The cellular basis of contracture of the palmar fascia in patients who have Dupuytren disease involves the generation of intracellular force and the transmission of this force to the surrounding tissue. A specialized cell, the myofibroblast, supposedly generates this intracellular force. Recently published studies from our laboratory demonstrated that the cytoskeleton of the myofibroblast contains non-muscle myosin and not smooth-muscle myosin, suggesting that it utilizes a non-muscle contractile system. In addition, these studies identified the extracellular glycoprotein fibronectin, not the basal-lamina-specific glycoprotein laminin, at the surface of myofibroblasts, suggesting that the transmission of the intracellular force to the surrounding tissue also occurs by a non-muscle mechanism. Because of the lack of proteins that are specific to smooth muscle in the specialized cell in Dupuytren disease, we prefer the term specialized contractile fibroblast to describe this type of cell. To determine the mechanism by which the intracellular force may be transmitted to the surrounding tissue, we examined the ultrastructure of the connection of the cytoskeleton of the specialized contractile fibroblast to the surrounding extracellular matrix. By electron microscopy, extracellular filamentous material was identified at the surface of the specialized contractile fibroblast. These extracellular fibrils were found to be in close association with intracellular bundles of actin microfilaments, resulting in specialized transmembranous associations at the surface of the specialized contractile fibroblast. Bundles of filamentous extracellular material were found to extend from the surface of the specialized contractile fibroblast, connecting it with the surrounding matrix and also with adjacent specialized contractile fibroblasts.(ABSTRACT TRUNCATED AT 250 WORDS)