Murine hindlimb lymphedema model: optimization and evaluation of radiation.

Background: Post-surgical lymphedema frequently occurs following lymph node dissection. The murine tail is the most commonly used model to study secondary lymphedema. The murine hindlimb model offers a more clinically translatable approach but results in the literature have been inconsistent. The purpose of this study is to optimize the murine hindlimb lymphedema to achieve consistent results and assess the utility of radiation.

Methods: C57BL/6 mice underwent either 20-Gy irradiation of one hindlimb 7 days prior to surgery (n = 11) or no radiation (n = 9). For all mice, a circumferential skin incision was created at the proximal hindlimb. Lymphatics were identified and disrupted. Popliteal lymph nodes were excised. Paw thickness was measured and near-infrared laser lymphangiography was used to assess lymphatic function.

Results: The average paw thickness of the operated hindlimb in irradiated mice on postoperative day (POD) 14 was 3.5 ± 0.3 cm compared to 2.1 ± 0.05 cm on the contralateral limb (p = 0.0001). Lymphangiography on POD-42 showed significantly worse lymphatic function in the operated hindlimb compared to the control hindlimb (p = 0.003). For the non-radiated mice, the paw thickness was 2.5 ± 0.2 cm on POD-42 compared to the contralateral limb (2.1 ± 0.1 cm) (p = 0.0002) but smaller than radiated hindlimb group (3.2 ± 0.1 cm) (p = 0.0002). The nonradiated mice had significantly greater paw thickness than the control limb until POD-56 whereas the radiated mice sustained significant paw thickness to POD-90.

Conclusion: Radiation of the murine hindlimb model results in sustained lymphedema compared to non-irradiated mice. The murine hindlimb lymphedema model is clinically more translatable than the murine tail model with consistent results.