Lectin binding properties of bovine resting cartilage

The aim of this study was to evaluate the differential localisation of glycoconjugates of bovine hyaline cartilage matrix by lectin histochemistry, to compare the results of lectin histochemistry with those that can be obtained in the same tissue with PAS and alcian blue. Frozen and paraffin sections were stained with HE, PAS and alcian blue (pH 1.8). Alcian blue staining was carried out also after 1 and 24 hour digestion with bovine testicular hyaluronidase. Peroxidase conjugated WGA, PNA and RS lectins were tested on all sections before and after 1 hour digestion with bovine testicular hyaluronidase. The results show that all the lectins used in this study react with sugars linked to proteoglycans of territorial matrix, the reaction being increased in territorial, and induced in interterritorial matrix by 1 hour hyaluronidase digestion. Alcian blue at pH 1.8 and PAS were complementary, the former staining territorial, and the latter interterritorial matrix. After 1 hour hyaluronidase digestion, alcian blue stained also the interterritorial matrix. These results suggest that lectins react with low molecular weight proteoglycans and that short hyaluronidase digestion causes depolymerization of high molecular weight proteoglycans without loss of their glucidic components, allowing: a) penetration of alcian blue molecules into the macromolecular proteoglycan network; b) an increase of sugar residuals available for lectin histochemistry. Lectin histochemistry can be useful for differential localisation of glycoconjugates in bovine cartilage, especially if associated with short hyaluronidase digestion and conventional histochemical techniques.