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.
Fehrenbach
Antonia
A
Division of Electron Microscopy, Center of Anatomy, University of Göttingen, Göttingen, Germany. afehrenb@med.uni-marburg.de
Pufe
Thomas
T
Wittwer
Thorsten
T
Nagib
Ragi
R
Dreyer
Niels
N
Pech
Thomas
T
Petersen
Wolf
W
Fehrenbach
Heinz
H
Wahlers
Thorsten
T
Richter
Joachim
J
D000818:Animals; D015415:Biomarkers; D018893:Bronchoalveolar Lavage; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D008297:Male; D010100:Oxygen / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000473:pathology* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000378:metabolism* / Q000473:pathology; D020545:Respiratory Mucosa / Q000473:pathology*; D016707:Tissue Fixation; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
D015415:Biomarkers; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D010100:Oxygen