The long-term goal of these studies is to understand cellular and molecular mechanisms that control bone development and homeostasis. Previous accomplishments range from identification of extracellular matrix molecules, transcription factors and receptors/signaling molecules with critical functions in skeletal tissues to discovery of diseases caused by mutations in their genes. During the past funding period, mice with reduced expression of vascular endothelial growth factor (VEGF) in osteoblast precursor cells were found to have osteoporosis-like skeletons with reduced bone mass and increased bone marrow fat. To characterize the mechanisms by which VEGF regulates osteoblast and adipocyte fates in mesenchymal stem cells during bone homeostasis, extensive analyses of VEGF-dependent processes in vivo and in cultures of mesenchymal stem cells are now proposed. The experiments, based on data suggesting that VEGF controls osteoblast and adipocyte formation via unconventional, intracrine, mechanisms, address innovative hypotheses concerning the role of VEGF in mesenchymal stem cell differentiation to osteoblasts and adipocytes. Finally, based on the discovery that vascular endothelial cells can be converted to multipotent mesenchymal stem-like cells (EndMT), by mechanisms that are inhibited by VEGF, experiments are designed to explore the possibility of inducing EndMT as a way of promoting bone formation during surgical bone repair and to understand the roles of VEGF in this process.

Public Health Relevance

Osteoporosis is characterized by loss of bone mass and increased bone marrow fat, raising questions about how the balance between bone-forming cells and fat is regulated. This project addresses these questions in a mouse model of osteoporosis. In addition, based on the discovery that blood vessel-lining cells can be converted to bone- forming stem cells, ways of inducing such conversion during bone repair will be studied.

National Institute of Health (NIH)
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Research Project (R01)
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Study Section
Skeletal Biology Development and Disease Study Section (SBDD)
Program Officer
Tseng, Hung H
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Harvard University
Schools of Dentistry
United States
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Huang, Wei; Olsen, Bjorn R (2015) Skeletal defects in Osterix-Cre transgenic mice. Transgenic Res 24:167-72
Berendsen, Agnes D; Olsen, Bjorn R (2014) How vascular endothelial growth factor-A (VEGF) regulates differentiation of mesenchymal stem cells. J Histochem Cytochem 62:103-8
Dellinger, Michael T; Garg, Nupur; Olsen, Bjorn R (2014) Viewpoints on vessels and vanishing bones in Gorham-Stout disease. Bone 63:47-52
Berendsen, Agnes D; Olsen, Bjorn R (2014) Osteoblast-adipocyte lineage plasticity in tissue development, maintenance and pathology. Cell Mol Life Sci 71:493-7
Adams, Allysa; McBratney-Owen, Brandeis; Newby, Brittany et al. (2013) Presphenoidal synchondrosis fusion in DBA/2J mice. Mamm Genome 24:54-62
Volloch, Vladimir; Olsen, Bjorn R (2013) Why cellular stress suppresses adipogenesis in skeletal tissue, but is ineffective in adipose tissue: control of mesenchymal cell differentiation via integrin binding sites in extracellular matrices. Matrix Biol 32:365-71
Clarkin, Claire; Olsen, Bjorn R (2010) On bone-forming cells and blood vessels in bone development. Cell Metab 12:314-6
Harnagea, Catalin; Vallieres, Martin; Pfeffer, Christian P et al. (2010) Two-dimensional nanoscale structural and functional imaging in individual collagen type I fibrils. Biophys J 98:3070-7
Besschetnova, Tatiana Y; Kolpakova-Hart, Elona; Guan, Yinghua et al. (2010) Identification of signaling pathways regulating primary cilium length and flow-mediated adaptation. Curr Biol 20:182-7
Hou, Bo; Kolpakova-Hart, Elona; Fukai, Naomi et al. (2009) The polycystic kidney disease 1 (Pkd1) gene is required for the responses of osteochondroprogenitor cells to midpalatal suture expansion in mice. Bone 44:1121-33

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