Human serum and epithelial spread in tissue culture.

The dependence of epithelial spread on human serum in culture has been studied. Using measured pieces of mouse ear skin epithelial outgrowth about floating explants (epiboly) and from adherent explants was studied. Where compared directly the two systems show similar results. Because of its ease of quantitation, the adherent explant culture was studied in greater detail. In this system in the presence of serum appreciable spread was found only after 48 h but spread continued for at least the next 4 days. In the absence of serum only minimal epithelial spread occurred. Adding serum to deficient media enhanced spreading and removing serum from media depressed spreading. The extent of spread appeared independent of mouse age for the first 4-10 weeks though 2-week-old mouse skin showed quantitatively greater spreading. The activity in human serum responsible for epithelial spread acts under conditions of minimal DNA synthesis and is not reproduced by bovine serum albumin, fetuin, or serum that had been exposed to 100 degrees C for 5 min. The activity is not dialyzable and it is resistant to the protease inhibitors DFP and PMSF. These studies suggest that a specific serum component(s) serves to support epithelial spread in vitro.