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Status |
Public on Jan 12, 2007 |
Title |
Enhanced Bone Regeneration Associated with Decreased Apoptosis in Mice with Partial HIF-1Alpha Deficiency |
Organism |
Mus musculus |
Experiment type |
Expression profiling by array
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Summary |
HIF-1a activates genes under hypoxia and was hypothesized to regulate bone regeneration. Surprisingly, HET HIF-1a fracture calluses are larger, stronger and stiffer than WT HIF-1a calluses due to decreased apoptosis. These data identify apoptosis inhibition as a means to enhance bone regeneration.
Introduction: Bone regeneration subsequent to fracture involves the synergistic activation of multiple signaling pathways. Localized hypoxia following fracture activates hypoxia-inducible factor 1 alpha (HIF-1a) leading to increased expression of HIF-1 target genes. We therefore hypothesized that HIF-1a is a key regulator of bone regeneration
Materials and Methods: Fixed femoral fractures were generated in mice with partial HIF-1a deficiency (HET HIF-1a) and wild type littermates (WT HIF-1a). Fracture calluses and intact contralateral femurs from post fracture day (PFD) 21 and 28 (N=5-10) were subjected to MicroCT evaluation and 4-point bending in order to assess morphometric and mechanical properties. Molecular analyses were carried out on PFD 7, 10 and 14 samples (N=3) to determine differential gene expression at both mRNA and protein levels. Finally, TUNEL staining was performed on PFD 14 samples (N=2) to elucidate differential apoptosis.
Results: Surprisingly, fracture calluses from HET HIF-1a mice exhibit greater mineralization and are larger, stronger and stiffer. Microarray analyses focused on hypoxia-induced genes revealed differential expression (between genotypes) of several genes associated with the apoptotic pathway. Real-time PCR confirmed these results, demonstrating higher expression of pro-apoptotic PP2A and lower expression of anti-apoptotic BCL2 in WT HIF-1a calluses. Subsequent TUNEL staining demonstrates that WT HIF-1a calluses contain larger numbers of TUNEL positive chondrocytes and osteoblasts than HET HIF-1a calluses.
Conclusions: We conclude that partial HIF-1a deficiency results in decreased chondrocytic and osteoblastic apoptosis; thereby allowing the development of larger, stiffer calluses and enhancing bone regeneration. Furthermore, apoptosis inhibition may be a promising target for developing new treatments to accelerate bone regeneration. Keywords: Bone, Fracture, Apoptosis, Hypoxia, Microarray
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Overall design |
Unilateral femoral fractures were induced in WT HIF-1a and HET HIF-1a mice. Total RNA from fracture calluses corresponding to post fracture day (PFD) 7, 10 and 14 was analyzed. Comparisons were made between genotypes at each time point. Focused microarrays for hypoxia-induced and angiogenesis related genes were utilized.
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Contributor(s) |
Komatsu DE, Bosch-Marce M, Semenza GL, Hadjiargyrou M |
Citation(s) |
17181398 |
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Submission date |
Oct 20, 2006 |
Last update date |
Mar 16, 2012 |
Contact name |
Michael Hadjiargyrou |
E-mail(s) |
michael.hadjiargyrou@sunysb.edu
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Phone |
6316321480
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Fax |
6316328577
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Organization name |
Stony Brook University
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Department |
Biomedical Engineering
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Street address |
Psy A, Room 338
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City |
Stony Brook |
State/province |
NY |
ZIP/Postal code |
11794 |
Country |
USA |
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Platforms (2) |
GPL1121 |
SuperArray GEArray Q Series Mouse Angiogenesis Gene Array |
GPL1190 |
SuperArray GEArray Q Series Mouse Hypoxia Signaling Pathway Gene Array |
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Samples (12)
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Relations |
BioProject |
PRJNA97647 |
Supplementary file |
Size |
Download |
File type/resource |
GSE6091_RAW.tar |
30.0 Kb |
(http)(custom) |
TAR (of TXT) |
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