Ishidou Y, Kitajima I, Obama H, Maruyama I, Murata F, Imamura T, Yamada N, ten Dijke P, Miyazono K, Sakou T
Department of Orthopaedic Surgery, Faculty of Medicine, Kagoshima University, Japan.
J Bone Miner Res. 1995 Nov;10(11):1651-9. doi: 10.1002/jbmr.5650101107.
Type I receptors for bone morphogenetic proteins (BMPs), i.e., BMPR-IA and BMPR-IB, are transmembrane serine/threonine kinases, that bind osteogenic protein-1 (OP-1, also termed BMP-7) and BMP-4. Using antibodies specific to BMPR-IA and -IB, we have studied the expression of BMP type I receptors in the bone formation process during embryonic development and fracture healing. In the mouse embryo, both BMPR-IA and -IB were expressed in condensing mesenchymal cells at 13.5 days post coitum (p.c.). At 15.5 days p.c., expression of BMPR-IB, but not of BMPR-IA, was observed in the cells in perichondrium of developing cartilage. At 17.5 and 19.5 days p.c., expression of both receptors was observed in chondrocytes and in osteoblasts. In normal rat adult bone, expression of BMPR-IA, but not of BMPR-IB, was observed in osteoblasts in the periosteum. Three days after the femoral fracture, expression of BMPR-IA and -IB was up-regulated in cells at the proliferating osteogenic layer of the periosteum. On day 7, both receptors were found in fibroblast-like spindle cells and chondrocytes in the endochondral ossification sites, and osteoblasts in the newly formed trabecular bone. Expression of BMPR-IA was higher than that BMPR-IB in osteogenic layer on day 3 and in osteoblasts in the trabecular bone on day 7. On day 14, expression of BMP type I receptors was observed at similar sites, albeit with lower expression levels than were observed on day 7. The present data suggest that expression of BMP type I receptors is up-regulated during bone formation, and that they may play important roles in bone morphogenesis.
骨形态发生蛋白（BMP）的I型受体，即BMPR-IA和BMPR-IB，是跨膜丝氨酸/苏氨酸激酶，可结合成骨蛋白-1（OP-1，也称为BMP-7）和BMP-4。我们使用对BMPR-IA和-IB特异的抗体，研究了胚胎发育和骨折愈合过程中骨形成过程中BMP I型受体的表达。在小鼠胚胎中，BMPR-IA和-IB在交配后13.5天（p.c.）的凝聚间充质细胞中均有表达。在15.5天p.c.时，在发育中软骨的软骨膜细胞中观察到BMPR-IB的表达，但未观察到BMPR-IA的表达。在17.5和19.5天p.c.时，在软骨细胞和成骨细胞中均观察到两种受体的表达。在正常成年大鼠骨中，在骨膜中的成骨细胞中观察到BMPR-IA的表达，但未观察到BMPR-IB的表达。股骨骨折三天后，骨膜增殖性成骨层细胞中BMPR-IA和-IB的表达上调。在第7天，在软骨内骨化部位的成纤维细胞样纺锤体细胞和软骨细胞以及新形成的小梁骨中的成骨细胞中均发现了两种受体。在第3天的成骨层和第7天的小梁骨成骨细胞中，BMPR-IA的表达高于BMPR-IB。在第14天，在相似部位观察到BMP I型受体的表达，尽管表达水平低于第7天观察到的水平。目前的数据表明，BMP I型受体的表达在骨形成过程中上调，并且它们可能在骨形态发生中起重要作用。
