诱导立体网架上成纤维细胞表达成骨表型及其机制的研究

目的探讨诱导条件下的成纤维细胞在三维结构的聚乙醇酸（PGA）网架上表达成骨表型的可行性,以及肿瘤坏死因子α（TNF-α）对成纤维细胞骨形态发生蛋白（BMP）受体表型表达的影响。方法分离、纯化人皮肤成纤维细胞,实验用第2代细胞：（1）种植成纤维细胞于PGA网架上,进行体外旋转培养,并用含TNF-α（50U／ml）和BMP-2（0．1μg／ml）的条件培养液进行诱导。于1d,3、6周后利用倒置相差显微镜、扫描电镜、四环素荧光标记、茜素红染色方法观察细胞生长、骨样组织形成和矿化物沉积情况。上清液生化检测分析成骨性标志物分泌情况;（2）接种成纤维细胞于预置玻片或75cm。培养瓶中,用含TNF-α（50U／ml）的条件培养液进行一次性或连续性干预,采用逆转录聚合酶链反应和免疫组织化学技术,于2．4、6、8d后分别检测BMPⅠ型受体（BMPR-ⅠA和BMPR-ⅠB）mRNA表达及蛋白形成状况。结果诱导3周后三维网架上的成纤维细胞表达成骨表型,分泌成骨细胞特征性标志物：骨钙素（OCN）和骨特异性碱性磷酸酶（B-AKP）;分泌大量细胞外基质形成骨样组织;平面培养发现,TNF-α（50U／ml）连续干预8d可增高BMPR-ⅠB的mRNA表达和蛋白合成。结论三维立体网架上的成纤维细胞在诱导条件下能够向成骨型细胞转化,形成骨样组织,有希望作为一种新的成骨型细胞的种子细胞源;TNF-α为BMP-2的靶向作用提供条件,TNF-α和BMP-2联合应用是调节成纤维细胞表型转化的诱导条件之一。

Experiment on induction of fibroblasts on 3-D cell-foam structures to express osteoblastic phenotype and its mechanism

OBJECTIVE: To study the feasibility of osteogenic phenotype expression by human skin fibroblasts induced in polyglycolic acid (PGA) foams and the effect of tumor necrosis factor-alpha (TNF-alpha) on the expression of bone morphogenetic protein (BMP) receptors. METHODS: The fibroblasts were isolated, purified from human skin. (1) Fibroblasts were seeded onto PGA foams. The cell-PGA complexes were cultured in RCCS for 6 weeks, in the media of TNF-alpha (50 U/ml) and BMP-2 (0.1 microg/ml). 1 d, 3 and 6 weeks later, cells and extracellular matrix were investigated by electron microscopic and histochemistry observation respectively. Secretion of osteogenic markers were analyzed by biochemical methods. (2) Fibroblasts were seeded on the glass fragments or culture flasks and treated with TNF-alpha (50 U/ml) in different usage (one-time, all-time). The RT-PCR method and the immunohistochemistry fluorescence staining were used to examine the influence of TNF-alpha on the mRNA expression and the protein expression of the type I BMP receptors at 2, 4, 6, 8 d after treatment. RESULTS: Fibroblasts seeded on the PGA foams formed 3-dimensional matrix 3 weeks after seeding, which was demonstrated as osteo-tissue by tetracycline labeling and ARS staining. Cells secreted much more bone-specific alkaline phosphatase (B-AKP) and osteocalcin (OCN) into supernatant than the cells that were cultured in the media without TNF-a and BMP2. Eight days after all-time usage, the TNF-alpha (50 U/ml) increased the expression of the mRNA and protein of the type IB BMP receptor. CONCLUSIONS: Fibroblasts on 3-D cell-foam structures can express osteoblastic phenotype under certain inducing conditions. The numerous fibroblasts in body would be a promising resource for cell seeds candidate of tissue- engineered bone. TNF-alpha provides the essential condition for BMP2's target effect on fibroblasts, and combined use of TNF-alpha and BMP2 is one of the regulating factors.