Normal interstitial flow is critical for developmental lymphangiogenesis in the zebrafish.

The lymphatic system plays a critical role in the body's fluid and protein homeostasis, immune regulation, and dietary fat absorption. One of the major pathologies of the lymphatic system is primary lymphedema, which occurs in approximately 0.6% of live births and is caused by missing or impaired lymphatic vessels. Although there is a great need for medical intervention into diseases of the lymphatic system, very little is known about its development or how it maintains integrity over time. Recent studies have suggested that biophysical components, such as local extracellular fluid flow, may be important factors during initiation of lymphangiogenesis. We hypothesize that interstitial fluid flow functions as an important morphoregulator during developmental lymphangiogenesis. In the present study we use pharmacological agents and a mutant fish line to modulate interstitial flow. Our data confirm that a sufficient increase or decrease in interstitial flow can profoundly affect lymphatic patterning and may result in a lymphedema-like phenotype. Proper interstitial flow appears to be necessary during LEC migration for proper lymphatic development. These results support the contention that interstitial flow is an important morphoregulator of developmental lymphangiogenesis.