Analysis of microRNA expression in organ of Corti in neonatal and adult rats

ObjectiveTo characterize microRNA (miRNA) expression profile in microdissected auditory epithelia from the Corti’s Organ in new born and adult rats.MethodsThe TaqMan® MicroRNA Arrays were used to identify expression of microRNA in the new born and adult groups. GO analysis was applied to analyze the main function of the differential expression genes according to the Gene Ontology which is the key functional classification of NCBI. Similarly, Pathway analysis was used to find out the significant pathway of the differential genes according to KEGG, Biocarta and Reatome.ResultsIncreased expression was seen in 16 miRNAs in mature rat compared to new born rats, with increased folding ranging from 17 to 600 folds. Expression levels in 2 miRNAs were reduced in mature rats, namely rno–miR–29c and rno–miR–29a. The high–enrichment GOs targeted by over–expressed miRNAs were negative regulation of epithelial cell differentiation, common–partner SMAD protein phosphorylation, mesenchymal–epithelial cell signaling, regulation of transforming growth factor beta2 production, etc. Functional analysis of miRNAs by KEGG revealed that 19 signal transduction pathways were upregulated and 14 were downregulated.ConclusionsThe difference in miRNA expression patterns in the organ of Corti between neonatal and adult rats may be closely related to maturation of the organ of Corti and loss of proliferative capacity of inner ear hair cells, and TGFß signaling may play an important role in hair cells regeneration.