印第安豪猪(Ihh)信号通路介导甲状旁腺激素(PTH)促进骨折愈合过程中软骨内成骨的机制研究

It is now widely recognized that PTH administration will be an effective therapy for the enhancement of bone repair after fracture. Exogenous PTH preferentially increase the volume of cartilage and the rate of chondrocyte differentiation in the callus. However, whereby mechanism of PTH action on endochondral bone formation during fracture repair is unknown. The PTHrP/Ihh feedback loop plays an important role in regulating chondrocyte proliferation and differentiation of the growth plate. More recently, Studies implicate Ihh is expressed primarily by the prehypertrophic and hypertrophic chondrocytes in the callus after fracture. Additionally systemic PTH treatment was associated with Ihh upregulation and increased rate in chondrocyte maturation and differentiation by day 5 after fracture. Our studies also showed that expression of Ihh is significantly downregulated in the callus of PTH-/- mice by day 7 after fracture comparing with wild type mice. We concluded that endogenous PTH deficiency impairs fracture healing by inhibiting Hh signalling. These findings led to the hypothesis that the role of PTH in enhancing endochondral bone formation during fracture repair may be mediated by Ihh signalling. To test the hypothesis , we will culture chondrocyte and determine the role of PTH on chondrocyte and whether Ihh signalling activation modulate the role, and we will also create femur fracures in wild-type and PTH null mice, and analyze callus tissues by histology, histochemistry , immunohistochemistry, real-time RT-PCR and Western blots. The results will offer new insights into the mechanisms of PTH action on bone fracture healing and provide theoretic evidence for using PTH to treat bone fractures.

甲状旁腺素（PTH)对于骨折愈合具有重要调控作用。外源性PTH尤其可促进骨折愈合过程中软骨骨痂生成，并使软骨骨痂向骨性骨痂转换加快。目前其机制尚不清楚。印第安豪猪(Ihh)和甲状旁腺激素相关肽之间存在负反馈调节，共同调控长骨发育过程中软骨细胞增殖和分化。研究发现，骨折后骨痂中前肥大软骨细胞和肥大软骨细胞表达Ihh。给予外源性PTH后，小鼠骨折后5天Ihh表达明显上调，软骨细胞成熟分化加快。我们的研究发现，与野生型小鼠相比， PTH-/-小鼠骨折后7天骨痂Ihh表达明显下调，内源性PTH缺乏导致Ihh通路相对抑制，进而骨折愈合延迟。基于以上研究，我们假设：Ihh信号通路可能介导PTH促进骨折愈合中软骨内成骨。本项目将通过体内外实验，利用细胞和分子生物学手段以及基因敲除动物模型，验证Ihh信号通路介导PTH促进软骨内成骨的假设，揭示PTH促进骨折愈合的分子机制，为促进骨折愈合的治疗提供新靶点。

甲状旁腺素（PTH)对于骨折愈合具有重要调控作用。外源性PTH尤其可促进骨折愈合过程中软骨骨痂生成，并使软骨骨痂向骨性骨痂转换加快。目前其机制尚不清楚。印第安豪猪(Ihh)和甲状旁腺激素相关肽之间存在负反馈调节，共同调控长骨发育过程中软骨细胞增殖和分化。研究发现，骨折后骨痂中前肥大软骨细胞和肥大软骨细胞表达Ihh。给予外源性PTH后，小鼠骨折后5天Ihh表达明显上调，软骨细胞成熟分化加快。我们的研究发现，与野生型小鼠相比，PTH-/-小鼠骨折后7天骨痂Ihh表达明显下调，内源性PTH缺乏导致Ihh通路相对抑制，进而骨折愈合延迟。基于以上研究，我们假设：Ihh信号通路可能介导PTH促进骨折愈合中软骨内成骨。本项目将通过体内外实验，利用细胞和分子生物学手段以及基因敲除动物模型，验证Ihh信号通路介导PTH促进软骨内成骨的假设，揭示PTH促进骨折愈合的分子机制，为促进骨折愈合的治疗提供新靶点。