Studies on matrix components relevant to structure and function of the temporomandibular joint

Abstract

Proteoglycans (PGs), or their component glycosaminoglycan (GAG) chains, have long been recognized as small in quantity but as significant components for many connective tissues. The temporomandibular joint (TMJ) disc and synovial fluid were rarely investigated in this regard. This research was aimed at the biochemical analysis of the composition of collagen, GAGs and PGs in the normal human and porcine TMJ discs, and of PGs in the synovial fluid. 1. The collagen type analysis by gel electrophoresis revealed that the human and porcine TMJ discs were composed only of type I collagen. 2. The human TMJ disc contained 69.9% chondroitin sulfate, 24.5% dermatan sulfate, 5.6% hyaluronic acid and a trace amount of keratan sulfate, and the porcine TMJ disc, 5.8%, 91.4%, 2.8% and a trace amount, respectively. Immunohistochemical staining of the functional parts of the TMJ disc showed a universal distribution of these GAGs. 3. PGs were extracted from the TMJ disc with 4 M guanidine chloride and separated by ion-exchange and gel-filtration chromatography. A high molecular weight PG resembling the cartilage PG and two low molecular weight PGs having a core protein of Mr 40 K were isolated. 4. PGs suggested to be derived from the matrix of other tissues were found in the abnormal human synovial fluid. From these results it was suggested that the TMJ disc was thought not to be fibrocartilage but a fibrous tissue adapted against to the compressive and tensile force.