Analysis of the Collagen I and Fibronectin of Temporomandibular Joint Synovial Fluid and Discs

Abstract

The objective of this study was to investigate the content of synovial fluid aspirates and temporomandibular joint (TMJ) disc tissue for collagen I and total fibronectin in patients with closed lock. Fibronectin contains dual properties of assisting with wound healing and inducing cartilage degradation. Native fibronectin has been shown to assist with wound repair, whereas particular fibronectin fragments may degrade cartilage. In addition, collagen I is the major supporting protein of the TMJ disc and will degrade as osteoarthritis progresses. Fibronectin or collagen I expression in human TMJ synovial aspirates and disc tissue may indicate the proteins' involvement in closed lock. The hypothesis of this study is that TMJ discs and serum of patients with closed lock will contain an increased amount of fibronectin and decreased amount of collagen I. We analyzed a total of 8 diseased TMJ discs and 4 diseased synovial fluid aspirates. For our control samples, we assessed 5 synovial samples from healthy patients and control skin samples. Using an enzyme-linked immunosorbent assay allowed us to measure the total amount of fibronectin and collagen I in synovial aspirates. Furthermore, we used light microscopy to assess TMJ disc histology and collagen architecture in control skin samples. Lastly, using fluorescent staining, we examined fibronectin and collagen I expression in TMJ discs. We compared the fluorescent staining and light microscopy results of both proteins within each disc to confirm fibronectin and collagen I expression. Disc specimens with advanced morphologic pathology showed significant labeling for fibronectin in 3 of 3 cases and for collagen I in 4 of 4 cases. There was no considerable difference in detection of either fibronectin or collagen I in TMJ synovial aspirates from patients with advanced disc pathology compared with controls. The levels of fibronectin and collagen I in the TMJ disc and synovial fluid may be influenced by the stage of disease. The results did not provide a clear understanding of fibronectin and collagen I involvement with tissue repair in closed-lock cases. Detection of fibronectin fragments may provide more meaningful results.