Gene expression of periostin in the early stage of fracture healing detected by cDNA microarray analysis

Abstract

To comprehensively evaluate gene expression in the early stage of fracture healing, we used a cDNA microarray with 2304 cDNA clones derived from an oligo-capped mouse embryo library. Closed mid-diaphyseal fractures were created in mouse tibiae and expression profiles were analyzed 3 days after fracture. Six genes were up-regulated in comparison to those in unfractured bones and these included three genes previously identified but never shown to be present in fractures, periostin, calumenin, and FHL-1. Cloning of these genes has been completed but their expression pattern and function during fracture healing and bone formation remain to be elucidated. Up-regulation of the six genes was reconfirmed by semi-quantitative RT-PCR analysis. Spatial and temporal expression of one of the newly identified fracture-induced genes, periostin, was analyzed using in situ hybridization, because it displayed the highest up-regulation ratio. A signal for periostin was detected in undifferentiated mesenchymal cells and immature preosteoblastic cells in the periosteal tissues between days 3 and 14 after fracture. Northern analysis showed that periostin gene expression rapidly increased by day 3, reached a peak on day 7, and declined by day 14. These findings suggest that periostin is a specific marker for preosteoblasts and may play an important role in periosteal callus formation during the early stage of fracture healing.