[Differential expression of exosomal miRNAs in osteoblasts in osteoarthritis]

To analyze the differentially expressed exosomal miRNAs in subchondral osteoblasts in patients with osteoarthritis (OA) and to investigate the key miRNAs potentially involved in the occurrence and progression of OA.
 Methods: Subchondral bones were harvested from 6 patients with OA. All subjects were divided into two groups which was based on the severity of joint wear: An OA group, severely worn side of subchondral bone, and a control group, less worn side of subchondral bone. The exosomes were extracted from osteoblast cells and their characteristics were identified. Then exosomal miRNAs were extracted and sequencing analysis was conducted to compare the expression in the two groups. The most differentially expressed ones (log2Ratio≥2) were subject to miRNA target prediction and quantitative reverse transcription PCR (RT-qPCR) to further quantify the difference.
 Results: Osteoblast extractions were confirmed to be exosomes, which were small double-membranous vesicles with 30-200 nm in diameter and 50-150 nm in peak value of particle size under the scanning microscope. High-throughput sequencing revealed 124 miRNAs whose expression significantly increased in the OA group. The most differentially expressed one with maximum fold change was hsa-miR-4717-5p and its target gene was RGS2. RT-qPCR demonstrated hsa-miR-4717-5p expression in the OA group was relatively higher than that in the control group (2.243 vs 0.480, P<0.01).
 Conclusion: There is distinct difference in expression profiles of exosomal miRNAs in subchondral osteoblasts between patients with OA and normal subjects. Up-regulated expression of miRANs might participate in OA occurrance and progression.