Ultrastructural Localization of Integrin Subunits 4 and 3 Within the Migrating Epithelial Tongue of In Vivo Human Wounds

Robert A. Underwood ^1*, William G. Carter ¹, Marcia L. Usui ¹ and John E. Olerud ¹

¹ Department of Medicine (Dermatology) (RAU,MLU,JEO) and Department of Pathobiology (WGC), University of Washington, Seattle, Washington, and Fred Hutchinson Cancer Research Center, Seattle, Washington (WGC)

^* To whom correspondence should be addressed. E-mail: underwoo{at}u.washington.ed.

Submitted on July 7, 2008
Accepted on 17 September 2008

	Abstract

Subsequent to wounding, keratinocytes must quickly restore barrier function. In vitro wound models have served to elucidate mechanisms of epithelial closure and key roles for integrins 64 and 31. To extrapolate in vitro data to in vivo human tissues, we used ultrathin cryomicrotomy to simultaneously observe tissue ultrastructure and immunogold localization in unwounded skin and acute human cutaneous wounds. Localization of the 4 integrin subunit in unwounded skin shows dominant hemidesmosomal association and minor basal keratinocyte lateral filopodic cell-cell expression. Post wounding, 4 dominantly localized to cytokeratin rich regions (trailing edge hemidesmosomes) and minor association with lamellipodia (leading edge). 4 colocalizes with 3 within filopodia juxtaposed to wound matrix and increased concentrations of 4 were found in cytoplasmic vesicles within basal keratinocytes of the migrating tongue. 3 integrin subunit dominantly localized to filopodia within basal keratinocyte lateral cell-cell interfaces in unwounded skin and both cell-cell and cell-matrix filopodic interactions in wounded skin. This study indicates that 4 interacts with the extracellular environment through both stable and transient interactions and may be managed through a different endosomal trafficking pathway than 3. 3 integrin despite its ability to respond to alternate ligands post wounding, does so through a single structure, the filopodia.

Key Words: human, wound, healing, skin, integrin, keratinocyte, epithelial, migration, 64, 31

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