Dicer inhibition delays wound closure by increasing SUZ12 levels and regulating ITGAV levels in keratinocytes.

Delayed wound closure is a significant hallmark associated with diabetes. A previous study from our laboratory identified decreased levels of Dicer and miRNAs together with altered levels of wound healing genes in the wounded tissues of diabetic rats. Comprehensive regulators of these wound healing genes mapped onto the PRC2 (polycomb repressive complex 2) complex. Here we show that Dicer inhibition increases the transcript levels of core components of the PRC2 complex, namely Suz12 (suppressor of zeste 12) and Ezh2 (enhancer of zeste 2) and of Mtf2 (metal response element-binding transcription factor 2), its additional subunit, and elevates H3K27me3 levels in HaCaT cells. Such patterns of increase were also observed in the wounded tissues of diabetic rats as compared to those of normal rats. In a scratch assay in HaCaT cells, while Dicer inhibition significantly prevented wound closure, this was rescued by Suz12 siRNA but not by Ezh2 inhibition, suggesting that Suz12 mediates the effects of Dicer siRNA in these cells. In addition, as compared to scramble transfected cells, Dicer siRNA decreased the levels of integrin alphaV (Itgav), that is extensively implicated in the process of wound healing and this effect was rescued in the presence of Suz12 siRNA. Itgav harbors potential histone methylation marks across the gene length and Dicer inhibition, by increasing PRC2-mediated H3K27 methylation on Itgav, possibly decreases its transcription that subsequently impairs wound closure. These data put forth novel aspects of delayed wound closure as seen during diabetes and might be a potential target for therapeutic intervention.