Enhancement of incisional wound healing and neovascularization in normal rats by thrombin and synthetic thrombin receptor-activating peptides.

To better define thrombin-receptor interactions, we synthesized human thrombin peptides and identified binding-domain peptides that bind thrombin receptors and activate mitogenic signals (Glenn, K.C., G.H. Frost, J.S. Bergmann, and D.H. Carney. 1988. Pept. Res. 1:65-73). Treatment of full dermal dorsal incisions with a single topical application of thrombin receptor-activating peptide (TRAP-508) or human alpha-thrombin in saline enhances 7-d incisional breaking strength in normal rats up to 82% or 55% over saline-treated controls, respectively. Control wounds require approximately 11.5 d to achieve breaking strength equivalent to TRAP-treated wounds at day 7. Thus, a single application of TRAP accelerates healing, shifting the time course forward by up to 4.5 d. Histological comparisons at day 7 show more type I collagen, less evidence of prolonged inflammation, and an increase in number and maturity of capillaries in TRAP- and thrombin-treated incisions. Angiograms also show 50-65% more functional vascularization going across thrombin- and TRAP-treated surgical incisions. Thus, alpha-thrombin and thrombin peptides, such as those released following injury, appear to initiate or enhance signals required for neovascularization and wound healing. The ability to accelerate normal wound healing events with synthetic peptides representing receptor binding domains of human thrombin may offer new options for management of wound healing in man.

A synthetic peptide representing the thrombin receptor-binding domain enhances wound closure in vivo.

Our studies of alpha-thrombin as a growth factor have led to the development of a synthetic peptide (p508) that in vitro competes with thrombin for binding to high affinity receptors, and enhances mitogenic activity. To determine if this peptide could be used to accelerate wound closure in vivo, full thickness 6 mm dermal biopsy wounds on the dorsal skin of anesthetized rats were treated with p508 peptide, thrombin or PBS as control. At day 7, the p508 treated wound areas were 20% to 50% smaller than either thrombin or PBS treated wound sites. This suggests that p508 enhances aspects of wound healing, and avoids the normal in vivo regulatory mechanisms of intact thrombin.