Variability of von Willebrand factor‐related parameters in endothelial colony forming cells

ESSENTIALS: Endothelial colony forming cells (ECFCs) are a powerful tool to study vascular diseases ex vivo. Separate ECFC lines show variations in morphology and von Willebrand factor‐related parameters. Maximum cell density is correlated with von Willebrand factor expression in ECFCs. Variations in ECFC lines are dependent on the age and mesenchymal state of the cells. ABSTRACT: BACKGROUND: Endothelial colony forming cells (ECFCs) are cultured endothelial cells derived from peripheral blood. ECFCs are a powerful tool to study pathophysiological mechanisms underlying vascular diseases, including von Willebrand disease. In prior research, however, large variations between ECFC lines were observed in, among others, von Willebrand factor (VWF) expression. OBJECTIVE: Understand the relation between phenotypic characteristics and VWF‐related parameters of healthy control ECFCs. METHODS: ECFC lines (n = 16) derived from six donors were studied at maximum cell density. Secreted and intracellular VWF antigen were measured by ELISA. The angiogenic capacity of ECFCs was investigated by the Matrigel tube formation assay. Differences in expression of genes involved in angiogenesis, aging, and endothelial to mesenchymal transition (EndoMT) were measured by quantitative PCR. RESULTS: Different ECFC lines show variable morphologies and cell density at maximum confluency and cell lines with a low maximum cell density show a mixed and more mesenchymal phenotype. We identified a significant positive correlation between maximum cell density and VWF production, both at protein and mRNA level. Also, significant correlations were observed between maximum cell density and several angiogenic, aging and EndoMT parameters. CONCLUSIONS: We observed variations in morphology, maximum cell density, VWF production, and angiogenic potential between healthy control ECFCs. These variations seem to be attributable to differences in aging and EndoMT. Because variations correlate with cell density, we believe that ECFCs maintain a powerful tool to study vascular diseases. It is however important to compare cell lines with the same characteristics and perform experiments at maximum cell density.