Epigenetic reprogramming via EZH2 inhibition rescues fibroadipose pathogenesis in secondary lymphedema through activating PPARγ signaling.

Background: Secondary lymphedema, a progressive disorder characterized by pathological fibroadipose tissue accumulation, is a common problem after cancer treatment and orthopedic surgery. It remains a therapeutic enigma due to its self-perpetuating fibrotic cascade and lack of disease-modifying therapies. While current therapeutic approaches focus on symptom management and volume reduction, they don't address the epigenetic reprogramming driving fibrotic commitment-a process recently linked to enhancer of zeste homolog 2 (EZH2). Although EZH2 inhibitor EPZ6438 has been approved for clinical application, its therapeutic potential in fibroadipose pathogenesis remains unexplored, leaving a critical gap in understanding epigenetic factors in lymphedema progression. Methods: Human skin tissue was collected from lymphedema patients and normal controls. Histological/immunofluorescence staining and RNA sequencing were performed. In vivo, a mouse hind limb secondary lymphedema model was established by lymphadenectomy. EZH2 inhibitors (EPZ6438, GSK126) were intraperitoneally injected. Skin samples were collected for histological assessment and immuno-staining. In vitro, adipose-derived mesenchymal stem cells (AdMSCs) were treated with transforming growth factor beta 1 (TGFβ1) and EZH2 inhibitors. Western blot, RT-qPCR and ChIP-qPCR were carried out. Results: Fibrous tissue was observed in lymphedema samples, with concomitant elevation of EZH2 and H3K27me3 levels in the nucleus. RNA sequencing and gene set enrichment analysis (GSEA) revealed significant downregulation of the peroxisome proliferator-activated receptor (PPAR) signaling in lymphedema tissue. Pharmacological inhibition of EZH2 significantly attenuated cutaneous thickening, fibroadipose layer expansion, and collagen deposition in the mouse lymphedema model. PPARγ was induced while phospho-SMAD2/3 activation was suppressed. In TGFβ1 stimulated AdMSCs, EZH2 inhibition upregulated PPARγ expression and inhibited fibrogenic differentiation of the cells. Conclusion: EZH2 inhibitors exerted potent anti-fibrotic effects in secondary lymphedema though activating PPARγ signaling, offering novel insights and strategies for fibrotic disorders. The translational potential of this article: This study demonstrated that targeted inhibition of the EZH2-PPARγ axis effectively inhibited fibrogenic differentiation of AdMSCs and reduced fibroadipose tissue in secondary lymphedema, indicating it is a promising strategy for secondary lymphedema treatment, offering novel insights and strategy for musculoskeletal fibrotic disorders.