Effects of All-<i>Trans</i> Retinoic Acid on Lipopolysaccharide-Induced Synovial Explant

Abstract

The present study was conducted to assess the effect of all-trans retinoic acid (ATRA) on synovial explants from rats with rheumatoid arthritis (RA) induced by lipopolysaccharides (LPS). In our study, synovial membranes were excised from the knees of healthy adult Wistar female rats under sterile conditions. We first investigated the synoviums incubated in a control medium or in a medium containing 10 mg/mL LPS, each for 24, 48, and 72 h (LPS-experiment). The changes in inflammatory response from the synoviums were observed at different culture times. Then, we assessed the synoviums exposed to different ATRA concentrations for 24 h (ATRA-experiment). The controls (blank, model group, and solvent groups) were set up. The effects of ATRA on synovitis were evaluated by measuring the production of cytokines, and nitric oxide (NO) and the expression of cartilage damage related proteases. In the LPS-experiment, LPS contributed to the release of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-a), and matrix metalloproteinase-9 (MMP-9) in synovial explants. Importantly, LPS did not cause a significant pathological damage. The inflammatory response observed in this model was significant for 24 h, suggesting that LPS-induced synovial explants were successfully established. In the ATRA-experiment, ATRA suppressed the expression of IL-6, TNF-a, NO, a disintegrin and metalloprotease with thrombospondin motifs-4 (ADAMTS-4), MMP-3, and MMP-9. Taken together, ATRA exhibited inhibitory effects on LPS-induced synovial immune inflammatory response stimulated by the regulation of inflammatory mediators and cartilage damage related proteases in synovial explants, demonstrating a potential protective effect on synovitis and joint destruction in the patients with RA.

Effects of All-<i>Trans</i> Retinoic Acid on the Optimization of Synovial Explant Induced by Tumor Necrosis Factor Alpha

“…IL-6 is one of the pro-inflammatory cytokines most associated with the pathogenesis of RA, and is abundant in synovial fluid and serum of patients with RA (26). ELASA results showed that TNF-a can induce synovial membrane to produce a large amount of IL-6, reaching a high point after 24 h of incubation and then gradually decreasing, which was similar to the results of previous studies (20). It is possible that mechanical stimulation in the anatomical process causes IL-6 to surge and tends to stabilize over time.…”

“…The separated hindlimb tissues were soaked in 75% alcohol (Sinopharm Chemical Reagent Co., Ltd.) for 2 min, and then quickly removed and put into a pre-cooled phosphate-buffered saline (PBS) solution supplemented with penicillin and streptomycin (HyClone, Logan, UT, USA), temporarily stored in an ice box. Referring to the synovial membrane separation method adopted in the previous studies (20) and made some improvement, after separating synovial membrane and patellar ligament, quadriceps femoris was separated from the femoral shaft to the tibial end by sticking to the upper end of the femur. Since the synovial membrane covered the tendon surface, the quadriceps femoris could be gently lifted to completely expose the synovial membrane connected with the tendon.…”

“…We first compared the weight of rat synovial explants in the control groups and the TNF-a-challenged groups at different time points. Referring to the model design method of Hyc et al (24), the previous study of our laboratory (20) detailed the synovial membrane extraction process, but the method of opening the knee joint from popliteal fossa is more likely to damage the synovial membrane and cause certain mechanical stimulation. Therefore, in this study, we improved the synovial membrane extraction method again, and separated the quadriceps femoris from the upper femur to the tibial end by sticking closely to the femoral shaft, thus completely exposing the synovial membrane connected with the tendon.…”

“…But FLS culture in vitro could not maintain the initial morphology of synovial tissue for in-situ observation of various types of cells, so the response of synovial cells may be inconsistent with that of the whole tissue. In our previous study (20), a tissue culture model of synovitis was constructed by using lipopolysaccharides (LPS) in reference to the method of Hyc. Nevertheless, due to the short duration of cytokines produced by the LPS-induced model, the duration of ATRA intervention was limited.…”

Systemic Inflammation Impairs Mood Function by Disrupting the Resting-State Functional Network in a Rat Animal Model Induced by Lipopolysaccharide Challenge

“…One of the main reasons might be that the early cytokines such as TNF- α , IL-1 β , and IL-6 peak shortly after LPS injection and return to the baseline levels within hours [16], providing one explanation for the negative results observed in our study. Indeed, a number of studies have shown that proinflammatory cytokines and anti-inflammatory cytokines return to normal after 24 hours after LPS stimulation [16, 31, 32]. Depression is one of the most common symptoms observed in sepsis patients [2, 3].…”