Differential Expression of MicroRNAs in Normal and Inflamed Human Pulps

Introduction: MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression via posttranscriptional repression. They are critical to normal cellular function, and bioinformatic predictions indicate that at least one third of all messenger RNAs might be regulated by miRNAs. Although both the innate and adaptive immune responses are known to be regulated by miRNAs, their role in regulating endodontic disease has yet to be explored. The purpose of this study was to examine the differential expression of miRNAs in normal and inflamed human dental pulps and to explore their functional gene targets. Methods: After obtaining informed consent, we collected normal and inflamed human pulps (N = 30). Microarray and molecular biology techniques were then used for gene profiling and identifying functional gene targets. Results: Of the 335 human miRNAs identified in the pulp tissues, 3 miRNAs, miR-150(star), miR-584, and miR-766, were significantly up-regulated in inflamed pulps as compared with normal pulps (P < .003). Thirty-three miRNAs were down-regulated in the inflamed pulps (P < .003). The false discovery rate for these findings is estimated to be approximately 5%. The potential gene targets for these miRNAs include proinflammatory cytokines as well as other key mediators of the immune and inflammatory response to infection. Conclusions: Our data identify differential expression of miRNAs in healthy and diseased human dental pulps. These findings highlight the intricate and specific roles of miRNA in inflammation and immunity, both of which are key aspects of pulpal pathology. (J Endod 2012;38:746-752)