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Septum Transversum-Derived Mesothelium Gives Rise to Hepatic Stellate Cells and Perivascular Mesenchymal Cells in Developing Mouse Liver

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Septum Transversum-Derived Mesothelium Gives Rise to Hepatic Stellate Cells and Perivascular Mesenchymal Cells in Developing Mouse Liver Septum Transversum-Derived Mesothelium Gives Rise to Hepatic Stellate Cells and Perivascular Mesenchymal Cells in Developing Mouse Liver Kinji Asahina,1 Bin Zhou,2,3 William T. Pu,2,3 and Hidekazu Tsukamoto1,4 The septum transversum mesenchyme (STM) signals to induce hepatogenesis from the foregut endoderm. Hepatic stellate cells (HSCs) are sinusoidal pericytes assumed to origi- nate from the STM and participate in mesenchymal-epithelial interaction in embryonic and adult livers. However, the developmental origin of HSCs remains elusive due to the lack of markers for STM and HSCs. We previously identified submesothelial cells (SubMCs) beneath mesothelial cells (MCs) as a potential precursor for HSCs in developing livers. In the present study, we reveal that both STM in embryonic day (E) 9.5 and MC/SubMCs in E12.5 share the expression of activated leukocyte cell adhesion molecule (Alcam), desmin, and Wilms tumor 1 homolog (Wt1). A cell lineage analysis using MesP1Cre/Rosa26lacZflox mice identifies the mesodermal origin of the STM, HSCs, and perivascular mesenchymal cells (PMCs). A conditional cell lineage analysis using the Wt1CreERT2 mice demonstrates that Wt11 STM gives rise to MCs, SubMCs, HSCs, and PMCs during liver development. Furthermore, we find that Wt11 MC/SubMCs migrate inward from the liver surface to gen- erate HSCs and PMCs including portal fibroblasts, smooth muscle cells, and fibroblasts around the central veins. On the other hand, the Wt11 STM and MC/SubMCs do not con- tribute to sinusoidal endothelial cells, Kupffer cells, and hepatoblasts. Conclusion: our results demonstrate that HSCs and PMCs are derived from MC/SubMCs, which are traced back to mesodermal STM during liver development. (HEPATOLOGY 2011;000:000-000.) Abbreviations: Alcam, activated leukocyte cell adhesion molecule; CreERT2, Cre and modified estrogen receptor; E, embryonic day; EMT, epithelial- mesenchymal transition; FBs, fibroblasts; GFP, green fluorescent protein; HSCs, hepatic stellate cells; Jag1, Jagged 1; LL, left lobe; MCs, mesothelial cells; ML, epatic stellate cells (HSCs) are characterized median lobe; PFBs, portal fibroblasts; PMCs, perivascular mesenchymal cells; by the expression of desmin and storage of SECs, sinusoidal endothelial cells; SMA, a-smooth muscle actin; SMCs, smooth vitamin A in the liver.1 Upon injury, cyto- muscle cells; STM, septum transversum mesenchyme; SubMCs, submesothelial H cells; Wt1, Wilms tumor 1 homolog. kines and reactive oxygen species from injured hepato- From the 1Southern California Research Center for ALPD and Cirrhosis and cytes, Kupffer cells, and HSCs themselves trigger HSC Department of Pathology, Keck School of Medicine of the University of Southern activation.2,3 Activated HSCs lose vitamin A lipid, California, Los Angeles, CA; 2Department of Cardiology, Children’s Hospital Boston, Boston, MA; 3Harvard Stem Cell Institute, Harvard University, transform into a myofibroblastic phenotype expressing Cambridge, MA; 4Department of Veterans Affairs Greater Los Angeles alpha-smooth muscle actin (SMA), and synthesize Healthcare System, Los Angeles, CA.. proinflammatory cytokines and excessive extracellular Received October 8, 2010; accepted November 30, 2010. Supported by pilot project funding (to K.A.) from the National Institutes of matrix proteins. Thus, suppression of HSC activation Health P50AA011999 (to H.T.); R24AA12885 (to H.T.); and Medical is considered a major therapeutic target for treatment Research Service of Department of Veterans Affairs (to H.T.). Bin Zhou is of liver fibrosis.2 In addition to HSCs, different liver cumently affilized with Shanghai Institutes for Biological Sciences, Chinese mesenchymal cell types may serve as the source of Academy of science, Shanghai, China. 3 Address reprint requests to: Kinji Asahina, Ph.D., Southern California myofibroblasts in fibrosis. Electron microscopy sug- Research Center for ALPD and Cirrhosis, Keck School of Medicine of the gests that myofibroblasts are possibly derived from University of Southern California, 1333 San Pablo St., MMR 410, Los HSCs, portal fibroblasts (PFBs) in the portal area, Angeles, CA 90033-9141. E-mail: [email protected]; fax: (323) 442-3126. Copyright VC 2011 by the American Association for the Study of Liver Diseases. smooth muscle cells (SMCs) in the veins, and myofi- View this article online at wileyonlinelibrary.com. broblasts and fibroblasts (FBs) around the central DOI 10.1002/hep.24119 veins.4 Myofibroblasts derived from different sources Potential conflict of interest: Nothing to report. appear to participate in liver fibrogenesis, although Additional Supporting Information may be found in the online version of 1-3 this article. their origin remains to be determined. 