Injectable tissue-engineered bone repair of a rat calvarial defect.

Advances in bone repair have focused on the minimally-invasive delivery of tissue-engineered bone (TEB). A promising injectable biopolymer of chitosan and inorganic phosphates was seeded with mesenchymal stem cells (MSCs) and a bone growth factor (BMP-2), and evaluated in a rat calvarial critical size defect (CSD). Green fluorescent protein (GFP)-labeled MSCs are used to evaluate patterns of cell viability and proliferation. Prospective, controlled trial in an animal model. In 30 male rats, 8-mm calvarial CSDs were created, and divided into five groups of six animals each. In the experimental groups, the defects were injected with either chitosan gel, gel loaded with MSCs (0.3 × 106 cells/defect), gel loaded with BMP-2 (2 µg/defect), or gel loaded with both MSC and BMP-2. In the control group, the defect was left untreated. At 4 weeks, in vivo microcomputed tomography (micro-CT) analysis was performed. At 8 weeks, calvarial specimens were examined by micro-CT, histology, and immunohistochemistry. New areas of bone growth were seen in the defects of all treated animals. Micro-CT analysis revealed a significant (P < .001) time-dependent increase in the regeneration of bone volume and bone area in defects treated with gel/MSC/BMP-2 as compared to all other groups. Histological analysis confirmed this difference. GFP–labeled TEB was detected within the areas of new bone, indicating cell viability and contribution to new bone growth by the injected MSC. This study demonstrates that an injectable form of TEB using a chitosan gel, MSC, and BMP-2 can enhance bone formation in a rat calvarial CSD.

骨修复的进展集中在组织工程骨（TEB）的微创递送方面。一种由壳聚糖和无机磷酸盐组成的有前景的可注射生物聚合物，接种了间充质干细胞（MSCs）和一种骨生长因子（BMP - 2），并在大鼠颅骨临界尺寸缺损（CSD）中进行了评估。绿色荧光蛋白（GFP）标记的MSCs被用于评估细胞活力和增殖的模式。 在动物模型中进行的前瞻性对照试验。 在30只雄性大鼠中，制造了8毫米的颅骨CSD，并将其分为五组，每组六只动物。在实验组中，向缺损处分别注射壳聚糖凝胶、负载MSCs的凝胶（每个缺损0.3×10⁶个细胞）、负载BMP - 2的凝胶（每个缺损2微克），或者同时负载MSCs和BMP - 2的凝胶。在对照组中，缺损不做处理。在4周时，进行体内微计算机断层扫描（微CT）分析。在8周时，通过微CT、组织学和免疫组织化学检查颅骨标本。 在所有接受治疗的动物的缺损处都观察到了新的骨生长区域。微CT分析显示，与所有其他组相比，用凝胶/ MSCs / BMP - 2治疗的缺损中，骨体积和骨面积的再生有显著的（P <.001）时间依赖性增加。组织学分析证实了这种差异。在新骨区域内检测到了GFP标记的TEB，这表明注射的MSCs具有细胞活力并对新骨生长有贡献。 这项研究表明，使用壳聚糖凝胶、MSCs和BMP - 2的可注射形式的TEB能够促进大鼠颅骨CSD中的骨形成。