THROMBIN STIMULATES FIBROBLAST-MEDIATED COLLAGEN LATTICE CONTRACTION BY ITS PROTEOLYTICALLY ACTIVATED RECEPTOR

Fibroblast contraction is proposed to play an important role in tissue contraction during events such as wound healing. Thrombin has been im plicated to promote force generation in fibroblasts; however, its extr acellular mode of action is unclear. The purpose of this study was to determine the role thrombin and the activation of its receptor plays i n promoting the contraction of human fibroblasts in an in vitro collag en lattice contraction assay. Human alpha-thrombin promoted fibroblast contraction in a dose-dependent manner with maximal activity at 0.2 n M. In contrast, both hirudin-alpha-thrombin and D-phenylalanyl-L-propy l-L-arginyl chloromethyl ketone-alpha-thrombin, which lack enzymatic a ctivity, failed to elicit fibroblast contraction. Thus, the enzymatic activity of thrombin appears to be necessary for promotion of fibrobla st contraction. Northern analysis confirmed that these human fibroblas ts expressed mRNA for the human alpha-thrombin receptor. Moreover, the synthetic peptide (SFLLRNPND-KYEPF) representing the ''tethered ligan d'' portion of the activated alpha-thrombin receptor promoted fibrobla st contraction, while a control isomer peptide, in which the first two amino acids were reversed, failed to elicit this response. These find ings indicate that cu-thrombin promotes the contraction of adult human fibroblasts and that cleavage of the human alpha-thrombin receptor is sufficient to produce this response. (C) 1994 Academic Press,Inc.