Reepithelialization of Diabetic Skin and Mucosal Wounds Is Rescued by Treatment With Epigenetic Inhibitors.

Wound healing is a complex, highly regulated process and is substantially disrupted by diabetes. We show here that human wound healing induces specific epigenetic changes that are exacerbated by diabetes in an animal model. We identified epigenetic changes and gene expression alterations that significantly reduce reepithelialization of skin and mucosal wounds in an in vivo model of diabetes, which were dramatically rescued in vivo by blocking these changes. We demonstrate that high glucose altered FOXO1-matrix metallopeptidase 9 (MMP9) promoter interactions through increased demethylation and reduced methylation of DNA at FOXO1 binding sites and also by promoting permissive histone-3 methylation. Mechanistically, high glucose promotes interaction between FOXO1 and RNA polymerase-II (Pol-II) to produce high expression of MMP9 that limits keratinocyte migration. The negative impact of diabetes on reepithelialization in vivo was blocked by specific DNA demethylase inhibitors in vivo and by blocking permissive histone-3 methylation, which rescues FOXO1-impaired keratinocyte migration. These studies point to novel treatment strategies for delayed wound healing in individuals with diabetes. They also indicate that FOXO1 activity can be altered by diabetes through epigenetic changes that may explain other diabetic complications linked to changes in diabetes-altered FOXO1-DNA interactions. ARTICLE HIGHLIGHTS: FOXO1 expression in keratinocytes is needed for normal wound healing. In contrast, FOXO1 expression interferes with the closure of diabetic wounds. Using matrix metallopeptidase 9 as a model system, we found that high glucose significantly increased FOXO1-matrix metallopeptidase 9 interactions via increased DNA demethylation, reduced DNA methylation, and increased permissive histone-3 methylation in vitro. Inhibitors of DNA demethylation and permissive histone-3 methylation improved the migration of keratinocytes exposed to high glucose in vitro and the closure of diabetic skin and mucosal wounds in vivo. Inhibition of epigenetic enzymes that alter FOXO1-induced gene expression dramatically improves diabetic healing and may apply to other conditions where FOXO1 has a detrimental role in diabetic complications.

Innate cellular responses to the periodontal biofilm.

This chapter addresses the host responses to the microbial biofilm that constitutes the subgingival dental plaque. The host response to infection draws upon the innate, inflammatory and adaptive immune systems, whose role is to provide the appropriate response to the offending microorganisms. In some cases, this will be little or no response when encountering 'commensals', and in other cases a gradated response depending very much on the host's own determination of the pathogenic nature of the microbial insult: and herein lies the root of variation in host responses that govern individual susceptibility. In some individuals and with some bacteria this will be an innate-only response, others will need to invoke the inflammatory response, and yet others will require the adaptive immune response - be it cellular, humoral or both - to reduce or remove the challenge from the microbes. Of course these responses would be somewhat easier to predict with a single pathogen challenge, and become infinitely more complex as the biofilm increases in complexity. Oral infections, in particular gingival inflammation, originate from not just one but many microorganisms. This polymicrobial infection may result in chronic inflammation, which may lead to tissue destruction, as evident in chronic periodontitis. Although many organisms are present in the subgingival biofilm, interestingly, the putative pathogens associated with gingivitis and periodontitis may comprise very small fractions of the total biomass. An understanding of the interaction of structural and defensive host cells with the biofilm is pivotal to understanding periodontal disease etiology and to developing tailored therapeutics. Thus, this chapter addresses the main structural cells, i.e. epithelial cells, exposed to the biofilm.