Abstract
Purpose::
Tetraspanins are a family of cell-surface proteins consisting of more than 30 members that have been implicated in immune and wound healing activities, including cell adhesion and migration. CD9 and CD81 are two tetraspanin family members widely expressed in the retina.The purpose of this study was to examine the expression of CD9 and CD81 in the developing cornea, as well as in wound healing corneas and cultured corneal epithelium.
Methods::
Tetraspanin expression was examined by immunostaining with CD9 and CD81 antibodies. For development experiments, rat corneas were sectioned and immunostained at postnatal days 0, 2, 15 and 20. For wound healing studies, adult rat corneas were wounded with heptanol-soaked filter discs. Rats were sacrificed 16 hours after wounding, and control (unwounded) and wounded corneas were sectioned and immunostained. For cell culture experiments, primary rat corneal epithelial cells were established in culture, passaged onto fibronectin-coated plates, and immunostained with or without fixation. Both light and confocal microscopy was used to view stained cells.
Results::
Positive epithelial cell surface CD9 staining was observed in all sample types. In most tissue sections, CD9 staining was most intense on the anterior most cells and at the corneal surface. CD9 staining was also positive on all postnatal days examined. Following wounding, CD9 staining was positive at the wound margin, decreasing with distance from the margin. Corneal stromal cells had weak CD9 staining, and endothelial cells showed weak staining in some instances. Cultured epithelium was highly CD9 Positive. CD81 showed epithelial staining into the more basal cell layers, with minimal endothelial staining and the addition of stromal cell staining at postnatal day 2 and intense epithelial and stromal staining at day postnatal day 20. Stromal cells under the wound were also CD81 positive, as were cultured epithelial cells.
Conclusions::
CD9 and CD81 are present during rat corneal development and in cultured corneal epithelium, and are upregulated during wound healing. These proteins appear to be involved in corneal wound healing.
Keywords: cornea: epithelium • cornea: basic science • cornea: stroma and keratocytes