Surfactant pretreatment decreases long-term damage after ischemia-reperfusion injury of the lung

Objective: Lung ischemia-reperfusion injury (LIRI) is a risk factor for primary acute graft failure following lung transplantation. LIRI hereby contributes to morbidity and mortality after lung transplantation. We have previously shown that surfactant pretreatment ameliorates LIRI up to 1 week after reperfusion. However, the impact of surfactant pretreatment on long-term outcome following LIRI is unknown. Therefore, the objective of this study was to investigate the effect of surfactant pretreatment on long-term outcome following LIRI. Methods: Male Sprague-Dawley rats (n = 63) were randomized to receive intratracheally administered porcine surfactant (400 mg/kg) or no pretreatment. One hour thereafter, animals underwent 120 min of warm ischemia by clamping the bronchus, pulmonary artery and vein of the left lung. A third group was sham-operated; a fourth group served as unoperated controls. Animals were killed on day 30 or 90 after surgery. Arterial oxygenation and lung compliance were determined. Broncho-alveolar lavage fluid (BALf) was collected to assess surfactant function and alveolar protein. Leukocyte infiltration was determined by flowcytometry in BALf, lung tissue and thoracic lymph nodes. Lungs of three animals per group were used for histological assessment. Results: Lung compliance was lower on day 30 and day 90 after LIRI than in sham-operated controls (day 30 Vmax6.1 ± 2.1 vs 12.6 ± 1.3, day 90 6.9 ± 3.0 vs 12.1 ± 1.6; Cmaxday 30 0.49 ± 0.17 vs 1.08 ± 0.21, day 90 0.67 ± 0.31 vs 1.11 ± 0.17). Furthermore, the number of CD45RA+-lymphocytes in left lung tissue was decreased on day 90 compared to unoperated animals (230.633 ± 96.770 vs 696.347 ± 202.909) and the number of macrophages elevated in left BALf on day 90. HE slides of LIRI animals were scored as fibroproliferative with moderate atelectasis. Surfactant pretreatment improved lung compliance (Vmaxday 30 11.7 ± 1.8, day 90 11.1 ± 1.2; Cmaxday 30 1.04 ± 0.23, day 90 1.16 ± 0.21) and normalized the number of CD45RA+-lymphocytes (769.555 ± 421.016) in left lung tissue. Furthermore lung architecture on HE slides was on return to normal. However, more CD5+CD4+-lymphocytes on day 30 (754.788 ± 97.269 vs 430.409 ± 109.909) and more macrophages on day 90 (2.144.000 ± 630.633 vs 867.454 ± 383.220) were measured in pretreated lung tissue compared to LIRI animals. Conclusions: Severe LIRI caused extensive pulmonary injury up to 90 days postoperatively. Surfactant pretreatment normalized pulmonary function, but resulted in an increased number of CD5+CD4+-cells and macrophages in lung tissue.

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