Growth of keratinocytes in explant culture of mouse ear epidermis was studied. The addition of transferrin to the culture media improved growth. Transferrin fractionated from human and fetal calf serum increased outgrowths of the cultures when compared with commercially available transferrin. An acidic transferrin fraction was present in greater amount in human serum and in fetal calf serum than that found in commercial transferrin. This fraction was more abundant in serum from psoriatic patients than in serum of healthy subjects as shown by isotachophoresis. For the culture studies, preparation of this material was done by chromatography on DEAE-Sepharose 6B-CL columns. Further on, diferric transferrin was preferentially used in order to abolish variation due to iron saturation. Iron concentration higher than 5 microM was deleterious to cell growth. The basal culture medium contained transferrin depleted fetal calf serum in RPMI 1640 with 2 microM glutamine and antibiotics. Serum-free medium was used in some experiments. The additions were 1.7 microM insulin, 1.4 microM hydrocortisone, 10 microM ethanolamine and 10 microM phosphoethanolamine. A partially purified fraction of the acidic forms of transferrin (10-20 micrograms/ml medium) improved outgrowth when compared with a neutral fraction under these circumstances.
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