In situ localization of lectin‐binding glycoconjugates in the matrix of growth‐plate cartilage

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Abstract
In the distal hypertrophic zone of growth‐plate cartilage, the pericellular matrix surrounding individual chondrocytes and the territorial matrix uniting chondrocytes into columnar groups are invaded by metaphyseal endothelial cells prior to osteogenesis. In the present study, lectin‐binding glycoconjugates were analyzed in these two matrix compartments of growth‐plate cartilage from Yucatan swine. Nine lectin‐fluorescein conjugates were tested by a postembedment method on 1‐μm‐thick, nondecalcified, Epon‐embedded sections. Chondrocytes in all cellular zones were surrounded by a pericellular matrix which showed positive binding for peanut agglutinin (PNA), ricin agglutinin (RCA‐I), and soybean agglutinin (SBA). Binding by these lectins was sensitive to digestion with hyaluronidase, chondroitinase, and trypsin. Pericellular glyconconjugtes that bind RCA‐I and concanvalin A (CONA) after periodic acid oxidation, and which were sensitive to trypsin but not to chondroitinase or hyaluronidase, were present in the hypertrophic cell zone. Within the territorial matrix, binding of lectins specific for galactose, N‐acetylgalactosamine, and fucose showed gradients of intensity which became maximal at the last transverse septum. Lectin‐binding histochemistry more precisely differentiated the microheterogeneity of glycoconjugate distribution within these two matrix compartments than has been possible with other histochemical techniques. Lectin‐binding affinity is a potentially useful technique by which to isolate cartilage matrix macromolecules unique to specific cellular zones of the growth plate.