OBJECTIVE: Angiopoietin-1 (Ang-1) plays a critical role in the maintenance of hematopoietic stem cells (HSCs) in the bone marrow (BM) through its binding to the Tie2 receptor. Ang-2, another Tie2 ligand, is known to be an antagonist of Tie2/Ang-1 signaling in angiogenesis; however, its function in regulation of HSCs remains unclear. Here, we investigated the functional differences between Ang-1 and Ang-2 in the maintenance of HSCs. MATERIALS AND METHODS: We treated mouse BM lineage(-)Sca-1(+)c-Kit(+) side population(+) cells with Ang-1 and/or Ang-2, and evaluated angiopoietin function by gene expression analysis, immunocytochemical staining of phosphorylated Akt, a colony-formation assay, and a long-term BM reconstitution assay. RESULTS: Gene expression analysis and BM transplantation assay revealed that Ang-1 upregulated expression of p57, p18, Itgb1, Alcam, Tie2, Hoxb4, and Bmi1 genes in HSCs, while Ang-2 antagonized the effects of Ang-1. Ang-1 enhanced the phosphorylation of Akt, while Ang-2 again reduced the effect of Ang-1. The colony assay demonstrated that neither Ang-1, nor Ang-2 influenced the colony formation of HSCs. BM transplantation assay, following in vitro cultivation of HSCs with angiopoietins, showed that Ang-1 maintained long-term repopulating activity of HSCs, while the addition of Ang-2 interfered drastically with the effects of Ang-1. CONCLUSION: Gene expression analysis and BM transplantation assay demonstrated that Ang-1 maintained HSC activity in an in vitro culture. In contrast, Ang-2 reversed the effects of Ang-1/Tie2 signaling in the regulation of long-term HSCs. Our data suggest that Ang-1 is a dominant ligand for the Tie2 receptor in long HSCs in BM. Copyright 2010 ISEH - Society for Hematology and Stem Cells. Published by Elsevier Inc. All rights reserved.
OBJECTIVE:Angiopoietin-1 (Ang-1) plays a critical role in the maintenance of hematopoietic stem cells (HSCs) in the bone marrow (BM) through its binding to the Tie2 receptor. Ang-2, another Tie2 ligand, is known to be an antagonist of Tie2/Ang-1 signaling in angiogenesis; however, its function in regulation of HSCs remains unclear. Here, we investigated the functional differences between Ang-1 and Ang-2 in the maintenance of HSCs. MATERIALS AND METHODS: We treated mouse BM lineage(-)Sca-1(+)c-Kit(+) side population(+) cells with Ang-1 and/or Ang-2, and evaluated angiopoietin function by gene expression analysis, immunocytochemical staining of phosphorylated Akt, a colony-formation assay, and a long-term BM reconstitution assay. RESULTS: Gene expression analysis and BM transplantation assay revealed that Ang-1 upregulated expression of p57, p18, Itgb1, Alcam, Tie2, Hoxb4, and Bmi1 genes in HSCs, while Ang-2 antagonized the effects of Ang-1. Ang-1 enhanced the phosphorylation of Akt, while Ang-2 again reduced the effect of Ang-1. The colony assay demonstrated that neither Ang-1, nor Ang-2 influenced the colony formation of HSCs. BM transplantation assay, following in vitro cultivation of HSCs with angiopoietins, showed that Ang-1 maintained long-term repopulating activity of HSCs, while the addition of Ang-2 interfered drastically with the effects of Ang-1. CONCLUSION: Gene expression analysis and BM transplantation assay demonstrated that Ang-1 maintained HSC activity in an in vitro culture. In contrast, Ang-2 reversed the effects of Ang-1/Tie2 signaling in the regulation of long-term HSCs. Our data suggest that Ang-1 is a dominant ligand for the Tie2 receptor in long HSCs in BM. Copyright 2010 ISEH - Society for Hematology and Stem Cells. Published by Elsevier Inc. All rights reserved.
Authors: Kakali Sarkar; Sergio Rey; Xianjie Zhang; Raul Sebastian; Guy P Marti; Karen Fox-Talbot; Amanda V Cardona; Junkai Du; Yee Sun Tan; Lixin Liu; Frank Lay; Frank J Gonzalez; John W Harmon; Gregg L Semenza Journal: Cardiovasc Res Date: 2011-10-25 Impact factor: 10.787
Authors: Anna Szmigielska-Kaplon; Anna Krawczynska; Magdalena Czemerska; Agnieszka Pluta; Barbara Cebula-Obrzut; Katarzyna Szmigielska; Konrad Stępka; Piotr Smolewski; Tadeusz Robak; Agnieszka Wierzbowska Journal: Blood Transfus Date: 2014-09-12 Impact factor: 3.443