Expression of von Willebrand factor by human pulmonary endothelial cells in vivo

Whether von Willebrand factor (vWf) is variably expressed by endothelial cells (EC) of the human vascular tree or not is not known. Studies on animals showed that the varying degrees of vWf expression in pulmonary vessels was a reflection of EC heterogeneity. Neither the influence of age or sex nor that of pathophysiological factors such as pulmonary hypertension (PH) on vWf expression has been systematically analysed up to now. However, such information is essential for the design and delivery of site-selective drugs and genes as well as for the analysis of EC culture systems.

The variable degrees of vWf expression in lung tissue specimens from 64 patients (age: 6 weeks to 86 years) with and without PH were studied immunohistochemically and analysed statistically.

CD31-specific antibody was used as a control stain for EC. It produced equally strong staining reactions in all pulmonary EC. In contrast, vWf-specific antibody yielded negative or weakly positive staining reactions in capillary EC. The staining intensities increased hand in hand with vessel calibres. Besides, they increased statistically significantly with age and PH. Sex had no influence on vWf expression.

These findings show that (1) vWf expression by pulmonary EC is heterogeneous and specific for individual types of vessels, (2) age and PH enhance vWf expression, (3) vWf expression is indicative of altered EC activation but not of EC defects, and (4) elevated plasma levels of vWf correlate positively with raised coagulatory activities in older patients and in patients with PH.