GEO Accession viewer

NCBI > GEO > Accession Display

Not logged in | Login

GEO help: Mouse over screen elements for information.

Series GSE6091

Query DataSets for GSE6091

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

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

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.

Contributor(s)

Komatsu DE, Bosch-Marce M, Semenza GL, Hadjiargyrou M

Citation(s)

17181398

Submission date

Oct 20, 2006

Last update date

Mar 16, 2012

Contact name

Michael Hadjiargyrou

E-mail(s)

michael.hadjiargyrou@sunysb.edu