CONTROLLED INDUCTION OF FOCAL ADHESION DISASSEMBLY AND MIGRATION IN PRIMARY FIBROBLASTS

Fibroblast migration is an integral component of biological processes such as wound healing and embryogenesis. Previous experiments examinin g fibroblast locomotion from tissue explants have shown that migrating fibroblasts lack, or contain only transient, focal adhesions (focal c ontacts). Focal adhesions are specialized regions of tight cell-matrix interaction, assembled by a complex process of transmembrane signalli ng. Although the explant model has been used for studying several aspe cts of fibroblast locomotion, it is limited by the lack of control ove r migration, and only a small percentage of the cells actually locomot ing. Therefore, we have developed an in vitro model for cultured fibro blast strains where the presence or absence of focal adhesions can be manipulated, and in the latter case 70% of these cells become locomoto ry. The stimulus used to decrease the percentage of cells containing f ocal adhesions, and hence enhance locomotion, was newborn rat heart-co nditioned medium (HCM). Addition of HCM to rat embryo fibroblasts indu ced both chemokinesis and chemotaxis. Cells disassembled focal adhesio ns on a variety of extracellular matrix substrates after approximately 6 h of stimulation with HCM; conversely, removal of HCM promoted refo rmation of focal adhesions within 12-24 h. HCM-stimulated fibroblasts which lacked focal adhesions concomitantly lacked F-actin stress fiber s and focal concentrations of vinculin and talin. Therefore, fibroblas t migration can be readily controlled in an on-off manner through cond itioned medium, which influences the absence or presence of focal adhe sions.