Collagen fibers evaluation after rhBMP-2 insertion in critical-sized defects

The objective of this investigation was to assess the quantity of collagen fibers with different dosages of recombinant human bone morphogenetic protein, type 2 (rhBMP-2) associated with two different carriers, monoolein and poloxamer gels, in critical bone defects created in the calvaria of Wistar rats. Forty male adult Wistar rats were divided into eight groups of 5 animals each-group I: critical bone defect with application of 1 microg of rhBMP-2 combined with monoolein gel; group II: 3 microg of rhBMP-2 combined with monoolein gel; group III: 7 microg of rhBMP-2 combined with monoolein gel; group IV: 1 microg of rhBMP-2 combined with poloxamer gel; group V: 3 microg of rhBMP-2 combined with poloxamer gel; group VI: 7 microg of rhBMP-2 combined with poloxamer gel; group VII: monoolein gel only and group VIII: poloxamer gel only. A critical-sized defect of 6mm diameter was produced in the left parietal bone using a surgical round bur and a high-speed micromotor. The bone defects were filled according to the group that animals belonged and after two weeks the rats were perfused and their calvarial bones were removed for histological processing, and collagen fibers quantification. Differences among the eight groups were statistically analyzed by Anova and Bonferroni test (p<0.05). The results did not show statistical difference between the groups, in exception, between the comparisons II and III. According to the experimental methodology used in this research, it was observed, in a general way, a qualitative inverse relationship between collagen fibers presence and rhBMP-2 quantity inserted in the critical bone defect, associated or not to a material carrier.