The Expression And Effect Of IL-6,Cox-2 In Canine Mandible Distraction Osteogenesis And Bone Defect Healing

Objective:To approach the scientific mechanism of bone regeneration in distraction osteogenesis,we had examined the expression level of interleukin-6(IL-6)and cyclooxygenase-2(COX-2)during canine mandible distraction osteogenesis.Meanwhile we had compared the expression level of both cell factors' between in DO group and in acute lengthening group.Methods:We selected 28 adult dogs,which had been ramdomly divided to three groups:control group(n=4),acute lengthening group(n=12)and DO group(n=12).In DO group the dogs were underwent bilateral mandibular osteotomy between the first and second molars,and two custom-made distraction devices were fixed in the both two osteotomy regions.After a latency period of 7 days post-osteotomy,the distraction devices had beenactivated at a rate of 1mm per day and for 10 days.In acute lengthening group dogs were as the DO group as underwent bilateral mandibular osteotomy in the same region and acutely lengthened to 10mm and fixed by titanium plates.In both groups, four dogs were respectively sacrificed on day 6th of distraction period,on week 2nd and 8th of consolidation period.Callus of the both groups and that located the same region of control group were harvested.The spatial and temporal expression patterns of IL-6 and COX-2 were studied using immunohistochemistry.The X-ray examination was taken respectively on day 1st,week 2nd,4th and 8th after completion of distraction.Results:X-ray found that the density of new bone in both DO group and acutely lengthening group was enhanced gradually as time of fixation elapsed. But the new bone density in DO was higher than acute lengthening group at the same time.Using immunohistochemistry IL-6&COX-2 were detected in both DO group and acute lengthening group and expressed strongly in the regenerated callus,none of which was detected in control group.The IL-6&COX-2 were expressed in osteoblast cells,osteoclast cells,fibroblast cells,cartilage cell and the regenerated bone matrix.The expression of IL-6&COX-2 in DO group showed higher than that in acute lengthening group.Meanwhile the expression of IL-6&COX-2 of the two experimental group showed higher than that in control group,and finally gradually decreased with the time of consolidation elapsing.Conclusion:IL-6&COX-2 might participate the process of distraction osteogenesis and bone defect healing and accelerate the new bone forming.Both IL-6&COX-2 were the sensitive markers of tissue damage and inflammation and detected in DO.So it was suggested that micro- trauma might play an important role to activate the DO procedure.