Profiling and bioinformatics analysis of differentially expressed circular RNAs in human intervertebral disc degeneration

The functional changes of nucleus pulposus (NP) cells are considered to be the initiating factors of intervertebral disc degeneration (IDD), and the differentially expressed circRNAs in NP cells may play an important role in the process of IDD. To identify circular RNAs (circRNAs) associated with human IDD, we isolated the NP cells from human degenerated and non-degenerated intervertebral disc and identified NP cells by microscopy and cell proliferation. CircRNA microarray expression profiles were obtained from NP cells of degenerated and non-degenerated intervertebral disc and further validated by quantitative reverse transcription PCR (qRT-PCR). The expression data were analyzed by bioinformatics. Microarray analysis identified 7294 circRNAs differentially expressed in degenerated human IDD NP cells. Among them, 3724 circRNAs were up-regulated and 3570 circRNAs were down-regulated by more than 2 folds. After validating by qRT-PCR, we predicted the possible miRNAs of the top dysregulated circRNAs using TargetScan, and miRanda. Furthermore, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the most modulated circRNAs regulate the viability, degradation, apoptosis and oxidative stress in NP cells, and the possible mechanism underlying IDD was discussed. These results revealed that circRNAs may play a role in IDD and might be a promising candidate molecular target for gene therapy.