Morphological and molecular analyses of bone repair

骨是具有较强再生能力的组织之一，但骨修复的分子机制尚不完全清楚。为了通过分析骨折愈合过程中基因表达的变化来探讨骨修复的分子机制，我们进行了多次实验，得到了以下结果。我们首先用RT-PCR检测了小鼠肋骨骨折后几种mrna的表达。在骨折前的肋骨中未发现Sonic hedgehog （Shh）和Indian hedgehog （Ihh）的明显mrna。骨折12-24小时后，我们发现Shh mRNA水平相当高。骨折48 ~ 72 h后表达量下降。骨折后第5天未发现Shh mRNA。骨折3天后Ihh mRNA表达。骨折24-48小时后BMP-2 mRNA表达增加，BMP-4、BMP-7 mRNA表达无明显变化。这些结果表明Shh可能在骨折修复早期诱导BMP-2中发挥重要作用。此外，Cbfa1 mRNA的表达在骨折72小时后增加，Cbfa1是成骨细胞分化和骨形成的重要转录因子。我们现在正通过原位杂交研究这些基因的表达模式。

Although bone is one of tissues with strong regenerating ability, molecular mechanism of bone repair has not been fully understood. In order to investigate molecular mechanism of bone repair by analysis of changes in gene expression during fracture healing, we conducted several experiments and obtained the following results.We first examined expression of several mRNAs after fracture of mouse ribs by RT-PCR.Apparent mRNAs for Sonic hedgehog (Shh) and Indian hedgehog (Ihh) were not found in ribes before fracture. After 12-24 hours of fracture, we found substantial level of Shh mRNA.Its expression decreased after 48-72 hours of fracture. No Shh mRNA was found on day 5 after fracture. Expression for Ihh mRNA was found after 3 days of fracture. Expression of BMP-2 mRNA increased after 24-48 hours of fracture, while no apparent changes in expression of BMP-4 and BMP-7 mRNAs was found. These results indicated that Shh may play an important role in induction of BMP-2 at early phase of fracture repair. In addition, expression of mRNA for Cbfa1, which is an essential transcription factor of osteoblast differentiation and bone formation, increased after 72 hours of fracture. We are now investigating the expression pattern of these genes by in situ hybridization.