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(Circulation Research. 2003;92:701.)
© 2003 American Heart Association, Inc.

Editorials

Lessons From Lymph

Flow-Guided Vessel Formation

Richard T. Lee

From the Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Mass.

Correspondence to Richard T. Lee, MD, Partners Research Facility, 65 Landsdowne St, Room 279, Cambridge, MA 02139. E-mail rlee@rics.bwh.harvard.edu

Key Words: lymph • angiogenesis • mechanotransduction • endothelium

An extract of the first 250 words of the full text is provided, because this article has no abstract.

Lymphangiogenesis doesn’t get much attention compared with its better-known cousin, angiogenesis. Perhaps that’s because lymphatic vessels don’t carry blood or platelets, and next to arteries or even veins, lymphatics are flimsy weaklings that are barely able to withstand 20 mm Hg before bursting.¹ Yet clinical disorders of the lymphatic system occur commonly. Lymphedema, including the common postsurgical and postradiation forms and the rare inherited forms, has no successful therapy. Cancer metastasis occurs frequently by lymphatics, and lymphatic destruction by the parasitic filariasis diseases is among the leading cause of worldwide chronic disability.

The lymphatic system starts as an open-ended transport system in interstitial spaces, in contrast with the closed-loop circulation for blood.R2-128041 ^2,3 Protein-rich fluid is gathered by open lymphatic capillaries that drain into progressively larger lymphatic vessels. Collecting lymphatics converge into two major ducts, the thoracic duct, which drains most of the body’s lymph into the left subclavian vein, or the smaller right lymphatic duct, which drains into the right subclavian vein. Along the way back to the blood circulation, lymph passes through at least one lymph node, where immunological presentation of antigens and filtering can occur.

Despite the obvious macroscopic differences between the lymphatic and blood circulations, there are close parallels as well (Table). Larger lymphatics have valves like veins and also have smooth muscle–regulated tone that is nitric oxide–responsive.⁴ In fact, Sabin proposed in 1902 that the lymphatic system arises by endothelial budding from embryonic veins.⁵ Although others have proposed that the lymphatic system develops independently . . . [Full Text of this Article]