组织工程技术修复犬牙槽骨缺损的实验研究

目的　研究以犬骨髓基质细胞 (bonemarrowstromalcells ,BMSC)为种子细胞 ,利用组织工程技术修复水平型牙槽骨缺损的可行性。方法　抽取成年犬骨髓 ,用梯度离心法获取单个核细胞 ,经条件培养液体外诱导培养后 ,进行组织化学、免疫细胞化学、扫描电镜检测 ,并将培养的第 3代细胞与藻酸钙形成复合物。在犬双侧下颌第 3、4前磨牙和第 1磨牙颊侧制备冠根向深 5mm的水平型牙槽骨缺损 ,用以下方法进行治疗 :(1)细胞 藻酸钙复合物修复组 ;(2 )藻酸钙对照组 ;(3)空白对照组。4、12、2 4周后经组织学检查骨缺损修复情况。并比较 12周时实验组与对照组的修复效果。结果在体外经诱导培养的BMSC可表达AKP、cbfa1、Ⅰ型胶原等 ,表现出成骨细胞活性 ;4、12、2 4周细胞 藻酸钙复合物修复部位显示逐渐有骨形成 ;第 12周时 ,实验组牙槽嵴高度可增高 2 4mm± 0 9mm ,达到原来的 4 8 5 9% ,空白对照组增高 0 8mm± 0 8mm ,达到原来的 15 76 % ,材料对照组增高 1 0mm± 0 9mm ,达到原来的 19 74 % ,实验组的牙槽嵴增高度和修复率与两对照组均有显著性差异(P <0 0 1)。结论　能以BMSC为种子细胞 ,以藻酸钙为支架材料 ,利用组织工程技术部分修复水平型牙槽骨缺损。

Repair of alveolar bone defect with tissue engineered bone: an experimental study of dogs

OBJECTIVE: To study the feasibility of repairing experimental horizontal alveolar bone defects by tissue engineering based on bone marrow stromal cells (BMSC). METHODS: Dog bone marrow mononuclear cells were isolated from the bone marrow by gradient centrifugation and then cultured in conditional medium to be induced to become osteogenic. Immunohistochemistry was used to examine the expression of core-binding factor alpha subunit 1 (Cbfa1), osteocalcin (OCN), and type I collagen in the cultured BMSCs. Histochemical technique was used to examine the expression of alkaline phosphatase (AKP) in the BMSCs. Inversed phase-contrast microscopy and electron microscopy were used to observe the morphology and proliferation of the BMSCs. Induced BMSCs at passage 3 were harvested and mixed with calcium alginate to form a gelatin form cell-scaffold construct. A horizontal alveolar bone defect (5 mm high) was created surgically in each buccal side of the mandibular premolars 3 and 4 and molar 1 of 11 dogs. The defects was randomly repaired with a cell-scaffold construct (experimental group, 20 teeth), calcium alginate alone (control group A, 15 teeth), or left untreated (control group B, 12 teeth). At four, twelve, and twenty-four weeks after operation, 2, 7, 2 dogs were killed respectively and block sections of mandibular bones at the defects were collected and processed for gross and histological observation as well as X-ray examination. The status of bone repair 12 weeks after operation in the 3 groups was compared. RESULT: In vitro induced BMSCs exhibited an osteogenic phenotype. Since the passage 3 calcium salt sedimentation could be seen in the extracellular stroma of BMSCs. Cbfa1, type I collagen, and AKP were expressed in the BMSCs in every passage. OCN was expressed since the second passage. Histologically, bone nodule structure was observed in the experimental group 4 weeks after operation. The engineered bone became more mature, similar to the normal bone, 12 weeks after operation. Twelve weeks after operation, the alveolar ridge regeneration amounted to a repair height of 2.43 +/- 0.93 mm, 0.98 +/- 0.87 mm, and 0.78 +/- 0.75 mm and reached 48.59%, 19.74%, and 15.76% of the original height in the experimental group, control group A, and control group B respectively, with a significant difference between the experimental and control groups A and B (all P < 0.01). CONCLUSION: BMSCs can be induced to become osteogenic and be used as seed cells to engineer bone tissue and repair experimental alveolar bone defect.