Expression of neurotrophic factors and their receptors during osteoinduction of recombined human bone morphogenetic protein-2 / 中国矫形外科杂志

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 protein-2(rhBMP-2)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,rhBMP-2/collagen sponge and collagen sponge were implanted into the right thigh muscle pouches of two groups respectively.Tissues in the implanted sites of two groups were removed on the 7~(th),14~(th) and 21~(st) day after implantation.Histological,immunohistochemical and RT-PCR analyses were performed to detect osteoinductive effect of rhBMP-2 and the expression of NTFs and Trk.[Result]RhBMP-2/collagen sponge displayed a potent ability inducing bone formation,while the expression of NTFs and Trk was observed in the course of osteoinduction by rhBMP-2.Especially on the 7~(th) 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 14~(th) and 21~(st) day.BDNF was only observed in chondrocytes and cartilage matrix,and TrkB was expressed in chondroblasts and chondrocytes at the 7~(th) day after implantation.Expression of NT-3 was similar to that of NGF,while TrkC was expressed in chondroblasts and chondrocytes on day 7.Expression 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 rhBMP-2 express NTFs and Trk,which suggests that NTFs may play an important role in the osteogenesis initiated by BMP through direct and indirect pathways.