Functional aspects of endothelial phenotypes in the human heart. Immunohistochemical evaluation of endothelial adhesion molecule expression

Background and Purpose: The endothelial lining is a confluent monolayer of thin and rhomboid-shaped cells, that covers the inner surface of all blood vessels. However, the essential role of endothelial cells in all aspects of cardiovascular physiology, homeostasis and the pathogenesis of most cardiovascular diseases no longer remains controversial. Although much evidence has been achieved regarding the molecular functioning of transcription factors and regulatory proteins, many questions on endothelial heterogeneity with regard to function and morphology at various vascular sites remain unanswered. In this study, an immunohistochemical map of endothelial adhesion molecule expression at various vascular sites of the healthy human heart is created. Using this map, the authors examined whether expression patterns are distinctive by their molecular function at their site of origin. Furthermore, immunohistochemical findings were associated with the clinical situation. Material and Methods: Tissue samples from eleven different vascular locations of healthy human hearts were analyzed using immunohistochemistry. Endothelial adhesion molecules of the selectin, immune globulin supergene, and integrin families, some complementary cellular adhesion molecules, and the von Willebrand factor were analyzed. Results: Endothelial adhesion molecule expressions were found to be characteristic of all vascular sites investigated. Thus, molecules involved in inflammatory reactions were predominantly expressed within the myocardial microvasculature, whereas molecules serving for endothelial anchorage toward extracellular matrix components could be observed especially on endocardial and valvular surfaces. Apart from that, a parallel expression of immunologically relevant as well as integrin molecules were found to be characteristic of coronary arteries. Conclusion: To the authors' knowledge, this is the first report on site-specific expression characteristics for all vascular sites of the human heart. Thus, our data provide important novel information, which ultimately will help to bring some light into the field of cardiac physiology.