Expression of metalloproteinases and their tissue inhibitors in inflamed gingival biopsies

Objectives: Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are known to be involved in the periodontal disease process. Results of in vivo MMPs and TIMPs gene expressions in the gingiva, though, are still controversial. In the present study, we compared the gene expression of MMP-1, -2, -9, -13 and TIMP-1, -2 in healthy and inflamed gingiva. Methods: 38 gingival samples were collected from gingivitis (n = 10), advanced chronic periodontitis (n = 10), generalized aggressive periodontitis (n = 8) and periodontally healthy individuals (n = 10). Total RNA isolated from those samples was subjected to reverse transcription followed by amplification by polymerase chain reaction (RT-PCR). Products were visualized in agarose gels and quantified by optical densitometry. Samples were also processed for gelatin zymography and Western blotting for MMP-2 and MMP-9 in order to assess for post-transcriptional MMP regulation at the protein level. Results: The frequencies and levels of transcripts encoding MMPs and TIMPs were found to be not significantly different among groups (p > 0.05, Fisher's Exact and Kruskall-Wallis tests). There is a trend towards higher MMP-2 and -9 gelatinase activities in the inflamed samples, although not statistically significant. In contrast, zymography and Western blotting studies show that MMP-2 is virtually absent in the chronic periodontitis group. Conclusion: These results could reflect a complex regulation of MMPs and TIMPs' gene expression in the course of gingival inflammation. They also reveal a great biological diversity even among individuals with similar periodontal status.