SDF-1通过诱导干细胞动员促进牵张成骨的实验研究

Distraction osteogenesis (DO), which is hailed as the endogenous tissue engineering bone, repairs bone defects by using the tissue self-regenerative process. However, the rather long course of treatment and the probability of bone nonunion had restricted the development of this technology. We found in preliminary studies that stromal cell-derived factor -1 (SDF-1) was up-regulated in distraction gap, and that SDF-1 can recruit mesenchymal stem cells (MSC) to distraction gap during DO. Therefore, it is speculated that the exogenous SDF-1 can induce autologous MSC migrate to distraction gap and promote bone formation. We will use the mandibular DO model of rat to explicit the role of migrated MSC in DO by investigating whether ex vivo-expanded green fluorescent protein (GFP) labeled MSC can home to DO site after infusion via tail vein. We will apply the exogenous SDF-1 to distraction gap and observe the changes of migrated MSC and osteogenic efficiency by the methods of immunohistochemistry, laser capture microdissection, histomorphology and micro-CT. We will also accelerate the distraction velocity after applying the exogenous SDF-1, to evaluate the bone formation and explore the feasibility of shortening DO course. This project will provide way to the clinical improvement of DO technique.

牵张成骨（DO）利用了组织自再生的过程修复了骨缺损，被誉为“内源性组织工程骨”。然而，过长的疗程以及可能出现的成骨不良等并发症，仍然严重制约着该项技术的发展。我们在前期研究中发现，基质细胞衍生因子-1（SDF-1）在DO新生骨痂内表达上调，且SDF-1可通过与其受体的结合诱导外周间充质干细胞（MSC）迁移至牵张间隙。由此推测外源性SDF-1可能通过诱导自体MSC迁移起到促进牵张成骨的作用。我们将采用大鼠下颌骨DO模型，通过静脉注射GFP标记的MSC，并在新生骨痂内对其进行检测，明确MSC迁移在DO骨再生中的作用；通过在牵张区局部应用外源性SDF-1，并采用免疫组织化学、激光捕获显微切割、组织形态学、显微CT等手段，观察牵张区MSC数量变化及成骨效率变化；通过局部应用SDF-1并加快牵张速率，评价其新骨形成效果，从而探讨缩短DO疗程的可行性。本项目将为临床进一步改进DO技术提供新的思路。

牵张成骨（DO）利用了组织自再生的过程修复了骨缺损，被誉为“内源性组织工程骨”。然而，过长的疗程以及可能出现的成骨不良等并发症，仍然严重制约着该项技术的发展。我们在前期研究中发现，基质细胞衍生因子-1（SDF-1）在DO新生骨痂内表达上调，且SDF-1可通过与其受体的结合诱导外周间充质干细胞（MSC）迁移至牵张间隙。由此推测外源性SDF-1可能通过诱导自体MSC迁移起到促进牵张成骨的作用。骨形成蛋白-2(BMP-2)是已知的促进成骨作用较强的因子之一，其可有效地诱发MSC向成骨分化。因此，理论上二者应该具有协同促进新骨形成作用。我们采用大鼠下颌骨DO模型，通过静脉注射GFP标记的MSC，同时在牵张区局部应用外源性SDF-1，并在新生骨痂内进行检测，发现所有标本均有不同数量的GFP-MSCs迁移至牵张区新生骨痂，且迁移细胞的数量与牵张区局部的SDF-1浓度呈正相关；在预先封闭MSCs的CXCR4受体后，迁移细胞数显著减少。这证实了我们的前期推测。我们还采用了兔下颌骨牵张成骨模型，在牵张区局部应用可吸收凝胶缓释的小剂量SDF-1／BMP-2，结果发现SDF-1／BMP-2组牵张区新生骨小梁厚度、密度较单独应用SDF-1或BMP-2明显增大，提示了SDF-1与BMP-2在牵张区可能起到了协同作用，即SDF-1促进MSC迁移至牵张间隙，BMP-2促进迁移的MSC向成骨方向分化。研究结果为临床进一步改进DO技术提供了新的思路。.