In Vivo Observation of Leukocyte-Endothelium Interaction in Ischemia Reperfusion Injury With the Dorsal Window Chamber and the Effects of Pentoxifylline on Reperfusion Injury Cigdem Unal, M.D.,* ,1 Cenk Sen, M.D.,* Deniz Iscen, M.D.,* and Hakki Dalcik, M.D.† *Department of Plastic and Reconstructive Surgery, †Department of Histology and Embryology, Kocaeli University Medical Faculty, Kocaeli, Turkey Submitted for publication February 1, 2006 Objective. Ischemia reperfusion injury can cause fail- ure in microsurgical operations. Interaction between leukocytes and endothelium is recognized as an integral step in ischemia reperfusion injury. Pentoxifylline is a methylxanthine derivative that has pharmacological properties that can be beneficial in ischemia reperfusion injury. The aim of this study was to investigate the in vivo effect of pentoxifylline on leukocyte-endothelium interaction in ischemia reperfusion injury. Methods. Intravital fluorescent microscopy was used to observe leukocyte-endothelium interaction in a “dorsal window chamber” model. Twenty-eight post- capillary veins were analyzed in group 1, and twenty- two in group 2. Group 1 received 25 mg/kg pentoxifyl- line 20 min before reperfusion. Group 2 received an equivalent volume of 0.9% saline at the same time. The period of ischemia was 4 h. Results. Quantification of leukocyte ‘sticking’ and ‘rolling’ was done before ischemia and at 30, 60, and 120 min after reperfusion. Offline video analysis was used for evaluating the results. Statistical evaluation showed that pentoxifylline significantly attenuated leukocyte ‘sticking’ and ‘rolling’ in postcapillary venules. It was also effective in preventing ‘no-reflow’ when com- pared with the control group. Conclusion. These results indicate pentoxifylline di- minishes leukocyte-endothelium interaction, and may have a therapeutic role in preventing ischemia reper- fusion injury in microsurgical operations. © 2007 Elsevier Inc. All rights reserved. Key Words: ischemia reperfusion injury; window chamber; in vivo, pentoxifylline; leukocyte endothe- lium interaction. INTRODUCTION Microvascular surgical procedures, including free tissue transfers involve an obligatory period of isch- emia. It is the restoration of blood flow after this isch- emic period that paradoxically initiates a cascade of events that leads to additional cell injury beyond that caused by ischemia [1]. Restoration of blood flow after an ischemic period causes a leokocyte-endothelium in- teraction characterized by chemotactic accumulation, aggregation, and subsequent adhesion of circulating leukocytes to the microvascular endothelium [2]. Activation of leukocytes causes the release of toxic mediators, and impairment of endothelial barrier; this cascade of events is called “reflow paradox.” Failure of capillary perfusion after reperfusion starts is called “no reflow” [2]. Experimental and clinical therapeutic in- tervention of postischemic cellular dysfunction focuses on the reperfusion period. Quantitive and functional analysis of microhemodynamic parameters of skin, and skeletal muscle can be assessed by intravital microscopy technique. Functional capillary density, RBC velocity, vessel diameter, microvascular hematocrit, changes in vascular permeability, loss of endothelial integrity, cel- lular transport, and cell viability can be studied using chambers implanted on the backs of hamsters [3], mice [4], and rats [5]. Pentoxifylline is a methylxanthine derivative that has a variety of pharmacological properties that can be beneficial in ischemia reperfusion injury [6]. These properties include the ability to increase red cell de- formability [7, 8], decrease blood viscosity [7, 8], atten- uate the release of proinflammatory cytokines [9, 10], and block interactions between leukocytes and endo- thelial cells [11]. Pentoxifylline that is preferentially used in the treatment of chronic occlusive arterial dis- ease, may be a particular candidate to counteract the 1 To whom correspondence and reprint requests should be ad- dressed at Department of Plastic and Reconstructive Surgery, Ko- caeli University Faculty of Medicine, Kocaeli, Turkey. E-mail: cigdem_75@hotmail.com. Journal of Surgical Research 138, 259 –266 (2007) doi:10.1016/j.jss.2006.05.019 259 0022-4804/07 $32.00 © 2007 Elsevier Inc. All rights reserved.