Immunohistochemical localization of articular cartilage proteoglycan and link protein in situ using monoclonal antibodies and lectin-binding methods

Abstract

Lectins have specificity for certain carbohydrate structures in macromolecules. Lectins are, therefore, useful histochemical tools for demonstrating the composition and localization of components of connective tissue matrices, such as articular cartilage. In order to assess the significance of observed lectin-binding patterns, experiments were performed in which monoclonal antibodies against chondroitin sulphate- and keratan sulphate-containing proteoglycans and link proteins were applied to sections of bovine articular cartilage after enzymatic digestion with chondroitinase ABC and keratanase. The following conclusions were made: (1) Binding of peanut agglutinin (PNA) in the interterritorial matrix predominantly indicates the presence of keratan sulphate, but may also detect O-linked oligosaccharides of proteoglycans. (2) In normal cartilage wheat germ agglutinin (WGA) binds nearly exclusively to keratan sulphate. In cartilage degraded with chondroitinase ABC and keratanase this lectin may also detect carbohydrates in link protein due to enhanced accessibility. Binding of WGA to O-linked oligosaccharides may eventually occur. (3) In enzymatically digested cartilage matrix, staining with soybean agglutinin (SBA) may be due to link protein, but not to chondroitin sulphate, because specific breakdown of the glycosaminoglycan chain is required for binding of SBA. (4) Ulex europaeus agglutinin I (UEA I) binding sites are only detectable in digested cartilage matrix.

Keratan sulphate is present in developing chick skin in vivo where it could constitute a barrier to advancing neurites as observed in vitro

“…It may inhibit neural crest cell migration (Perris et al, 1991) and can inhibit cell adhesion and neurite outgrowth in vitro (Cole and McCabe, 1991;Smith-Thomas et al, 1994). It thus shows similar properties to CS and furthermore could be a binding site for PNA (Hoedt-Schmidt et al, 1993).…”

Overexpression of Soybean Agglutinin Binding Sites in Hyperplastic Dental Epithelium in Osteopetrotic (OP/OP) Mice.

“…Furthermore, a cell surface proteoglycan that bears both chondroitin and heparan sulfate chains (19) is transiently lost when epithelia change their shape and is transiently expressed by mesenchymal cells undergoing morphogenetic tissue interactions (24,25). In this context, since specific breakdown of chondroitin sulfate chain is required for binding of SBA (6), the overexpression of SBA binding sites on the cell membrane of the hyperplastic dental epithelium may be interpreted as resulting from an alteration or degradation of carbohydrate moieties of proteoglycans (and possibly those of glycolipids and glycoproteins) on such cell surface. This is probably due secondary to pathological aberrations residing in the dento-skeletal microenvironment of OP/OP mice.…”

Identity of Urinary Trypsin Inhibitor-binding Protein to Link Protein

“…Our previous finding demonstrated that UTI may be able to bind hyaluronic acid via the LP molecule since UTI fails to directly bind hyaluronic acid (7). Link protein is present on a wide variety of cells, including skin and fibroblasts (8), chondrocytes (9), chondrosarcoma cells (10 -13), synovial cells (14), aorta (15), trachea (16), and hepatocytes (17)(18)(19). Characteristics of the LP molecule have been studied by a number of different laboratories (20,21), and it has been shown to mediate the interaction between proteoglycans and hyaluronic acid (22,23), a characteristic that may allow it to demonstrate pericellular matrix formation and stabilization (hyaluronic acid-rich matrix formation) (17).…”