The ability of cells to sense and respond to changes in oxygen tension is critical for many developmental, physiological, and pathological processes, including angiogenesis, control of blood flow and tissue repair. In many oxygen sensitive tissues, hypoxic stress induces the expression of genes whose products act in concert to facilitate the supply of metabolic energy. Among these are genes coding for erythropoietin (EPO), vasoactive endothelial growth factor (VEGF), the glucose transporters, nitric oxide synthetase and tyrosine hydroxylase. In skeletal tissue, intramembranous and endochondral ossification occur in close association and proximity to capillary in-growth and angiogenesis. In addition, disruption of normal afferent blood supply occurs following fracture and leads to hypoxia of adjacent tissue. Based on these observations, we reasoned that cells of mesenchymal origin including osteoblasts were ideally positioned in bone to sense and respond to fluctuations in oxygen and nutrient supply. Consistent with this concept, osteoblasts and osteocytes respond to hypoxia by elevating the level of the hypoxia-inducible factor 1 (HIF-1), an evolutionarily conserved master regulator of the hypoxic response, which in turn, transactivates VEGF and other HIF-1 target genes. We therefore hypothesize that osteoblasts use the HIF-1alpha pathway to sense reduced oxygen tension and transmit signals that impinge on angiogenic and osteogenic gene programs. To test this hypothesis we will use genetically altered mice to determine the cellular and molecular impact of gain of HIF-1alpha function through targeted overexpression of a stable HIF-1 molecule or loss of HIF-1alpha by conditional mutagenesis in osteoblasts during bone development and following bone injury. Complementary in vitro studies in primary osteoblasts will attempt to determine whether HIF-1alpha impacts osteoblast growth and differentiation independent of the vasculature.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR049410-04
Application #
7232072
Study Section
Skeletal Biology Development and Disease Study Section (SBDD)
Program Officer
Sharrock, William J
Project Start
2004-08-01
Project End
2009-04-30
Budget Start
2007-05-01
Budget End
2008-04-30
Support Year
4
Fiscal Year
2007
Total Cost
$283,660
Indirect Cost
Name
University of Alabama Birmingham
Department
Pathology
Type
Schools of Medicine
DUNS #
063690705
City
Birmingham
State
AL
Country
United States
Zip Code
35294
Dirckx, Naomi; Tower, Robert J; Mercken, Evi M et al. (2018) Vhl deletion in osteoblasts boosts cellular glycolysis and improves global glucose metabolism. J Clin Invest 128:1087-1105
Dewan, Ashvin K; Tomlinson, Ryan E; Mitchell, Stuart et al. (2015) Dysregulated TGF-? signaling alters bone microstructure in a mouse model of Loeys-Dietz syndrome. J Orthop Res 33:1447-54
Farber, Charles R; Reich, Adi; Barnes, Aileen M et al. (2014) A novel IFITM5 mutation in severe atypical osteogenesis imperfecta type VI impairs osteoblast production of pigment epithelium-derived factor. J Bone Miner Res 29:1402-11
Bogan, Rosalind; Riddle, Ryan C; Li, Zhu et al. (2013) A mouse model for human osteogenesis imperfecta type VI. J Bone Miner Res 28:1531-6
Riddle, Ryan C; Leslie, Julie M; Gross, Ted S et al. (2011) Hypoxia-inducible factor-1? protein negatively regulates load-induced bone formation. J Biol Chem 286:44449-56
Wan, Chao; Shao, Jin; Gilbert, Shawn R et al. (2010) Role of HIF-1alpha in skeletal development. Ann N Y Acad Sci 1192:322-6
Shomento, Stacy H; Wan, Chao; Cao, Xuemei et al. (2010) Hypoxia-inducible factors 1alpha and 2alpha exert both distinct and overlapping functions in long bone development. J Cell Biochem 109:196-204
Weinstein, Robert S; Wan, Chao; Liu, Qinglan et al. (2010) Endogenous glucocorticoids decrease skeletal angiogenesis, vascularity, hydration, and strength in aged mice. Aging Cell 9:147-61
Zhang, Fengjie; Qiu, Tao; Wu, Xiangwei et al. (2009) Sustained BMP signaling in osteoblasts stimulates bone formation by promoting angiogenesis and osteoblast differentiation. J Bone Miner Res 24:1224-33
Riddle, Ryan C; Khatri, Richa; Schipani, Ernestina et al. (2009) Role of hypoxia-inducible factor-1alpha in angiogenic-osteogenic coupling. J Mol Med (Berl) 87:583-90

Showing the most recent 10 out of 18 publications