title: Twist-1 Enhances Bone Marrow Mesenchymal Stromal Cell Support of Hematopoiesis by Modulating CXCL12 Expression.
abstract: Twist-1 encodes a basic helix-loop-helix transcription factor, known to contribute to mesodermal and skeletal tissue development. We have reported previously that Twist-1 maintains multipotent human bone marrow-derived mesenchymal stem/stromal cells (BMSC) in an immature state, enhances their life-span, and influences cell fate determination. In this study, human BMSC engineered to express high levels of Twist-1 were found to express elevated levels of the chemokine, CXCL12. Analysis of the CXCL12 proximal promoter using chromatin immunoprecipitation analysis identified several E-box DNA sites bound by Twist-1. Functional studies using a luciferase reporter construct showed that Twist-1 increased CXCL12 promoter activity in a dose dependent manner. Notably, Twist-1 over-expressing BMSC exhibited an enhanced capacity to maintain human CD34 + hematopoietic stem cells (HSC) in long-term culture-initiating cell (LTC-IC) assays. Moreover, the observed increase in HSC maintenance by Twist-1 over-expressing BMSC was blocked in the presence of the CXCL12 inhibitor, AMD3100. Supportive studies, using Twist-1 deficient heterozygous mice demonstrated a significant decrease in the frequency of stromal progenitors and increased numbers of osteoblasts within the bone. These observations correlated to a decreased incidence in the number of clonogenic stromal progenitors (colony forming unit-fibroblasts) and lower levels of CXCL12 in Twist-1 mutant mice. Furthermore, Twist-1 deficient murine stromal feeder layers, exhibited a significant decrease in CXCL12 levels and lower numbers of hematopoietic colonies in LTC-IC assays, compared with wild type controls. These findings demonstrate that Twist-1, which maintains BMSC at an immature state, endows them with an increased capacity for supporting hematopoiesis via direct activation of CXCL12 gene expression.
authors.affiliation: Mesenchymal Stem Cell Laboratory, University of Adelaide, Adelaide, South Australia, Australia.|South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.|Department of Haematology, SA Pathology, Adelaide, South Australia, Australia.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Arthur
authors.affiliation: Mesenchymal Stem Cell Laboratory, University of Adelaide, Adelaide, South Australia, Australia.|South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Cakouros
authors.affiliation: Mesenchymal Stem Cell Laboratory, University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Lachlan
authors.initials: L
authors.lastname: Cooper
authors.affiliation: Mesenchymal Stem Cell Laboratory, University of Adelaide, Adelaide, South Australia, Australia.|South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.
authors.forename: Thao
authors.initials: T
authors.lastname: Nguyen
authors.affiliation: Mesenchymal Stem Cell Laboratory, University of Adelaide, Adelaide, South Australia, Australia.|South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.
authors.forename: Sandra
authors.initials: S
authors.lastname: Isenmann
authors.affiliation: Myeloma Research Laboratory, School of Medicine, Faculty of Health Sciences, University of Adelaide, Adelaide, South Australia, Australia.|South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.
authors.forename: Andrew C W
authors.initials: AC
authors.lastname: Zannettino
authors.affiliation: Division of Molecular Medicine, Beckman Research Institute of the City of Hope, Duarte, California, USA.
authors.forename: Carlotta A
authors.initials: CA
authors.lastname: Glackin
authors.affiliation: Mesenchymal Stem Cell Laboratory, University of Adelaide, Adelaide, South Australia, Australia.|South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.
authors.forename: Stan
authors.initials: S
authors.lastname: Gronthos
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000378:metabolism*; D054377:Chemokine CXCL12 / Q000096:biosynthesis* / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation; D006410:Hematopoiesis; D006801:Humans; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D051879:Twist-Related Protein 1 / Q000235:genetics / Q000378:metabolism*
chemical_list: C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; C515256:Cxcl12 protein, mouse; D009687:Nuclear Proteins; C103173:TWIST1 protein, human; D051879:Twist-Related Protein 1; C067250:Twist1 protein, mouse
keywords: Bone marrow stromal cells; CXCL12; Hematopoiesis; Hematopoietic stem cells; Mesenchymal stem cell; SDF-1; Twist