Why Enamel Cells?
Dental enamel cells offer many benefits as a research model for investigating biomedically important aspects of calcium cellular biology including:
- bulk calcium handling
- toxicity avoidance
- transepithelial calcium transport
- biomineralization
What dental enamel cells do
- Enamel cells produce tooth enamel, the most highly calcified tissue (40% calcium by weight)
- The principal enamel cell type, termed 'ameloblast', forms a tight epithelial monolayer covering the developing tooth surface
- Accessory epithelial cells separate the ameloblast layer from the
adjacent vascularised connective tissue which provides sustenance
(and calcium) to the enamel epithelium [see Figure]
Functionally distinct developmental stages
- Enamel is produced in two major stages termed secretion and maturation. First a protein-rich extracellular matrix is secreted on top of dentine to form a template layer of immature enamel. Second the soft enamel matrix is highly calcified and dehydrated to produce steel-hard mature enamel
- Enamel cells undergo distinct developmental phases of cytodifferentiation, matrix secretion, and maturation and then finally disappear by physiological cell death ('apoptosis') before tooth eruption
- Protein synthesis and secretion is the principal cell function during secretion phase. Calcium transport is the dominant function during maturation but the cells are also involved in deproteinating and dehydrating the extracellular enamel matrix
- Calcium has important roles in cell differentiation, protein secretion and cell death besides its central role in enamel mineralization. Accordingly we anticipated that distinct calcium-oriented molecular phenotypes would accompany the major stages of enamel cell development
Elongate cell morphology
- Ameloblasts are elongate and polarised cells with distinct morphologies
at each of the major developmental stages [see Figure]
- These features provide an excellent opportunity to elucidate the topography and function of calcium-handling machinery in enamel cells
Calcium-handling proteins are developmentally regulated and hyperabundant
- We have found that enamel cells contain an unusually high abundance of intracellular calcium homeostasis proteins, consistent with their calcium-oriented biology. It appears that enamel epithelium could surpass brain as the richest tissue expressing multiple calcium-binding proteins
- Our findings show that distinct 'calcium-binding protein fingerprints' exist for the major developmental stages of enamel formation. Already this has provided several novel insights to structure-function associations
- All calcium-handling proteins characterised in enamel cells are
structurally identical to those expressed in other cell types (see ToothPrint
database).
Accordingly findings from enamel cells will likely be of broader biological
relevance [see review]
A scarce tissue source
- Human enamel epithelium is not readily available and no authentic enamel cell lines have been reported for any species
- Rat and mouse enamel formation has been most comprehensively characterised and appears to be a good model for human. However murine enamel epithelium is a very small tissue. We have found that biochemical investigations of rat and mouse enamel cells are feasible subject to use of appropriately high sensitivity and microscale approaches [see review]
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