We examined the hypothesis that maturation ameloblasts degrade enamel matrix in a manner analogous to bone matrix degradation mediated by osteoclasts. Thus, we assessed the distribution of the cation-independent mannose 6-phosphate receptor (MRP) and lysosomal enzymes in the enamel organ and in the alveolar bone surrounding the rat incisor. The MPR was observed on the ruffled border of the ruffle-ended ameloblast (RA) but not on the distal call membrane of the smooth-ended ameloblast (SA), although both cells demonstrated strong immunoreactivity in the Golgi region. Immunogold localization of cathepsin B showed more labelling on the distal end of RA than SA, indicating that the source of the extracellular cathepsin B was likely the RA. Since MPR and lysosomal enzymes were also detected on the ruffled border of osteoclasts, our immunocytochemical approach provides strong evidence for a similarity between the maturation of enamel, as mediated by RAs, and bone matrix degradation by osteoclasts. / We also examined the nature of the basement membrane-like structure between maturation ameloblasts and the surface of enamel, and the possible role it may play in the maturation of enamel. We used high resolution electron microscopy combined with immunohistochemical localization of laminin, heparan sulfate proteoglycan (HSPG) and type IV collagen. Our results indicated that this structure was a highly specialized basement membrane unusually rich in HSPG. The cord network was replaced by a network of fine filaments, identified as core filaments of cords containing type IV collagen. A proposed role for this basement membrane is likely to be mediation of firm attachment of maturation ameloblasts to the surface of the enamel. / Since integrins play an essential role in cell-substratum interactions, we investigated the distribution of the integrin beta1 subunit on osteoclasts and ameloblasts. Immunocytochemistry showed significant concentrations of beta1 integrin at the ruffled border of osteoclasts, and negligible staining at the sealing zone. Since beta1 integrin localization was higher in the RA than the SA, we suggest that beta1 may have a role in the cell modulations. This role is likely to be recognition of extracellular matrix components and consequent interaction of RA with that matrix. The findings that the ruffled border of both RAs and osteoclasts display the most intense labelling for beta1 integrin, further supports our hypothesis that these cells are functionally similar.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.34498 |
| Date | January 1997 |
| Creators | Al Kawas, Sausan. |
| Contributors | Warshawsky, H. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Faculty of Dentistry) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001601586, proquestno: NQ36951, Theses scanned by UMI/ProQuest. |
Page generated in 0.0018 seconds