RESUMEN
Extracellular matrices without animal components and with high mechanical strength are needed for the development of the next generation of viable skin replacements. The goal of this study was to determine the optimal concentration of epidermal growth factor (EGF) to maximize the strength and collagen content of cell-derived matrix (CDM) produced by fibroblasts in vitro in serum-free media. Scaffold-free CDM samples were produced by human dermal fibroblasts in the presence of 0-50 ng/mL EGF in chemically defined media. After 21 days of culture, a membrane inflation system was used to measure the biaxial tensile strength, failure stretch ratio, and thickness of each treatment group. The fibroblasts treated with 5 ng/mL EGF produced the thickest matrix (270 microm). A thinner (130 microm) matrix, produced when the fibroblasts were treated with 0.5 ng/mL, had an ultimate tensile strength (895 kPa), greater than two times that of the other treatment groups. The fibroblasts treated with 0.5 ng/mL also had the highest collagen density (23.5 mg/cm(3)). Fibroblasts stimulated with the lowest (0.05 ng/mL) and highest (50 ng/mL) concentrations of EGF produced significantly weaker matrices and lower collagen densities. There was no significant correlation between UTS and collagen density suggesting that mechanisms other than density contribute to the strength of the matrix. Taken together, these data indicate that the optimal EGF concentration depends upon the relative importance of matrix strength and volume in a given application and that 0.5-5.0 ng/mL EGF promotes production of a robust extracellular matrix in only 3 weeks.