Sinusoid development and morphogenesis may be stimulated by VEGF‐Flk‐1 signaling during fetal mouse liver development

Abstract

Early morphogenesis of hepatic sinusoids was histochemically and experimentally analyzed, and the importance of VEGF‐Flk‐1 signaling in the vascular development was examined during murine liver organogenesis. FITC‐gelatin injection experiments into young murine fetuses demonstrated that all primitive sinusoidal structures were confluent with portal and central veins, suggesting that hepatic vessel development may occur via angiogenesis. At 12.5–14.5 days of gestation, VEGF receptors designated Flk‐1, especially their mature form, were highly expressed in endothelial cells of primitive sinusoidal structures and highly phosphorylated on their tyrosine residues. At the same time, VEGF was also detected in hepatoblasts/hepatocytes, hemopoietic cells, and megakaryocytes of the whole liver parenchyma. Furthermore, the addition of VEGF to E12.5 liver cell cultures significantly induced the growth and branching morphogenesis of sinusoidal endothelial cells. Therefore, VEGF‐Flk‐1 signaling may play an important role in the growth and morphogenesis of primitive sinusoids during fetal liver development. Developmental Dynamics 239:386–397, 2010. © 2009 Wiley‐Liss, Inc.

Vascular pathobiology in chronic liver disease and cirrhosis – Current status and future directions

“…Both forms of angiogenesis, sprouting and intussusceptive, appear to be important in normal liver physiology and in pathophysiologic states, including liver organogenesis [50,51], liver regeneration [12,52], chronic liver diseases with fibrosis [53], nodular regenerative hyperplasia [45], hepatocarcinogenesis [54], and tumour angiogenesis [45]. …”

Endoderm Generates Endothelial Cells during Liver Development

“…Hepatic blood vessels consist of the hepatic artery and three types of venous vessels (the portal veins, hepatic veins, and sinusoids) that differentiate as the liver bud expands around embryonic day 10.5 (E10.5) in the mouse embryo. Based on the position of the hepatic vessels and differential expression of connexins and the NOTCH ligand Jagged1, the origin of the hepatic endothelium was proposed to be the adjacent vasculature, including omphalomesenteric veins for the portal veins (Shiojiri et al., 2006), the cardinal vein and the sinus venosus for the hepatic veins (Shiojiri et al., 2006), and the omphalomesenteric and cardinal veins for the sinusoids (Sugiyama et al., 2010). Although interpretations from studies seeking to define the precise origins of the hepatic vasculature differ, the dogma is that the hepatic endothelium is of mesodermal origin.…”

Immunomagnetic exclusion of PECAM-1-positive endothelial cells in fetal mouse liver cell cultures causes impaired growth and gene expression of hepatoblasts and stellate cells

“…These data are well consistent with the work using Flk-1 knockout mice by Matsumoto et al (13), in which the presence of Flk-1-expressing endothelial cells was shown to play a decisive role in hepatic primordium morphogenesis. During liver organogenesis, hepatic endothelial cells develop along the primordium, and are located close to hepatic cords and stellate cells throughout development (18,23,24). The hepatic vascular system, including the portal veins, central veins and primitive sinusoids, develops with different phenotypes from early stages of the organogenesis, and primitive sinusoid structures, in which endothelial cells, stellate cells and hepatoblasts have a configuration similar to that in hepatic lobules of the adult, are already formed in fetal livers (14,22,28).…”

“…Liver primordium develops as an endodermal diverticulum in the anterior intestinal portal region in mammalian embryos, from which hepatic cords invade the subjacent septum transversum mesenchyme, and also extend into the wall of the omphalomesenteric veins and posterior cardinal veins as we thrust our fingers into an inflated balloon (2,21,24), leading to the formation of an immature liver having primitive sinusoid structures and abundant hemopoietic cells (22). The primitive sinusoid structures are constructed by endothelial cells and stellate cells, which resemble sinusoids of the adult liver in their cellular configuration and extracellular matrix deposition (22).…”

“…After washing in 1% bovine serum albumin (BSA)/TBS, the beads were incubated with a rat anti-mouse PECAM-1 antibody (1/250 dilution) at room temperature for 30 min, washed twice with 10% fetal bovine serum (FBS) (Sigma Chemical Co., St. Louis, MO, USA)/DM-160 (Kyokuto Seiyaku Co. Ltd., Tokyo, Japan), and then used for cell exclusion experiments. Livers were dissected out from E12.5 mouse fetuses and then diced (24). Diced livers were treated with 10 mM O,O'-bis (2-aminoethyl)ethyleneglycol-N,N,N',N'-tetraacetic acid (EGTA) dissolved in Dulbecco's modified Eagle's medium (DMEM) (Gibco, Grand Island, NY, USA) containing 10% FBS on ice for 30 min.…”