低氧对骨髓间充质干细胞成骨分化的影响及机制研究

The development of the bone tissue engineering brings hope to the repairation of the jaw defect.Although the BMSCs are the ideal seed cells for the bone tissue engineering and possess high ability of directed osteogenesis differentiation in vitro.In vivo,however,this ability is largely limited.hypoxia conditions in local jaw defect are the main factor that restricts the differentiation of BMSCs.Recent investigations have proved that Id is a kind of gene sensitive to oxygen and its expression is upregulatated continuously under hypoxia conditions.Besides,the alteration of id family's expression during the osteogenesis differentiation is the key factor that guarantees the differentiation can be successfully completed.According to those mentioned above,Id may be the key factor mediating the restriction on osteogenesis differentiation of the BMCSs under hypoxia conditions, with the mechanism being unknown.Id can activate the factor PPARγrelated to the adipogenic differentiation,from which we can postulate that the factor PPARγ may participate in the restriction on osteogenesis differentiation of the BMCSs mediated by Id under hypoxia conditions.Blocking PPARγdoes not fully promote osteogenic differentiation,there have other means to induced adipogenesis under hypoxia. HDAC4 can be induced by hypoxia to inhibit differentiation of osteoblasts by reduce the expression of Runx2, suggesting that inhibiting HDAC4 could promote osteogenic differentiation of BMSCs..We plan to investigate the approaches of the restriction on the osteogenesis differentiation of BMCSs mediated by Id and the mechanism of the regulation of Id expression under hypoxia conditions and uncover the role of id in the restriction on osteogenesis differentiation through hypoxia regulation system,transcriptomics,iRNA and some other methods.

BMSCs是骨组织工程理想的种子细胞在体外具有良好的成骨分化能力，但是其体内成骨能力却非常有限。骨损伤的低氧环境是限制BMSCs成骨分化的主要因素。低氧可持续上调Id分子，且Id分子在BMSCs成骨分化过程中的表达变化，是BMSCs成骨分化顺利进行的关键，提示Id分子可能是低氧抑制BMSCs成骨分化的关键分子。Id分子可活化成脂分化因子PPARγ，其可能参与低氧下Id分子对BMSCs的成骨抑制。低氧也可通过其他途径诱导脂肪分化，阻断PPARγ并不能完全促进成骨分化。低氧可上调HDAC4降低Runx2的表达抑制成骨，抑制HDAC4可以促进成骨分化。本研究拟采用低氧控制系统、转录组学、RNA干扰等技术，探讨低氧通过Id抑制BMSCs成骨分化的途径及调控机制，验证HDAC4对成骨分化的抑制作用；寻求低氧抑制BMSCs成骨分化的因素，为BMSCs体内成骨的临床应用提供理论基础和新的策略。

低氧环境是限制骨损伤中BMSCs成骨分化的主要因素，但低氧如何调控其分化目前尚不清楚。本研究对低氧调控BMSCs的成骨分化进行研究，发现低氧可持续上调Id分子。将BMSCs置于低氧环境下，在成骨诱导分化过程中分析检测发现Id可调控PPARγ及HDAC4从而下调Runx2影响BMSCs的成骨分化；采用转录组芯片技术筛选低氧条件下调控Id的关键通路分子，利用不同的阻断策略阻断PPARγ及抑制HDAC4，发现在低氧环境下可增加BMSCs的成骨分化；建立大鼠骨缺损模型，构建不同靶分子的干扰载体及载体处理的大鼠BMSCs，进行体内成骨分析研究。对低氧环境下BMSCs定向成骨分化及其调控机制的揭示，将为其在骨组织工程中的应用研究带来新的希望和制备策略。