Effects of serum and serum-derived factors on growth and differentiation of mouse keratinocytes |
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Authors: | F Bertolero M E Kaighn R F Camalier U Saffiotti |
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Institution: | (1) Present address: Ispra Establishment, Radiochemistry Division, Commission of the European Communities, Joint Research Centre, I-21020 Ispra (Varese), Italy;(2) Laboratory of Experimental Pathology, National Cancer Institute, Frederick Cancer Research Facility, Building 560, Room 32-60, 21701-1013 Frederick, MD |
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Abstract: | Summary Mouse epidermal keratinocytes (MK cells) were grown as replicating subcultures at clonal density, in a serum-free, low calcium
basal medium supplemented with seven different growth factors (Bertolero et al., Exp. Cell. Res. 155:64–80, 1984). This serum-free
system was used to investigate the activity of cells. bovine serum (FBS) and of serum-derived factors on the growth and differentiation
of MK cells. Unfractionated, whole FBS inhibited growth and induced terminal differentiation of normal MK cells. The growth
inhibitory activity was considerably reduced by passing whole FBS over a resin (Chelex) to remove Ca2+ and other di- and trivalent cations. It is not known whether this treatment removed other factors.
Addition of individual serum components either stimulated or inhibited cell-growth and differentiation. Fetuin, a major α-globulin
of FBS, and high density lipoprotein strongly inhibited the colony forming efficiency (CFE) of MK cells, whereas bovine serum
albumin increased the CFE 4.5-fold and stimulated the growth rate as well. The addition of impure commercial preparations
of platelet-derived growth factor inhibited the CFE and induced the morphological features of squamous terminally-differentiating
keratinocytes.
As reported in other systems, transforming growth factor beta (TGF-β) inhibited the growth of secondary keratinocytes in a
dose-dependent manner. Thus, at least three factors present in FBS inhibited growth whereas others were stimulatory. These
observations explain the difficulties in obtaining replicating subcultures of mouse keratinocytes in serum-supplemented media
and emphasize the importance of a serum-free system for studies on growth control and carcinogenesis in keratinocytes.
Editor’s Statement This report contributes significantly to our knowledge of keratinocyte cell biology in two ways. First,
a serum-free medium has been developed that can now be used by many investigators to define growth versus differentiation
factors for these cells. This is important since several impure or relatively crude preparations of factors are known to influence
these cells. Second, the finding that TGF-Beta is an inhibitor of keratinocyte growth opens new avenues to investigate the
biochemical events leading to differentiation. David A. Sirbasku |
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Keywords: | keratinocytes serum factors growth differentiation |
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