Comparative Gene Expression Analysis of the Coronal Pulp and Apical Pulp Complex in Human Immature Teeth

• This study compared the gene expression profiles of human coronal pulp (CP) and the apical pulp complex (APC) with the aim of elucidating whether any differences found can explain differences in their functions.
• The apical papilla and covering follicular tissue were inseparably related to each other and function as a unit.
• The expression levels of genes related to dentin mineralization, neurogenesis, and neurotransmission were higher in the CP in human immature teeth, whereas those of immune-related and tooth development–related genes were higher in the APC.

IntroductionThis study determined the gene expression profiles of the human coronal pulp (CP) and apical pulp complex (APC) with the aim of explaining differences in their functions.MethodsTotal RNA was isolated from the CP and APC, and gene expression was analyzed using complementary DNA microarray technology. Gene ontology analysis was used to classify the biological function. Quantitative reverse-transcription polymerase chain reaction and immunohistochemical staining were performed to verify microarray data.ResultsIn the microarray analyses, expression increases of at least 2-fold were present in 125 genes in the APC and 139 genes in the CP out of a total of 33,297 genes. Gene ontology class processes found more genes related to immune responses, cell growth and maintenance, and cell adhesion in the APC, whereas transport and neurogenesis genes predominated in the CP. Quantitative reverse-transcription polymerase chain reaction and immunohistochemical staining confirmed the microarray results, with DMP1, CALB1, and GABRB1 strongly expressed in the CP, whereas SMOC2, SHH, BARX1, CX3CR1, SPP1, COL XII, and LAMC2 were strongly expressed in the APC.ConclusionsThe expression levels of genes related to dentin mineralization, neurogenesis, and neurotransmission are higher in the CP in human immature teeth, whereas those of immune-related and tooth development–related genes are higher in the APC.