VEGF-C is required for intestinal lymphatic vessel maintenance and lipid absorption.
Bottom Line: We show here that VEGF-C is necessary for perinatal lymphangiogenesis, but required for adult lymphatic vessel maintenance only in the intestine.VEGF-C was expressed by a subset of smooth muscle cells adjacent to the lacteals in the villus and in the intestinal wall.Our findings indicate that the lymphangiogenic growth factors provide trophic and dynamic regulation of the intestinal lymphatic vasculature, which could be especially important in the dietary regulation of adiposity and cholesterol metabolism.
Affiliation: Wihuri Research Institute and Translational Cancer Biology Program, Biomedicum Helsinki University of Helsinki, Helsinki, Finland.Show MeSH
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Mentions: Next, we sought to identify the cell types that express VEGF-C in the adult intestine. Previous work from our laboratory showed that VEGF-C is expressed in arterial smooth muscle cells (SMCs) both in mice and humans (Partanen et al, 2000; Paavonen et al, 2002; Karkkainen et al, 2004). To define the cells expressing VEGF-C and its receptors, we performed β-Gal staining of intestines from Vegfc/LacZ (Karkkainen et al, 2004), Vegfr3/LacZ (Dumont et al, 1998), and Vegfr2/LacZ (Shalaby et al, 1995) mice. VEGF-C staining in the villi was weak in comparison with VEGFR-3 and VEGFR-2 stainings, in lymphatic and blood vessels, respectively (Fig2A and B). Higher resolution analysis combined with immunohistochemistry demonstrated VEGF-C expression in SMCs, in the inner circular muscle layer of the intestinal wall, in arterial smooth muscle, and in a subset of the SMC fibers in the villus (Fig2C). In the villi, the VEGF-C β-Gal signal was most prominent adjacent to the LYVE1-counterstained lymphatic vessels (Fig2D). The intestinal wall of the Vegfc/LacZ mice showed a prominent arterial β-Gal staining pattern, which was further analyzed by PECAM-1 counterstaining of cross sections (Fig2E), which confirmed VEGF-C expression in the arterial SMCs. Whole-mount confocal microscopy showed a close contact between the lacteal vessels and the SMC fibers in the basal part of the villus where also β-Gal staining of VEGF-C was detected (Fig2D and F). These results suggest that SMCs in the villi and in the intestinal wall provide an important source for VEGF-C, which is required to maintain the lymphatic vessel architecture in the intestine. It should be noted that SMC contractility in the villi has been suggested to be important for dietary lipid absorption and that VEGF-C can induce contraction of the SMCs around the collecting lymphatic vessels in normal and pathological conditions (Hosoyamada & Sakai, 2005, 2007; Breslin et al, 2007; Gogineni et al, 2013).
Affiliation: Wihuri Research Institute and Translational Cancer Biology Program, Biomedicum Helsinki University of Helsinki, Helsinki, Finland.