TISSUE ORIGIN AND EXTRACELLULAR-MATRIX CONTROL NEUTRAL PROTEINASE ACTIVITY IN HUMAN FIBROBLAST 3-DIMENSIONAL CULTURES

Remodeling of the extracellular matrix by fibroblasts is an important step in the process of wound healing and tissue repair. We compared th e behavior of fibroblasts from two different tissues, dermis and gingi va, in three-dimensional lattices made of two different extracellular matrix macromolecules, collagen and fibrin. Cells were grown in monola yer cultures from normal skin or gingiva and seeded in three-dimension al lattices made of either collagen or fibrin. Photonic and scanning e lectron microscopy did not reveal any morphological differences betwee n the two types of fibroblasts in both sets of lattices. Both types of fibroblasts retracted collagen lattices similarly and caused only a s light degradation of the collagen substratum. By contrast, when seeded in fibrin lattices, gingival fibroblasts completely digested their su bstratum in less than 8 days, whereas only a slight fibrin degradation was observed with dermal fibroblasts. The ability of gingival but not dermal fibroblasts to express high levels of tissue plasminogen activ ators (tPA) when cultured in fibrin lattices was assessed on an immuno logical basis. Also, deprivation of plasminogen-contaminating fibrinog en preparations or use of tPA inhibitors markedly inhibited both fibri nolysis and retraction rates of fibrin lattices by gingival fibroblast s. Casein-zymography confirmed the intense proteolytic activity induce d by fibrin in gingival fibroblasts. It was inhibited by aprotinin and phenyl methylsulfonyl fluoride (PMSF), two non-specific inhibitors of serine proteinases, and by E-amino-caproic acid (epsilon ACA), an inh ibitor of plasminogen activators. Monolayer cultures exhibited only tr ace amounts of caseinolytic activity. Our results demonstrate that the expression of proteinases by fibroblasts is dependent not only on the ir tissue origin but also on the surrounding extracellular matrix. The intense fibrinolytic activity of gingival fibroblasts in fibrin latti ces may explain partially the high rate of healing clinically observed in gingiva. (C) 1996 Wiley-Liss, Inc.