title: Inhibiting actin depolymerization enhances osteoblast differentiation and bone formation in human stromal stem cells.
abstract: Remodeling of the actin cytoskeleton through actin dynamics is involved in a number of biological processes, but its role in human stromal (skeletal) stem cells (hMSCs) differentiation is poorly understood. In the present study, we demonstrated that stabilizing actin filaments by inhibiting gene expression of the two main actin depolymerizing factors (ADFs): Cofilin 1 (CFL1) and Destrin (DSTN) in hMSCs, enhanced cell viability and differentiation into osteoblastic cells (OB) in vitro, as well as heterotopic bone formation in vivo. Similarly, treating hMSC with Phalloidin, which is known to stabilize polymerized actin filaments, increased hMSCs viability and OB differentiation. Conversely, Cytocholasin D, an inhibitor of actin polymerization, reduced cell viability and inhibited OB differentiation of hMSC. At a molecular level, preventing Cofilin phosphorylation through inhibition of LIM domain kinase 1 (LIMK1) decreased cell viability and impaired OB differentiation of hMSCs. Moreover, depolymerizing actin reduced FAK, p38 and JNK activation during OB differentiation of hMSCs, while polymerizing actin enhanced these signaling pathways. Our results demonstrate that the actin dynamic reassembly and Cofilin phosphorylation loop is involved in the control of hMSC proliferation and osteoblasts differentiation.
authors.affiliation: Molecular Endocrinology Laboratory (KMEB), Odense University Hospital, University of South Denmark, DK-5000 Odense C, Denmark. Electronic address: lchen@health.sdu.dk.
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.affiliation: Molecular Endocrinology Laboratory (KMEB), Odense University Hospital, University of South Denmark, DK-5000 Odense C, Denmark.
authors.forename: Kaikai
authors.initials: K
authors.lastname: Shi
authors.affiliation: Molecular Endocrinology Laboratory (KMEB), Odense University Hospital, University of South Denmark, DK-5000 Odense C, Denmark.
authors.forename: Charles Edward
authors.initials: CE
authors.lastname: Frary
authors.affiliation: Molecular Endocrinology Laboratory (KMEB), Odense University Hospital, University of South Denmark, DK-5000 Odense C, Denmark.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Ditzel
authors.affiliation: Molecular Endocrinology Laboratory (KMEB), Odense University Hospital, University of South Denmark, DK-5000 Odense C, Denmark; Department of Spine Surgery, Honghui Hospital, Xi'an JiaoTong University College of Medicine, 710054 Xi'an, China.
authors.forename: Huimin
authors.initials: H
authors.lastname: Hu
authors.affiliation: Molecular Endocrinology Laboratory (KMEB), Odense University Hospital, University of South Denmark, DK-5000 Odense C, Denmark.
authors.forename: Weimin
authors.initials: W
authors.lastname: Qiu
authors.affiliation: Molecular Endocrinology Laboratory (KMEB), Odense University Hospital, University of South Denmark, DK-5000 Odense C, Denmark; Danish Stem Cell Center (DanStem), Panum Institute, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Moustapha
authors.initials: M
authors.lastname: Kassem
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D001854:Bone Marrow Cells / Q000166:cytology; D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D051338:Cofilin 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051345:Destrin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism; D006801:Humans; D054461:Lim Kinases / Q000378:metabolism; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology; D010012:Osteogenesis / Q000187:drug effects; D010590:Phalloidine / Q000633:toxicity; D010766:Phosphorylation / Q000187:drug effects; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D051338:Cofilin 1; D051345:Destrin; D034741:RNA, Small Interfering; D010590:Phalloidine; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; C515892:LIMK1 protein, human; D054461:Lim Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4
keywords: Actin polymerizing and depolymerizing factors; Bone formation; Human stromal stem cells; Osteoblastic differentiation