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Differences in integrin expression during avian corneal stromal development
1Department of Anatomy and Cellular Biology, Tufts University School of Medicine, Boston, Massachusetts 02111.
Purpose:
The purpose of this study was to determine whether there are changes in integrin expression associated with the spatial and temporal variations in matrix expression that occur during specific stages in corneal stromal development.
Methods:
Immunofluorescence techniques were used to analyze beta 1-containing integrins and alpha v beta 3 localization both in situ and in cell cultures.
Results:
In situ, beta 1 and alpha v beta 3 were present with different patterns of localization, and these varied with developmental stage. beta 1-containing integrins were present on most cells, whereas alpha v beta 3 was present on cells at the corneal-scleral epitheliomesenchymal interface during migration of keratocyte precursors; very little alpha v beta 3 was localized in keratocytes. Keratocytes and undifferentiated periocular mesenchyme cells grown in vitro also exhibited differences in localization of beta 1-containing integrins and alpha v beta 3. All focal adhesions contained beta 1, whereas a subset contained both beta 1 and alpha v beta 3, indicating potential functional differences in focal adhesions. In addition, most periocular mesenchyme cells exhibited alpha v beta 3-containing focal adhesions throughout, but the majority of keratocytes contained only peripherally located alpha v beta 3-positive focal adhesions. The localization of both beta 1-containing integrins and alpha v beta 3 was modulated by time allowed for attachment and spreading.
Conclusions:
Keratocytes and undifferentiated periocular mesenchyme cells exhibit developmental differences in integrin localization in situ. These two cell types also exhibit different patterns of alpha v beta 3 localization in vitro, possibly as a result of developmental differences in ligand-binding properties. beta 1-containing integrins and alpha v beta 3 define different types of focal adhesions, implying different functions. These differences in expression may be important in the initiation of cellular migration in the early stages of corneal development, as well as in the transition from the undifferentiated to the differentiated keratocyte phenotype.