Methods: Twenty formalin-fixed, paraffin embedded specimens of actinic cheilitis, and five specimens of normal lower lip vermillion, were examined. The streptavidin-biotin complex method was performed for MMP-9 and MMP-12 in serial sections of our specimens. MMP immunohistochemistry was evaluated using a semiquantitative immunoreactive score based on the percentage of positive cells and their staining intensity.
Results:Immunostaining for MMP-12 was clearly detected enhanced in most of the cases of actinic cheilitis (18/20),examined within the fragmented, distorted, and thickened elastic fibers.MMP-9 showed very weak reaction with the elastotic material (1/20) in actinic cheilitis lesions.Furthermore immunoreactivity for MMP-12 was detected in macrophages and for MMP-9 in polymorphonuclear leukocytes. In normal specimens we did not find any immunoreactivity for MMP-9 and MMP-12.
Conclusions: The restricted distribution of potential MMP-9 producing cells may explain the diminished immunoreactivity of MMP-9 in elastotic materials in sun damaged lip.In normal lip MMP-12 does not bind to normal elastin or in this condition, no abnormal accumulations of macrophages exist, as possible sources of MMP-12. MMP-12 possibly takes part in the reparative remodeling process by trying to cleave the abnormal elastotic material. Our results suggest that especially matrix metalloproteinase-12 may play an important role in remodeling events occuring in the connective tissue during long-term exposure to sunlight in the actinic cheilitis lesions.