胰岛素样生长因子1对BMP9介导肌源性间充质干细胞成骨作用的影响及机制研究

Bone is one of the few organs that retain the potential for regeneration in adult body, and is the only tissue that can undergo continual remodelling throughout life. Efficacious bone regeneration should have an important impact on the clinical management of many bone and musculoskeletal disorders, such as with segmental bone loss, fracture non-union, and failed spinal fusion. Muscel-derived mesenchymal stem cells (MD-MSCs) hold great promise for tissue bioengineering and regenerative medicine. MD-MSCs are adherent muscle stromal cells that can self-renew and differentiate into osteogenic, chondrogenic, adipogenic, and myogenic lineages. BMP9 (also known as growth differentiation factor 2, or GDF-2) was first identified in the developing mouse liver . We have demonstrated that BMP9 is the probaly potent osteogenic BMPs in MSCs. It is conceivable that other growth factors may act synergistically on BMP9-induced bone formation. we propose to investigate the effect of insulin-like growth factor 1 (IGF1) on BMP9-induced bone formation. IGF1 plays an important role in prenatal growth and development. IGF1 transduces its signaling through IGF-IR and activates the PI3K/Akt pathway or the MAPK pathway. We have found that endogenous IGF1 expression is relatively low in MD-MSCs. Exogenous expression of IGF1 can potentiate BMP9-induced bone formation and bone regeneration. The proposed work is devoted to elucidate the molecular basis behind the synergistical effect between IGF1 and BMP9 in MD-MSCs both in vitro and in vivo. A successful completion of our proposed studies should not only expand our understanding about BMP9-IGF1 crosstalks but also lead to the development of a novel strategy for efficacious bone regeneration.

各种原因所致骨缺损、骨不连是临床常见但尚未解决的难题，传统治疗疗效不理想。干细胞基因治疗为此提供了一种解决途径。肌源性间充质干细胞（MD-MSCs）是重要的成骨种子细胞,促进其细胞增殖、成骨分化及机制探讨是目前研究的热点。课题组前期研究发现：BMP9诱导成骨能力强，是一种较理想的成骨因子；IGF1可能协同调控BMP9介导的成骨分化作用，促进高效成骨，但具体机制不明。本课题拟利用组织培养、干细胞移植和MicroCT三维定量分析等技术，将外源IGF1和/或BMP9作用于MD-MSCs细胞、裸鼠胚肢及动物成骨模型，通过成骨及发育指标的检测，研究IGF1对BMP9诱导成骨作用的影响；采用BMPR-RSmad报告系统、腺病毒干扰、AktDN及iAkt检测技术等对BMP9与IGF1信号通路间的交叉调控作用进行深入探讨。本项目将为研究IGF1对BMP9介导成骨作用的影响及机制做一些探索性工作。

骨组织工程是一种代替骨移植来治疗相关骨病的理想的方法。BMP9已被证明是最强的成骨诱导因子之一，通过增强BMP9诱导的成骨分化将会极大的促进组织工程骨的进展。本研究项目主要研究胰岛素样生长因子1（IGF1）在BMP9诱导的成骨分化中的作用，并对其中的相关机制进行了探讨。研究表明，间充质干细胞中均可以检测到IGF1和BMP9的表达。外源性的IGF1可以增加BMP9诱导的成骨早期指标碱性磷酸酶的表达，骨基质的矿化，以及异位骨的形成。而且，IGF1可以增强BMP9诱导的软骨内成骨。进一步探讨机制，我们发现IGF1可以增强BMP9诱导的BMP/Smad信号通路的激活。而且，PI3蛋白激酶抑制剂LY294002可抑制由 BMP9介导的ALP活性，提示PI3K/AKT可能和BMP9介导的成骨信号通路具有交叉调节作用。本研究项目表明，IGF1可以显著增强BMP9介导的间充质干细胞的成骨作用,其可能的机制是BMP/Smad通路的增强以及PI3K/AKT信号通路的交叉调节。受本研究项目的支持，课题组已发表9篇SCI论文,还有1篇SCI论文已经被接受。项目的后续研究在2016年已经获得国家自然科学基金的支持，课题组将进一步分析IGF1能否逆转地塞米松对骨髓间充质干细胞成骨分化的抑制作用以及可能的分子机制，进一步丰富对糖皮质激素性骨质疏松症发病机制的认识,为临床预防和治疗糖皮质激素性骨质疏松症提供新思路。