Tβ4 stimulates endothelial cell migration in vitro and in vivo by acting as a potent chemo-attractant factor. Research studies published by NIH were the first to report that Tβ4 could stimulate human endothelial cell migration and differentiation in cell culture. Endothelial cells are the major cell type responsible for the formation of blood vessels. It has been found that Tβ4 is a substrate for transglutaminase (factor XIIIa), an enzyme that plays an essential role in blood clotting, the very first step in the wound healing process.