Epithelial migration in organ culture. Role of protein synthesis as determined by metabolic inhibitors

Acidic fibroblast growth factor overexpression in corneal epithelial wound healing

aFGF expression was studied in normal and regenerating cornea of adult rats. aFGF mRNA and proteins were expressed mainly in corneal epithelium but not in stroma. After burning of the epithelium by iodine vapours, the intact epithelial cells migrated to cover the wounded area during the first 4 days and then divided to reconstitute a normal multilayered epithelium 6 days after injury. aFGF mRNA localized by in situ hybridization on regenerating epithelium showed a peak between 6 hr and 2 days after denudation, decreasing to basal levels 6 days later. This induction of aFGF mRNA preceded the increased amount of aFGF peptides, as assessed by indirect immunofluorescence staining. Thus aFGF overexpression is clearly correlated with active migration in epithelial wound healing.

Enhancement of vinculin synthesis by migrating stratified squamous epithelium

A 110-115-kD protein is present at levels 27-fold higher in migratory epithelium in the rat cornea than in stationary epithelium. This protein represents 2.7% of the total protein in migratory epithelium 6-h postabrasion wound and 0.1% of the total protein in stationary epithelium. Our findings demonstrate that this 110-115-kD protein is vinculin. In Western blots comparing proteins from migratory and control epithelium, antibody against vinculin cross-reacted with the 110-115-kD protein. Using immunoslot blots, vinculin was determined to be present at maximal levels 6 h postabrasion wound, at levels 22- and 8-fold higher than control at 18 and 48 h, respectively, returning to control levels 72 h postwounding. Vinculin was also localized by indirect immunohistochemistry in migrating corneal epithelium. 3-mm scrape wounds were allowed to heal in vivo for 20 h. In flat mounts of these whole wounded corneas, vinculin was localized as punctate spots in the leading edge of migrating epithelium. In cryostat sections, vinculin was localized as punctate spots along the basal cell membranes of the migrating sheet adjacent to the basement membrane and in patches between cells as well as diffusely throughout the cell. Only very diffuse localization with occasional punctate spots between adjacent superficial cells was present in stationary epithelium. The increased synthesis of vinculin during migration and the localization of vinculin at the leading edge of migratory epithelium suggest that vinculin may be involved in cell-cell and cell-substrate adhesion as the sheet of epithelium migrates to cover a wound.

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.

Epithelial migration in organ culture. A morphological and time lapse cinematographic analysis of migrating stratified squamous epithelium

The migration of stratified squamous epithelium in organ cultures of rat palatal explants has been studied using scanning and transmission electron microscopy. The scanning microscope revealed plate-like folds at the margins, and microvilli on the bodies of cells. These structures were most highly developed on those cells nearest the leading edge of the sheet of cells and are interpreted as an index of cells that are migrating. The cells at the leading edge have broad flat pseudopodia in direct contact with the collagen bundles. A time lapse cinemicrographic study showed that the net forward movement of cells (nuclei) remote from the leading edge was at least as great as that at the leading edge immediately in front of them and the distance they travelled was greater than that of the leading edge. In transmission electron micrographs of these migrating epithelial cells from in vivo wounds, profiles that could correspond to the microvilli and plate-like folds could be found on the surface of the migrating cells. The results of this study suggest a simple model for the particular type of movement that occurs in stratified squamous epithelium in healing wounds where a mass of cells is produced that can both migrate into the wound and undergo stratification and cornification. A tracked vehicle shedding a broken track is used as an analogy of the model proposed.

Clinicopathologic effects of cancer chemotherapeutic agents on human buccal mucosa

Specimens of buccal mucosa obtained at autopsy from 216 patients were examined for histopathologic alterations. Atrophic oral epithelium was found in thirty cases. A retrospective study of the hospital records revealed that thirteen of these latter patients had been on a cancer chemotherapeutic regimen prior to death. There was a significantly higher incidence of atrophy in the chemotherapy group (p less than 0.001) than in control patients. These findings, as well as the expected inherent susceptibility of rapidly replicating oral epithelial cells to metabolic inhibitors, suggest a causal relationship between oral atrophy and the administration of cancer chemotherapeutic agents. This atrophy may therefore represent a preliminary stage of mucosal alteration that ultimately progresses to the clinical sequelae of stomatitis and oral ulcerations frequently encountered during cancer chemotherapy. Some alternative mechanisms are also discussed.