Lymph flow regulates collecting lymphatic vessel maturation in vivo
Daniel T. Sweet, … , Peter F. Davies, Mark L. Kahn
Daniel T. Sweet, … , Peter F. Davies, Mark L. Kahn
Published July 27, 2015
Citation Information: J Clin Invest. 2015;125(8):2995-3007. https://doi.org/10.1172/JCI79386.
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Research Article Angiogenesis Cardiology Development Oncology Vascular biology

Lymph flow regulates collecting lymphatic vessel maturation in vivo

Abstract

Fluid shear forces have established roles in blood vascular development and function, but whether such forces similarly influence the low-flow lymphatic system is unknown. It has been difficult to test the contribution of fluid forces in vivo because mechanical or genetic perturbations that alter flow often have direct effects on vessel growth. Here, we investigated the functional role of flow in lymphatic vessel development using mice deficient for the platelet-specific receptor C-type lectin–like receptor 2 (CLEC2) as blood backfills the lymphatic network and blocks lymph flow in these animals. CLEC2-deficient animals exhibited normal growth of the primary mesenteric lymphatic plexus but failed to form valves in these vessels or remodel them into a structured, hierarchical network. Smooth muscle cell coverage (SMC coverage) of CLEC2-deficient lymphatic vessels was both premature and excessive, a phenotype identical to that observed with loss of the lymphatic endothelial transcription factor FOXC2. In vitro evaluation of lymphatic endothelial cells (LECs) revealed that low, reversing shear stress is sufficient to induce expression of genes required for lymphatic valve development and identified GATA2 as an upstream transcriptional regulator of FOXC2 and the lymphatic valve genetic program. These studies reveal that lymph flow initiates and regulates many of the key steps in collecting lymphatic vessel maturation and development.

Authors

Daniel T. Sweet, Juan M. Jiménez, Jeremy Chang, Paul R. Hess, Patricia Mericko-Ishizuka, Jianxin Fu, Lijun Xia, Peter F. Davies, Mark L. Kahn

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Figure 3

Failure of mesenteric lymphatic vessel remodeling and valve initiation in Clec2–/– mice.

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Failure of mesenteric lymphatic vessel remodeling and valve initiation i...
(A–F) Analysis of mesenteric lymphatic vessel morphology and patterning at E15.5 (A and B), E16.5 (C and D), and E18.5 (E and F) in Prox1-GFP BAC transgenic embryos. White arrows indicate sites of lymphatic valve formation. Vascular architecture and valve formation are shown diagrammed on the right. Scale bars: 200 μm. (G and H) Quantitation of valve number (G) and vessel branchpoint number (H) in E18.5 Clec2–/– and Clec2+/+ mesenteric lymphatics. n = 9 embryos per genotype. (I) Schematic of the late gestation WT mesenteric lymphatic network demonstrating vessels denoted as primary, secondary, and tertiary based on branching and distance from the intestine. (J) Quantitation of lymphatic vascular hierarchy in E18.5 Clec2–/– and Clec2+/+ embryos. Lymphatic vessel width was measured at the 3 levels of the lymphatic vascular tree indicated in I. n = 4 embryos per genotype. At least 6 vessels at each level were measured per embryo. All values are means ± SEM. *P < 0.05, ***P < 0.001, calculated by Student’s t test.