[Purification and partial characterization of proteoglycans of bovine articular disc]

The temporomandibular joint (TMJ) provides articulation between the jaw and cranium, which associate with jaw movement and growth. The articular disc of TMJ separates the surfaces of the temporal bone and mandibular condyle. An understanding of its biochemical composition is very important, because the TMJ exhibits variety of pathological derangements including anterior displacement of disc. Proteoglycan (PG), major component of the disc, is one of the non-collagenous protein, which relates to the tissue viscoelasticity and physiological stress. This paper describe the isolation and characterization of proteoglycans from bovine articular disc. Articular discs obtained from bovine were cutted into small pieces. They were then extracted with 0.05 M Tris-HCl buffer, pH 7.4, containing 4 M guanidium HCl (Gdm HCl) and protease inhibitors for 12h at 4 degrees C. PGs were isolated by chromatography of Gdm HCl extract. The sequential chromatography steps consisted of ion-exchange chromatography on DEAE-Sephacel in 4 M Urea, rechromatography of FPLC Superose 6 in 4 M Urea. The two forms of PGs (on SDS-PAGE, Mr = 120-130 K and 200 K) were isolated by these steps. The core protein of two forms of PGs liberated by chondroitinase ABC were shown by SDS-PAGE as Mr = 58,000. Also the glycosaminoglycan (GAG) chains of PGs liberated by papain digestion were shown by SDS-PAGE as Mr = 70-80 K. Moreover GAG chains of PGs were consisted of chondroitin sulfate A, C and dermatan sulfate. Antisera raised against bovine periodontal ligament PGs cross-react with core protein of disc PGs (obtained after chondroitinase digestion), but not with bone small PG. These data suggested that two forms of PGs have a identical core protein. However 120-130 K PG might have one GAG chain, and 200 K PG might have two GAG chains. These small PGs were different from bone small PG, especially dermatan sulfate contents, which may be important in disc tissue.