| Objective: To study the combined effect of exogenous basic fibroblast growth factor(bFGF)and platelet-derived growth factor(PDGF)on the healing process of tibia fractures in rats,and to provide experimental reference for early clinical treatment of patients with nonunion or delayed fracture healing.Methods:Forty-eight male SD rats were randomly divided into four groups: A(bFGF),B(PDGF),C(bFGF + PDGF),D(control group)(n=12).Rats in each group were asked to establish a model of right middle tibia fractures according to the aseptic operation and treated with intramedullary internal fixation(Kirschner wire,D=1mm).Rats in group A,group B and group C were injected with drug into the sites of the fracture at the third day after operation,once a day for 7 days.Fractures were treated with 0.3 mL normal saline containing different drug(A: 100 ng bFGF,B: 100 ng PDGF,C:100ng b FGF+ 100 ng PDGF)in groups A,B,C.Respectively,the same amount of normal saline in group D.After 2 and 4 weeks,the arterial blood were harvested from 6 rats of each group.Then the rats were taken to X-ray examination to collect the gross specimens in fracture area.The specimens were treated with HE staining to perform the histological observation,and the expressions of ALP in the bone callus were measured by ELISA.The levels of VEGF,BMP-2 and IGF-1 in serum were measured by protein chip technique at 2 weeks and 4 weeks.Results:After 2and 4 weeks,the gross specimen shows that the newborn hard tissue size,hardness and callus maturity,stability in group A,group B and group C were significantly higher than group D.Group C was significantly better than other groups.Two weeks after operation,the X-ray scan shows that the local fracture line of group C is blurred and the fracturespace is smaller than that of the other group.The local fracture line of group A and group B is visible,slightly lighter than that of group D,the end of fracture can be seen as a cable-like low-density shadow.4 weeks after surgery,the X-ray scan shows that the fracture line in group C rats disappears,visible shuttle external callus shadow and the formation of bone bridge and bridge fracture ends appear;the fracture line in group A and group B rats almost disappear,the fractures end blunts,a high density of callus can be observed and connects the ends of fractures.the rat limb fracture line is clearly visible,the fracture gap is smaller compared with that at 2 weeks.Meanwhile,the fracture line in group D rats is still clearly visible and fracture gap shrinks after 2 weeks.Histological observation found: after 2 weeks postoperatively,the cartilage callus and fibrous callus in group C rats can be seen,the cartilage cell proliferation and cartilage callus is apparent,new bone trabecula and blood vessels are more significant than other groups;fiber callus and cartilage callus formation in group A and group B can be seen,in which fibrous callus is obvious;while group D is based on fibrous callus.At 4 weeks postoperatively,the trabecular bone in group C was mature,and a large number of mature lamellar bone and a large number of bone marrow cells appear in the medullary cavity.It can be easily observed that obvious calcification and trabecular bone in group A and group B increase,mature plate bone formation and bone marrow cells in the pulp cavity shows;fibrous callus of group D decreased and cartilage callus increased,osteoblast proliferation active.At 2weeks and 4 weeks after operation,the trabecular bone osteogenesis index of C callus is significantly higher than other groups and there is statistical significance(P < 0.05),group A and group B are higher than the group D,but lower than the group C,it is statistically significant(P < 0.05).The content of ALP in callus is measured by ELISA.The content of ALP in callus of group C is the highest in the groups at 2 weeks and 4 weeks after operation,and the difference is statistically significant(P < 0.05).At 2 weeks after operation,group A and group B are higher than group D and less than group C,and the difference is statistically significant(P<0.05).There is no significantdifference between group A,group B and group D at 4 weeks postoperatively(P> 0.05).Serum biochemical indicators show that: the serum levels of VEGF in group A,group B and group C are significantly higher than those in control group(P <0.05),group C is the highest,followed by B>A>D.At 4 weeks postoperatively,the serum levels of VEGF in group C are still the highest among the four groups(P <0.05).There is no significant difference among other groups(P> 0.05).At 2 weeks postoperatively,the serum BMP-2 level in group C is higher than that in other groups(P <0.05).The serum BMP-2 level in group B is higher than that in group A and group D(P <0.05).There is significant difference among all groups at 4 weeks after operation(P <0.05).After 2 weeks,the rank of IGF-1 content in serum of rats is C>B>A>D(P< 0.05).At 4 weeks after operation,it is smaller in group A,B and D than the level in group C(P <0.05),but there is no significant difference.Conclusions:1 Local injection of exogenous basic fibroblast growth factor or platelet derived growth factor can promote the healing of tibial fractures in rats,and combined injection is superior to the injection alone.2 Local combined injection of exogenous basic fibroblast growth factor and platelet-derived growth factor can increase the expression of VEGF,BMP-2,IGF-1and ALP,which may be a mechanism to promote the healing of tibial fractures in rats.3 Exogenous basic fibroblast growth factor and platelet-derived growth factor play a synergistic role in enhancing the expression of VEGF and IGF-1in rats. |
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