Abstract

Background: Tooth eruption requires the chronological expression of a series of genes in the dental follicle (DF). Protein kinase A (PKA) is a major phosphorylation pathway in the cells, and may regulate
the expression of tooth eruption genes.
Material/Methods: In vivo, we studied the expression of the regulatory (R) and catalytic (C) subunits of PKA in the DF of newborn rats. In vitro, dental follicle cells (DFC) were treated with a specific PKA
inhibitor, and then the gene expression of monocyte chemotactic protein-1 (MCP-1), colonystimulating factor-1 (CSF-1) and parathyroid hormone-related protein receptor (PTHrP-R) was determined. Cells also were treated with either phorbol-12-myristate-13-acetate or dibutyryl- cAMP, and the gene expression for RIα, RIβ, RIIα and RIIβ of PKA was examined.
Results: The results indicate that RIα of PKA is the predominant subunit in the DF with steady expression from days 1 to 11 postnatally. In contrast, expression of the RIβ, RIIα, RIIβ subunits
are progressively reduced over this time period. However, there is a sharp decline of RIβ expression at postnatal day 3. The expression of the C subunits slightly decreases at days 3 and 5 with a greater decrease at day 7 postnatally. The specific PKA inhibitor reduces MCP-
1 gene expression and translation, as well as moderately reducing CSF-1 and PTHrP-R expression.
Conclusions: The reduction of the RIβ subunit in the rat DF at day 3 may result in an elevated PKA activity to trigger the maximal burst of gene expression of MCP-1 and CSF-1 seen at this time.

Keywords: Animals, Newborn, Cells, Cultured, Chemokine CCL2 - genetics, Chemokine CCL2 - metabolism, Cyclic AMP-Dependent Protein Kinases - chemistry, Cyclic AMP-Dependent Protein Kinases - genetics, Cyclic AMP-Dependent Protein Kinases - metabolism, Dental Sac - growth & development, Dental Sac - metabolism, Gene Expression Regulation, Developmental, Macrophage Colony-Stimulating Factor - genetics, Macrophage Colony-Stimulating Factor - metabolism, Protein Subunits, Receptor, Parathyroid Hormone, Type 1 - genetics, Receptor, Parathyroid Hormone, Type 1 - metabolism, Tooth Eruption - genetics