IRF2BP2-FOSL2 interaction regulates SOX9-mediated cartilage regeneration in osteoarthritis models
Hao Zhou, Tiantian Lu, Zhuoqun Gao, Can Cui, Zhiqiang Fang, Yu You, Jing Jiang, Jinjin Xu, Fang Wei, Jing Yu, Hu Zhou, Jinsong Li, Jian Luo, Lei Zhang, Yunyun Jin
Hao Zhou, Tiantian Lu, Zhuoqun Gao, Can Cui, Zhiqiang Fang, Yu You, Jing Jiang, Jinjin Xu, Fang Wei, Jing Yu, Hu Zhou, Jinsong Li, Jian Luo, Lei Zhang, Yunyun Jin
View: Text | PDF
Research Article Bone biology Cell biology

IRF2BP2-FOSL2 interaction regulates SOX9-mediated cartilage regeneration in osteoarthritis models

Abstract

Osteoarthritis (OA) is the most common degenerative joint disease. However, the molecular mechanisms underlying OA-induced cartilage degeneration remain elusive. Here, we identify IFN regulatory factor 2 binding protein 2 (IRF2BP2) as an important regulator of chondrocyte differentiation and articular cartilage regeneration. Irf2bp2 deficiency promoted chondrogenesis and inhibited chondrocyte terminal differentiation by transcriptionally upregulating the key chondrogenic marker SRY-box transcription factor 9 (SOX9), inducing its ectopic expression in the hypertrophic zone. Cartilage-specific KO of Irf2bp2 elevated SOX9 levels, attenuated OA progression in the destabilization of the medial meniscus (DMM) model, and enhanced cartilage regeneration and hyalinization in the microfracture model. Mechanistically, IRF2BP2 bound to and stabilized Fos-related antigen 2 (FOSL2), an activator protein 1 (AP-1) family member, thereby facilitating FOSL2/c-Jun complex formation and repressing SOX9 expression. Adeno-associated virus–mediated (AAV-mediated) FOSL2 overexpression reversed the protective phenotype observed in Irf2bp2-deficient mice. These findings establish the Hippo/IRF2BP2/FOSL2/SOX9 regulatory axis as critical for cartilage regeneration. Importantly, AAV-mediated IRF2BP2 knockdown, pharmacological targeting of the IRF2BP2/AP-1 axis using T-5224, and delivery of a peptide that disrupts IRF2BP2-FOSL2 binding via intra-articular injection all preserved cartilage integrity, offering potential therapeutic strategies for OA and cartilage regeneration.

Authors

Hao Zhou, Tiantian Lu, Zhuoqun Gao, Can Cui, Zhiqiang Fang, Yu You, Jing Jiang, Jinjin Xu, Fang Wei, Jing Yu, Hu Zhou, Jinsong Li, Jian Luo, Lei Zhang, Yunyun Jin

×

Figure 2

Cartilage-specific deletion of Irf2bp2 attenuates OA progression and associated pain.

Options: View larger image (or click on image) Download as PowerPoint
Cartilage-specific deletion of Irf2bp2 attenuates OA progression and ass...
(A) Western blot analysis of HA-IRF2BP2 expression in primary articular chondrocytes isolated from HA-Irf2bp2 mice at P1 following a 24-hour treatment with IL-1β and TNF-α. Data are representative of 3 independent biological replicates. (B) IF staining analysis of IRF2BP2 expression in 12-week-old WT mice 8 weeks after sham or DMM surgery. Scale bar: 100 μm. Original magnification, ×4. (C) Schematic outline of sham and DMM surgery after deletion of Irf2bp2 in male Irf2bp2Acan and Irf2bp2Col2-ERT2 mice. (D and E) Pain was measured by von Frey assay and a radiant heat paw-withdrawal test in Irf2bp2fl/fl and Irf2bp2Acan mice (n = 15) (D) or Irf2bp2fl/fl and Irf2bp2Col2-ERT2 mice (n = 13) (E). (F and G) SO staining of knee joint cartilage in Irf2bp2fl/fl and Irf2bp2Acan mice (F) or Irf2bp2fl/fl and Irf2bp2Col2-ERT2 mice (G) after sham or DMM surgery. Scale bars: 100 μm. (H and I) OARSI scores for samples in F (n = 9) and (G) (n = 5). (J and K) IF staining for SOX9 and COL2A1 in Irf2bp2fl/fl and Irf2bp2Acan mice (J) or Irf2bp2fl/fl and Irf2bp2Col2-ERT2 mice (K) after sham or DMM surgery. Scale bars: 100 μm. Original magnification, ×10. (L and M) Quantification of the expression of SOX9 and COL2A1 in J and K (n = 4). Data are shown as the mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001, by 2-way ANOVA, followed by Tukey’s multiple-comparison test (D, E, H, I, L, and M). In B, J, and K, dotted and curved lines indicate the surface of articular cartilage.