Effects of Hypoxia/Reoxygenation on Angiogenic Factors and Their Tyrosine Kinase Receptors in the Rat Myocardium

The process of angiogenesis is initiated primarily as a consequence of hypoxic stimulation at the cellular and molecular level. Although several angiogenic growth factors have been identified, at present a detailed understanding of the interplay among inducing stimuli, growth factors, and their respective molecular targets remains to be evaluated. Here we report the effects of progressively increasing durations of moderate hypoxia on the protein expression profiles and tissue distribution patterns of the vascular endothelial growth factor system and the angiopoietin/Tie system in the adult rat myocardium. The relative temporal trends of expression of the various components of these two systems, as well as apparent relationships between Flk-1 and angiopoietin-2 and between Flt-1 and Tie-1, suggest a probable sequence of involvement during myocardial angiogenesis, as proposed in our model. Such relationships may potentially be utilized in formulating strategies for sequential gene therapy to achieve clinically relevant myocardial angiogenesis.