Midkine, a heparin-binding growth factor, and its roles in atherogenesis and inflammatory kidney diseases

The heparin-binding protein midkine is a potent growth factor with emerging roles in numerous inflammatory diseases. Beyond its characterization in embryogenesis and organ development, ample insights into its function have been collected from experimental disease models using knockout animals or knockdown intervention strategies. Here a comprehensive overview on midkine and its functions in atherogenesis and kidney diseases is provided. Molecular clues to key signalling pathways (Akt, ERK, HIF1α) and key events in atherosclerotic vessels link midkine expression with vascular smooth muscle proliferation and (neo)angiogenesis. In acute and chronic kidney diseases, midkine expression is upregulated in tubular as well as endothelial cells. Experimental disease models that mimic diabetic nephropathy and/or immunologic glomerular damage indicate dichotomous midkine activities, with cytoprotective as well as injurious effects. This review also pinpoints the commonalities of the disease models. An understanding of the underlying molecular events will be required in order to design a targeted intervention into cardiovascular or renal diseases as well as inflammatory processes.