The Semb Laboratory
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Aim: The laboratory headed by Professor, Center Director Henrik Semb focus on how cell polarity and tissue architecture control cell fate specification, as well as the translation of this basic knowledge into more reliable strategies in regenerative medicine, in particular human pluripotent stem cell-based cell therapy in diabetes.
Recently, we reported ground-breaking results showing that apical polarity and normal pancreatic tissue architecture is required for beta cell specification. The emerging concept from this work is that apical polarity plays a central role in coordinating morphogenetic processes and cell fate specification. We hypothesize that the lack of progress in generating glucose-responsive beta cells from human embryonic stem cells (hESCs) under current 2D culture conditions in vitro is due to failure to regulate apical polarity and the assembly of the epithelial intercellular signalling processes necessary for beta cell birth. We propose to establish a mechanism for how cell polarity within the multicellular epithelial environment during lumen and tube formation lead to efficient beta cell birth in vivo, and to translate these results into new 3D in vitro differentiation strategies of hESCs. These strategies will facilitate hESC-derived multipotent pancreatic progenitors to undergo the necessary dynamic changes in cell polarity, cell adhesion and cell migration for beta cell birth, and thereby overcome current bottlenecks in generating functional beta cell from hESCs.
3D live organ imaging: We have developed an in vitro system to study pancreatic morphogenesis in whole pancreatic explants using confocal imaging. Taking advantage of existing fluorescent reporter mouse strains and combining them with our own newly generated reporter for apical polarity we can follow tubulogenesis and delamination live with single cell resolution and monitor and quantify each event, such as a changes in cell polarity and microlumen fusion event, over time. We are aiming to implement this system to perform comparative live analysis of our mouse models as well as to monitor the effect of various cell signaling agonists/antagonists.
The impact of cell polarity and tubulogenesis on cell type specification: Using the developing pancreas as model system, we are studying the basic mechanisms of RhoGTPase-mediated cell polarization of epithelial cells and how this control lumen formation and tubulogenesis in vivo. Special focus is on how these events balance the expansion of endocrine progenitor cells and their differentiation into insulin producing beta cells. We are using various mouse mutant models to address these questions in combination with the above-mentioned unique 3D live imaging system.
Isolation and characterization of hESC-derived multipotent pancreatic progenitors and their differentiation towards functional insulin producing cells: We have generated pancreas specific reporter cell lines (eg PDX1-GFP) using classical gene targeting by homologous recombination. Using these reporter lines we are addressing important questions such as the molecular mechanisms for expansion of multipotent human pancreatic progenitors and their differentiation into glucose-responsive beta cells via Neurogenin3 endocrine progenitors as well as the identification of new cell surface markers for distinct beta cell progenitors.
- Edsbagge, J., Johansson, J., Esni, F., Luo, Y., Radice, G., and Semb, H. Vascular function and sphingosine-1-phosphate regulate development of the dorsal pancreatic mesenchyme. Development 132, 1085-1092, 2005. “We proposed a new model for how blood vessel-derived sphingosine-1-phosphate stimulates growth and budding of the dorsal pancreatic endoderm by induction of mesenchymal cell proliferation.”
- Brolén, G.K.C., Heins, N., Edsbagge, J., and Semb, H. Signals from the embryonic mouse pancreas induce differentiation of human embryonic stem cells into insulin-producing beta cell-like cells. Diabetes 54, 2867-2874, 2005. “We showed for the first time that signals from the embryonic mouse pancreas induce differentiation of human embryonic stem cells into mono-hormonal insulin+ beta-cell-like cells.”
- Xian, X., Håkansson, J., Lindblom, P., Betsholtz, C., Gerhardt, H., and Semb, H. Pericytes limit tumor cell metastasis. J Clin Invest 116, 642-51, 2006. “We presented a new model for how tumor cells trigger metastasis by perturbing pericyte-endothelial cell-cell interactions.”
- Ellerström, C., Strehl, R., Moya, K., Andersson, K., Bergh, C., Lundin, K., Hyllner, J., and Semb, H. Derivation of a xeno-free human embryonic stem cell line. Stem Cells. 24, 2170-6, 2006. “We report the establishment and characterization of a xeno-free pluripotent diploid normal hESC line”
- Kesavan, G., Wolfhagen Sand, F., Greiner, T., Johansson, J., Kobberup, S., Wu, X., Brakebusch, C., and Semb, H. Cdc42-mediated tubulogenesis controls cell specification. Cell 139 (Nov), 791-801, 2009. “We showed that Cdc42 is essential for tube formation, specifically for initiating microlumen formation and later for maintaining apical cell polarity in vivo, and that lumens/tubes provide the correct microenvironment for proper control of cell-fate choices of multipotent progenitors.”
- Ameri, J., Ståhlberg, A., Pedersen, J., Johansson, J.K., Johannesson, M., Artner, I., and Semb, H. FGF2 Specifies hESC-Derived Definitive Endoderm into Foregut/Midgut Cell Lineages in a Concentration Dependent Manner. Stem Cells 28, 45-56, 2010. “We showed for the first time that FGF2 specifies hESC-derived definitive endoderm into different foregut lineages (liver, pancreas, lung) in a dosage-dependent manner.”
- Fischer, Y., Ganic, E., Ameri, J., Xian, X., Johannesson, M., and Semb, H. NANOG reporter cell lines generated by gene targeting in human embryonic stem cells. PLoS One 2;5(9), pii: e12533, 2010. “We report generation of NANOG reporter hESC lines using gene targeting by homologous recombination to elucidate the regulation and function of NANOG in pluripotent hESCs.”
- Wolfhagen Sand, F., Hörnblad, A., Johansson, J.K., Lorén, C., Edsbagge, J., Ståhlberg, A., Magenheim, J., Ilovich, O., Mishani, E., Dor,Y., Proia, R.L., Ahlgren, U. and Semb, H. Growth-limiting role of endothelial cells in endoderm development. Dev Biol, 15, 267-77, 2011. “We showed that endothelial cells limit progenitor cell expansion in several foregut-derived organs.”