Analysis of the mechanism by which nerve growth factor promotes callus formation in mice with tibial fracture

Abstract

The aim of the present study was to analyze the mechanism by which nerve growth factor (NGF) promotes callus formation in mice with tibial fracture. NGF transgenic homozygotic mice and NGF wild homozygotic mice were selected to construct non-stabilized fracture model of tibia. The mice were sacrificed on days 7, 14 and 21, respectively, and each group had a sample with 8 mice at each point in time. X-ray radiography and safranin fast green were used to observe fracture healing and in situ hybridization was used to examine the NGF mRNA expression of tibia at each phase of fracture healing. Tartrate-resistant acid phosphatase (TRAP) staining of callus tissue and the expression level of TRAP mRNA were combined to observe osteoclast formation. COL2A1, a chondrocyte differentiation-related gene in callus, and the mRNA level of SOX9 were combined to observe chondrocyte differentiation. It was found that under X-ray radiography, the fracture of NGF transgenic homozygotic mice healed in advance (P<0.05). Cartilage and bone tissue were identified by safranin and fast green staining. The residual cartilage on the callus tissue of NGF transgenic homozygotic mice had decreased significantly (P<0.05). The NGF mRNA expression level in each phase of callus formation of NGF transgenic homozygotic mice was significantly higher than that of the wild group (P<0.05). The number of positive cells in NGF-TRAP staining at each time point after fracture and the NGF mRNA expression level was markedly higher than that of the wild group, and the expression levels of COL2A1 and SOX9 mRNA were distinctively higher than that of the wild group. In conclusion, NGF potentially improves the healing of tibial fracture by osteoclast formation. Additionally, an increase in the number of osteoblasts in the NGF transgenic homozygotic mice compared with the wild-type mice may be achieved by cartilage differentiation due to NGF increasing the COL2A1 and SOX9 mRNA expression levels.

Enhanced Bone Formation in Osteoporotic Mice by a Novel Transplant Combined with Adipose-derived Stem Cells and Platelet-rich Fibrin Releasates

“…IGF-1 plays an important role in cell proliferation, differentiation, and apoptosis and is the major mediator of the effect of growth hormone on both bone growth and mineralization 57 , via decreasing osteoblast apoptosis and promoting osteoblastogenesis through the phosphoinositide 3-kinase 58 . NGF promotes cartilage differentiation and increases osteoclast formation and healing of mice tibial fractures by increasing the levels of COL2A1 and SOX9 mRNA expression, and may be used for the prevention and treatment of OP 59 . Some of the cytokines primarily enhance osteoclastic bone resorption, e.g., interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor, while others, e.g., IGF, PDGF, and TGF-β, primarily stimulate bone formation 53 .…”

Effects of Early Life Stress on Bone Homeostasis in Mice and Humans

“…This response pattern is suggestive for a higher rate of bone turnover and lower bone healing capacities as a consequence of early life stress, suggesting a concurrent joint downregulation, reduced bone remodeling and long-term destabilization. The neurotrophin NGF is important for the expression of cholinergic and sensory neuronal factors, and hence for the development and the repair of bone, as demonstrated by reduced bone length when absent [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. The neuropeptide NPY promotes osteoblast differentiation and balances the effects of stress-induced bone loss through beta-adrenergic stimulation, both with consequences for bone remodeling during healing [ 10 , 53 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 ].…”

“…In addition, neurotrophic growth factors such as nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) that guide outgrowing nerve fibers to bony areas requiring innervation are of interest. Stress alters their expression, and they can also act as direct and indirect growth factors for osteoblasts [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. Latest studies indicate that psychosocial stress can lead to structural and functional changes in neuronal plasticity, neuronal marker expression, mitochondria and inflammation [ 4 , 27 , 28 ], possibly resulting in downstream alterations of bone homeostasis [ 29 , 30 , 31 , 32 , 33 ].…”

Effects of early life stress on bone homeostasis in mice and humans

“…In addition, neurotrophic growth factors such as nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) that guide outgrowing nerve fibers to bony areas requiring innervation are of interest. Stress alters their expression, and they can also act as direct and indirect growth factors for osteoblasts [14][15][16][17][18][19][20][21][22][23][24][25][26]. Latest studies indicate that psychosocial stress can lead to structural and functional changes in neuronal plasticity, neuronal marker expression, mitochondria and inflammation [4,27,28], possibly resulting in downstream alterations of bone homeostasis [29][30][31][32][33].…”

“…This response pattern is suggestive for a higher rate of bone turnover and lower bone healing capacities as a consequence of early life stress, suggesting a concurrent joint downregulation, reduced bone remodeling and long-term destabilization. The neurotrophin NGF is important for the expression of cholinergic and sensory neuronal factors and hence for the development and the repair of bone, as demonstrated by reduced bone length when absent[14][15][16][17][18][19][20][21][22][23][24][25][26].The neuropeptide NPY promotes osteoblast differentiation and balances the effects of stress-induced bone-loss through beta-adrenergic stimulation, both with consequences for bone remodeling during healing[10,53,[56][57][58][59][60][61][62][63]. The neuropeptide VIPR1, finally, promotes bone mineralization[64][65][66][67][68] while TACR1 regulates osteoblasts, osteoclasts and mesenchymal stem cell functionality associated with protection from osteoporosis [2, 62, 69-85].…”