HDAC9 and periodontitis: Histone acetylation and histone deacetylation are associated with several cellular processes, including gene transcription, and the relevance of analyzing markers of such functions in inflamed gingival tissues was demonstrated by Cantley et al.26They analyzed gingival biopsies obtained from sites with periodontitis or gingivitis and reported that HDAC levels overall were higher in periodontitis lesions and that the expression of HDAC1 in endothelial cells was the most conspicuous difference between periodontitis and gingivitis specimens.