Lymphatics in nanophysiology.

Lymphatic vessels are essential for fluid transport and tissue homeostasis. Recent discoveries identified several genes, including Prox1 and VEGF-C, which are required for the lymphatic vessel development in physiological conditions as well as under pathological conditions such as chronic inflammation and tumor progression. Lymphatic vessels show morphological structures that are distinct between the initial lymphatic vessels and collectors, reflecting their respective functions of fluid absorption and transport. These differential structures are crucial for the physiological function of lymphatic vasculature. VEGF-A-mediated chronic inflammation impairs the fundamental structure of the initial lymphatic vessels, leading to delayed transport of nano-scaled fluorescence tracers. This article discusses recent findings that have clarified the biological function of lymphatic vessels in physiological and pathological settings. Assessments of the lymphatic function at nano-scale levels address the major contribution of lymphatic vessels to the kinetics of drug delivery and excretion.