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[Promotion effect of nuclear factor kappa B p65 on early fracture healing of rat radius by elevating prostaglandins E2 production and regulating inhibitor of DNA binding 2 protein expression].

OBJECTIVE
Series of complicated molecule signal pathway are involved in the bone regeneration. To explore the possibility of nuclear factor kappa B (NF-kappaB) which is taken as the "key activation" during the fracture healing and provide the laboratory evidence for the gene therapy of nonunion or delayed union of fractures.


METHODS
Thirty-three adult male Wistar rats (weighing 180-220 g) were selected and divided randomly into 4 groups: group A (the control group, n=3), the rigth lower segments of radius were injected with normal saline 0.3 mL for 7 days, once per day; group B (Bay 11-7082 injection group, n=6), the middle and distal radius were injected with normal saline containing 50 pmol/L NF-kappaB inhibitor Bay 11-7082 0.3 mL for 7 days, once per day; group C (fracture group, n=12), the right middle and distal radius were cut by a sharp scissors to form per fracture model; and group D (Bay 11-7082 treatment group, n=12), based on group C, 0.3 mL of 50 micromol/L Bay 11-7082 were injected into the fracture site for 7 days, once per day. The callus tissues were harvested at 3, 7, 14, and 28 days after fracture for Western blot analysis, alkaline phosphatase (ALP) activity assessment, prostaglandins E2 (PGE2) production assay, and histological observation.


RESULTS
The rats of all groups were survival till the experiment completion. At 3 and 7 days after injection, there was no significant difference in the ALP activity and PGE2 production between group B and group A (P > 0.05); but group C was significantly higher than group A (P < 0.01) and group D was significantly lower than group A (P < 0.01). The expressions of NF-kappaB p65, bone morphogenetic protein 7 (BMP-7), and inhibitor of DNA binding 2 (Id2) were observed at fracture sites of 4 groups. There was no significant difference in the expressions of NF-kappaB p65, BMP-7, and Id2 between group B and group A (P > 0.05); the expressions of NF-kappaB p65 and BMP-7 were significantly higher and the expression of Id2 was significantly lower in group C than group A (P < 0.01); and the expressions of NF-kappaB p65 and BMP-7 were significantly lower and the expression of Id2 was significantly higher in group D than group A (P < 0.01). The histological observation showed that a lot of osseous callus formed in group C at 14 and 28 days.


CONCLUSION
but osseous callus just began to form in group D at 28 days. NF-kappaB p65 can facilitate early fracture healing of rat radius by elevating the PGE2 production and regulating BMP-7 and Id2 expression.