Immunodetection of connexins and cadherins in corneal fibroblasts and myofibroblasts

Purpose. In normal cornea, stromal fibroblasts (keratocytes) interact with one another by gap junctions. After corneal wounding, the remaining corneal stroma cells are phenotypically fibroblasts and myofibroblasts. For insight into the respective roles of fibroblasts and myofibroblasts in wound healing, the authors have investigated the molecular basis of cell-cell interaction in cultures of corneal fibroblasts and corneal myofibroblasts. Methods. Using Western blot analysis and immunofluorescent microscopy, the authors determined the relative expression and localization of junction proteins-connexins, cadherins, and cadherin-associated proteins (catenins)- in cultured fibroblasts and myofibroblasts. Results. In cultured corneal fibroblasts, the gap junction protein, connexin43, was highly expressed and was localized to dense maculae; cadherins were not detected in cell-cell contacts. Cultured myofibroblasts showed the opposite pattern: Cadherins were highly expressed and localized at the cell-cell contacts, whereas myofibroblast connexin43 was primarily intracellular. Myofibroblast cadherin was identified by a pan-cadherin antibody as a molecule of 135 kDa that reacted weakly with an N-cadherin monoclonal antibody. In addition, cadherin-associated cytoplasmic proteins, α- and β-catenins, co-localized with cadherin at the cell-cell borders of the myofibroblasts. Conclusions. The presence of connexin43 at the cell-cell borders of corneal fibroblasts is consistent with a primary communication role of junctions in confluent corneal fibroblasts. In contrast, the presence of cadherin at the cell-cell borders of myofibroblasts may provide a site for insertion of actin filaments. A cadherin-actin association could support actin-based force generation for effective wound closure.