A Novel Lymphosome-Based Long-Lasting Rat Tail Model of Lymphedema

Abstract Secondary extremity lymphedema is a chronic and progressive condition caused by obstructed lymphatic drainage, commonly following lymphadenectomy, infection, or trauma. Rodent models are preferred for experimental lymphedema research due to cost-effectiveness and reproducibility. Currently, rat tail models encounter limitations due to transient swelling and their inability to fully replicate the comprehensive pathophysiology of lymphedema, particularly concerning the effects of lymph node removal. We developed a series of rat tail lymphedema models incorporating skin resection, deep lymphatic vessel disruption, and gluteal lymph node (GLN) excision to assess effects on lymphatic architecture, inflammation, and fibrosis. Indocyanine green (ICG) lymphography was used to visualize lymphatic function. Tail volume and circumference were measured weekly, and histological assessments quantified fibrosis and fibroadipose thickening. Bulk RNA sequencing was performed to characterize the inflammatory processes triggered by GLN removal. The combined model (skin removal, deep lymphatic disruption, and GLN excision) resulted in severe and persistent lymphedema marked by progressive swelling and pronounced fibrosis. ICG lymphography confirmed disruption of superficial lymphatic flow with partial recanalization of deep channels. Notably, lymphangiogenesis was observed at the GLN excision site, forming compensatory pathways connecting the tail to the popliteal lymph nodes. Histology revealed extensive collagen deposition and fibroadipose thickening in groups with lymph node removal, with the combined model showing the most pronounced changes. Bulk RNA-sequencing confirmed the removal of GLN involving the inflammatory and fibrosis process in the tail model. This lymphosome-based rat tail model successfully replicates key features of lymphedema, including sustained swelling, lymphatic disruption, inflammation, and fibrosis.