Distribution of β1 integrin during development of chick tarsometatarsal skin in vivo and in vitro

Abstract

To determine the role of β1 integrin in chick tarsometatarsal skin development, we examined the localization of the β1 integrin immunohistochemically in vivo and in vitro by light and electron microscopy. β1 integrin was present over the entire cell surface of undifferentiated epidermis at early stages (Days 5, 9, 13). Marked changes in the localization of β1 integrin occurred during epidermal keratinization and stratification, i.e., expression of β1 integrin decreased in the superficial and intermediate cell layers from Day 13 to Day 17. After 17 days in vivo, when keratinization of the epidermis was completed, the distribution of β1 integrin was confined to the basal layer of the epidermis in a pericellular distribution. During all stages examined, fibroblasts in the dermis were also stained. Immunoelectron microscopic study revealed that β1 integrin was located on the plasma membrane of keratinocytes and dermal fibroblasts. The change in β1 integrin localization that occurred in vivo could be reproduced in cultures of developing skin in which keratinization (differentiation) or mucous metaplasia (transdifferentiation) had been induced in vitro by hydrocortisone or retinol treatment, respectively. A monoclonal antibody against β1 integrin caused striking changes in the epidermal keratinization process and in the basement membrane structure in vitro, i.e., inhibition of keratinization and detachment of the basement membrane from the basal surface of the epidermis. These results indicate that β1 integrin plays an important role in cell-cell and cell-extracellular matrix interactions, which are important for epidermal development of the tarsometatarsal skin.