Musculoskeletal connective tissue cells with muscle: expression of muscle actin in and contraction of fibroblasts, chondrocytes, and osteoblasts.

The expression of the gene for a muscle actin in certain nonmuscle cells and the contraction of these connective tissue cells has been associated with several important physiological and pathological processes; the contraction of healing skin wounds and the contracture in Dupuytren's disease being two notable examples. Studies in recent years have shown that a much wider variety of connective tissue cells than previously considered, including cells in many of the musculoskeletal tissues, e.g., chondrocytes and osteoblasts, can express the gene for alpha-smooth muscle actin and can display contractile behavior. These findings suggest that muscle actin-enabled cell contraction may also be playing important roles in the other connective tissues comprising the musculoskeletal system, namely, tendon, ligament, meniscus, intervertebral disc, articular cartilage, and bone.