Understanding endothelialization: Chemotaxis, adhesion and proliferation on acellular surfaces

Physiological wound healing is a process that consists of a highly orchestrated sequence of events stimulated by various growth factors. The biological half-lives of growth factors are short so in order to apply them therapeutically they must be delivered in an efficient manner. Immobilization of growth factors at the target site may potentially enhance their effect. The overall objective of this research is to better engineer the re-endothelialization of acellular surfaces that encounter blood flow. It is possible to increase FGF-1 specificity to wound sites without diminishing its chemotactic or mitogenic properties as well as retain thrombin resistance using R136K as the parent FGF-1. A 43.3-kDa collagen-binding fusion protein (CBDR136K) consisting of both R136K [FGF-1 with the Arginine at the 136 site changed to Lysine via site directed mutagenesis] and a collagen binding domain derived from Clostridium histolyticum collagenase was produced. The changes to FGF-1 do not alter its mitogenic nor chemotactic response to HUVEC or NIH 3T3 cells. In the presence of thrombin R136K and CBDR136K maintain their chemotactic properties while that of FGF-1 is reduced by a half. Using a Biacore 3000 binding to KW(POG)8 was examined. KW(POG)8 is a synthetic collagen peptide. The binding dissociation constant for FGF-1, R136K, CBD, CBDR136K were 5.1 x 10 -6 M, 3.4 x 10-6 M, 0.89 x 10-8 M, and 1.1 x 10-8 M respectively. The smaller the binding dissociation constant is the greater the affinity between the specific protein and the collagen peptide used. Therefore these results suggest the CBD motif increases FGF-1 ability to bind to synthetic collagen. CBDR136K may be used to immobilize growth factors at the site of damaged tissue.