• miR-203 and miR-210 are regulators of keratinocyte function

We demonstrated that SM upregulates miR-203 in primary human keratinocytes under normoxia and hypoxia, and augments hypoxia-induced levels of miR-210 in these cells thereby affecting cellular viability, proliferation, and differentiation. These deficiencies were efficiently counteracted by the application of specific inhibitors of miR-203 and miR-210 (anti-miRs), providing evidence that miRNAs are key regulators in normal and SM-affected keratinocyte functionality (Deppe J. et al., Toxicology Letters, 2016).

• mRNA and miRNA transcriptome analysis of SM-exposed keratinocytes

In our recent project funded by DFG and Bundeswehr, we discovered a SM-triggered pathomechanism involving miR-497-5p and its target survivin which contributes to keratinocyte dysfunction. Transcriptome analysis using RNA-seq in NHEK revealed that SM evoked differential expression of 1896 mRNAs and 25 miRNAs with many of these RNAs known to be involved in keratinocyte function and wound healing. We demonstrated that keratinocyte differentiation and proliferation were efficiently regulated by miRNAs induced in skin cells after exposure to SM. The inhibition of miR-497-5p counteracted SM-induced premature differentiation and stimulated proliferation of NHEK. In addition, we showed that microneedle-mediated transdermal application of lipid-nanoparticles containing miR-497-5p inhibitor restored survivin biosynthesis and cellular functionality upon exposure to SM using human skin biopsies. Our findings expand the current understanding of SM-associated molecular toxicology in keratinocytes and highlight miR-497-5p as feasible clinical target for specific skin therapy in SM-exposed patients and beyond (Fig. 3).