Changes in beta 4 integrin expression and localization in vivo in response to corneal epithelial injury.

PURPOSE To determine whether production and localization of beta 4 integrin is altered during in vivo corneal epithelial cell migration in response to debridement wounding. METHODS Rat corneas were wounded and animals were killed at times ranging from 3 hours to 14 days. At various time points, corneal epithelial integrins were quantitated by gel electrophoresis and immunoblotting of epithelial extracts and then were localized by immunohistochemistry. RESULTS As early as 6 hours after wounding, an increase in the amount of the beta 4 integrin subunit expressed per microgram of total protein was observed. The level of beta 4 continued to increase until wound closure. By 14 days after wounding, beta 4 expression returned to control levels. The level of expression of beta 1 and alpha (v) integrins were found not to change significantly throughout migration. Immunohistochemical analyses using antibodies against either the beta 4 integrin subunit or HD1, a hemidesmosomal plaque component, showed that in control sections, beta 4 integrin and HD1 codistributed in a linear staining pattern above the basement membrane. As early as 4 hours after wounding, beta 4 was present in both basal and suprabasal epithelial cells, and HD1 was retained at the basal aspect of the epithelial basal cells. CONCLUSIONS These data show that changes in expression and localization of beta 4 integrin occur in the corneal epithelium in response to debridement wounding in vivo. Previously, we had shown that quantitative changes in beta 4 integrin expression do not occur in an in vitro organ culture model used for the study of corneal epithelial cell migration. Increased beta 4 expression may not be required for migration per se, but it may be play a role in either stabilizing cell:cell or cell:substrate adhesion in vivo or in preparing cells to undergo mitosis during restratification.