perfusion of both the pulmonary and the bronchial circulation. Thus far, no systematic screening studies followed by in vivo large animal reevaluation including stereological analysis of intrapulmonary edema exist concerning the influence of retrograde preservation on postischemic lung function after preservation with low potassium dextran (LPD) solution (Perfadex).

MATERIALS AND METHODS

For initial screening in an extracorporeal rat model eight lungs, each, were preserved for 4 h using antegrade or retrograde preservation with LPD solution (Perfadex; PER(ant)/PER(ret)). Respiratory and hemodynamic results after reperfusion were compared to low-potassium Euro-Collins (LPEC). For systematic reevaluation, five pig lungs, each, were preserved correspondingly for 27 h, and results were compared to sham-operated control lungs. In both models, edema formation was quantified stereologically. Statistics comprised different ANOVA models.

RESULTS

In both models, use of PER(ret) resulted in significantly higher oxygenation capacity, lower inspiratory pressures, and lower amounts of intraalveolar edema as compared to PER(ant). Results of PER(ret) were not different from sham controls in the in vivo model; furthermore, a continuous retrograde elimination of blood clots from pulmonary microcirculation was noticed.

CONCLUSIONS

Retrograde application of LPD solution (Perfadex) results in significant functional and histological improvement as compared to antegrade perfusion. This innovative technique can be applied very easily in clinical practice and might be an ideal adjunct to further optimize the results after lung transplantation with LPD-based graft protection.

Reduced vascular endothelial growth factor correlates with alveolar epithelial damage after experimental ischemia and reperfusion

BACKGROUND

After clinical lung transplantation, the amount of vascular endothelial growth factor (VEGF) was found to be decreased in the bronchoalveolar lavage from lungs with acute lung injury. Since Type II pneumocytes are a major site of VEGF synthesis, VEGF depression may be an indicator of pulmonary epithelial damage after ischemia and reperfusion.

METHODS

Using an established rat lung model, we investigated the relationship between VEGF protein expression, oxygenation capacity and structural integrity after extracorporeal ischemia and reperfusion (ischemia 6 hours at 10 degrees C, reperfusion 50 minutes) and preservation with either low-potassium dextran solution (Perfadex 40 kD, n = 8) or Celsior (n = 6). Untreated, non-ischemic lungs served as controls (n = 5 per group). Perfusate oxygenation was recorded during reperfusion. An enzyme-linked immunoassay (ELISA) for VEGF protein and reverse transcription-polymerase chain reaction (RT-PCR) for mRNA splice variants were determined on tissue collected from the left lungs, whereas the right lungs were fixed by vascular perfusion for VEGF immunohistochemistry as well as structural analysis by light and electron microscopy. Tissue collection by systematic uniform random sampling was representative for the whole organ and allowed for quantification of structures by stereological means.

RESULTS

After ischemia and reperfusion, the 3 major VEGF isoforms, VEGF(120), VEGF(164) and VEGF(188), were present. VEGF protein expression was reduced, which correlated significantly with perfusate oxygenation (r = 0.736; p = 0.002) at the end of reperfusion. It was inversely related to Type II cell volume (r = 0.600; p = 0.047). VEGF protein was localized by immunohistochemistry in Type II pneumocytes, alveolar macrophages as well as bronchial epithelium, and staining intensity of Type II cells was reduced after ischemia and reperfusion. Alveolar edema did not occur but significant interstitial edema accumulated around vessels and in the blood-gas barrier, which showed a higher degree of epithelial damage after preservation with Celsior compared with the other groups.

CONCLUSIONS

Depression in VEGF protein expression can be considered an indicator for increased alveolar epithelial damage. Preservation with low-potassium dextran solution resulted in improved oxygenation and tissue integrity compared with Celsior.

Nitroglycerin alters alveolar type II cell ultrastructure after ischemia and reperfusion

BACKGROUND

Although administration of nitric oxide (NO) has been suggested to reduce pulmonary reimplantation response, concerns remain about cytotoxic side effects.

METHODS

Using light and electron microscopy, we examined the effects of the NO donor nitroglycerin (NTG) (0.1 mg/ml) as a supplement to the preservation solution Celsior on the structural integrity of rat lungs after extracorporeal ischemia (4 hours at 10 degrees C) and reperfusion (50 minutes) (IR). We performed evaluation in comparison with Celsior alone after IR using either standard antegrade perfusion through the pulmonary artery or retrograde perfusion through the left atrium as an alternative way to improve the preservation quality. Untreated, non-ischemic lungs served as controls (n = 5 per group). We recorded respiratory and hemodynamic parameters during reperfusion. Tissue collection using systematic uniform random sampling was representative for the whole organ and allowed stereologic quantification of structures.

RESULTS

After IR, histochemistry revealed no breaks in the alveolo-capillary barrier and we detected no alveolar flooding. Edema formed in the peribronchovascular cuffs, of which the volume fraction was increased (p =.008). Vasoconstriction of the smaller arteries accompanied antegrade flush, which occurred neither after administration of NTG nor after retrograde flush, as shown by immunostaining for alpha-smooth muscle actin. Treatment with NTG was associated with focal disintegration of Type II cells, which displayed edematous swelling of distinct cell compartments and lysis of mitochondria and cells. Nitroglycerin prevented alveolar collapse, which was increased in the other IR groups (p = 0.013). We observed alterations in intra-alveolar surfactant components.

