Reduced thrombogenicity of type VI collagen as compared to type I collagen.

Type VI collagen has been recently identified as a major constituent of vascular subendothelium where it serves as a binding site for von Willebrand factor. The present study compares the functional characteristics of type VI collagen with those of type I collagen with respect to platelet aggregating and secretory activities. The differences between the two collagens in platelet aggregation and serotonin and beta-thromboglobulin release were found to be highly significant (p < 0.001, p < 0.0007, p < 0.005 respectively). Our results indicate that under in vitro conditions, type VI collagen stimulates a significantly lesser platelet activation and aggregation response than collagen I, suggesting that type VI collagen may play a role in vivo to limit the platelet thrombotic response following injury to the vascular subendothelium.