Lymphatic endothelium

The lymphatic endothelium refers to a specialized subset of endothelial cells located in the sinus systems of draining lymph nodes. Specifically, these endothelial cells line the branched sinus systems formed by afferent lymphatic vessels, forming a single-cell layer which functions in a variety of critical physiological processes. These lymphatic endothelial cells contribute directly to immune function and response modulation, provide transport selectivity, and demonstrate orchestration of bidirectional signaling cascades. Additionally, lymphatic endothelial cells may be implicated in downstream immune cell development as well as lymphatic organogenesis. (Jalkanen, S., Salmi, M. 2020) Until recently, lymphatic endothelial cells have not been characterized to their optimal potential. This system is very important in the function of continuous removal of interstitial fluid and proteins, while also having a significant function of entry for leukocytes and tumor cells. This leads to further research that is being developed on the relationship between lymphatic endothelium and metastasis of tumor cells (Pepper, M. S., & Skobe, M. 27 October 2003). The lymphatic capillaries are described to be blind ended vessels (closed on one end), and they are made up of a single non-fenestrated layer of endothelial cells; The lymph capillaries function to aid in the uptake of fluids, macromolecules, and cells. Although they are generally similar to blood capillaries, the lymph capillaries have distinct structural differences. Lymph capillaries consist of a more wide and irregular lumen, and the endothelium in lymph capillaries is much thinner as well (S. Pepper, Skobe 2003). Their origin has been speculated to vary based on them being dependent on specific tissue environments, and powered by organ-specific signals.(L. Gutierrez-Miranda, K. Yaniv, 2020). A lymph capillary endothelial cell is distinct from other endothelial cells in that collagen fibers are directly attached to its plasma membrane.

Although lymphatics were first described by Hippocrates in 400 BC and rediscovered as "milky veins in the gut of a well fed dog" in the 17th century by Gasparo Aselli, they were ignored for centuries until in 1937 Howard Florey showed that lymphatics enlarge in inflammation. At this stage vascular and lymphatic endothelia were seen to be morphologically distinct and lymphatic vessels considered less important. Later it was discovered that VEGF-R3 and VEGF-C/VEGF-D were the key growth factors controlling lymphatic endothelial proliferation. Markers of lymphatic endolthelium were not discovered until relatively recently. These being LYVE-1 (Jackson et al., 1999) and podoplanin (Kerjaschki, 1999).

See also

• Lymphatic system
• Immune system

Further reading

• Jalkanen, S., Salmi, M (2020). "Lymphatic endothelial cells of the lymph node". Nature Reviews Immunology. 20 (9): 566–578. doi:10.1038/s41577-020-0281-x. PMID 32094869. S2CID 211265611.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• Jackson DG (2003). "The lymphatics revisited: new perspectives from the hyaluronan receptor LYVE-1". Trends in Cardiovascular Medicine. 13 (1): 1–7. doi:10.1016/S1050-1738(02)00189-5. PMID 12554094.
• Banerji S, Ni J, Wang SX, et al. (1999). "LYVE-1, a new homologue of the CD44 glycoprotein, is a lymph-specific receptor for hyaluronan". Journal of Cell Biology. 144 (4): 789–801. doi:10.1083/jcb.144.4.789. PMC 2132933. PMID 10037799.
• Cunnick GH, Jiang WG, Gomez KF, Mansel RE (2001). "Lymphangiogenesis quantification using quantitative PCR and breast cancer as a model". Biochemical and Biophysical Research Communications. 288 (4): 1043–1046. doi:10.1006/bbrc.2001.5869. PMID 11689016.
• Mouta Carreira C, Nasser SM, di Tomaso E, et al. (2001). "LYVE-1 is not restricted to the lymph vessels: expression in normal liver blood sinusoids and down-regulation in human liver cancer and cirrhosis". Cancer Research. 61 (22): 8079–84. PMID 11719431.
• Cursiefen C, Schlötzer-Schrehardt U, Küchle M, et al. (2002). "Lymphatic vessels in vascularized human corneas: immunohistochemical investigation using LYVE-1 and podoplanin". Investigative Ophthalmology & Visual Science. 43 (7): 2127–35. PMID 12091407.
• Strausberg RL, Feingold EA, Grouse LH, et al. (2003). "Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences". Proceedings of the National Academy of Sciences, USA. 99 (26): 16899–16903. doi:10.1073/pnas.242603899. PMC 139241. PMID 12477932.
• Huang SS, Tang FM, Huang YH, et al. (2003). "Cloning, expression, characterization, and role in autocrine cell growth of cell surface retention sequence binding protein-1". Journal of Biological Chemistry. 278 (44): 43855–43869. doi:10.1074/jbc.M306411200. PMID 12912978.
• Clark HF, Gurney AL, Abaya E, et al. (2003). "The secreted protein discovery initiative (SPDI), a large-scale effort to identify novel human secreted and transmembrane proteins: a bioinformatics assessment". Genome Research. 13 (10): 2265–2270. doi:10.1101/gr.1293003. PMC 403697. PMID 12975309.
• Gerhard DS, Wagner L, Feingold EA, et al. (2004). "The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC)". Genome Research. 14 (10B): 2121–2127. doi:10.1101/gr.2596504. PMC 528928. PMID 15489334.
• Otsuki T, Ota T, Nishikawa T, et al. (2007). "Signal sequence and keyword trap in silico for selection of full-length human cDNAs encoding secretion or membrane proteins from oligo-capped cDNA libraries". DNA Research. 12 (2): 117–126. doi:10.1093/dnares/12.2.117. PMID 16303743.
• Liu T, Qian WJ, Gritsenko MA, et al. (2006). "Human plasma N-glycoproteome analysis by immunoaffinity subtraction, hydrazide chemistry, and mass spectrometry". Journal of Proteome Research. 4 (6): 2070–2080. doi:10.1021/pr0502065. PMC 1850943. PMID 16335952.
• Kimura K, Wakamatsu A, Suzuki Y, et al. (2006). "Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes". Genome Research. 16 (1): 55–65. doi:10.1101/gr.4039406. PMC 1356129. PMID 16344560.
• Nguyen VA, Kutzner H, Fürhapter C, et al. (2006). "Infantile hemangioma is a proliferation of LYVE-1-negative blood endothelial cells without lymphatic competence". Modern Pathology. 19 (2): 291–298. doi:10.1038/modpathol.3800537. PMID 16424896.
• Gu B, Alexander JS, Gu Y, et al. (2007). "Expression of lymphatic vascular endothelial hyaluronan receptor-1 (LYVE-1) in the human placenta". Lymphatic Research and Biology. 4 (1): 11–17. doi:10.1089/lrb.2006.4.11. PMC 3072054. PMID 16569201.
• Llovet JM, Chen Y, Wurmbach E, et al. (2007). "A molecular signature to discriminate dysplastic nodules from early hepatocellular carcinoma in HCV cirrhosis". Gastroenterology. 131 (6): 1758–1767. doi:10.1053/j.gastro.2006.09.014. PMID 17087938.