The osteoinductive properties of Nell-1 in a rat spinal fusion model
The osteoinductive properties of Nell-1 in a rat spinal fusion model
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DOI：
10.1016/j.spinee.2006.04.020
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发表时间：
2007-01-01
期刊：
影响因子：
4.5
通讯作者：
Wang, Jeffrey C.
中科院分区：
文献类型：
--
作者：
Lu, Steven S.;Zhang, Xinli;Wang, Jeffrey C.
背景：重组生长因子骨形态发生蛋白-2 (BMP-2) 和 BMP-7 目前已批准用于人类，但与各种不良反应相关，包括异位骨形成和局部炎症反应。替代生长因子的开发可能有助于最大限度地减少当前骨诱导疗法的副作用。 Nell-1（Nel 样分子-1；Nel [一种在编码表皮生长因子样结构域的神经组织中强烈表达的蛋白质]）是一种新型分泌分子，它似乎比 BMP 更特异地作用于成骨细胞，而 BMP 可以作用于多种细胞类型。从分子角度来看，Nell-1直接受runt相关转录因子2（Runx2/Cbfa1）的调控，这是控制骨形成的主调控基因。先前的研究表明，Nell-1 在体外加速成骨分化，在体内加速颅骨形成。我们假设 Nell-1 也可能在脊柱融合中有效形成骨。 目的：我们的主要目的是评估在脱矿骨基质 (DBM) 载体中直接使用 Nell-1 进行腺病毒基因传递是否可以改善大鼠模型中的脊柱融合。由于腺病毒载体可以持续输送生长因子，因此在蛋白质研究之前用于初步可行性测试。 研究设计/设置：两组 20 只无胸腺大鼠在 L4-L5 处接受后外侧横突间脊柱融合，植入的 DBM 载体含有编码 Nell-1 (AdNell-1) 的腺病毒或对照 Lac Z (AdLacZ)。没有植入细胞。 6周时处死20只大鼠以评估脊柱融合情况。方法：所有动物在2、4和6周时接受Faxitron X光检查，6周时进行手动脊柱触诊，并在6周时进行高分辨率微型计算机断层扫描（microCT）。通过以下方式评估脊柱融合率：1) 6 周 Faxitron 图像； 2）由三名独立观察员手动触诊； 3）显微CT； 4）组织学。通过苏木精-伊红和马森三色染色对脱钙的冠状切片脊柱节段进行新骨形成评估。结果：所有差异均达到统计学显着性。 6周后，在DBM携带者中直接应用腺病毒Nell-1，与Lac Z对照相比，获得了显着更高的脊柱融合率：通过手动触诊，Nell-1与20% Lac Z相比，分别为60%；通过显微CT和组织学分析，分别为70% Nell-1与20% Lac Z。骨质量和成熟度的组织学评估显示，6 周时，所有 Nell-1 处理的标本中的骨骼均比 Lac Z 更成熟、质量更高。结论：通过 microCT 和组织学评估脊柱融合比手动触诊更准确。在 DBM 载体中直接应用腺病毒 Nell-1，在 6 周时比 Lac Z 对照获得了显着更高的脊柱融合率。与文献中使用直接应用腺病毒 BMP 的其他报道相比，在 DBM 载体中直接应用腺病毒 Nell-1 也实现了显着更高的脊柱融合率。在同种异体移植载体中直接应用腺病毒BMP，在8周时实现了BMP-2的8%融合和BMP-7的16%融合。这些结果表明 Nell-1 可能是一种有效的骨诱导分子。此外，主骨调节基因 Runx2 对 Nell-1 的调节表明，与影响多种细胞类型的 BMP 相比，Nell-1 可能在成骨细胞中更具体地发挥其作用。总体而言，Nell-1 可以满足当前对骨诱导因子的需求。 (C) 2007 Elsevier Inc. 保留所有权利。
BACKGROUND CONTEXT: Recombinant growth factors bone morphogenetic protein-2 (BMP-2) and BMP-7 are currently approved for human use but are associated with various adverse effects including ectopic bone formation and local inflammatory reaction. The development of alternative growth factors may help minimize the adverse effects of current osteoinductive therapeutics. Nell-1 (Nel-like molecule-1; Nel [a protein strongly expressed in neural tissue encoding epidermal growth factor like domain]) is a novel secretory molecule that appears to act more specifically on osteoblasts than the BMPs, which can act on multiple cell types. From a molecular point of view, Nell-1 is directly regulated by runt-related transcription factor 2 (Runx2/Cbfa1), a master regulatory gene controlling bone formation. Previous studies showed that Nell-1 accelerates osteogenic differentiation in vitro and calvarial bone formation in vivo. We hypothesize that Nell-1 may also effectively form bone in spinal fusion.PURPOSE: Our primary aim was to assess if direct adenoviral gene delivery with Nell-1 in a demineralized bone matrix (DBM) carrier can improve spinal fusion in a rat model. Because adenoviral vectors allow for sustained growth factor delivery, they were used for initial feasibility testing before protein studies.STUDY DESIGN/SETTING: Two groups of 20 athymic rats underwent posterolateral intertransverse process spinal fusion at L4-L5 with implanted DBM carrier containing either adenovirus coding for Nell-1 (AdNell-1) or control, Lac Z (AdLacZ). No cells were implanted. The 20 rats were sacrificed at 6 weeks for evaluation of spinal fusion.METHODS: All animals underwent Faxitron radiographs at 2, 4, and 6 weeks, manual spine palpation at 6 weeks, and high-resolution micro computerized tomography (microCT) at 6 weeks. Spinal fusion rate was assessed by: 1) 6-week Faxitron images; 2) manual palpation by three independent observers; 3) microCT; and 4) histology. New bone formation was assessed by hematoxylin-eosin and Masson trichrome staining on decalcified, coronally sectioned spine segments.RESULTS: All differences achieved statistical significance. After 6 weeks, direct application of adenoviral Nell-1 in a DBM carrier achieved significantly higher rates of spinal fusion over Lac Z controls: 60% Nell-1 versus 20% Lac Z by manual palpation and 70% Nell-1 versus 20% Lac Z by microCT and histology. Histological assessment of bone quality and maturity revealed more mature, higher quality bone in all the Nell-1 treated specimens relative to Lac Z at 6 weeks.CONCLUSIONS: Spinal fusion is more accurately assessed by microCT and histology than manual palpation. Direct application of adenoviral Nell-1 in a DBM carrier achieved significantly higher rates of spinal fusion over Lac Z controls at 6 weeks. Direct application of adenoviral Nell-1 in a DBM carrier also achieved significantly higher rates of spinal fusion over other reports in the literature using direct adenoviral BMP application. Direct application of adenoviral BMP in an allograft carrier achieved 8% fusion for BMP-2 and 16% fusion for BMP-7 at 8 weeks. These results indicate that Nell-1 may be a potent osteoinductive molecule. In addition, the regulation of Nell-1 by the master bone regulatory gene, Runx2 suggests that Nell-1 may exert its effects more specifically in osteoblastic cells than BMPs which affect multiple cell types. Overall, Nell-1 may fulfil a current need for an osteoinductive factor. (C) 2007 Elsevier Inc. All rights reserved.