GLYCOCONJUGATE EXPRESSION OF CHONDROCYTES AND PERICHONDRIUM DURING HYALINE CARTILAGE DEVELOPMENT IN THE RAT

Alterations in the expression of glycoconjugate structures during cart ilage development in the chondrocranium, nasal skeleton, Meckel's cart ilage, limb buds, vertebral bodies and ribs were investigated comparat ively in 13 to 21-d-old rat embryos. The binding patterns of 24 biotin ylated lectins were analysed in serial sections and compared with resu lts obtained using histochemical methods. Proteoglycan distribution, a ssessed by conventional staining procedures, was not associated with l ectin binding sites. During early fetal development, hyaluronate conce ntrations were enhanced in areas of prospective chondrogenesis. With f ew exceptions, the lectins showed a general increase in intensity of b inding to mesenchymal structures. Con A (Canavalia ensiformis), DSL (D atura stramonium), and WGA (Triticum vulgare) displayed a ubiquitous d istribution of binding sites. After incubation with LCA (Lens culinari s), PSA (Pisum sativum), STL (Solanum tuberosum), and VAA (Viscum albu m), characteristic differences in binding intensity between focal area s of developing mesenchyme were seen. DBA (Dolichus biflorus), ECL (Er ythrina cristagalli), GSL I (Griffonia simplicifolia), LTA (Lotus tetr agonobolus), SJA (Saphora japonica), UEA I (Ulex europaeus) and VVL (V icia villosa) consistently failed to bind. During chondrogenesis a gen eral reduction of lectin staining was detected. In early stages of dev elopment GSL II (Griffonia simplicifolia) was a specific marker of the prechondral blastema in the viscerocranium. PNA (Arachis hypogaea) se lectively labelled the prevertebral blastema. In contrast, condensing mesenchyme of limb buds and viscerocranium was not stained. Using RCA (Ricinus communis), it was possible to distinguish chondroblasts from mature cells. All chondrocytes were stained by PSA, PHA-E, PHA-L (Phas eolus vulgaris E and L), and WGA, whereas Con A, LCA, and GSL II detec ted distinct differences between cartilage with different localisation s. Cartilage matrix was constantly negative. Applying GSL II it was po ssible to distinguish specific segments of the perichondrium. From our results we conclude that especially high mannose oligosaccharides are amplified during development. Terminal sialic acid molecules, branche d intralaminar glucose and/or mannose, respectively, internal galactos e-(beta 1,4)-N-acetylglucosamine sequences as well as galactose-(beta 1,3)-N-acetylgalactosamine sequences in a preterminal position are dif fusely distributed in mesenchymal tissue. In contrast, no evidence for the presence of terminal GlcNAc(beta 1,4)GlcNAc sequences and termina l alpha-fucosyl residues in (1,2) or (1,3)-linkage was obtained. Chond rogenesis appears to be correlated with a general reduction in the ext ent of expression of oligosaccharide structures. No proof of terminal N-acetylgalactosamine and alpha-galactose moieties was found, whereas our staining results document the expression of terminal beta-galactos e structures in restricted areas of the developing mesenchyme. Regulat ion of cartilage growth may correlate with the expression of accessibl e N-acetylglucosamine structures in circumscribed segments of the peri chondrium. The results suggest that the elucidation of the functional role of alterations in complex carbohydrate structures deserves attent ion, although the precise physiological significance of these findings remains to be established.