Abstract
The goal of the study was to characterize the transcriptome profiles of human ameloblasts and odontoblasts, evaluate molecular pathways and advance our knowledge of the human “dentome”. Laser capture microdissection was used to isolate odontoblasts and ameloblasts from human tooth buds (15-20week gestational age) from 4 fetuses. RNA was examined using Agilent 41k whole genome arrays at 2 different stages of enamel formation, presecretory and secretory. Probe detection was considered against the array negative control to control for background noise. Differential expression was examined using Significance Analysis of Microarrays (SAM) 4.0 between different cell types and developmental stages with a false discovery rate of 20%. Pathway analysis was conducted using Ingenuity Pathway Analysis software. We found that during primary tooth formation, odontoblasts expressed 14,802 genes, presecretory ameloblasts 15,179 genes and secretory ameloblasts 14,526 genes. Genes known to be active during tooth development for each cell type (eg COL1A1, AMELX) were shown to be expressed by our approach. Exploring further into the list of differentially expressed genes between the motile odontoblasts and non-motile presecretory ameloblasts we found several genes of interest that could be involved in cell movement (FN1, LUM, ASTN1). Furthermore, our analysis indicated that the Phospholipase C and ERK5 pathways, that are important for cell movement, were activated in the motile odontoblasts. In addition our pathway analysis identified WNT3A and TGFB1 as important upstream contributors. Recent studies implicate these genes in the development of Schimke immuno-osseous dysplasia. The utility of laser capture microdissection can be a valuable tool in the examination of specific tissues or cell populations present in human tooth buds. Advancing our knowledge of the human dentome and related molecular pathways provides new insights into the complex mechanisms regulating odontogenesis and biomineralization. This knowledge could prove useful in future studies of odontogenic related pathologies.
Highlights
Tooth formation or odontogenesis is strictly regulated at the molecular level and involves multiple complex processes including development of highly specialized cells that produce unique extracellular matrices and mineralized tissues including the hardest tissue in the body, enamel [1]
Using the negative control spots to eliminate background at 95% confidence level, we found that during tooth formation odontoblasts expressed 14,802 genes, pre-secretory ameloblast expresses 15,179 genes and secretory ameloblast expresses 14,526 genes
Examination of murine tooth development using many different approaches suggested that more than 300 genes are involved in the tooth formation [23]
Summary
Tooth formation or odontogenesis is strictly regulated at the molecular level and involves multiple complex processes including development of highly specialized cells that produce unique extracellular matrices and mineralized tissues including the hardest tissue in the body, enamel [1]. Dentin forming odontoblasts, on the other hand, continue to lay down matrix and remain functional throughout the life of a tooth [5]. These cells are able to react to stimuli and lay down reparative or reactionary dentin when the tooth experiences environmental insults. Many of the molecular mechanisms involved in tooth formation and the specific genes and interactions that control odontogenesis remain unknown
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