神经营养因子家族及其受体在重组人骨形态发生蛋白

摘  要：［目的］通过观察重组人骨形态发生蛋白2（rhBMP2）诱导成骨过程中神经营养因子（NTFs）家族及受体的表达，探讨神经营养因子在BMP骨诱导中的作用。［方法］建立小鼠右侧股后部异位成骨模型，实验组植入rhBMP2胶原复合物，对照组仅植入相同体积的胶原海绵。分别于术后7、14和21 d取材，进行组织学、免疫组化及RTPCR检测。［结果］组织学证实rhBMP2胶原复合物具有良好的骨诱导能力，而对照组未见成骨。术后第7 d，在大量软骨形成期NGF和TrkA阳性染色达到高峰，成纤维细胞、成软骨细胞、软骨细胞、肥大软骨细胞和成骨细胞中均有阳性表达；BDNF在软骨细胞及软骨基质中有阳性染色，其受体TrkB仅在成软骨细胞和软骨细胞中有表达；NT3与NGF表达相似，其受体TrkC仅在成软骨细胞和软骨细胞中有阳性染色。术后第14 d，NGF和TrkA阳性表达局限于部分成骨细胞、骨样细胞和成骨样细胞；NT3在软骨细胞、成骨细胞中明显表达。术后21 d，只有少量成骨细胞、成骨样细胞中有NGF和TrkA的表达。RTPCR检测结果显示，NTFs mRNA于术后第7 d表达最高，与免疫组化中蛋白质的表达结果相一致。［结论］NTFs及其受体在rhBMP2诱导成骨过程明显表达，提示NTFs可能通过直接和间接的方式协同BMP的诱导成骨过程。
    关键词：骨形态发生蛋白；  骨诱导；  神经营养因子；  受体
    Abstract：［Objective］To identify the expression of neurotrophic factors（NTFs）and their high affinity receptors（Trk）during the bone induction by recombined human bone morphogenetic protein2（rhBMP2）and discuss possible roles of NTFs on the osteoinductive activity of BMP［Method］After a total of 36 ICR mice were divided into experimental group and control group at random,rhBMP2/collagen sponge and collagen sponge were implanted into the right thigh muscle pouches of two groups respectivelyTissues in the implanted sites of two groups were removed on the 7th,14th and 21st day after implantationHistological,immunohistochemical and RTPCR analyses were performed to detect osteoinductive effect of rhBMP2 and the expression of NTFs and Trk［Result］RhBMP2/collagen sponge displayed a potent ability inducing bone formation,while the expression of NTFs and Trk was observed in the course of osteoinduction by rhBMP2Especially on the 7th day in the experimental group,NGF and TrkA positive immunostaining reached the peak in the stage of chondrogenesis,including chondroblasts,chondrocytes,hypertrophic chondrocytes and osteoblasts,then decreased in the number of positive cells and the intensity of immunostaining on the 14th and 21st dayBDNF was only observed in chondrocytes and cartilage matrix,and TrkB was expressed in chondroblasts and chondrocytes at the 7th day after implantationExpression of NT3 was similar to that of NGF,while TrkC was expressed in chondroblasts and chondrocytes on day 7Expression level of the mRNA of NTFs peaked at 7 days after the implantation,then decreased,which was nearly coincident with immunohistochemical results［Conclusion］Many different kinds of cells are induced by rhBMP2 express NTFs and Trk,which suggests that NTFs may play an important role in the osteogenesis initiated by BMP through direct and indirect pathways    Key words：Bone morphogenetic protein;  Osteoinduction;  Neurotrophic factors;  Receptor
    骨形态发生蛋白（bone morphogenetic protein，BMP）能诱导未分化间充质细胞不可逆地分化形成骨和软骨，在骨折愈合和骨修复过程中发挥着重要作用。研究表明，在骨折愈合中，除了BMP的诱导成骨作用外，尚有其他众多因子的表达和参与，如TGFβ、VEGF、IGFI和bFGF等，以促进新骨的形成和成熟。神经营养因子（neurotrophic factors，NTFs）家族在中枢和外周神经元的生长、发育、分化和维持正常存活中起着重要的作用〔1〕。NTFs及其受体Trk在全身广泛分布，并在骨折愈合过程中有明显的表达〔2〕，外源性NGF具有促进骨折愈合的作用〔3〕。但是在外源性BMP诱导成骨过程中是否也有NTFs及Trk的表达尚未见报道。本文对rhBMP2异位诱导成骨过程中NTFs、Trk的表达和NTFs mRNA的表达规律的研究进行报道。