Relation between cell density and the secretion of von Willebrand factor and prostacyclin by human umbilical vein endothelial cells

In this study, the relation between the density of human umbilical vein endothelial cells (HUVECs) cultured on TCPS and (crosslinked) collagen, and the secretion of von Willebrand factor (vWF) and prostacyclin (PGI 2) was determined. Collagen was crosslinked using N-(3-dimethylaminopropyl)- N′-ethylcarbodiimide (EDC) in combination with N-hydroxy-succinimide (NHS), resulting in a matrix containing 14 free primary amino groups per 1000 amino acid residues after crosslinking (E/N14C). HUVECs were seeded on E/N14C, non-crosslinked collagen (N-Coll) and fibronectin-coated TCPS at densities ranging from 2500 to 50,000 cells/cm 2. After 1 day of culture, both basal and A23187-stimulated secretion of vWF (expressed per 1,000,000 cells) was considerably increased at low cell densities (i.e. below 5000 cells/cm 2) on all substrates. Secretion of PGI 2 gradually increased with decreasing cell densities below 10,000 cells/cm 2. After 10 days of proliferation, cell numbers on all substrates exceeded 50,000 cells/cm 2, irrespective of the seeding density. Concomitantly, the initial higher secretion of PGI 2 and vWF at the lowest seeding densities was decreased after longer times of culture, to values comparable to those obtained for higher seeding densities.