Gene expression of TGF-β superfamily during healing of bone fracture

BMP在骨再生中起着重要作用。本实验观察了大鼠下颌骨骨折愈合过程中骨形态发生蛋白（BMP）和骨形态发生蛋白受体（BMPR）的分布。骨折后1 ~ 2d，骨缝内的成纤维细胞样细胞和肌肉组织中的结缔组织细胞出现免疫反应。从第3天开始发现纤维化，在成纤维细胞中发现强烈的免疫反应。软骨形成开始于第4天，免疫反应见于成软骨细胞、增殖期和静止期软骨细胞，而在肥大软骨细胞中未见免疫反应。破骨细胞在骨折部位有明显的骨吸收，破骨细胞内有强烈的免疫反应。从第7天开始观察到骨形成，软骨逐渐被骨取代。成骨细胞沿着新生骨小梁呈强免疫反应。BMPR-IB的免疫组化定位与BMPR-IA和BMPR-II的免疫组化定位相同。这些结果表明，骨形成蛋白在骨折愈合过程中的软骨和骨形成，特别是在破骨细胞的骨吸收中起着核心作用。

BMPs play a fundamental role in bone regeneration. Localization of BMP and BMPR (BMP receptor) was investigated during healing of mandibular fractures in rats.The immunoreactivities of BMP and receptors showed the same distributions. The immunoreactions were observed in fibroblast-like cells in bone fissures with blood clots and connective tissue cells in muscular tissue from 1 to 2 days after the bone fracture. Fibrosis was found from 3 days, and intense immunoreactions were found in the fibroblasts. Cartilage formation started from 4 days, and the immunoreactions were found in the chondroblasts, proliferative and resting chondrocytes, but not in hypertrophic chondrocytes. Bone resorption in osteoclasts was observed in the region of the bone fracture, and intense immunoreactions were found in the osteoclasts. Bone formation was observed from 7 days and cartilage was gradually replaced by bone. Intense immunoreactions were found in osteoblasts along newly formed bone trabeculae. Immunoreactions of osteoblasts were gradually decreased after 14 days, and they were not found at 28 days.The immunohistochemical localization of BMPR-IB showed the same distribution patterns as those with BMPR-IA and II. These results suggest that BMPs play a central role in cartilage and bone formation during healing of bone fractures, particularly in bone resorption by osteoclasts.