BIOCHEMISTRY AND MINERALIZATION OF TOOTH CEMENTUM

点击翻译按钮获取中文摘要

These studies are directed towards obtaining a basic understanding of the structure and organization of the extracellular matrix components of the bovine tooth cementum and their potential role(s) in mineralization. The detailed structure of the most abundant organic component, type I collagen, will be studied by quantifying the molecular distribution of the covalent intermolecular cross-links and their precursor aldehydes in the collagen fibrils. This will be performed by quantitative analysis of these compounds and determination of their molecular loci within the fibril by isolating these peptides from the NaB3H4-reduced tissue. Based on the data, we can obtain information concerning the specific three-dimensional structure of collagen fibrils of cementum which is essential for stabilization of the tissue and plays an important role in the tissue's mineralization. These data will be compared with those of dentin and alveolar bone obtained from the same teeth and jaws. We will also isolate and study the structure of the major phosphoproteins of this tissue, potential nucleators for mineralization, present in EDTA-soluble as well as insoluble fractions. The phosphoproteins in the latter fraction are strongly associated with mineral and insoluble collagen fibrils. The molecular origin of the newly described phosphoprotein-associated bifunctional cross-links, histidinoalanine and lysinoalanine, and their functional significance in molecular organization will be pursued by isolating the cross-linked peptides and identifying the molecular loci of these compounds within the peptides. In addition, the major proteoglycans, another anionic component, will be isolated and analyzed by agarose- polyacrylamide gel electrophoresis and subjected to detailed biochemical/immunochemical analysis with the large panel of monoclonal antibodies directed against epitopes present on connective tissue proteoglycans. Immunohistochemical techniques will also be used to examine their tissue distribution and their potential interaction with collagen fibrillar network in relation to mineralization of cementum. Finally, the induction rates, growth rates and localization of mineral induced by those anionic proteins in cementum (phosphoproteins and proteoglycans) immobilized on insoluble collagen fibrils will be studied and compared on TEM level. This type of study will provide information concerning the involvement of these macromolecules and their interactions with collagen in the mineralization process.