Effects of cytokines on gingival fibroblasts in vitro are modulated by the extracellular matrix

Fibroblast function in gingival tissue is thought to be regulated by the local cellular environment – both the extracellular matrix and soluble factors. In an attempt to artificially re-create this situation fibroblasts have been cultured within 3-dimensional collagen gels in an environment more physiologically comparable to connective tissue. Using such a model we investigated the effects of the extracellular matrix on gingival fibroblast growth and synthetic activity and on the cellular responsiveness to 4 soluble factors – epidermal growth factor (EGF), platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF- β ₁) and interleukin-1 β (IL-1 β ). Fibroblasts cultured within collagen gels showed similar growth rates, an increased production of collagen but reduced levels of hyaluronan synthesis in comparison to cells in monolayer culture. Cellular responsiveness to soluble mediators was also modulated by the collagen matrix, with a generalised reduction in response by cells embedded within the matrix. The stimulatory effects of EGF and PDGF on cell growth in monolayer over a 14-day period were only found during the initial stages of culture within gels. Similarly the stimulation of matrix production by cells induced by TGF- β ₁, on plastic was reduced or even negated when cells were cultured in collagen gels. On plastic IL-1 β significantly stimulated cell growth but had no effect on either collagen or hyaluronan production by fibroblasts. In gel cultures, this cytokine had no effect on cell proliferation, but significantly inhibited both collagen and hyaluronan synthesis. These findings further illustrate the usefulness of fibroblast-populated collagen gels as a model system for studying the modulatory effects of soluble factors and extracellular matrix molecules on fibroblast function in vitro .