牛骨形态发生蛋白异位诱导小鼠成骨的超微结构观察

Ultrastructural observation of heterotopic bone formation induced by bovine bone morphogenetic protein

目的：牛骨形态发生蛋白（ｂＢＭＰ）植入小鼠肌袋后可诱导血管周围的间充质细胞分化形成软骨和骨组织．但ｂＢＭＰ诱导异位成骨过程的超微结构研究报道甚少．本研究的目的是利用透射电子显微镜（ＴＥＭ）观察ｂＢＭＰ植入区间充质细胞向生骨细胞分化及成骨的超微结构变化．方法：将牛骨中提取的ｂＢＭＰ５ｍｇ植入小鼠股部肌间隙内，术后５，９，１４和２１ｄ取材，制备光镜及电镜标本，镜下观察组织超微结构的变化．结果：ｂＢＭＰ植入后５ｄ，植入区内发现大量肥大的间充质细胞及纤维母细胞样细胞聚集；术后９ｄ，成熟的软骨细胞出现并可见丰富的细胞外软骨基质；术后１４ｄ，软骨细胞变性，基质钙化明显，骨母细胞功能活跃；术后２１ｄ，骨母细胞深陷于钙化基质中形成骨细胞，骨髓腔出现，原始骨髓形成．结论：ｂＢＭＰ能诱导具有分化潜能的间充质细胞进行分化，产生一个完整的骨发育过程．

Objective: The bovine bone morphogenetic protein (bBMP) can induce differentiation of perivascular mesenchymal type cells into cartilage and bone inside the mouse's muscle pouch. But there were fewer studies on the ultramicroscopic aspects of bone formation induced by bBMP. The objective of this research is to investigate the transformation of the mesenchymal cells into osteogenetic cells and bone development by transmission electron microscope. Methods: BALB/c male mice were implanted with 5 mg of bBMP in the right hamstring muscles. Samples were harvested 5, 9, 14 and 21 days after implantation of the bBMP, and examined under light as well as trasmission electron microscope. Results: Five days after transplantation of the bBMP, numerous hypertrophied mesenchymal cells and fibroblast like cells were observed to migrate and proliferate in the area of implanted bBMP. By 9 days, the mature chondrocytes, showing many short cytoplasmic processes, were surrounded by an abundant extracellular cartilage matrix. By 14 days, several chondrolytic foci were evident and there was significantly increased mineralization in the matrix. Osteoblasts appeared and exhibited well developed granular endoplasmic reticulum. By 21 days, there was further remodelling of the bone, and the roughly ovoid ossicle was filled almost entirely with bone marrow elements including erythrocytic and granulocytic series and megakaryocytes. Conclusions: This finding indicates that the mesenchymal cells in the region of implanted bBMP differentiat into cartilage and bone. The natural sequence of bone development is induced by bBMP.