Objectives. Enamel matrix derivative (EMD) is an effective biomaterial for periodontal tissue regeneration and might stimulate angiogenesis. In order to clarify mechanisms underlying its biological activity, we separated two EMD fractions with different molecular weight protein components and investigated their effects on human umbilical vein endothelial cells (HUVECs) in vitro. Methods. Fraction Low-Molecular Weight (LMW) included proteins with a molecular weight (M.W.) <8 kDa. Fraction LMW-depleted included proteins with M.W. >8 kDa and lower than approximately 55 kDa. The effect of EMD fractions on proliferation/viability, apoptosis, migration and expression of angiopoetin-2 (ang-2), von Willebrand factor (vWF), E-selectin, intracellular adhesion molecules 1 (ICAM-1), vascular endothelial growth factor (VEGF) receptors Flt-1 and KDR was investigated. Results. The proliferation/viability of HUVECs was inhibited by both LMW and LMW-depleted at concentrations 100 mu g/ml, whereas EMD slightly increased cell proliferation/viability. The expression of all investigated proteins was up-regulated by EMD. However, differences in the effect of EMD fractions on the protein expression were observed. The effect of LMW-depleted on the expression of ICAM-1 and E-selectin was markedly higher compared to LMW. In contrast, the expression of vWF and VEGF receptors Flt-1 and KDR was primarily affected LMW than by LMW depleted. The expression of ang-2 was not influenced by LMW and LMW-depleted. HUVECs migration was stimulated more strongly by LMW than by EMD and LMW-depleted. Conclusion. Our in vitro study shows that the proteins composing EMD have different and specific biological activities and consequently have the ability to cover different aspects of EMD's biological and clinical effects. (C) 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.