TRPM2-mediated feed-forward loop promotes chondrocyte damage in osteoarthritis via calcium-cGAS-STING-NF-κB pathway

Introductions: Osteoarthritis (OA) is a significant contributor to disability in the elderly population. However, current therapeutic options are limited. The transient receptor potential melastatin 2 (TRPM2) is involved in a range of disease processes, yet its role in OA remains unclear.

Objectives: To investigate the role of TRPM2 in OA.

Methods: Cartilage samples were collected from patients with osteoarthritis (OA) and mice with OA to examine TRPM2 expression levels. To investigate the effects of TRPM2 modulation on the destabilization of the medial meniscus (DMM) induced knee OA in mice, we utilized TRPM2 knockout mice and employed adenovirus-mediated overexpression of TRPM2. Furthermore, siRNA-mediated TRPM2 knockdown or plasmid-mediated TRPM2 overexpression was conducted to explore the role of TRPM2 in IL-1β-induced chondrocytes. The regulatory mechanism of IL-1β on TRPM2 expression was screened by signaling pathway inhibitors, and the transcription factors and binding sites of TRPM2 were predicted using the database. The binding of RELA (NF-κB-p65) to the Trpm2 promoter was verified by chip-PCR and ChIP-qPCR. The therapeutic potential of Ca²⁺ chelation with BAPTA-AM for the treatment of osteoarthritis (OA) was investigated.

Results: An increased expression of TRPM2 was observed in the cartilage of OA patients and OA mice. Furthermore, mice deficient in Trpm2 exhibited a protective effect against DMM-induced OA progression. In contrast, TRPM2 overexpression resulted in exacerbation of DMM-induced OA and thepromotion of an OA-like phenotype of chondrocytes. TRPM2 was upregulated by IL-1β in an NF-κB-p65-dependent manner. Subsequently, the TRPM2-Ca²⁺-mtDNA-cGAS-STING-NF-κB axis in the progression of OA was validated. Furthermore, inhibition of the TRPM2-Ca²⁺ axis with BAPTA-AM effectively attenuated established OA.

Conclusions: Our data collectively revealed a pathological feedback loop involving TRPM2, Ca²⁺, mtDNA, cGAS, STING, and NF-κB in OA chondrocytes. This suggests that disrupting this loop could be a viable therapeutic approach for OA.