Erythropoietin inhibits post-ischemic leukocyte adhesion but does not affect rejection in murine cardiac allografts.
BACKGROUND
This study was aimed to assess the pleiotropic effects of non-hematopoietic doses of erythropoietin (Epo) on post-ischemic microcirculatory dysfunction and inflammation in murine cardiac allografts.


METHODS
Epo was given intraperitoneally 2 hours prior to explantation (Epo-donor) or 2 hours prior to the onset of reperfusion (Epo-recipient). Controls were not treated. Intravital fluorescence microscopy (IVM) was used to assess post-ischemic coronary microcirculatory dysfunction.


RESULTS
IVM exhibited decreasing capillary blood flow velocities and functional capillary densities (FCD) in controls. Capillary diameters and venular blood flow characteristics showed no significant changes over time. Epo-treatment had no effect on coronary microhemodynamics. Post-ischemic inflammation was characterized by augmented macromolecular leakage. Microvascular permeability decreased in the Epo-donor group (p < 0.05). Leukocyte rolling in coronary post-capillary venules decreased during reperfusion from 64 ± 16 to 19 ± 16 cells/min/mm, whereas firm adhesion increased from 333 ± 135 to 479 ± 154 cells/mm(2) in controls. Capillary leukocyte plugging remained stationary over time with approximately 4 to 6 cells/HPF. Firm adhesion was inhibited in the Epo-recipient group, resulting in 84 ± 34 cells/mm(2) at 6 hours of reperfusion (p < 0.05). Capillary leukocyte plugging was also reduced in the Epo-recipient group (p < 0.05). Epo exerted no effect on leukocyte rolling. Histology revealed significant myocardial edema formation in allografts, without any alteration by Epo treatment. Immunohistochemistry indicated the involvement of resident cardiac mast cells. Allograft rejection was not affected by Epo treatment.


CONCLUSIONS
We demonstrate that non-hematopoietic treatment with Epo inhibits acute post-ischemic myocardial leukocyte sequestration, without affecting microcirculatory dysfunction and allograft rejection.
Schramm
René
R
Clinic of Cardiac Surgery, Ludwig-Maximilians-University Munich, Munich, Germany. reneschramm@live.de
Kirsch
Sarah
S
Schäfers
Hans-Joachim
HJ
Langer
Frank
F
Scheuer
Claudia
C
Nickels
Ruth
R
Harder
Yves
Y
Menger
Michael D
MD
D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects; D003331:Coronary Vessels; D004921:Erythropoietin / Q000494:pharmacology*; D006084:Graft Rejection; D016027:Heart Transplantation / Q000379:methods*; D007962:Leukocytes / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008833:Microcirculation; D017202:Myocardial Ischemia / Q000517:prevention & control*; D014184:Transplantation, Homologous
D002316:Cardiotonic Agents; D004921:Erythropoietin