Chondrons from articular cartilage. (IV). Immunolocalization of proteoglycan epitopes in isolated canine tibial chondrons.

Abstract

Chondrons have recently been extracted from adult articular cartilages and techniques developed to study their structure and composition in isolation. This study introduces methods to immobilize isolated canine chondrons in thin layers of agarose gel for immunohistochemistry and future in vitro studies. An antibody to Type VI collagen which stained the chondron in suspension was used to successfully validate the system and its feasibility for immunoelectron microscopy. Monoclonal and polyclonal antibodies to a variety of epitopes on the proteoglycan molecule were tested on fresh and fixed plugs cored from chondron-agarose gels. Plugs were immunolabeled with peroxidase-diaminobenzidine before or after digestion with testicular hyaluronidase or chondroitinase ABC. Trypsin/chymotrypsin were used to challenge epitopes of the core protein. The results indicate that epitopes to keratan sulfate, chondroitin sulfate, hyaluronate binding region, and core protein are localized in the chondron. Consistent staining was found in the tail and interconnecting segments between chondrons, whereas staining of the pericellular matrix and capsule adjacent to the chondrocyte varied according to the enzyme pre-treatment employed. We conclude that isolated chondrons are rich in proteoglycan monomer, which is particularly concentrated in the tail and interconnecting segments of the chondron where it could function to protect and stabilize the chondrocyte.

Growth factor regulation of chondrocyte integrins. Differential effects of insulin‐like growth factor 1 and transforming growth factor β on α1β1 integrin expression and chondrocyte adhesion to type VI collagen

“…The functional consequence of decreased alpl-mediated adhesion of chondrocytes to type VI collagen seen in TGFP-treated cells is not known, but it could potentially have a negative impact on assembly and maintenance of the pericellular matrix, which is rich in type VI collagen (13). The finding that an antibody to the a1 integrin subunit blocked 75% of the adhesion of chondrocytes to type VI collagen indicates that alp1 serves as a primary chondrocyte receptor for type VI collagen.…”

Alterations in sulfated chondroitin glycosaminoglycans following controlled cortical impact injury in mice

“…Similar to the MAB2030, the immunogen was a partially purified preparation of articular cartilage treated with cABC (Poole et al, 1991). MAB2035 does not react with native proteoglycans, isolated-4-sulfate, or chondroitin-6-sulfate chains, or with tetrasaccharides or disaccharides of chondroitin-4-sulfate (Poole et al, 1991).…”

“…Similar to the MAB2030, the immunogen was a partially purified preparation of articular cartilage treated with cABC (Poole et al, 1991). MAB2035 does not react with native proteoglycans, isolated-4-sulfate, or chondroitin-6-sulfate chains, or with tetrasaccharides or disaccharides of chondroitin-4-sulfate (Poole et al, 1991). This antibody has also been used to detect the activity of cABC expressed in adult bone marrow mononuclear cells transplanted into CNS injury site (Coulson-Thomas et al, 2008).…”

Discrimination of meniscal cell phenotypes using gene expression profiles

“…Versican has been suggested to play a role in cell adhesion, migration and proliferation (Wight, 2002) and thus may be more dependent on the development stage of the tissue, as shown in a study comparing skeletally immature and mature rabbits (Hellio Le Graverand et al, 1999). Collagen VI, a main constituent of the pericellular matrix (Poole et al, 1988;McDevitt and Webber, 1990), exhibits higher expression in the inner region, which can be attributed to the fact that the more fi broblast-like cells of the outer region lack an organized pericellular matrix (McDevitt et al, 2002).…”