Ultrastructural distribution of acidic glycosaminoglycans associated with matrix vesicle-mediated calcification in mouse progenitor predentine

Abstract

The ultrastructural localization of acidic glycosaminoglycans, presumed to be proteoglycans, was examined during initial matrix vesicle-mediated calcification in dentine, by using ruthenium red (RR) staining, high iron diamine thiocarbohydrazide silver proteinate (HID-TCH-SP) staining, and an enzymatic digestion method. Progenitor predentine 2-10 micron width of developing mouse molar tooth germs was used throughout the present study. The outer surface membrane of the intact matrix vesicles had a strong affinity for RR. The RR positive materials appeared beaded and extended perpendicularly from the vesicle membrane. They tended to disappear with the disruption of the vesicular membrane, which resulted from overextension due to needle-like, crystal-like structures. The HID-TCH-SP stain deposits, approximately 10 nm in diameter, were densely distributed around the intact matrix vesicles, though few were found inside them. Some matrix vesicles that were presumably disrupted, however, contained smaller stain deposits. On the outer surface membrane of the disrupted vesicles, HID-TCH-SP stain deposits were fewer in number. The results obtained from enzymatic degradation studies showed that the anionic materials on the outer surface membrane of the matrix vesicles were represented by chondroitin-4-sulfate and/or chondroitin-6-sulfate. We suggest that chondroitin sulfates attached to the outer leaflet of the vesicular membrane play an important role during the incipient stage of the matrix vesicle-mediated calcification process.

Structure and organization of odontoblasts

“…3a). They have been described as the site of initial mineralization (Bernard, 1972;Larsson and Bloom, 1973;Katchburian, 1973;Goldberg and Septier, 1983;Ozawa and Yamamoto, 1983;Bonucci, 1984;Kogaya and Furuhashi, 1985). In cartilage and bone, as well as in dentin, matrix vesicle-induced mineral- ization is noted only in the initial early phase of matrix dentin, like those in cartilagenous growth plates and at mineralization (Slavkin et al, 1972;Kardos and Hub-sites of initial intramembranous bone formation bard, 1982; Takagi et al, 1989).…”

“…Matrix vesicles also contain proteoglycans that can bind calcium ions (Kogaya and Furuhashi, 1985;Takagi et al, 1989). EDX analysis also shows that the highest peak for sulfur is in matrix vesicles, indicating the presence of proteoglycans (Takagi et al, 1989).…”

The mineralization of mantle dentine and of circumpulpal dentine in the rat: an ultrastructural and element-analytical study

“…In case of mantle dentine the mineralization is initiated by matrix vesicles (Bonucci 1984;Kogaya and Furuhashi 1985), whereas the mineralization of circumpulpal dentine is mediated by the apposition of concentric layers of mineralizable matrix forming the socalled calcospherites or mineral globuli, which grow and eventually coalesce with neighbouring globuli. However, Boyde and Reith (1969) could not find such calcospherites in the circumpulpal dentine of rat molar crowns.…”

Proteolytic Enzymes in Otosclerosis

“…The role of acidic glucosaminoglycans in the bone matrix polymerization-depolymerization process has not yet received adequate attention. For example, an increased cathep sin D activity means a higher risk of the pro duction of acidic glucosaminoglycans in an amount sufficient to cause advanced cal cium binding [9,11], resulting in a distur bance of the mineralization (otosclerotic foci contain low concentrations of metal ions: Ca, Mg) [16]. On the other hand, cathepsin D is strongly involved in the procollagencollagen post-translational processing.…”