Bk. Pilcher et al., THROMBIN PROMOTION OF ISOMETRIC CONTRACTION IN FIBROBLASTS - ITS EXTRACELLULAR MECHANISM OF ACTION, Plastic and reconstructive surgery, 96(5), 1995, pp. 1188-1195
Isometric force generated by fibroblasts plays an essential role in ti
ssue contraction during normal wound healing and pathologic contractur
es. Thrombin, a serine protease present in all wounds, has been shown
to promote wound healing. The purpose of this study was to determine t
he extracellular mechanism by which thrombin promotes isometric contra
ction by fibroblasts in an in vitro collagen lattice model of tissue c
ontraction. The amount of isometric force generated by human fibroblas
ts can be measured directly with a stabilized collagen lattice attache
d to a force transducer. Thrombin promoted isometric contraction by hu
man fibroblasts in a dose-dependent manner. In addition, thrombin-prom
oted isometric contraction is dependent on the enzymatic and anionic b
inding activity of thrombin, as demonstrated by inhibition with specif
ic enzymatic and anionic binding inhibitors. These results suggest tha
t thrombin may promote isometric contraction by fibroblasts through th
e enzymatic cleavage of its cell surface receptor, resulting in a ne i
u amino terminus that serves as a ''tethered ligand'' to activate the
receptor directly. To test this mechanism of action, a synthetic pepti
de (SFLLRN) representing the ''tethered ligand'' region of the activat
ed thrombin receptor was synthesized and examined for its ability to p
romote isometric contraction by fibroblasts. This peptide promoted fib
roblast contraction in a dose-dependent manner. In contrast, a control
isomer peptide (FSLLRN), in which the two amino-terminal amino acids
were reversed, failed to promote this response. These findings demonst
rate that human alpha-thrombin promotes isometric contraction by human
fibroblasts and that binding to and cleavage of its cell surface rece
ptor are integral to this response.