title: Three-dimensional nanofibrillar surfaces promote self-renewal in mouse embryonic stem cells.
abstract: The regulation of mouse embryonic stem cell (mESC) fate is controlled by the interplay of signaling networks that either promote self-renewal or induce differentiation. Leukemia inhibitory factor (LIF) is a cytokine that is required for stem cell renewal in mouse but not in human embryonic stem cells. However, feeder layers of embryonic fibroblasts are capable of inducing stem cell renewal in both cell types, suggesting that the self-renewal signaling pathways may also be promoted by other triggers, such as alternative cytokines and/or chemical or physical properties of the extracellular matrix (ECM) secreted by feeder fibroblasts. We have recently used a synthetic polyamide matrix (Ultra-Web) whose three-dimensional (3D) nanofibrillar organization resembles the ECM/basement membrane. Growth of mESCs on this nanofibrillar surface greatly enhanced proliferation and self-renewal in comparison with growth on tissue culture surfaces without nanofibers, despite the presence of LIF in both systems. Enhanced proliferation and self-renewal of the stem cells on nanofibrillar surfaces were correlated with the activation of the small GTPase Rac, the activation of phosphoinositide 3-kinase (PI3K) pathway, and the enhanced expression of Nanog, a homeoprotein required for maintenance of pluripotency. Inhibitors of PI3K reduced the expression level of Nanog in mESCs cultured on 3D nanofibrillar surfaces. These results provide support for the view that the three-dimensionality of the culture surface may function as a cue for the activation of Rac and PI3K signaling pathways, resulting in stem cell proliferation and self-renewal.
authors.affiliation: Department of Pharmacology, UMDNJ-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, New Jersey 08854, USA. nurekasa@umdnj.edu
authors.forename: Alam
authors.initials: A
authors.lastname: Nur-E-Kamal
authors.forename: Ijaz
authors.initials: I
authors.lastname: Ahmed
authors.forename: Jabeen
authors.initials: J
authors.lastname: Kamal
authors.forename: Melvin
authors.initials: M
authors.lastname: Schindler
authors.forename: Sally
authors.initials: S
authors.lastname: Meiners
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002452:Cell Count; D018929:Cell Culture Techniques / Q000379:methods*; D002454:Cell Differentiation; D049109:Cell Proliferation; D048429:Cell Size; D004268:DNA-Binding Proteins / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology*; D024022:Fibrillar Collagens / Q000737:chemistry*; D018398:Homeodomain Proteins / Q000378:metabolism; D051379:Mice; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D000071317:Nanog Homeobox Protein; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D015398:Signal Transduction; D013234:Stem Cells / Q000378:metabolism / Q000502:physiology*; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D004268:DNA-Binding Proteins; D024022:Fibrillar Collagens; D018398:Homeodomain Proteins; D000071317:Nanog Homeobox Protein; C475540:Nanog protein, mouse; D014212:Tretinoin; D019869:Phosphatidylinositol 3-Kinases; D000469:Alkaline Phosphatase; D020559:Monomeric GTP-Binding Proteins