Preservation of microvascular integrity in murine orthotopic tracheal allografts by clopidogrel.

BACKGROUND: Survival after lung transplantation is mainly limited by the development of chronic lung allograft dysfunction (CLAD). The aim of this study was to investigate if platelet inhibition by clopidogrel has a functionally relevant influence on the microvascular integrity of orthotopic tracheal allografts as an anatomic basis for the development of CLAD.

METHODS: We orthotopically transplanted C57Bl/6 (H-2) tracheas into CBA.J (H-2) recipients which afterwards received clopidogrel (1mg/kg). Morphometric analysis was performed by measuring epithelial height in proportion to thickness of the lamina propria (ELR). Tissue oxygenation was determined using a fluorescence quenching technique and graft perfusion monitoring was performed by Laser Doppler Flowmetry and lectin-binding assay. Immunohistochemistry was used for detection of CD31 and iNOS while iron deposition was shown with Prussian blue reaction. Quantitative RT-PCR analysis was used for gene expression analysis.

RESULTS: Isografts maintained good oxygenation and perfusion throughout the experiment, while both were drastically reduced in allografts. Treatment with clopidogrel attenuated graft hypoxia and reduced loss of perfusion. Additionally, clopidogrel led to increased ELR while iron deposition was impaired. Gene expression analysis revealed elevated levels of angiogenic VEGF in the clopidogrel group. Improved endothelial function shown by immunohistochemistry (CD31, iNOS).

CONCLUSIONS: Continuous administration of clopidogrel significantly improved tissue oxygenation, limited microvascular leakiness, and prevented airway ischemia. These data demonstrate that clopidogrel ameliorates microvascular injury during acute airway rejection which is a known predisposing factor for the development of CLAD.