EXTRACELLULAR-MATRIX INTERACTIONS .2. EXTRACELLULAR-MATRIX STRUCTURE IS IMPORTANT FOR GROWTH-FACTOR LOCALIZATION AND FUNCTION

The influence of extracellular matrix components and of extracellular matrix structure on in vitro cell growth was investigated in the UWOV2 (Pf), protein-free cell culture model, This cell line constitutively produces an ordered extracellular matrix in the absence of any exogenous protein or growth factor. Extracellular matrix from UWOV2 (Pf) cells was found to contain both transforming growth factor beta (TGF beta) and platelet-derived growth factor (PDGF), which were shown to have an autostimulatory role for UWOV2 (Pf) cell growth. Matrix structure was shown to be important for allowing expression of the functional activity of these two growth factors. In addition, a nonuniform distribution of PDGF, embedded within the matrix structure, was demonstrated by immunoelectronmicroscopy. Apart from these two well-defined growth factors, additional but as yet unidentified growth stimulatory factor(s) were extractable from UWOV2 (Pf) extracellular matrix, These investigations indicate the potential role of extracellular matrix both as a mechanism for concentrating as well as modulating the function of cellular growth factors.