[Expression of nerve growth factor and its receptor during osteoinduction of recombined human bone morphogenetic protein 2].
OBJECTIVE
To identify the expression of nerve growth factor (NGF) and its high affinity receptor (tyrosine kinase receptor A, TrkA) during bone induction by recombined human bone morphogenetic protein 2 (rhBMP-2) by immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR) and to discuss the role of NGF on the bone induction of the BMP.


METHODS
Thirty-six ICR mice were divided into the experimental group and the control group at random. rhBMP-2 /collagen sponge and collagen sponge were implanted into the right thigh muscle pouches of the mice in the experimental group and the control group, respectively. The tissues in the implanted site of the two groups were removed on the 7th, 14th and 21st day after the implantation. Histological, immunohistochemical and RT-PCR analyses were performed to detect osteoinductive effects of rhBMP-2 and the expression of NGF and TrkA.


RESULTS
Gross observation showed that a solid lump was found in the right thigh in the experimental group on the 7th day and became harder on the 14th and 21st day, which was not found in the control group. rhBMP-2 /collagen sponge displayed a potent ability to induce bone formation, while immunostaining for NGF and TrkA was observed in the course of osteoinduction by rhBMP-2. On the 7th day in the experimental group, NGF positive immunostaining reached the peak in the stage of chondrogenesis and there were a large number of cells expressing NGF, including fibroblasts, chondroblasts, chondrocytes, and osteoblasts; then, there was a decrease in the number of the positive cells and in the intensity of immunostaining on the 14th and 21st day. Staining of TrkA was similar to that of NGF. The expression level of the mRNA of NGF during the course of bone induction peaked 7 days rhBMP-2/collagen is a kind of satisfactory osteoinductive after the implantation and then decreased.


CONCLUSIONS
material, and many different kinds of cells induced by rhBMP-2 can express NGF and TrkA, which suggests that NGF may play an important role in the osteogenesis initiated by exogenous BMP through direct and indirect pathways.
Xia
Shengli
S
Department of Orthopaedics, Ninth People's Hospital, Medical College of Shanghai, Jiaotong University, Shanghai, 200011, PR China.
Dai
Kerong
K
Tang
Tingting
T