title: Dynamics of gene expression during bone matrix formation in osteogenic cultures derived from human embryonic stem cells in vitro.
abstract: Characterization of directed differentiation protocols is a prerequisite for understanding embryonic stem cell behavior, as they represent an important source for cell-based regenerative therapies. Studies have investigated the osteogenic potential of human embryonic stem cells (HESCs), building upon those using pre-osteoblastic cells, however no consensus exists as to whether differentiating HESCs behave in a similar manner to the traditionally used osteoblastic progenitors. Thus, the aim of the current investigation was to define the gene expression pattern of osteoblastic differentiating HESCs, treated with ascorbic acid phosphate, beta-glycerophosphate and dexamethasone over a 25 day period. Characterization of the gene expression dynamics revealed a phasic pattern of bone-associated protein synthesis. Collagen type I and osteopontin were initially expressed in proliferating immature cells, whereas osterix was up-regulated at the end of active cellular proliferation. Subsequently, mineralization-associated proteins, bone sialoprotein and osteocalcin were detected. In light of this dynamic expression pattern, we concluded that two distinguishable phases occurred during osteogenic HESC differentiation; first, cellular proliferation and secretion of a pre-maturational matrix, and second the appearance of osteoprogenitors with characteristic extracellular matrix synthesis. Establishment of this model provided the foundation of a time-frame for the additional supplementation with growth factors, BMP2 and VEGF. BMP2 induced the expression of principle osteogenic factors, such as osterix, bone sialoprotein and osteocalcin, whereas VEGF had the converse effect on the gene expression pattern.
authors.affiliation: Center for Oral Biology, Institute of Odontology, Karolinska Institutet, P. O. Box 4064, SE-141 04 Huddinge, Sweden.
authors.forename: Elerin
authors.initials: E
authors.lastname: Kärner
authors.forename: Carl-Magnus
authors.initials: CM
authors.lastname: Bäckesjö
authors.forename: Jessica
authors.initials: J
authors.lastname: Cedervall
authors.forename: Rachael V
authors.initials: RV
authors.lastname: Sugars
authors.forename: Lars
authors.initials: L
authors.lastname: Ahrlund-Richter
authors.forename: Mikael
authors.initials: M
authors.lastname: Wendel
mesh_terms: D001205:Ascorbic Acid / Q000494:pharmacology; D001857:Bone Matrix / Q000378:metabolism*; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D049109:Cell Proliferation; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D053595:Embryonic Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D005786:Gene Expression Regulation; D005994:Glycerophosphates / Q000494:pharmacology; D006801:Humans; D008954:Models, Biological; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics*; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D005994:Glycerophosphates; D042461:Vascular Endothelial Growth Factor A; D003907:Dexamethasone; D001205:Ascorbic Acid; C031463:beta-glycerophosphoric acid