Immunohistochemical localization of collagen VI in arthrofibrosis

Arthrofibrosis is a disabling complication after knee trauma and surgery. Clinically, it is characterized by pain and joint stiffness due to massive connective tissue proliferation. In similar pathological conditions with fibrotic transformation such as lung fibrosis or superficial fibromatoses, an increased expression of collagen type VI has been reported. Collagen VI, which forms a filamentous network, is thought to serve as an anchoring element between collagen I/III fibrils and basement membranes and as a cell binding structure. Collagen VI may also play a contributing role in the pathogenesis of arthrofibrosis. The aim of the present study was therefore to demonstrate the localization and distribution of type VI collagen in arthrofibrotic tissue. Tissue samples from the infrapatellar fat pad and intercondylar synovia of 13 patients suffering from arthrofibrosis were taken at surgery. The expression of type VI collagen was studied immunohistochemically using an immunoperoxidase method for light microscopic visualization. Histologic analysis showed a synovial hyperplasia with inflammatory cell infiltration and vascular proliferation. Compared with normal synovial tissue, type VI collagen was widely distributed as a network subsynovially and around the capillary walls. The results of the present study suggest that dysregulation of collagen VI synthesis could be an important contributing factor in the complex mechanisms of disordered matrix protein deposition leading to arthrofibrosis.