The efficacy of silicone gel occlusion in the treatment of hypertrophic scarring has been well documented. In vitro evidence has been reported suggesting that this effect is mediated through normalization of epidermal hydration and a concomitant attenuation of epidermal activation. Activated keratinocytes are characterized by altered patterns of keratin expression, cytokine and growth factor signaling. In an attempt to study this phenomenon in vivo, we have established a novel murine cutaneous wound model which accurately recapitulates the proliferation of epidermal keratinocytes and altered spectrum of cytokeratin expression consistent with the activated keratinocyte phenotype. Introduction of silicone gel occlusion in our model results in attenuation of keratinocyte activation as well as modulation of cytokine and growth factor signaling pathways suggesting accelerated restoration of the basal keratinocyte phenotype. We observe that occlusion results in a marked downregulation of keratin-6 expression (a marker of keratinocyte activation) and a decrease in JAK/STAT dependant cytokine signaling activity. Conversely, occlusion appears to accelerate the TGF-beta mediated restoration of the basal keratinocyte phenotype.  Further we have developed a novel technique which allows for the rapid, reproducible isolation of murine epidermal cells from full thickness skin specimens resulting in epidermal specificity (as measured by differential expression of keratin-14 and desmin) comparable to digestion with dispase while better preserving RNA quality and gene expression profiles. This technique makes possible the accurate profiling of gene expression profiles arising specifically in the epidermal layer of mouse skin. Analyzing differences in these expression patterns between occluded and non-occluded skin allows detailed investigation into the modulation of presumed signals between epidermal keratinocytes and dermal fibroblasts by silicone gel occlusion or other interventions.

Cytokeratin 6 gene expression in nonoccluded mouse skin