Effects of adenovirus-mediated knockdown of IRAK4 on synovitis in the osteoarthritis rabbit model

Muzhe Li,Huiyun Li,Zhiwei Chen,Han Yin,Xuling Luo,Xun Ran

doi:10.1186/s13075-021-02684-8

Abstract

BackgroundThe use of interleukin-1 receptor-associated kinase 4 (IRAK4) inhibitor as a treatment for the inflammatory joint disease is a promising method. However, its underlying mechanism in osteoarthritis (OA) remains unclear. The purpose of this study is to look into the effects of adenovirus-mediated knockdown of IRAK4 on synovitis in the OA rabbit model.MethodsAd-shIRAK4 was injected two weeks after anterior cruciate ligament resection. Six weeks later, the rabbits were killed. The expression of IRAK4, TNFR-associated factor 6(TRAF6), TGF-activated kinase 1(TAK1), p-IKB kinase (p-IKK), p-nuclear factor kappa-B (p-NFκB), p38, and p-p38 in the synovial membrane was detected by western blot, qRT-PCR, and immunohistochemistry analysis. Immunohistochemistry was to detect the expression of IRAK4 proteins in articular cartilage. H&E staining was to assess the pathological changes of synovium and cartilage. The levels of interleukin (IL)-1β, tumor necrosis factor-α(TNF-α), and MMP-13 in the synovial fluid were measured by ELISA. X-ray and micro-computerized tomography (μCT) scans were used to assess knee joint conditions and microstructure of subchondral bone.ResultsIRAK4 expression levels in synovial tissues of the OA model group exhibited a significant upward trend. Ad-shIRAK4 significantly reduced IRAK4 mRNA expression in synovium tissues. Notably, Ad-shIRAK4 suppressed the Toll-like receptor/interleukin-1 receptor (TLR/IL-1R) signaling. In addition, in the Ad-shIRAK4 treatment group, we can see less inflammatory cell infiltration and reduced hyperplasia and angiogenesis. The levels of IL-1β, TNF-α, and MMP-13 in the synovial fluid in the OA model group were significantly higher than that in the control group, which were reduced by Ad-shIRAK4 treatment. Finally, Results of HE stains, immunohistochemistry, and μCT showed that Ad-shIRAK4 treatment has a protective effect on cartilage damage.ConclusionsIRAK4 is significantly upregulated in the synovium from the osteoarthritis rabbit model. In addition, Ad-shIRAK4 reduced the expression of IRAK4 and suppressed TLR/IL-1R signaling in the synovium from the osteoarthritis rabbit model. Ad-shIRAK4 could alleviate synovitis and cartilage degradation in the osteoarthritis rabbit model, and thus alleviate the symptoms of OA and prevent the progression of OA.Graphical abstract

Highlights

OA is a bone and joint degenerative condition
KellgrenLawrence grading revealed that the control group was at Grade 0 and the OA group was at Grade 3–4 (Fig. 1E) To compare the expression of interleukin-1 receptor-associated kinase 4 (IRAK4) in normal synovium with that in OA synovium, we found that compared with the sham operation group, IRAK4 expression levels in synovial tissues of the OA model group exhibited a significant upward trend through quantitative analysis of protein. (Fig. 1C, D)
Ad-shIRAK4 reduced the expression of IRAK4 and suppressed Toll-like receptor (TLR)/IL-1R signaling in the synovium from the osteoarthritis rabbit model (Fig. 3C, D)

Summary

Introduction

Cartilage breakdown, osteophyte production, and subchondral osteosclerosis are the most common pathological symptoms. Studies have pointed out that synovitis is directly related to clinical symptoms such as joint swelling and inflammatory pain [4]. Osteoarthritis synovium produces inflammatory mediators, such as IL-1β and TNF-α, which disrupt the balance between cartilage matrix degradation and repair, leading to cartilage breakdown. Taking synovial membrane as the target to intervene the expression of inflammatory factors is helpful to alleviate the symptoms of OA, and it will be an important strategy to improve the pathological process of OA [5]. The use of interleukin-1 receptor-associated kinase 4 (IRAK4) inhibitor as a treatment for the inflammatory joint disease is a promising method. The purpose of this study is to look into the effects of adenovirus-mediated knockdown of IRAK4 on synovitis in the OA rabbit model

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