Project description:Microvascular endothelial cells (EC) display a high degree of phenotypic and functional heterogeneity among different organs. Organ-specific EC control their tissue microenvironment by angiocrine factors in health and disease. Liver sinusoidal EC (LSEC) are uniquely differentiated to fulfil important organ-specific functions in development, under homeostatic conditions, and in regeneration and liver pathology. Recently, Bmp2 has been identified by us as an organ-specific angiokine derived from LSEC. To study angiocrine Bmp2 signaling in the liver, we conditionally deleted Bmp2 in LSEC using EC subtype-specific Stab2-Cre mice. Genetic inactivation of hepatic angiocrine Bmp2 signaling in Stab2-Cre;Bmp2fl/fl (Bmp2LSECKO) mice caused massive iron overload in the liver, and increased serum iron levels and iron deposition in several organs similar to classic hereditary hemochromatosis. Iron overload was mediated by decreased hepatic expression of hepcidin, a key regulator of iron homeostasis. Thus, angiocrine Bmp2 signaling within the hepatic vascular niche represents a constitutive pathway indispensable for iron homeostasis in vivo that is non-redundant with Bmp6. Notably, we demonstrate that organ-specific angiocrine signaling is essential not only for the homeostasis of the respective organ, but also for the homeostasis of the whole organism.
Project description:Liver sinusoidal endothelial cells (LSEC) represent a unique, organ-specific type of discontinuous endothelial cells. LSEC instruct the hepatic vascular niche by paracrine-acting angiocrine factors. Recently, we have shown that LSEC-specific transcriptional regulator GATA4 induces expression of BMP2 in cultured endothelial cells (EC) in vitro. Furthermore, angiocrine Bmp2 signaling in the liver in vivo was demonstrated to control iron homeostasis. Here, we investigated GATA4-dependent autocrine BMP2 signaling in endothelial cells by gene expression profiling. GATA4 induced a large cluster of inflammatory endothelial response genes in cultured EC, which is similar to previously identified virus-induced and interferon-associated responses. Treating the cells with the BMP2 inhibitor Noggin counter-regulated the GATA4-dependent inflammatory phenotype of EC, indicating that BMP2 is indeed the major driver. In contrast to continuous EC, LSEC were less prone to activation by BMP2. Notably, GATA4-dependent induction of the inflammatory EC response gene cluster was attenuated by over-expression of the LSEC-specific transcriptional modifier LMO3 while hepatocyte activation was fully preserved, indicating conserved BMP2 synthesis. In summary, our data suggest that transcriptional counter-regulation by GATA4 and LMO3 in LSEC prevents autocrine induction of an inflammatory phenotype, while maintaining angiocrine BMP2-mediated cell communication in the liver vascular niche.
Project description:Liver sinusoidal endothelial cells (LSEC) represent a unique, organ-specific type of discontinuous endothelial cells. LSEC instruct the hepatic vascular niche by paracrine-acting angiocrine factors. Recently, we have shown that LSEC-specific transcriptional regulator GATA4 induces expression of BMP2 in cultured endothelial cells (EC) in vitro. Furthermore, angiocrine Bmp2 signaling in the liver in vivo was demonstrated to control iron homeostasis. Here, we investigated GATA4-dependent autocrine BMP2 signaling in endothelial cells by gene expression profiling. GATA4 induced a large cluster of inflammatory endothelial response genes in cultured EC, which is similar to previously identified virus-induced and interferon-associated responses. Treating the cells with the BMP2 inhibitor Noggin counter-regulated the GATA4-dependent inflammatory phenotype of EC, indicating that BMP2 is indeed the major driver. In contrast to continuous EC, LSEC were less prone to activation by BMP2. Notably, GATA4-dependent induction of the inflammatory EC response gene cluster was attenuated by over-expression of the LSEC-specific transcriptional modifier LMO3 while hepatocyte activation was fully preserved, indicating conserved BMP2 synthesis. In summary, our data suggest that transcriptional counter-regulation by GATA4 and LMO3 in LSEC prevents autocrine induction of an inflammatory phenotype, while maintaining angiocrine BMP2-mediated cell communication in the liver vascular niche.
