Lectin-binding histochemistry of normal and osteoarthritic cartilage tissue

Fluorescein isothiocyanate (FITC) labelled lectins were applied to study the topographical localisation and distribution of cellular as well as extracellular glycoconjugates in histological sections of normal and degenerative cartilage tissue. Using a biochemically induced model of osteoarthrosis (OA) in the knee joints of rats, the binding pattern of several lectins (wheat germ agglutinin (WGA), concanavalin A (Con A), Ulex europeus agglutinin I (UEA I), soybean agglutinin (SBA), and peanut agglutinin (PNA] in degenerative cartilage was compared with results obtained from normal healthy tissue. In response to osteoarthritic metabolic lesions the binding pattern of WGA revealed an increased cellular staining throughout the whole depth of the tissue which represents the compensatory activity of chondrocytes. The increased anabolic cell activity is maintained by enzymatic degradation of pericellular glycosaminoglycans. Osteoarthritic cartilage exposed positive fluorescence with labelled Con A demonstrating alterations in the composition of matrix glycoconjugates. The incubation of normal healthy cartilage tissue with UEA I, SBA, and PNA resulted in a completely negative staining pattern. In contrast, we could show that the affinity of UEA I to the extracellular matrix was high in degenerative cartilage indicating degradation of matrix macromolecules. The obtained data revealed a significant difference of the lectin-binding pattern between osteoarthritic and normal cartilage tissue. Therefore it can be concluded that lectins are useful histochemical tools to characterize alterations in the integrity of joint tissue by their specific binding patterns.