1 2 ASAHINA ET AL. HEPATOLOGY, Month 2011 During mouse embryogenesis, the liver is formed as SubMCs seem to migrate inward and differentiate into a diverticulum of the foregut endoderm around em- HSCs. A similar observation was also reported in bryonic day (E) 9.5 in mice.5,6 The ventral region of developing human liver, in which HSCs appear to the foregut endoderm invades the surrounding septum grow from SubMCs beneath the liver capsule.15 In transversum mesenchyme (STM) and gives rise to hep- support of this notion, isolated Alcamþ MC/SubMCs atoblasts that are capable of differentiating into both stored vitamin A lipids, a functional feature of differ- hepatocytes and biliary epithelial cells.5,6 Electron mi- entiated HSCs when cultured in collagen gel with reti- croscopic observation suggests trapping of the STM nol.13 Based on these data, we hypothesized that MC/ between growing hepatoblasts and possible develop- SubMCs give rise to HSCs and PMCs in developing ment of HSCs from the STM in the mouse fetal livers.13 liver.7 As supportive evidence, the STM and HSCs We recently demonstrated that HSCs are mesoder- share expression of Foxf1 and Lhx2 during embryo- mal in origin by a cell lineage analysis using the genesis.8,9 However, a definitive answer for the STM- MesP1Cre and Rosa26lacZ mice.13 However, the HSC notion has not been attained due to the lack of MesP1þ cells in early embryos contribute to a broad specific markers for tracing the STM and HSC range of mesoderm components.16 Thus, it remains to lineages. be determined how the STM and mesothelium partici- Besides the STM, different developmental origins pate in the generation of HSCs from MesP1þ mesoderm were proposed for HSCs including the liver mesothe- during liver development. Furthermore, it is not known lium, neural crest, bone marrow, endoderm, and meso- whether HSC and other liver cell types such as hepato- derm.1 With respect to the neural crest notion, a cell blasts and SECs are derived from the same precursor. In lineage analysis using Wnt1Cre and Rosa26 mice failed the present study we traced the cell lineages of the STM to support it.10 In chick embryos, the liver mesothe- and mesothelium by a conditional cell lineage analysis lium contributes to HSCs and sinusoidal endothelial using the Wt1CreERT2 mice.17 This analysis demonstrates 11 cells (SECs). In mouse embryos, the liver mesothe- that Wt1þ STM in E9.5 gives rise to MC, SubMCs, lium may delaminate and become incorporated to the HSCs, and PMCs in a manner involving inward migra- sinusoidal walls, as shown by the use of Wilms tumor tion of Wt1þ MC/SubMCs from the liver surface to 1 homolog (Wt1)-LacZ mice.12 Although several generate HSCs and PMCs during liver morphogenesis. observational studies suggested the contribution of the STM or mesothelium to HSCs,7-9,11,12 definitive answers to these notions have not been attained by rig- Materials and Methods orous genetic-based lineage-tracing methods. Mice. MesP1Cre, Wt1CreERT2, Rosa26lacZflox, Rosa The determination of an HSC lineage is important 26mTmGflox mice were described previously.16-19 Ta- for better understanding of how different mesenchymal moxifen (Sigma) dissolved in ethanol was emulsified in cell types organize liver morphogenesis in embryos and sesame oil at 12.5 mg/mL and 2 mg of tamoxifen was how phenotypes of HSCs and PFBs are determined injected intraperitoneally to the pregnant mice from and regulated in liver fibrosis. As the first step toward E10.5. Before E10.5 embryos, we failed to induce this goal, we have identified markers for HSCs and lacZ expression in the STM by injection of 2 mg ta- characterized their phenotype in mouse embryos.13 Fe- moxifen, despite the strong expression of Wt1 in the tal HSCs express desmin and p75 neurotrophin recep- STM. Before E9.0 embryos, a fetal-placental circula- tor in E12.5 livers.13,14 In addition to these markers, tion is yet to be established and tamoxifen injected mesenchymal cells around the veins express SMA and into the mother may not be delivered efficiently to the Jagged 1 (Jag1).13,14 We termed these mesenchymal embryos. We also experienced that tamoxifen treat- cells as perivascular mesenchymal cells (PMCs), ment before E10.5 embryos often results in abnormal because the bile duct is not formed around E12.5 and bleeding in utero and termination of embryogenesis. portal and central veins morphologically cannot be dis- Thus, we injected a reduced tamoxifen dose of 1.5 mg tinguished.13 Mesothelial cells (MCs) covering liver twice at E7.5 and E8.5 and examined the embryos at surface express podoplanin.13 Beneath MCs, we identi- E9.5 and E11.5. Although some embryos still died by fied unique mesenchymal cells named as ‘‘submesothe- this method, surviving embryos did not show any signs lial cells (SubMCs).’’13 MCs and SubMCs are sepa- of abnormalities. Mice were used in accordance with rated by the basal lamina and both cell types express protocols approved by the Institutional Animal Care activated leukocyte cell adhesion molecule (Alcam) and and Use Committee of the University of Southern Wt1 in E12.5 livers. Interestingly, Alcamþdesminþ California. HEPATOLOGY, Vol. 000, No. 000, 2011 ASAHINA ET AL. 3 X-gal Staining. Embryos were fixed with 4% para- also expresses Alcam and desmin (Fig.
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