Characterization of glycoconjugate expression during development of Meckel's cartilage in the rat

The staining patterns of 24 biotinylated lectins were analyzed in serial sections of the mandible of 13- to 21-day-old rat embryos by means of the avidin-biotin-peroxidase method. A ubiquitous distribution of binding sites was demonstrated after incubation with Con A (Canavalia ensiformis), DSL (Datura stramonium; except bone matrix), and WGA (Triticum vulgare). ECL (Erythrina cristagalli), GSL I (Griffonia simplicifolia), SJA (Saphora japonica), VVL (Vicia villosa), DBA (Dolichus biflorus), UEA I (Ulex europeus), and LTA (Lotus tetragonobolus) were constantly negative. In early stages of development, GSL II (Griffonia simplicifolia II) was a selective marker of prechondral blastema. In contrast, PNA (Arachis hypogaea) did not stain condensing mesenchyme. During chondrogenesis of Meckels's cartilage a general decrease of lectin binding was observed. Mature cartilage matrix was constantly negative. Chondrocytes were marked by the lectins PSA (Pisum sativum), WGA, PHA-E, and PHA-L (Phaseolus vulgaris E and L). A strong GSL II binding was restricted to the mesial-superior region of the perichondrium. In later stages, several lectins revealed significant differences between preskeletal ("central") areas and the remaining ("peripheral") mesenchyme. A clear binding reaction was noted in central regions by applying LEA (Lycopersicon esculentum) and STL (Solanum tuberosum), while the peripheral tissue was only faintly stained. Developing bone was specifically marked by succinylated WGA (sWGA). The lectins LCA (Lens culinaris) and RCA (Ricinus communis) bound to fibers and extracellular matrix of the connective tissue. Jacalin (Artocarpus integrifolia) and SBA (Glycine max) binding sites were found in macrophages. Affinity of VAA (Viscum album) increased parallel with maturation of endothelial cells. Specific lectin-binding patterns revealed no correlation with the distribution of glycosaminoglycans. The results demonstrate a general reduction of oligosaccharide structures during development of Meckel's cartilage. From our observations we conclude that intralaminar glucose and/or mannose sequences as well as terminal sialic acid molecules are ubiquitously distributed, while terminal alpha-fucose was constantly negative. Lectin-binding patterns of macrophages may reflect the presence of specifically linked terminal galactose. Our findings indicate that oligosaccharides terminating in N-acetylglucosamine are bone-specific. The significance of the restricted staining of the perichondrium by GSL II remains to be elucidated.