Chumappumkal Joseph, BilgimolDe Pablo Moreno, Juan AndrésFalah, NiccaLora Cacho, Miavon Drygalski, Annette2025-10-232025-10-232025-09-02Chumappumkal Joseph B, De Pablo-Moreno JA, Falah N, Lora Cacho M, Von Drygalski A. Defective lymphangiogenesis and iron removal after hemarthrosis in factor VIII-deficient mice are rectified with therapeutic factor VIII administration: implications for joint health. Journal of Thrombosis and Haemostasis 2025:S1538783625005422. https://doi.org/10.1016/j.jtha.2025.08.016.1538-793310.1016/j.jtha.2025.08.016https://hdl.handle.net/20.500.14352/125334Acknowledgments This investigator-initiated study was supported by Sanofi (to A.v.D.) and University of California San Diego discretionary funds (to A.v.D.). Murine Fc factor VIII used in this study was provided by Sanofi. Slide scanning and confocal microscopy were performed at the School of Medicine Microscopy Core, University of California San Diego, which is supported by grant P30NS047101. We thank Eric Y. Chang for providing histology equipment infrastructure.Background Maladaptive lymphangiogenesis after hemarthrosis in factor(F)VIII-deficient (knockout [KO]) mice facilitates synovial iron accumulation. Objectives To investigate the effect of FVIII treatment on lymphangiogenesis, iron clearance, and joint health after hemarthrosis. Methods Two days after knee injury/bleed (subpatellar needle puncture) FVIII-KO mice were separated into 3 groups receiving (1) intravenous saline, (2) recombinant human FVIII for 2 days, or (3) murine (m)FcFVIII for 14 days. FVIII activity levels were measured repeatedly (peak/trough) for 14 days. Joint tissues were processed at 2 and 4 weeks postbleed for Prussian blue staining (iron), CD68 (macrophage), αSMA (vascular remodeling), and LYVE1 (lymphangiogenesis) immunohistochemistry, and Safranin-O-Green staining (cartilage health). Results Joint injury caused profound hemarthrosis. Mice treated with mFcFVIII maintained stable FVIII activity levels for 14 days (troughs 29%-38%). Pronounced synovial iron accumulation colocalizing with macrophages, along with severely impaired lymphangiogenesis and joint health parameters, were present in saline-treated mice at 2 and 4 weeks when compared with baseline. Short-term recombinant human FVIII administration resulted in partially impaired lymphangiogenesis and iron clearance with delayed recovery of joint health parameters. In contrast, mice treated with mFcFVIII experienced rapid iron clearance alongside normal lymphangiogenesis, associated with fast and effective normalization of joint health parameters, particularly with respect to cartilage health. Conclusion Prolonged FVIII availability in the “mild hemophilia range” (± Fc-mediated effects) after hemarthrosis seem critical for lymphangiogenesis, rapid iron removal, and joint repair, including glycosaminoglycan-dependent cartilage restoration. Intensified courses of FVIII treatment in patients may therefore be beneficial for postbleed management.engAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/journal article1538-7836https://doi.org/10.1016/j.jtha.2025.08.016https://www.sciencedirect.com/science/article/pii/S1538783625005422open access616.15612.019577ArthropathyFactor VIIIHemarthrosisHemophiliaHemosiderinInflammationIronLymphangiogenesisMacrophagesHematologíaFisiología animal (Biología)Bioquímica (Biología)3207.08 Hematología2401.13 Fisiología Animal2403 Bioquímica