Innovative Combination Therapy Targets m6A Pathway for Rheumatoid Arthritis

A recent study published in the journal *Engineering* on June 24, 2025, has unveiled a promising combination therapy for rheumatoid arthritis (RA) that effectively mitigates joint erosion by targeting the m6A methylation pathway. Conducted by a collaborative team from the China-Japan Friendship Clinical Medical College and other research institutions, this study emphasizes the therapeutic potential of triptolide (TP) and medicarpin (Med) in treating RA, a progressive autoimmune disorder characterized by chronic inflammation and bone destruction.

Rheumatoid arthritis is primarily driven by the overactivation of osteoclasts (OCs), cells responsible for bone resorption. Traditional treatments often fail to reverse existing joint damage and may come with significant side effects. The innovative approach explored in this study combines TP, an anti-inflammatory compound with a narrow therapeutic window, with Med, a flavonoid known for its anti-inflammatory and anti-bone destruction properties. By examining the synergistic effects of these compounds, the researchers aimed to enhance treatment efficacy while minimizing toxicity.

Utilizing a collagen-induced arthritis (CIA) rat model, the researchers assessed the impact of TP, Med, and their combination on disease progression and bone erosion. Results demonstrated that the combined therapy significantly alleviated arthritis symptoms and delayed disease onset. Notably, administering TP and Med at half the doses of their respective monotherapies resulted in superior efficacy in reducing bone erosion and inhibiting osteoclastogenesis compared to either drug alone.

Micro-CT imaging and histological analyses revealed that the combination therapy effectively improved bone volume and reduced bone surface-to-volume ratios in the ankle and knee joints of CIA rats. In addition, tartrate-resistant acid phosphatase (TRAP) staining and F-actin ring assays indicated a significant decrease in both the number and functionality of OCs, underscoring the therapy's potential in inhibiting bone resorption.

The study delved into the molecular mechanisms underlying the synergistic effects of TP and Med, identifying their roles in modulating the m6A methylation pathway by targeting methyltransferase-like 3 (METTL3) and YT521-B homology domain family protein 1 (YTHDF1), respectively. METTL3, an m6A methyltransferase, promotes the methylation of OC-related mRNAs, while YTHDF1, an m6A reader protein, enhances their translation and stability. The combination of TP and Med effectively disrupted this pathway, leading to decreased expression of key OC-related genes such as Nfatc1, c-Fos, Dc-stamp, Atp6v0d2, and Ctsk.

To validate these findings, the researchers also conducted in vitro experiments using primary bone marrow mononuclear cells (BMMs) from mice. Results confirmed that TP and Med inhibited RANKL-induced osteoclastogenesis and bone resorption in a dose-dependent manner. Furthermore, RNA immunoprecipitation (RIP) assays demonstrated a direct interaction between METTL3 and YTHDF1 with OC-related mRNAs, further corroborating their regulatory role in osteoclastogenesis.

An additional focus of the study was the inflammatory response in CIA rats. The combination therapy was found to modulate levels of pro-inflammatory and anti-inflammatory cytokines, including significant reductions in IL-1β and IL-6. Moreover, the treatment facilitated the replenishment of regulatory T cells (Tregs) in the spleen, which are crucial for maintaining bone tissue homeostasis.

This research provides compelling evidence that the TP and Med combination offers a novel therapeutic strategy for RA by targeting the m6A methylation pathway. The findings highlight METTL3 and YTHDF1 as potential therapeutic targets and underscore the significance of exploring combination therapies to enhance treatment efficacy and reduce adverse effects. Future studies are anticipated to focus on optimizing dosing regimens and further elucidating the mechanisms of action, aiming to translate these findings into clinical practice.

The study, titled "Increased Alleviation of Bone Destruction in Individuals with Rheumatoid Arthritis via the Coinhibition of the METTL3 and YTHDF1 Axis by the Combination of Triptolide and Medicarpin," is authored by Yi Jiao, Zhaoran Wang, Wenya Diao, Qishun Geng, Xing Wang, Xiaoxue Cao, Tong Shi, Jiahe Xu, Lu Zhao, Zihan Wang, Tiantian Deng, Lei Yang, and Tingting Deng. Their work highlights the promising direction of future research in combating rheumatoid arthritis and improving patient outcomes.