Department of Surgery and Cedars-Sinai Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.
Mol Pharm. 2011 Oct 3;8(5):1592-601. doi: 10.1021/mp200226c. Epub 2011 Sep 13.
Vertebral compression fractures (VCFs), the most common fragility fractures, account for approximately 700,000 injuries per year. Since open surgery involves morbidity and implant failure in the osteoporotic patient population, a new minimally invasive biological solution to vertebral bone repair is needed. Previously, we showed that adipose-derived stem cells (ASCs) overexpressing a BMP gene are capable of inducing spinal fusion in vivo. We hypothesized that a direct injection of ASCs, designed to transiently overexpress rhBMP6, into a vertebral bone void defect would accelerate bone regeneration. Porcine ASCs were isolated and labeled with lentiviral vectors that encode for the reporter gene luciferase (Luc) under constitutive (ubiquitin) or inductive (osteocalcin) promoters. The ASCs were first labeled with reporter genes and then nucleofected with an rhBMP6-encoding plasmid. Twenty-four hours later, bone void defects were created in the coccygeal vertebrae of nude rats. The ASC-BMP6 cells were suspended in fibrin gel (FG) and injected into the bone void. A control group was injected with FG alone. The regenerative process was monitored in vivo using microCT, and cell survival and differentiation were monitored using tissue specific reporter genes and bioluminescence imaging (BLI). The surgically treated vertebrae were harvested after 12 weeks and subjected to histological and immunohistochemical (against porcine vimentin) analyses. In vivo BLI detected Luc-expressing cells at the implantation site over a 12-week period. Beginning 2 weeks postoperatively, considerable defect repair was observed in the group treated with ASC-BMP6 cells. The rate of bone formation in the stem cell-treated group was two times faster than that in the FG-treated group, and bone volume at the end point was 2-fold compared to the control group. Twelve weeks after cell injection the bone volume within the void reached the volume measured in native vertebrae. Immunostaining against porcine vimentin indicated that the ASC-BMP6 cells contributed to new bone formation. Here we show the potential of injections of BMP-modified ASCs to repair vertebral bone defects in a rat model. Our results could pave the way to a novel approach for the biological treatment of traumatic and osteoporosis-related vertebral bone injuries.
椎体压缩性骨折（VCFs）是最常见的脆性骨折，每年约有 70 万例损伤。由于骨质疏松患者的开放性手术涉及发病率和植入物失败，因此需要一种新的微创生物方法来修复椎骨。此前，我们已经证明，过表达 BMP 基因的脂肪源性干细胞（ASCs）能够在体内诱导脊柱融合。我们假设，将设计为瞬时过表达 rhBMP6 的 ASCs 直接注射到椎骨骨缺损中，将加速骨再生。我们分离了猪 ASC，并使用编码报告基因荧光素酶（Luc）的慢病毒载体进行标记，该报告基因受组成型（泛素）或诱导型（骨钙素）启动子的控制。首先用报告基因标记 ASCs，然后用编码 rhBMP6 的质粒进行核转染。24 小时后，在裸鼠尾骨的椎骨上创建了 ASC-BMP6 细胞的骨缺损。将 ASC-BMP6 细胞悬浮在纤维蛋白凝胶（FG）中并注入骨缺损中。对照组仅注射 FG。使用 microCT 在体内监测再生过程，并使用组织特异性报告基因和生物发光成像（BLI）监测细胞存活和分化。在 12 周后收获经手术处理的椎骨，并进行组织学和免疫组织化学（针对猪波形蛋白）分析。在体内 BLI 检测到植入部位表达 Luc 的细胞在 12 周的时间内。术后 2 周开始，用 ASC-BMP6 细胞治疗的组观察到明显的缺陷修复。干细胞治疗组的成骨速度比 FG 治疗组快两倍，终点时的骨体积是对照组的两倍。细胞注射 12 周后，骨缺损内的骨体积达到了天然椎骨测量的体积。针对猪波形蛋白的免疫染色表明，ASC-BMP6 细胞有助于新骨形成。在这里，我们展示了注射 BMP 修饰的 ASC 修复大鼠模型中椎骨缺损的潜力。我们的结果可能为外伤性和与骨质疏松症相关的椎骨损伤的生物治疗开辟新途径。
