Lymphatic vessels: new targets for the treatment of inflammatory diseases.

The lymphatic system plays an important role in the physiological control of the tissue fluid balance and in the initiation of immune responses. Recent studies have shown that lymphangiogenesis, the growth of new lymphatic vessels and/or the expansion of existing lymphatic vessels, is a characteristic feature of acute inflammatory reactions and of chronic inflammatory diseases. In these conditions, lymphatic vessel expansion occurs at the tissue level but also within the draining lymph nodes. Surprisingly, activation of lymphatic vessel function by delivery of vascular endothelial growth factor-C exerts anti-inflammatory effects in several models of cutaneous and joint inflammation. These effects are likely mediated by enhanced drainage of extravasated fluid and inflammatory cells, but also by lymphatic vessel-mediated modulation of immune responses. Although some of the underlying mechanisms are just beginning to be identified, lymphatic vessels have emerged as important targets for the development of new therapeutic strategies to treat inflammatory conditions. In this context, it is of great interest that some of the currently used anti-inflammatory drugs also potently activate lymphatic vessels.