Matrix metalloproteinase-1 and -8 in gingival crevicular fluid during orthodontic tooth movement: a pilot study during 1 month of follow-up after fixed appliance activation

The role of matrix metalloproteinases (MMPs) in response to mechanical forces in orthodontic tooth movement has only been partially clarified. In the present in vivo pilot study, the presence, levels, and degree of activation of MMP-1 and -8 were measured daily for 1 month in gingival crevicular fluid (GCF) of patients treated with orthodontic fixed appliances. GCF samples were collected from five orthodontic patients and three controls from one upper or lower central incisor or from one upper canine before fixed appliance activation and every 24 hours for 1 month thereafter. The molecular forms and activation degrees of MMP-1 and -8 in GCF were analysed by Western blotting, and MMP-8 levels determined by immunofluorometric assay (IFMA).IFMA revealed, during the study period, on average 12-fold higher levels (56 +/- 50 versus 4.6 +/- 4 microg/l) of MMP-8 in orthodontic GCF than in control GCF. The MMP-8 levels in orthodontic GCF were lower than those detected in gingivitis and periodontitis GCF, but significantly higher than in control GCF. IFMA analysis was confirmed by Western blot analysis showing elevated MMP-8 levels from orthodontic GCF relative to control GCF. Forty-one per cent of total MMP-8 immunoreactivities were high-molecular weight complexes (>100 kDa), 32 per cent in the 75 kDa pro-polymorphonuclear (PMN)-MMP-8 form, 14 per cent in the 60 kDa active-PMN-MMP-8 form, and 13 per cent in the 55 kDa fibroblast-type pro-MMP-8 form. In the GCF of orthodontic patients no MMP-1 immunoreactivities were detected. MMP-8 and -1 levels in the control GCF were low and not detectable.These results demonstrate that in vivo in human GCF, elevation and partial activation of multiple species of PMN- and fibroblast-type MMP-8 reflect periodontal remodelling during orthodontic tooth movement.