Project description:The liver is a largest solid organ in the body and is majorly composed of HCs, ECs, KCs, and HSCs, which spatially interact and cooperate each other to maintain liver homeostasis. However, the complexity and molecular mechanisms underlying the crosstalk between these different cell types remain to be revealed. Here, we generated mice with conditional deletion of Bmp9/10 in different liver cell types and demonstrated that HSCs was the major source of BMP9 and BMP10 in the liver. Using transgenic ALK1 (receptor for BMP9/10) reporter mice, we found that ALK1 is expressed on KCs and ECs other than HCs and HSCs. KCs from Bmp9/10HSC-KO (conditional deletion of Bmp9/10 from HSCs) mice lost their signature genes expression, such as ID1/3, CLEC4F, VSIG4 and CLEC2, and were replaced by monocyte-derived macrophages. ECs from Bmp9/10HSC-KO mice also lost their identity and were transdifferentiated to continuous ECs, ultimately leading to collagen IV deposition and liver fibrosis. Hepatic ECs expressed several angiocrine factors, such as BMP2, BMP6, Wnt2 and Rspo3, to regulate liver iron metabolism and metabolic zonation. We found that these angiocrine factors were significantly decreased in ECs from Bmp9/10HSC-KO mice, which further resulted in liver iron overload and disruption of HCs zonation. In addition, focal fatty liver spontaneously occurred in Bmp9/10HSC-KO mice at the age of 28W. In summary, we demonstrated that HSCs play a central role in mediating liver cell-cell crosstalk via production of BMP9/10 to maintain liver health.
Project description:Mutations in repulsive guidance molecule c (RGMc) / hemojuvelin (HJV) cause juvenile hemochromatosis, an aggravated iron overload disorder that presents early in life. Patients with juvenile hemochromatosis, and RGMc knockout mice, have diminished expression of the key iron-regulatory peptide, hepcidin. This suggests that RGMc plays a critical role in the regulation of iron homeostasis; however the mechanisms of RGMc actions are unknown. Recent studies have shown that RGMc directly binds to the growth factors, bone morphogenetic protein 2 and 6 (BMP2 and BMP6), and it is possible that this interaction regulates aspects of iron metabolism. We used microarrays to examine the effects of RGMc on BMP2- and BMP6-mediated gene expression. In our experimental model we treated Hep3B liver cells that had been serum starved for 16 hours as follows: (1) un-treated, (2) BMP2, (3) BMP2 + 10-fold molar excess of Noggin (a potent BMP2 inhibitor), (4) BMP2 + 20-fold molar excess of RGMc, (5) BMP6, (6) BMP6 + 10-fold molar excess of Noggin, (7) BMP6 + 20-fold molar excess of RGMc. Binding was allowed to proceed for BMP and Noggin or RGMc for 3 hr at 20°C prior to treatment of Hep3B cells. Treatment time was 4 hr at which cells were collected for RNA isolation.
Project description:The role of bone morphogenetic protein 2 (Bmp2)in regulating the transformation of the uterine stroma during embryo implantation in the mouse was investigated by the conditional ablation of Bmp2 in the uterus using the (PR-cre) mouse. Experiment Overall Design: Bmp2 gene ablation was confirmed by real-time PCR analysis in the PR-cre; Bmp2fl/fl (termed Bmp2d/d) uterus. While littermate controls average 0.9 litter of 6.2 ± 0.7 pups per month, Bmp2d/d females are completely infertile. Analysis of the infertility indicates that whereas embryo attachment is normal in the Bmp2d/d as in control mice, the uterine stroma is incapable of undergoing the decidual reaction to support further embryonic development. Recombinant human BMP2 can partially rescue the decidual response, suggesting that the observed phenotypes are not due to a developmental consequence of Bmp2 ablation. Microarray analysis demonstrates that ablation of Bmp2 leads to specific gene changes, including disruption of the Wnt signaling pathway, Progesterone receptor (PR) signaling, and the induction of prostaglandin synthase 2 (Ptgs2). Taken together, these data demonstrate that Bmp2 is a critical regulator of gene expression and function in the murine uterus.
Project description:Mutations in repulsive guidance molecule c (RGMc) / hemojuvelin (HJV) cause juvenile hemochromatosis, an aggravated iron overload disorder that presents early in life. Patients with juvenile hemochromatosis, and RGMc knockout mice, have diminished expression of the key iron-regulatory peptide, hepcidin. This suggests that RGMc plays a critical role in the regulation of iron homeostasis; however the mechanisms of RGMc actions are unknown. Recent studies have shown that RGMc directly binds to the growth factors, bone morphogenetic protein 2 and 6 (BMP2 and BMP6), and it is possible that this interaction regulates aspects of iron metabolism. We used microarrays to examine the effects of RGMc on BMP2- and BMP6-mediated gene expression.
Project description:Iron induces hepcidin by activating bone morphogenetic protein (BMP)6-SMAD signaling, which is critical for regulation of systemic iron homeostasis. High iron levels induce BMP6 production in liver endothelial cells, but the molecular mechanisms by which iron regulates BMP6 are incompletely understood. To address this, we performed RNA-sequencing on sorted liver endothelial cells from iron-adequate and iron-loaded mice.
Project description:Iron is an essential trace element whose absorption is usually tightly regulated in the duodenum. HFE-related hereditary hemochromatosis (HH) is characterized by abnormally low expression of the iron-regulatory hormone, hepcidin, which results in increased iron absorption. The liver is crucial for iron homeostasis as it is the main production site of hepcidin. The aim of this study was to explore and compare the genome-wide transcriptome response to Hfe deficiency and dietary iron overload in murine liver and duodenum.