Baseline Lymphatic Dysfunction Amplifies the Negative Effects of Lymphatic Injury.

Genetic mutations and obesity increase the risk of secondary lymphedema, suggesting that impaired lymphatic function before surgical injury may contribute to disease pathophysiology. Previous studies show that obesity not only decreases lymphatic function, but also markedly increases pathologic changes, such as swelling, fibroadipose deposition, and inflammation. However, although these reports provide circumstantial evidence supporting the hypothesis that baseline lymphatic defects amplify the effect of lymphatic injury, the mechanisms regulating this association remain unknown. Baseline lymphatic morphology, leakiness, pumping, immune cell trafficking, and local inflammation and fibroadipose deposition were assessed in wild-type and Prox1-haploinsufficient (Prox1) mice, which have previously been shown to have abnormal vasculature without overt evidence of lymphedema. In subsequent experiments, wild-type and Prox1 mice underwent popliteal lymph node dissection to evaluate the effect of lymphatic injury. Repeated testing of all variables was conducted 4 weeks postoperatively. At baseline, Prox1 mice had dilated, leaky lymphatic vessels corresponding to low-grade inflammation and decreased pumping and transport function, compared with wild-type mice. Popliteal lymph node dissection resulted in evidence of lymphedema in both Prox1 and wild-type mice, but popliteal lymph node dissection-treated Prox1 mice had increased inflammation and decreased lymphatic pumping. Subclinical lymphatic dysfunction exacerbates the pathologic changes of lymphatic injury, an effect that is multifactorial and related to increased lymphatic leakiness, perilymphatic accumulation of inflammatory cells, and impaired pumping and transport capacity. These findings suggest that preoperative testing of lymphatic function may enable clinicians to more accurately risk-stratify patients and design targeted preventative strategies.