Smad7在Sox9增强BMP2诱导软骨分化中的作用和机制研究

Cartilaginous pathologies, from degenerative disorders to traumatic injuries, present a very difficult clinical challenge for cartilage lack of regenerative capabilities. While the efficacy of current clinical practices in cartilage repair remains controversial, alternative cartilage tissue engineering is being considered. Bone morphogenetic protein 2 (BMP-2) has been confirmed as one of the most powerful chondrogenic inducer However BMP2 also increase a series of negative factors of chondrogenic differentiation.Our previous studies have shown expression of Sox9 can enhance BMP2-induced chondrogenic marker and inhibit ossification markers while the Sox9 could not induce MSCs chondrogenic differentiation alone.These data suggest Sox9 can regulate BMP2 pathway to enhance chondrgenic differentiation,however the target of Sox9 is unknown. However,Smad7,seem to be potential target for its feature of inhibiting chondrgenic differentiation by blocking Smad1/5/8 and MAPK pathway.Previous studies have shown the potential fact that Smad7 can be related with triggering endochondral ossification and ECM disrupting..Our previous studies have shown expression of Sox9 can enhance BMP-2-induced chondrogenic differentiation and inhibit ossification while the Smad7 being suppressed significantly . The phenomenon indicates Smad7 expression can be downregulated by Sox9.And Smad7 may play dual role in endochondral ossification.But the mechanisms remain unknown.And there is no systemic research about the cellular and molecular mechanisms about that..We attempt to discover that：1.whether Sox9 enhance BMP2 induced chondrogenic differentiation by inhibiting Smad7 or not and the related mechanism .2.whether Smad7 can trigger endochondral ossification in BMP2 induced chondrogenic differentiation.This research aims to find relationship between Sox9 and Smad7 and understand better mechanism of Smad7 .We want to gain optimal cocktail of growth factors and effectors that most effectively to stimulates the generation of cartilage.

BMP2诱导MSC成软骨分化是目前软骨组织工程研究热点，如何增强BMP2促软骨作用，削弱负向因素成为研究重点之一。 我们发现：Sox9可有效增强BMP2诱导软骨化分化的作用，但不能单独诱导软骨化，它是否通过调节BMP2下游发挥促软骨作用？它调节的关键基因又是什么？目前国内外未见报道。Smad7在BMP2诱导软骨化同时被上调，Smad7作为软骨分化的负性因子且近来发现Smad7可能是软骨终末成熟骨化的重要调节因子。那么Sox9是否通过靶向调节Smad7而增强BMP2诱导软骨化的能力？我们发现Sox9可抑制BMP2诱导下的Smad7表达。本项目拟通过研究验证如下假设：1.Sox9通过靶向抑制Smad7促进BMP2的成软骨作用.2.抑制Smad7可阻碍软骨终末成熟骨化。研究结果有助于认识Sox9对Smad7调控关系，Smad7在软骨形成与终末成熟骨化中的作用，为靶向调控软骨组织工程提供新思路。

软骨缺损是临床上的治疗难点，构建成软骨活性的组织工程软骨具有广阔的运用前景。前期研究发现BMP2介导的间充质干细胞软骨分化是生物工程软骨构建的有效方式，然而BMP2介导的软骨内成骨不利于成软骨分化和软骨表型维持，通过高表达Sox9可有效协同BMP2诱导的成骨，抑制软骨内成骨，我们发现Sox9可能通过抑制Smad7达到了这一效果，然而具体机制尚不清楚，Smad7在BMP2介导的软骨化过程中的作用尚不明确。本课题通过重组腺病毒系统对BMP2介导过程中Smad7的作用及其与Sox9的关系进行了研究，并通过开发生物工程软骨水凝胶为BMP2诱导的软骨形成与稳定提供理想的生物工程材料。本课题指出了生物工程软骨构建与稳定了新干预靶点和信号轴，为生物工程软骨开发提供了理论依据，同时开发了CMC-ACP，GOP生物工程水凝胶，推动软骨组织工程技术的发展和解决临床难题，提供相关实验基础和理论依据.