Department of Biochemistry, Medical School and Research Institute for Endocrine Sciences, Chonbuk National University, Jeonju, Jeonbuk, 561-756, Republic of Korea.
Bone. 2011 Sep;49(3):447-54. doi: 10.1016/j.bone.2011.05.020. Epub 2011 Jun 1.
Allografting has become widely available for the elimination of morbidity due to autogenous bone grafting procedures for spinal fusion. Enhancement of stable bone formation could facilitate this procedure. COMP-Ang1 is a recombinant chimeric protein of angiopoietin-1 that induces angiogenesis and vascular enlargement. We investigated the osteogenic potential of COMP-Ang1 for spinal fusion with allograft based on the enhancement of angiogenesis.
Sixty Sprague-Dawley rats underwent bilateral posterior and posterolateral arthrodesis with allograft at L3-4 and L4-5. The animals were divided into three groups (n=20 each): (1) no treatment (sham group); (2) the bovine serum albumin-impregnated collagen sponge group (BSA group); 3) the COMP-Ang1-impregnated collagen sponge group (COMP-Ang1 group). Animals were sacrificed at six weeks for evaluation of spinal fusion using manual palpation, radiographs, and biomechanical and histomorphometric assessments. Total RNA was prepared from the fusion site and analyzed for osteogenic marker protein expression using RT-PCR analysis.
The fusion rates determined by manual palpation were 38.9% in the sham group, 42.1% in the BSA group, and 89.5% in the COMP-Ang1 group. Optical density of fusion masses in the COMP-Ang1 group was significantly higher than those in the sham and BSA groups (p<0.001). Total bone volume was significantly higher in the COMP-Ang1 group than in the sham and BSA groups (p<0.001). The mechanical strength was significantly greater in the COMP-Ang1 group than in the sham and BSA groups (p<0.01). Histologically, the fusion site of the COMP-Ang1 group showed a larger number of reactive bones compared with those in the BSA and sham groups. Immunostaining of endothelial cells for factor VIII revealed that COMP-Ang1 group showed higher levels of vascularity in the fusion site. Runt-related transcription factor 2 and its target genes were significantly up-regulated in the COMP-Ang1 group.
COMP-Ang1 induced radiologically and histologically demonstrable active osteogenesis by promoting angiogenesis in spinal fusions. It was concluded that COMP-Ang1 enhances spinal fusion and hence the strength of the fusion.
同种异体移植已广泛应用于消除因脊柱融合而进行的自体骨移植手术引起的发病率。增强稳定的骨形成可以促进这一过程。COMP-Ang1 是血管生成素 1 的重组嵌合蛋白，可诱导血管生成和血管扩大。我们基于血管生成的增强作用，研究了 COMP-Ang1 用于同种异体移植脊柱融合的成骨潜力。
60 只 Sprague-Dawley 大鼠在 L3-4 和 L4-5 行双侧后路和后外侧关节融合术，并使用同种异体移植物。将动物分为三组（每组 20 只）：（1）无治疗（假手术组）；（2）牛血清白蛋白浸渍胶原海绵组（BSA 组）；（3）COMP-Ang1 浸渍胶原海绵组（COMP-Ang1 组）。6 周时，通过手动触诊、X 线片以及生物力学和组织形态计量评估来评估脊柱融合情况，并对融合部位的总 RNA 进行提取，通过 RT-PCR 分析检测成骨标记蛋白的表达。
通过手动触诊确定的融合率分别为假手术组 38.9%、BSA 组 42.1%和 COMP-Ang1 组 89.5%。COMP-Ang1 组融合质量的光密度明显高于假手术组和 BSA 组（p<0.001）。COMP-Ang1 组总骨体积明显高于假手术组和 BSA 组（p<0.001）。COMP-Ang1 组的机械强度明显大于假手术组和 BSA 组（p<0.01）。组织学上，与 BSA 组和假手术组相比，COMP-Ang1 组的融合部位有更多的反应性骨。因子 VIII 的内皮细胞免疫染色显示，融合部位的血管密度较高。Runt 相关转录因子 2 及其靶基因在 COMP-Ang1 组中显著上调。
COMP-Ang1 通过促进脊柱融合部位的血管生成，诱导影像学和组织学上可观察到的活跃成骨。结论是 COMP-Ang1 增强了脊柱融合，从而增强了融合的强度。
