Appearance of the myofibroblastic phenotype in Dupuytren's disease is associated with a fibronectin, laminin, collagen type IV and tenascin extracellular matrix.

The proliferative nodules of Dupuytren's disease are electron microscopically characterized by the occurrence of myofibroblasts with a basal lamina-like material. As reported in the literature, immunohistochemical investigations showed a fibronectin matrix but failed to demonstrate laminin. This discrepancy between electron microscopic features and immunohistochemical findings prompted us to examine the composition of extracellular matrix (fibronectin, laminin, collagen type IV and tenascin) in relation to the myofibroblast phenotype in proliferative nodules from 13 native surgical specimens of nodular palmar fibromatosis (Dupuytren's disease). The immunohistochemical staining for fibronectin was positive within the whole palmar aponeurosis and was particularly intense in the proliferative areas, whereas laminin, collagen type IV and tenascin labelling was restricted to the alpha-smooth muscle actin-positive proliferative nodules. To exclude definitively an unspecific laminin labelling, SDS-PAGE and immunoblot were performed. The electrophoretic pattern of Dupuytren's disease tissue revealed laminin and was in congruence with human placental tissue used as positive control. The results substantiate an extracellular matrix formation by myofibroblasts with fibronectin, laminin, collagen type IV and tenascin as constituents. Therefore, laminin expression can no longer be considered to be a distinguishing feature between myofibroblasts and smooth muscle cells.