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Effects of adenovirus-mediated knockdown of IRAK4 on synovitis in the osteoarthritis rabbit model
Muzhe Li1, Huiyun Li1, Xun Ran1
1Department of Orthopedic, The First Affiliated Hospital, Hengyang Medical School, University of South China, No. 69, Chuanshan Road, Hengyang City, 421001, Hunan Province, China.
Background:
The 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.
Methods:
Ad-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.
Results:
IRAK4 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.
Conclusions:
IRAK4 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.
Insights
Interleukin-1 receptor-associated kinase 4 (IRAK4) inhibition reduced synovitis and cartilage degradation in an osteoarthritis rabbit model. Adenovirus-mediated knockdown of IRAK4 alleviated symptoms and slowed disease progression.
Area of Science:
- Biomedical Science
- Immunology
- Orthopedics
Background:
- Osteoarthritis (OA) is an inflammatory joint disease with unclear mechanisms.
- Interleukin-1 receptor-associated kinase 4 (IRAK4) inhibitors show promise for OA treatment.
Purpose of the Study:
- To investigate the effects of adenovirus-mediated knockdown of IRAK4 on synovitis in an OA rabbit model.
- To elucidate the underlying mechanisms of IRAK4 in OA pathogenesis.
Main Methods:
- Adenovirus-mediated short hairpin RNA (shRNA) targeting IRAK4 (Ad-shIRAK4) was administered to OA rabbits.
- Synovial tissue and fluid were analyzed for IRAK4 expression, inflammatory markers (IL-1β, TNF-α), and matrix metalloproteinase-13 (MMP-13).
- Histopathology, immunohistochemistry, X-ray, and micro-CT scans assessed synovitis, cartilage damage, and subchondral bone microstructure.
Main Results:
- IRAK4 expression was significantly upregulated in the synovium of OA rabbits.
- Ad-shIRAK4 treatment reduced IRAK4 mRNA and protein levels, suppressed Toll-like receptor/interleukin-1 receptor (TLR/IL-1R) signaling.
- Ad-shIRAK4 decreased inflammatory cell infiltration, hyperplasia, angiogenesis, and levels of IL-1β, TNF-α, and MMP-13.
- Ad-shIRAK4 treatment protected against cartilage damage and improved subchondral bone microstructure.
Conclusions:
- IRAK4 is a key mediator of synovitis and cartilage degradation in OA.
- IRAK4 knockdown alleviates OA symptoms and prevents disease progression.
- Targeting IRAK4 represents a potential therapeutic strategy for osteoarthritis.
