Exosomal circ-BRWD1 contributes to osteoarthritis development through the modulation of miR-1277/TRAF6 axis

Zhenye Guo,Min Liu,Mingming Kang,Zhi Lv,Weifu He,Feng Zhao,Feida Wang,Huan Wang

doi:10.1186/s13075-021-02541-8

Abstract

BackgroundCircular RNAs (circRNAs) can act as vital players in osteoarthritis (OA). However, the roles of circRNAs in OA remain obscure. Herein, we explored the roles of exosomal circRNA bromodomain and WD repeat domain containing 1(circ-BRWD1) in OA pathology.MethodsIn vitro model of OA was constructed by treating CHON-001 cells with interleukin-1β (IL-1β). Quantitative real-time polymerase chain reaction (qRT-PCR) assay was used for circ-BRWD1, BRWD, miR-1277, and TNF receptor-associated factor 6 (TRAF6) levels. RNase R assay was conducted for the feature of circ-BRWD1. Transmission electron microscopy (TEM) was employed to analyze the morphology of exosomes. Western blot assay was performed for protein levels. Cell Counting Kit-8 (CCK-8) assay, flow cytometry analysis, and 5-Ethynyl-2′-deoxyuridine (EDU) assay were adopted for cell viability, apoptosis, and proliferation, respectively. Enzyme-linked immunosorbent assay (ELISA) was carried out for the concentrations of interleukin-6 (IL-6) and interleukin-8 (IL-8). Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were used to analyze the interaction between miR-1277 and circ-BRWD1 or TRAF6.ResultsCirc-BRWD1 was increased in OA cartilage tissues, IL-1β-treated CHON-001 cells, and the exosomes derived from IL-1β-treated CHON-001 cells. Exosome treatment elevated circ-BRWD1 level, while exosome blocker reduced circ-BRWD1 level in IL-1β-treated CHON-001 cells. Silencing of circ-BRWD1 promoted cell viability and proliferation and repressed apoptosis, inflammation, and extracellular matrix (ECM) degradation in IL-1β-stimulated CHON-001 cells. For mechanism analysis, circ-BRWD1 could serve as the sponge for miR-1277 to positively regulate TRAF6 expression. Moreover, miR-1277 inhibition ameliorated the effects of circ-BRWD1 knockdown on IL-1β-mediated CHON-001 cell damage. Additionally, miR-1277 overexpression relieved IL-1β-induced CHON-001 cell injury, while TRAF6 elevation restored the impact.ConclusionExosomal circ-BRWD1 promoted IL-1β-induced CHON-001 cell progression by regulating miR-1277/TRAF6 axis.

Highlights

Osteoarthritis (OA) is a slow-developing degenerative joint disease with a high incidence, which is related to age, obesity, tension, strain, trauma, joint deformities, and other factors [1, 2]
Circ-Bromodomain and WD repeat domain containing 1 (BRWD1) was upregulated in OA cartilage tissues and IL-1β-induced CHON-001 cells At the beginning, Quantitative real-time polymerase chain reaction (qRT-PCR) assay was conducted to detect the expression level of circ-BRWD1 in OA cartilage specimens and normal cartilage specimens
The results showed that circ-BRWD1 level was markedly increased in OA cartilage specimens compared to normal controls (Fig. 1A)

Summary

Introduction

Osteoarthritis (OA) is a slow-developing degenerative joint disease with a high incidence, which is related to age, obesity, tension, strain, trauma, joint deformities, and other factors [1, 2]. OA is characterized by structural change of subchondral bone, inflammation of synovitis, and destruction of cartilage matrix [3, 4]. At present, methods such as anti-inflammatory analgesics and artificial joint replacement surgery are mainly used to reduce OA patient’s joint pain and control its progress; the side effects and high costs hinder their wide application [5, 6]. It has been documented that circRNAs are abundant in exosomes and can be transferred into other cells to regulate biological functions [13]. We explored the roles of exosomal circRNA bromodomain and WD repeat domain containing 1(circ-BRWD1) in OA pathology

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Results

Discussion

Conclusion