Background Differential expression of miRNAs and altered regulation of their target genes has been shown to contribute to pathophysiology of many diseases. In addition, circulating miRNAs may serve as diagnostic and/or prognostic biomarkers.
Objectives To analyse a large set of cell-free circulating miRNAs in patients with axial spondyloarthritis (AxSpA) and to investigate their relationship with spinal involvement.
Methods Total RNA was isolated using phenol-chloroform extraction from plasma of 5 healthy controls (HC), 5 patients with non-radiographic AxSpA (nr-AxSpA) and 10 patients with radiographic AxSpA (5 patients with radiographic sacroiliitis and no spinal involvement; 5 patients with the presence of syndesmophytes). Equal amount of RNA was used for reverse transcription. MiRNAs were analysed using TaqMan® Low Density Array (Applied Biosystems). dCt method was used for relative quantification as follows: dCt = Ct(miRNA) − Ct(array average). Average of dCt for single miRNA was used for further x-fold calculation.
Results Out of total 760 miRNAs, 162 miRNAs were detected in a group of HC, 156 miRNAs in patients with nr-AxSpA and 110 in patients with radiographic AxSpA. All patients with AxSpA had at least 2-fold lower levels of 56 miRNAs, e.g. miR-27a, miR-146a and miR-181a (8 of them at least 5-fold), while showed at least 2-fold higher levels of 4 miRNAs when compared with HC. In patients with radiographic AxSpA, 75 miRNAs were of at least 2-fold lower levels (14 of them at least 5-fold), while 3 miRNAs were of at least 2-fold higher levels in comparison with the group of nr-AxSpA patients and HC.
Following changes were observed in patients with AxSpA with a progressing degree of spinal involvement: In patients with nr-AxSpA, 18 miRNAs showed at least 2-fold decrease (3 of them at least 5-fold), while 9 miRNAs showed at least 2-fold increase in comparison with HC. In patients with radiographic AxSpA with no spinal involvement, 71 miRNAs showed at least 2-fold decrease (13 of them at least 5-fold), while 6 miRNAs showed at least 2-fold increase in comparison with nr-AxSpA. In patients with radiographic AxSpA with a presence of syndesmophytes, 6 miRNAs showed at least 2-fold decrease, while 15 miRNAs showed at least 2-fold increase in comparison with radiographic AxSpA presenting with no spinal involvement. Importantly, 4 miRNAs showed at least 1.5-fold decrease in levels across all stages with progressing spinal damage.
Conclusions Comprehensive analysis of cell-free circulating miRNAs revealed differential expression of several miRNAs in patients with AxSpA according to different stages of the disease. Some of these deregulated miRNAs were shown to play a role in innate immunity and new bone formation. This data suggest involvement of miRNAs in the process of AxSpA development and their potential use as biomarkers of disease severity.
Acknowledgements This work was supported by IGA project no. NT 14498, project of MHCR for conceptual development of research organization 023728 and BT-Cure
Disclosure of Interest None declared