Aspects of the glycome of endochondral ossification

Abstract

Comparatively little is known about the glycome (the set of glycans and glycoconjugates made by the cell, tissue or organism) of bone and cartilage. The glycome has a high-density coding capacity and is important in post-translational modification. Lectin histochemistry provides insights into the glycome and we applied this technique to an ectopic ossification site in human bronchial cartilages. Our results show that cartilage matrix at the site of erosion by chondroclasts has a limited but definite glycoprofile. In contrast, bone matrix does not express many lectin ligands. Chondroclasts have an extensive glycoprofile similar to that of, but not identical to, osteoclasts. N and O glycans are both expressed in the zone of presumptive mineralization and are relevant to that process. Bone trabecular lining cells communicate with osteocytes via intracanalicular processes and some lectin ligands were expressed by these three components. Mast cells and angiogenesis were prominent. Since cartilage normally resists vascular penetration by the secretion of antiangiogenesis factors it is postulated that the hypertrophic chondrocytes in the mineralization zone produce proteases which inhibit antiangiogenesis and facilitate angiogenesis by mast cells.