CONCLUSION

These findings indicate pathologic effects of NTG treatment on alveolar epithelial integrity. Therefore, we suggest further critical evaluation of NTG/NO for therapeutic use in lung transplantation.

Comparative evaluation of Celsior solution versus Viaspan in a pig liver transplantation model

BACKGROUND

In a pig liver transplantation model, we compared the effects of Celsior solution (CS), an extracellular preservation solution, with Viaspan (University of Wisconsin solution, UW) on graft function and animal survival.

METHODS

Pig livers were flushed with either CS or UW solution and cold-stored for 12 hr (group 1) or for 8 to 10 hr (group 2). Grafts were transplanted orthotopically. Intrahepatic reduced and oxidized glutathione and adenine nucleotides were evaluated 1 hr after reperfusion. Liver function of transplanted animals was monitored for up to 6 days by serum transaminases, total bilirubin, purine nucleoside phosphorylase, and prothrombin levels.

RESULTS

In group 1, all animals died within 24 hr after reperfusion regardless of the preservation solution used. In group 2, no significant difference was seen in survival between the CS (72%) and the UW (67%) groups 6 days after transplantation, and there were no statistically significant differences in the biochemical data. There were no differences in histological evaluation of the livers at the time of death or killing of the animals between the CS and UW groups.

CONCLUSION

Within the limits of this pilot study, CS is equivalent to UW in terms of graft function and animal survival.

Retrograde flush perfusion with low-potassium solutions for improvement of experimental pulmonary preservation

BACKGROUND

Optimal preservation of post-ischemic organ function is a continuing challenge in clinical lung transplantation. Retrograde instillation of preservation solutions has the theoretic advantage of achieving homogeneous distribution in the lung because of perfusing both the pulmonary and the bronchial circulation. So far, we have seen no experimental studies that include stereologic analysis of intrapulmonary edema concerning the influence of retrograde preservation on post-ischemic lung function after preservation with Perfadex and Celsior.

METHODS

In an extracorporeal rat model, we perfused 8 lungs, each, using either antegrade or retrograde perfusion technique with Celsior (CE(ant)/CE(ret)) and Perfadex (PER(ant)/PER(ret)). Results were compared with low-potassium Euro-Collins. Post-ischemic lungs were reventilated and reperfused mechanically. We continuously monitored relative oxygenation capacity (ROC), pulmonary artery pressure, flush time, and wet/dry ratio. Furthermore, we used stereologic means to evaluate edema formation. Statistics comprised different analysis of variance models.

RESULTS

Relative oxygen capacity of CE(ant)-protected lungs was superior to that of PER(ant) preservation (p = 0.05). Use of PER(ret) resulted in significantly higher ROC as compared with PER(ant) (p < 0.001) and was comparable to results obtained with CE-preservation, which was not further improved with retrograde application.

CONCLUSIONS

Celsior provides better lung preservation than does Perfadex when administered antegradely. Retrograde application of Perfadex results in significant functional improvement as compared with antegrade perfusion, which reaches the standard of Celsior-protected organs. Additional in vivo experiments in combination with ultrastructural analysis are warranted to further evaluate retrograde delivery of preservation solutions, which could be used in clinical lung transplantation to further optimize current results.

Beneficial effect of lung preservation is related to ultrastructural integrity of tubular myelin after experimental ischemia and reperfusion

Ischemia/reperfusion (I/R) injury results in the impairment of surfactant activity. The hypothesis that the differences in lung preservation quality obtained by EuroCollins (EC) and Celsior (CE) solutions were related to surfactant alterations was tested. To avoid extensive structural damage and edema formation, which can secondarily affect the surfactant system, lungs were stored for a short ischemic period (2 h at 10 degrees C) and reperfused (50 min) in an isolated perfused rat lung model after preservation with either potassium-reduced (40 mmol) EC40 or with CE. Using a modified stereological approach ultrastructure, total amount and distribution of phospholipid membranes composing tubular myelin (tm) and small (s) and large (l) unilameliar vesicles (ul) were investigated in the organ in lungs fixed by vascular perfusion either in situ (controls) or after I/R (n = 5 per group). The total amount of intraalveolar surfactant was increased after I/R. However, a significant amount (p = 0.008) of tm was displaced into the alveolar lumen and showed wider meshes of the tm lattices than did the controls (p = 0.023) where almost all tm was epithelial. In lungs preserved with EC40, epithelial tm was significantly reduced (p = 0.018), resulting in a higher ratio (p = 0.034) of surface-inactive small ul (0.05 to 0.3 microm) to surface-active epithelial tm. In the CE group approximately 50% of the total tm pool was epithelial. This was accompanied by higher parenchymal air space and improved functional parameters. Epithelial and endothelial cell-specific immunostaining did not reveal any gross damage of the blood-gas barrier. In summary, improved lung function during reperfusion was associated with beneficial effects of lung preservation on tm integrity after I/R. These observations suggest that preservation solutions ameliorate events leading to surfactant disturbance even before extensive lung injury is manifested.

Overview and future practice patterns in cardiac and pulmonary preservation

Heart and lung transplantation have become standard therapy for many patients with end-stage heart and lung disease. Successful transplantation requires preservation of allografts until they can be implanted and reperfused. In the decades since the transplantation of thoracic organs became a clinical reality, many advances have been made in preoperative donor management, procurement, and preservation techniques. This article summarizes the state of the art in heart and lung preservation and review some of the areas of current research that may lead to improvements in preservation techniques in the future.