Functional recovery of fluid drainage precedes lymphangiogenesis in acute murine foreleg lymphedema.

Secondary lymphedema in humans is a common consequence of axillary lymph node dissection (ALND) to treat breast cancer. It is commonly hypothesized that lymphatic growth is required to increase fluid drainage and ameliorate lymphedema. Although there is a pronounced alteration in the balance of interstitial forces regulating fluid transport that sustains the chronic form of lymphedema, it is presently unknown whether changes occur to the balance of interstitial forces during acute lymphedema that may play a role in the recovery of fluid drainage. Here, we compared the relative importance of lymphangiogenesis of lymphatic vessels and interstitial flows for restoring fluid drainage and resolving acute lymphedema in the mouse foreleg after ALND. We found that removal of the axillary lymph nodes reduced lymph drainage in the foreleg at days 0 and 5 postsurgery, with fluid tracer spreading interstitially through subcutaneous tissues. Interstitial fluid drainage returned to normal by day 10, whereas functional regrowth of lymphatic vessels was first detected by indocyanine green fluorescence lymphography at day 15, demonstrating that the recovery of interstitial fluid drainage preceded the regrowth of lymphatic vessels. This was confirmed by the administration of VEGF receptor-3-neutralizing antibodies, which completely blocks lymphatic regrowth. It was found that the recovery of interstitial fluid drainage and the natural resolution of acute lymphedema produced by ALND were not hindered by VEGF receptor-3 neutralization, demonstrating that interstitial fluid drainage recovery and the resolution of acute lymphedema are lymphangiogenesis independent. The data highlight the central role of the interstitial environment in adapting to lymphatic injury to increase fluid drainage.