[Localisation of TGF-beta and PDGF and their relevance for the pathogenesis of arthrofibrosis]

Arthrofibrosis is a disabling complication after knee trauma and surgery and is characterised clinically by joint stiffness. Due to an immune response, the proliferation of fibroblasts and synthesis of extracellular matrix proteins are increased. The cytokines transforming growth factor beta (TGF-beta) and platelet-derived growth factor (PDGF) are critical players in tissue fibrosis, stimulating cell proliferation and the production of various extracellular matrix proteins. Tissue samples from the infrapatellar fat pad and intercondylar synovia of seven patients (age 18-49 years) suffering from arthrofibrosis were taken at surgery. The mean interval between trauma and arthrolysis was 14.3 months. All samples were stained with haematoxylin and eosin, and monoclonal and polyclonal antibodies were applied for immunohistological localisation of TGF-beta and PDGF. The percentage of both cytokines was then analysed using an image analysis system. Tissue samples with no macroscopic pathology of the synovial tissue from eight patients for anterior cruciate ligament replacement served as controls. Immunostaining for TGF-beta and PDGF was found to be increased in arthrofibrotic tissue. Both cytokines could be detected subsynovially around inflammatory cells. The profibrotic cytokines TGF-beta and PDGF play an important role in the pathogenesis of arthrofibrosis. Both cytokines are key mediators of tissue fibrosis.