诱导骨生长因子Nell-1与牵张成骨技术相结合用于促进骨再生的研究

High-speed and high-energy trauma often leads to long limbs bone defect, and the existing treatment is complex and curative effect is unsatisfactory. It is urgent to improve. Through stretching fracture callus, distraction osteogenesis stimulates local to form new bone constantly and connects large areas bone defect simply. However, new bone biomechanical property is poor and need a long period to restore after operation. New bone growth factor Nell-1 could induce osteoblast differentiation and mineralization specifically, and the ability of promoting differentiation is stronger than that of hyperplasia, the forming bone tissue being more kin to cortical bone. The detailed mechanism needs to be studied further. It is reported that Nell-1 applied into distraction osteogenesis has not been found in domestic and foreign research. This subject tries to complete a preliminary experiment in vitro of Nell-1. On the basis of dynamic observation on rat femurs distraction osteogenesis, the role of the new bone growth factors in distraction osteogenesis was studied. After Nell-1 gene transfecting bone marrow stromal cells, dynamic observation of transplanted cell transformation, involved growth factors and bone formation confirmed the role of Nell-1 in distraction osteogenesis, which provided experimental evidence and theoretical basis for further clinical research.

高速高能四肢创伤常导致难以处理的大段骨缺损，现有治疗方法复杂、疗效一般，急需改进。牵张成骨通过逐渐牵拉骨折骨痂，刺激局部不断形成新骨，从而连接大段骨性缺损，治疗方法简便，但周期长，新骨生物力学性能差，术后需长期改建。新的骨生长因子Nell1可特异性诱导成骨细胞的分化及矿化，与已广泛应用的促骨生长因子BMPs的不同之处是促分化强于促增生，其形成的骨组织更近似于皮质骨。但其详细机制仍需进一步研究，且国内外尚未见报道将其应用于四肢牵张成骨中促进成骨、矿化及愈合。本课题拟在完成Nell1的初步体外实验及对大鼠股骨牵张成骨动态观察的基础上，研究这一新的骨生长因子在牵张成骨中的作用，将Nell1基因转染荧光标记的骨髓基质细胞应用于大鼠股骨牵张成骨模型，动态观察移植细胞转归、相关生长因子变化及骨形成，明确Nell1与骨髓基质细胞协同作用下在牵张成骨中的作用，为进一步应用于临床提供实验及理论依据。

骨折是严重影响人民群众身体健康的常见病症。随着经济社会的发展和人口老龄化的加剧，导致骨折发生的因素出现新的特点。如何有效促进骨折愈合、快速恢复骨骼的功能、提高骨折的治愈率，成为目前临床治疗骨折的热点和难题。NELL1因子是一种具有成骨作用的细胞因子。在促进成骨方面，相比BMP-2、BMP-7等缺乏成骨细胞特异性的因子，NELL1因子具有更好的成骨分化特性。本研究旨在揭示NELL-1因子在骨折愈合过程中促骨生成的作用，同时观察骨折后干细胞向骨折断端归巢的现象，研究干细胞归巢后的转归及作用机制。首先，成功自制闭合型骨折制备器，建立可靠的小鼠股骨闭合型骨折内固定模型；其次，构建出同时携有绿色荧光蛋（GFP）报告基因和NELL1基因的重组腺病毒载体Ad-GFP-NELL1，经扩增、纯化后转染小鼠骨髓基质细胞(BMSCs)，体外评价显示其对细胞的生长无明显影响。在骨折后不同时间点注射骨髓间充质干细胞，结合Micro-CT技术，评估骨折愈合进程，动态观察NELL1在骨折局部的的转归、相关生长因子的变化及新骨形成情况，从而明确Nell-1基因在骨折愈合中的作用，为进一步应用于临床提供实验及理论依据。