Plasma levels of syndecan-4 (ryudocan) are elevated in patients with acute myocardial infarction.

Syndecan-4 (ryudocan) is a cell-surface heparan sulfate proteoglycan, which plays an important role in a variety of biological functions including regulation of blood coagulation. cell adhesion, and cell growth. In this study, we measured plasma levels of syndecan-4 in patients with acute myocardial infarction using an enzyme-immunoassay, and found that they were extremely high, with a peak of average (10.5 +/- 5.6 ng/ml, 2 weeks after onset), as compared with those in normal subjects (0.078 +/- 0.030 ng/ml) (p < 0.001). We also observed a distinct expression of syndecan-4 in the repair region of the damaged cardiac tissues with infarction, but not in intact region, by immunohistochemical analysis. To clarify the mechanism of syndecan-4 induction, we investigated the hypoxia effect on its expression, and found that hypoxia treatment up-regulated the gene expression of syndecan-4 in various types of cells. Taken together, it is suggested that syndecan-4 is induced by hypoxia stimuli in ischemic heart tissues, and may function as a tissue-repair molecule via biological mediators such as heparin-binding growth factors.