Matrix adhesion characteristics of corneal myofibroblasts.

PURPOSE To investigate the adhesion characteristics of corneal myofibroblasts in a cell culture model. METHODS Immunocytochemistry, immunoprecipitation, western blot analysis, and attachment assays were used to evaluate matrix adhesion characteristics of myofibroblasts. RESULTS Myofibroblasts, defined by their expression of the smooth muscle isoform of alpha-actin, were evaluated and compared with fibroblasts. Myofibroblasts had larger vinculin-containing focal adhesions and expressed more of the classic fibronectin receptor (FNR) alpha5beta1 per cell. However, myofibroblasts had less surface expression of the higher molecular weight alpha4 subunit of another FNR, alpha4beta1, than did fibroblasts. Myofibroblasts adhered more avidly in an integrin-dependent manner to fibronectin than did fibroblasts. The attachment to fibronectin was actin-dependent for both phenotypes, but the myofibroblasts' adhesion was more resistant to disruption by cytochalasin than were fibroblasts'. In addition to the previously described expression of a 135-kDa classic cadherin, myofibroblasts also expressed a 115-kDa mesenchymal cadherin, cadherin-11. CONCLUSIONS Differentiation of corneal fibroblasts into myofibroblasts is associated with characteristics that would indicate that the latter have a special role in wound closure. The increase in focal and cell adhesion molecules that accompanies smooth muscle-specific actin expression provides the basis for the myofibroblasts' enhanced cell-fibronectin and cell-cell adhesion.