Scleraxis在糖皮质激素抑制肌腱干细胞成肌腱分化中的作用及其分子机制研究

Glucocorticoid-induced tendon rupture is very common in clinical practice, and the rerupture risk is rather high. The mechanism remains unclear. Large number of studies demonstrated that glucocorticoid-induced tendon rupture and decreased self-repair ability is associated with the inhibition of differentiation of TSCs into tenocytes.. Previous study has demonstrated that the tenocytes in glucocorticoid-induced ruptured tendon decreased, dexamethasone（Dex）inhibits TSCs differentiation into tenocytes. Our preliminary experiment showed that scleraxis in glucocorticoid-induced ruptured tendon is down regulated. 4% uniaxial stretch antagonizes the inhibition of glucocorticoid on TSCs differentiation into tenocytes. We hypothesize that scleraxis is a key factor mediating the inhibition of glucocorticoid on TSCs differentiation into tenocytes and 4% uniaxial stretch can antagonize the inhibition through scleraxis. This project planed to be carried out from clinical specimens, rat tendon model in vivo, TSCs from rat in vitro by tissue and molecular biology techniques to study the mechanism of inhibition of TSCs differentiation into tenocytes induced by dexamethasone and the antagonism of moderate uniaxial stretch. And this project will illustrate the cellular and molecular mechanism of glucocorticoid-induced tendon rupture and self-repair ability decrease from a new vision and provide a new target for glucocorticoid-induced tendon rupture and difficulty to repair.

糖皮质激素导致肌腱自发性断裂非常常见，且手术后再次发生断裂的风险高，其机制尚不清楚。大量研究表明糖皮质激素导致肌腱自发断裂及降低肌腱自身修复功能与肌腱干细胞（TSCs）向肌腱细胞分化受阻有关。前期发现糖皮质激素导致的断裂肌腱中肌腱细胞减少，糖皮质激素抑制TSCs成肌腱分化，糖皮质激素导致的断裂肌腱scleraxis（Scx）表达降低；4%单轴牵伸拮抗Dex对TSCs成肌腱分化的抑制，故推测：Scx是介导糖皮质激素抑制TSCs成肌腱分化的重要因子，4%单轴牵伸可通过Scx拮抗糖皮质激素对TSCs成肌腱分化的抑制作用。本项目拟从临床标本、大鼠模型及体外实验，通过组织学和分子生物学技术研究Dex抑制TSCs成肌腱分化的分子机制及适度机械牵伸对Dex抑制TSCs成肌腱分化的拮抗作用。本课题拟从新的视觉阐明糖皮质激素导致肌腱自发断裂和自身修复困难发生的机制，并为其提供新的防治靶点。

糖皮质激素全身使用或者局部注射导致肌腱自发性断裂非常常见，且手术后再次发生断裂的风险高，其机制尚不清楚。大量研究表明糖皮质激素导致肌腱自发断裂及降低肌腱自身修复功能与肌腱干细胞（tendon stem cells, TSCs）向肌腱细胞分化受阻有关。前期发现糖皮质激素导致的断裂肌腱中肌腱细胞减少，糖皮质激素抑制TSCs成肌腱分化，糖皮质激素导致的断裂肌腱scleraxis（Scx）表达降低，故推测Scx是介导糖皮质激素抑制TSCs成肌腱分化的关键转录因子，本项目从临床标本、大鼠模型及体外实验，通过组织学和分子生物学技术研究糖皮质激素代表药物地塞米松（dexamethasone, Dex）对大鼠TSCs（rTSCs）分化的影响，Dex对大鼠TSCs Scx 的影响，Scx 在Dex 诱导的TSCs 异常分化中的作用，Scx 在适度单轴细胞牵伸载荷拮抗Dex 对TSCs 向肌腱细胞分化的抑制中的作用。研究发现：低浓度10nM的Dex促进rTSCs成肌腱分化的转录因子Scx表达，抑制成脂肪细胞分化转录因子C/EBPα的表达，而高浓度1uM Dex抑制rTSCs表达Scx，促进其其表达成脂分化转录因子C/EBPα。高浓度Dex作用于受体以后，受体与成肌腱分化的关键转录因子Scx的启动子上游-726~-734碱基GGCAAGGT结合，抑制其表达，从而抑制rTSCs向肌腱细胞分化。Scx是糖皮质激素抑制TSCs向肌腱细胞分化关键转录因子。本课题从糖皮质激素抑制TSCs向肌腱细胞分化角度阐释了肌腱自发断裂和自身修复困难发生的机制。