Warren S M, Mehrara B J, Steinbrech D S, Paccione M F, Greenwald J A, Spector J A, Longaker M T
Department of Surgery, Stanford University School of Medicine, Calif 94305-5148, USA.
Plast Reconstr Surg. 2001 Feb;107(2):441-53. doi: 10.1097/00006534-200102000-00021.
Distraction osteogenesis is a well-established method of endogenous tissue engineering. This technique has significantly augmented our armamentarium of reconstructive craniofacial procedures. Although the histologic and ultrastructural changes associated with distraction osteogenesis have been extensively described, the molecular mechanisms governing successful membranous distraction remain unknown. Using an established rat model, the molecular differences between successful (i.e., osseous union with gradual distraction) and ineffective (i.e., fibrous union with acute lengthening) membranous bone lengthening was analyzed. Herein, the first insight into the molecular mechanisms of successful membranous bone distraction is provided. In addition, these data provide the foundation for future targeted therapeutic manipulations designed to improve osseous regeneration. Vertical mandibular osteotomies were created in 52 adult male Sprague-Dawley rats, and the animals were fitted with customized distraction devices. Twenty-six animals underwent immediate acute lengthening (3 mm; a length previously shown to result in fibrous union) and 26 animals were gradually distracted (after a 3-day latency period, animals were distracted 0.25 mm twice daily for 6 days; total = 3 mm). Four mandibular regenerates were harvested from each group for RNA analysis on 5, 7, 9, 23, and 37 days postoperatively (n = 40). Two mandibular regenerates were also harvested from each group and prepared for immunohistochemistry on postoperative days 5, 7, and 37 (n = 12). In addition to the 52 experimental animals, 4 control rats underwent sham operations (skin incision only) and mandibular RNA was immediately collected. Control and experimental specimens were analyzed for collagen I, osteocalcin, tissue inhibitor of metalloproteinase-1, and vascular endothelial growth factor mRNA and protein expression. In this study, marked elevation of critical extracellular matrix molecules (osteocalcin and collagen I) during the consolidation phase of gradual distraction compared with acute lengthening is demonstrated. In addition, the expression of an inhibitor of extracellular matrix turnover, tissue inhibitor of metalloproteinase-1, remained strikingly elevated in gradually distracted animals. Finally, this study demonstrated that neither gradual distraction nor acute lengthening appreciably alters vascular endothelial growth factor expression. These results suggest that gradual distraction osteogenesis promotes successful osseous bone repair by regulating the expression of bone-specific extracellular matrix molecules. In contrast, decreased production or increased turnover of bone scaffolding proteins (i.e., collagen) or regulators of mineralization (i.e., osteocalcin) may lead to fibrous union during acute lengthening.
牵张成骨是一种成熟的内源性组织工程方法。该技术显著扩充了我们用于颅面重建手术的手段。尽管与牵张成骨相关的组织学和超微结构变化已被广泛描述，但成功进行膜内牵张的分子机制仍不清楚。利用已建立的大鼠模型，分析了成功（即逐渐牵张后骨愈合）和无效（即急性延长后纤维愈合）的膜内骨延长之间的分子差异。本文首次深入探讨了成功的膜内骨牵张的分子机制。此外，这些数据为未来旨在改善骨再生的靶向治疗操作奠定了基础。在52只成年雄性Sprague-Dawley大鼠中进行垂直下颌骨截骨术，并给动物安装定制的牵张装置。26只动物接受立即急性延长（3毫米；先前显示该长度会导致纤维愈合），26只动物逐渐牵张（经过3天的延迟期后，动物每天两次牵张0.25毫米，持续6天；总计 = 3毫米）。术后第5、7、9、23和37天从每组中采集4个下颌骨再生组织用于RNA分析（n = 40）。术后第5、7和37天也从每组中采集2个下颌骨再生组织并制备用于免疫组织化学分析（n = 12）。除了52只实验动物外，4只对照大鼠接受假手术（仅皮肤切口）并立即采集下颌骨RNA。对对照和实验标本分析I型胶原蛋白、骨钙素、金属蛋白酶组织抑制剂-1和血管内皮生长因子的mRNA和蛋白表达。在本研究中，与急性延长相比，逐渐牵张的巩固期关键细胞外基质分子（骨钙素和I型胶原蛋白）显著升高。此外，在逐渐牵张的动物中，细胞外基质周转抑制剂金属蛋白酶组织抑制剂-1的表达仍显著升高。最后，本研究表明，逐渐牵张和急性延长均未明显改变血管内皮生长因子的表达。这些结果表明，逐渐牵张成骨通过调节骨特异性细胞外基质分子的表达促进成功的骨修复。相比之下，骨支架蛋白（即胶原蛋白）或矿化调节剂（即骨钙素）的产生减少或周转增加可能导致急性延长期间的纤维愈合。
