Immobilized thrombin receptor agonist peptide accelerates wound healing inmice

To accelerate the healing processes in wound repair, attempts have been rep eatedly made to use growth factors including thrombin and its peptide fragm ents. Unfortunately, the employment of thrombin is limited because of its h igh liability and pro-inflammatory actions at high concentrations. Some cel lular effects of thrombin in wound healing are mediated by the activation o f protease activated receptor-1 (PAR-1). The thrombin receptor agonist pept ide (TRAP:SFLLRN) activates this receptor and mimics the effects of thrombi n, but TRAP is a relatively weak agonist. We speculated that the encapsulat ed peptide may be more effective for PAR-1 activation than nonimmobilized p eptide and developed a novel method for TRAP encapsulation in hydrogel film s based on natural and synthetic polymers. The effects of an encapsulated T RAP in composite poly(N-vinyl caprolactam)-calcium alginate (PVCL) hydrogel films were investigated in a mouse model of wound healing. On day 7 the wo und sizes decreased by about 60% under TRAP-chitosan-containing PVCL films, as compared with control films without TRAP. In the case of TRAP-polylysin e-conta-ining films no significant decrease in wound sizes was found. The f ibroblast/macrophage ratio increased under TRAP-containing films on day 3 a nd on day 7. The number of proliferating fibroblasts increased to 150% unde r TRAP-chitosan films on day 7 as compared with control films. The number o f [H-3]-thymidine labeled endothelial and epithelial cells in granulation t issues was also enhanced. Thus, the immobilized TRAP to PVCL-chitosan hydro gel films were found to promote wound healing following the stimulation of fibroblast and epithelial cell proliferation and neovascularization. Furthe rmore, TRAP was shown to inhibit the secretion of the inflammatory mediator PAF from stimulated rat peritoneal mast cells due to augmentation of NO re lease from the mast cells. The encapsulated TRAP is suggested to accelerate wound healing due to the anti-inflammatory effects and earlier development of the proliferative phase of wound healing.