DMT1-mediated iron overload accelerates cartilage degeneration in Hemophilic Arthropathy through the mtDNA-cGAS-STING axis

Introduction: Excess iron contributes to Hemophilic Arthropathy (HA) development. Divalent metal transporter 1 (DMT1) delivers iron into the cytoplasm, thus regulating iron homeostasis.

Objectives: We aimed to investigate whether DMT1-mediated iron homeostasis is involved in bleeding-induced cartilage degeneration and the molecular mechanisms underlying iron overload-induced chondrocyte damage.

Methods: This study established an in vivo HA model by puncturing knee joints of coagulation factor VIII gene knockout mice with a needle, and mimicked iron overload conditions in vitro by treatment of Ferric ammonium citrate (FAC).

Results: We demonstrated that blood exposure caused iron overload and cartilage degeneration, as well as elevated expression of DMT1. Furthermore, DMT1 silencing alleviated blood-induced iron overload and cartilage degeneration. In hemophilic mice, articular cartilage degeneration was also suppressed by intro-articularly injection of DMT1 adeno-associated virus 9 (AAV9). Mechanistically, RNA-sequencing analysis indicated the association between iron overload and cGAS-STING pathway. Further, iron overload triggered mtDNA-cGAS-STING pathway activation, which could be effectively mitigated by DMT1 silencing. Additionally, we discovered that RU.521, a potent Cyclic GMP-AMP Synthase (cGAS) inhibitor, successfully suppressed the downward cascades of cGAS-STING, thereby protecting against chondrocyte damage.

Conclusion: Taken together, DMT1-mediated iron overload promotes chondrocyte damage and murine HA development, and targeted DMT1 may provide therapeutic and preventive approaches in HA.