The Expression And Significance Of NOS In Mandiblar Distraction Osteogenesis Of Canine

Objective To investigate the expression and significance of nitric oxide synthase(NOS) during mandiblar distraction osteogenesis and bone trauma healing, to futher study the mechanism of distraction osteogenesis.Methods Twenty-eight adult dogs were randomly divided into DO group (12 dogs), acutely lengthening group (12 dogs)and control group(4 dogs).The bilateral mandibular osteodistraction between the first and second molar were performed and two custom-made distraction devices was fixed, after a lantency period of 7 days post-operation, distracted with a rate of 1mm/day in DO group. The total lengthening was 10mm.In the acutely lengthening group, bilateral mandibular osteotomy between the first and second molar were performed and fixed with titanium plates after being acutely lengthened 10mm.Four dogs were sacrificed respectively at the same time of the sixth day in distraction period, the second and eighth week of consolidation in the two experimental groups. Specimens macrography, histological and immunohistochemical examination were carried out.Results 1.specimens macrography The wound of two experimental groups healed well and haven't any infection. The fixation devices were steady and there were regenerated bones in the osteotomy gap of two experimental groups. 2. histological examination in the sixth day in distraction period the tissue damage was found in the distraction gap in DO group, more RBC leak out around vascellum and matrix, a great quantity of granulation tissue and inflammatory cell was found between distraction gap in acutely lengthening group, in the period of immobilization, the bone tissue in the distraction gap was mature gradually, intramembranous ossification was the main mode of ossification in DO group, while endochondral ossification was the main mode of ossification in acutely lengthening group. 3. Immunohistochemistry little expression of NOS were detectable in the normal bone. In the experimental groups the staining of iNOS was localized on the mesenchymal cells, fibroblasts, osteoblasts and few cartilaginous tissue, the staining of eNOS was localized on the vascular endothelial cells, mesenchymal cells and few osteoblasts, in the early of distraction period and the consolidation, the expression of local iNOS and eNOS was higher than that in the control group(P<0.05), the expression of local iNOS and eNOS in acutely lengthening group was higher than that in the control group(P<0.05), and lower than that in DO group(P<0.05), in the eight week of consolidation, the expression of local iNOS and eNOS was no statistic difference between three groups(P>0.05).Conclusions NOS are diferently expressed in various periods during DO and bone trauma healing, which indicates that they may be released and participate in promoting osteogenesis in DO and bone trauma healing; as a sensitive index of tissue trauma, NOS are highly expressed in the early of distraction, indicates that trauma may be present during DO, trauma may be one of the significant priming factors in DO.