Increased deposition of von Willebrand factor in the rat heart after local ionizing irradiation.
OBJECTIVE
Von Willebrand factor (vWf), a glycoprotein involved in blood coagulation, is synthesized by endothelial cells. Increased amounts of vWf in blood plasma or tissue samples are indicative of damaged endothelium. In the present study, mRNA expression and localization of vWf were determined in irradiated rat heart tissue.


METHODS
Sprague-Dawley rats received local heart irradiation with a single dose of 0, 15, or 20 Gy. Hearts were dissected at different time points (up to 16 months) after irradiation. In a second experiment, rats were injected with the radioprotector amifostine (160 mg/kg, i. p.) 15-20 min before irradiation and sacrificed after 6 months. Immunohistochemistry was performed using a polyclonal anti-vWf antibody. Serial sections were subjected to a general rat endothelial cell immunostaining (RECA-1) or a collagen staining (picrosirius red). mRNA expression was determined by using PCR.


RESULTS
In control tissue, all endothelial cells lining the lumen of the endocardium and coronary arteries, but not capillary endothelial cells, were stained for vWf. 1 month after irradiation with both 15 and 20 Gy, myocardial capillaries became immunoreactive. From 3 months onward, staining was observed also within the extracellular matrix (ECM) of fibrotic areas. At mRNA level, no changes in vWf could be observed at all time points after irradiation, suggesting that vWf deposition was not due to increased biosynthesis of the protein. In sections of amifostine-treated rat hearts, vWf staining was increased to a lesser extent.


CONCLUSIONS
These dose- and time-dependent increases in deposition of vWf indicate the presence of damaged endothelium in the irradiated rat heart. These increases in vWf accumulation precede development of fibrosis in the subendocardial layer and myocardium of the left ventricles, right ventricles, and atria.
Boerma
Marjan
M
Department of Clinical Oncology (K1-P), Leiden University Medical Center, The Netherlands. m.boerma@lumc.nl
Kruse
Jacqueline J C M
JJ
van Loenen
Marleen
M
Klein
Henriëtte R
HR
Bart
Cindy I
CI
Zurcher
Chris
C
Wondergem
Jan
J
D004999:Amifostine / Q000494:pharmacology; D000818:Animals; D003331:Coronary Vessels / Q000473:pathology / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004699:Endocardium / Q000473:pathology / Q000528:radiation effects; D004719:Endomyocardial Fibrosis / Q000473:pathology; D004730:Endothelium, Vascular / Q000473:pathology / Q000528:radiation effects*; D005109:Extracellular Matrix / Q000473:pathology / Q000528:radiation effects; D005260:Female; D015870:Gene Expression / Q000528:radiation effects; D006321:Heart / Q000528:radiation effects*; D011292:Premedication; D012333:RNA, Messenger / Q000235:genetics; D011833:Radiation Injuries, Experimental / Q000473:pathology*; D011837:Radiation-Protective Agents / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014841:von Willebrand Factor / Q000235:genetics*
D012333:RNA, Messenger; D011837:Radiation-Protective Agents; D014841:von Willebrand Factor; D004999:Amifostine