Megakaryocytes Contribute to the Bone Marrow-Matrix Environment by Expressing Fibronectin, Type IV Collagen, and Laminin

Authors

  • Alessandro Malara,

    1. Department of Molecular Medicine, University of Pavia, Pavia, Italy
    2. Biotechnology Research Laboratories, IRCCS San Matteo Foundation, Pavia, Italy
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  • Manuela Currao,

    1. Department of Molecular Medicine, University of Pavia, Pavia, Italy
    2. Biotechnology Research Laboratories, IRCCS San Matteo Foundation, Pavia, Italy
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  • Cristian Gruppi,

    1. Department of Molecular Medicine, University of Pavia, Pavia, Italy
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  • Giuseppe Celesti,

    1. Laboratory of Molecular Gastroenterology, IRCCS Humanitas Clinical and Research Center, Milan, Italy
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  • Gianluca Viarengo,

    1. Immunohaematology and Transfusion Service, Apheresis and Cell Therapy Unit, Pavia, Italy
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  • Chiara Buracchi,

    1. Department of Immunology and Inflammation, IRCCS Humanitas Clinical and Research Center, Milan, Italy
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  • Luigi Laghi,

    1. Laboratory of Molecular Gastroenterology, IRCCS Humanitas Clinical and Research Center, Milan, Italy
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  • David L. Kaplan,

    1. Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, USA
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  • Alessandra Balduini

    Corresponding author
    1. Department of Molecular Medicine, University of Pavia, Pavia, Italy
    2. Biotechnology Research Laboratories, IRCCS San Matteo Foundation, Pavia, Italy
    3. Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, USA
    • Correspondence: Alessandra Balduini, M.D., Biotechnology Research Laboratories, Department of Molecular Medicine, University of Pavia, IRCCS San Matteo Foundation, Viale Forlanini 6, 27100 Pavia, Italy. Telephone: 39-0382-502984; Fax: 39-0382-502990; e-mail: alessandra.balduini@tufts.edu

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Abstract

Megakaryocytes associate with the bone marrow vasculature where they convert their cytoplasm into proplatelets that protrude through the vascular endothelium into the lumen and release platelets. The extracellular matrix (ECM) microenvironment plays a critical role in regulating these processes. In this work we demonstrate that, among bone marrow ECM components, fibronectin, type IV collagen, and laminin are the most abundant around bone marrow sinusoids and constitute a pericellular matrix surrounding megakaryocytes. Most importantly, we report, for the first time, that megakaryocytes express components of the basement membrane and that these molecules contribute to the regulation of megakaryocyte development and bone marrow ECM homeostasis both in vitro and in vivo. In vitro, fibronectin induced a threefold increase in the proliferation rate of mouse hematopoietic stem cells leading to higher megakaryocyte output with respect to cells treated only with thrombopoietin or other matrices. However, megakaryocyte ploidy level in fibronectin-treated cultures was significantly reduced. Stimulation with type IV collagen resulted in a 1.4-fold increase in megakaryocyte output, while all tested matrices supported proplatelet formation to a similar extent in megakaryocytes derived from fetal liver progenitor cells. In vivo, megakaryocyte expression of fibronectin and basement membrane components was upregulated during bone marrow reconstitution upon 5-fluorouracil induced myelosuppression, while only type IV collagen resulted upregulated upon induced thrombocytopenia. In conclusion, this work demonstrates that ECM components impact megakaryocyte behavior differently during their differentiation and highlights a new role for megakaryocyte as ECM-producing cells for the establishment of cell niches during bone marrow regeneration. Stem Cells 2014;32:926–937

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