Expression profiling of human pulp tissue and odontoblasts <em>in vivo</em> and <em>in vitro</em>
Pääkkönen, Virve (2009-01-20)
Dentin forms the hard tissue portion of the dentin-pulp complex, while the dental pulp is soft connective tissue that retains the vitality of the dentin. Odontoblasts form the outermost cell layer of pulp and play a central role during dentin formation by producing and mineralizing the dentin matrix. The understanding of the defensive reactions in the dentin-pulp complex is limited. Information about the transcriptome and proteome of pulp tissue and odontoblasts would facilitate understanding of their functions during health and disease. The aim of this study was to investigate the expression profiles of human pulp tissue and odontoblasts in vivo and in vitro using large-scale expression analysis methods. Also, the suitability of these methods in pulp biological research in vivo and in vitro was evaluated.
cDNA microarray revealed only minor variation and 2-D electrophoresis combined with mass spectrometry revealed no differences between healthy and carious teeth pulp tissue in vivo. The effect of transforming growth factor β1 (TGF-β1) on pulp and odontoblasts was studied in vitro using oligonucleotide-based microarrays, and marked changes in the transcriptome were revealed, especially in the expression of chemokine- and cytokine-related genes. Transiently increased interleukin expression was confirmed at the protein level by antibody array.
DNA microarray analysis of native pulp tissue and odontoblasts was used to search for potential odontoblast markers. Only one gene related to extracellular matrix organization and biogenesis, matrilin 4, and two expressed sequence tags (ESTs), which represent transcribed sequences encoding possibly unknown genes, were identified in odontoblasts but not in pulp. Analysis of mature native odontoblasts and cultured odontoblast-like cells by DNA microarray revealed a high similarity (84%) between native and cultured cells. Also, differential expression levels of selected neuronal proteins were observed and confirmed at the mRNA and protein levels.
In conclusion, microarray is a powerful tool for pulp biology, especially for in vitro studies. TGF-β1 was revealed as a potent regulator of proinflammatory responses in the dentin–pulp complex. In addition, several potential odontoblast markers were identified by microarray, and the similarity of cultured odontoblast-like cells used in the study with native odontoblasts was confirmed.
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