Growth of human keratinocytes in a defined medium supplemented with growth factor of serum

In order to prepare a good medium for cultivation of keratinocytes, bovine serum was fractionated by precipitation with various concentrations of ammonium sulfate. The fractionated serum proteins were added to the basal medium at a concentration of 3 mg/ml. The best proliferation was observed in the medium supplemented with the 55-70% ammonium sulfate precipitated fraction. No growth of keratinocytes was observed when the medium was supplemented with the 0-35% fraction. The growth promotion by the 55-70% fraction was completely inhibited by the 0-35% fraction. These results have shown that the fractionation of serum protein clearly separated the growth-inhibitory factors and the growth-stimulating factors.