Microarray analysis of inflamed and healty dental pulp gene expression

Objective : In this study, inflamed and healthy dental pulp tissue samples were analyzed and compared in order to detect differences in gene expression. Methods: Dental pulp samples were obtained from extracted third molars. Four patients underwent extraction because of pain or high sensitivity due to deep caries (test group) and the remaining four patients (control group) underwent extraction for orthodontic reasons. The age range for the test group and the control group was 16-25 years. tRNA was isolated using SV Total RNA Isolation System. The results were analyzed by cluster, in order to identify a homogeneous set of genes. Data were analyzed by SAM and through ingenuity Pathway Analysis (IPA), which allows to identified the genes according to their location, the cellular components and to functions. Among the gene profiling we selected three genes, with functions in the inflammatory and immune response, CD40, IL1β and GPR35, whose expression was confirmed by RT-PCR. Results: The tRNA microarray revealed 993 genes profiles, 834 genes UP regulated and 159 DOWN regulated. CD40 was not statistically over-expressed compared to control samples. On the other hand IL1β and GPR35 were expressed at least four times compared to control samples. Those results were confirmed by RT-PCR analysis. Conclusion: Our results show how the different gene expression pattern could vary significantly between individual teeth. CD40 is a gene encoding for a protein which is a member of the TNF-receptor superfamily, and it is essential, working together with Il1β, in mediating a broad variety of immune and inflammatory responses. The GPR35 has an important role in immune modulation and control the release of chemotactic cytokines. The discrepancy between GPR35, IL1β and above all CD40 may reflect either the differences in the state of pulpitis, or the complex regulation of the immunitary system in pulp inflammation.