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Updated: Feb 15, 2026
Calvarial Model of Bone Augmentation in Rabbit for Assessment of Bone Growth and Neovascularization in Bone Substitution Materials
Published on: August 13, 2019
Differential transcriptional expression profiles of juvenile and adult calvarial bone
Oliver O Aalami1, Randall P Nacamuli, Ali Salim
1Department of Surgery, Stanford University School of Medicine, Stanford, Calif 94305-5148, USA.
Background:
It has widely been observed that young children are capable of reossifying large calvarial defects, while adults lack this endogenous tissue-engineering capacity. The ability of juvenile animals to regenerate calvarial defects has been investigated in multiple animal models, including mice. In this study, the authors used cDNA microarrays to investigate the expression of osteogenesis-associated genes upstream and downstream of Runx2 in juvenile and adult mouse calvaria.
Methods:
Nonsuture-associated parietal bone discs were harvested from 6-day-old (n = 50) and 60-day-old (n = 35) male CD-1 mice. After separation of the underlying dura mater and overlying pericranium, the calvarial discs were snap-frozen and RNA was extracted from pooled samples of calvaria for microarray analysis. Genes analyzed included cytokines, receptors, and cell-surface and matrix proteins both upstream and downstream of Runx2.
Results:
Genes associated with the Runx2 pathway had notably higher levels in the juvenile versus adult calvaria. All genes except for osteocalcin were expressed at least twofold higher in the juvenile calvaria. This pattern was validated with quantitative real-time polymerase chain reaction. In addition, mRNA for potent osteoinductive growth factors was present at higher levels in the juvenile compared with the adult calvaria.
Conclusions:
These findings reflect a genomic environment of active osteoblast differentiation and ossification in the juvenile calvaria compared with the adult "quiescent" calvarial tissue. These data suggest that a decreased osteogenic potential of adult calvarial osteoblasts may, in part, explain the inability of adult animals to heal calvarial defects.
Insights
Juvenile mice exhibit significantly higher expression of osteogenesis-associated genes, including those in the Runx2 pathway, compared to adult mice. This suggests a more active bone healing and regeneration capacity in young animals.
Area of Science:
- Molecular biology
- Developmental biology
- Regenerative medicine
Background:
- Young children can regenerate skull defects, unlike adults, indicating a loss of endogenous tissue engineering capacity with age.
- Previous studies explored juvenile animal models for calvarial defect regeneration.
- This study investigates gene expression related to bone formation in young versus adult mice.
Purpose of the Study:
- To compare the expression of osteogenesis-associated genes, both upstream and downstream of Runx2, in juvenile and adult mouse calvaria.
- To understand the molecular mechanisms underlying the difference in calvarial healing capacity between young and adult animals.
Main Methods:
- Calvarial bone discs were harvested from 6-day-old and 60-day-old CD-1 mice.
- RNA was extracted from pooled calvaria for cDNA microarray analysis.
- Genes analyzed included cytokines, receptors, cell-surface, and matrix proteins related to the Runx2 pathway.
Main Results:
- Genes in the Runx2 pathway showed significantly higher expression in juvenile calvaria compared to adult calvaria.
- All analyzed genes, except osteocalcin, were upregulated at least twofold in juvenile mice.
- Quantitative real-time PCR validated these microarray findings.
- Potent osteoinductive growth factors were found at higher levels in juvenile mice.
Conclusions:
- Juvenile calvaria display a genomic environment conducive to active osteoblast differentiation and ossification.
- Adult calvarial tissue is characterized by a "quiescent" state.
- Reduced osteogenic potential in adult calvarial osteoblasts may contribute to the impaired healing of calvarial defects in adult animals.
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