The in vitro effects on human dermal fibroblasts and the U937 human monocytic cell line of three phases of electrical microcurrents generated by the ACE Stimulator were investigated. The growth and viability of growing and confluent dermal fibroblasts were not directly influenced by the separate microcurrent phases. One form of microcurrent (designated phase 1) stimulated both dermal fibroblasts and U937 cells to secrete transforming growth factor-β1 (TGF-β1), which is an important regulator of cell-mediated inflammation and tissue regeneration, but none of the three phases stimulated secretion of the pro-inflammatory cytokine interleukin-6 by U937 cells. The stimulation of TGF-β1 secretion in these experiments was not dramatic (a median increase over control levels of 20–30%), although it could be biologically significant.
A range of cosmetics formulations with human patch-test data were supplied in a coded form, for the examination of the use of a combined in vitro permeability barrier assay and cell viability assay to generate, and then test, a prediction model for assessing potential human skin patch-test results. The target cells employed were of the Madin Darby canine kidney cell line, which establish tight junctions and adherens junctions able to restrict the permeability of sodium fluorescein across the barrier of the confluent cell layer. The prediction model for interpretation of the in vitro assay results included initial effects and the recovery profile over 72 hours. A set of the hand-wash, surfactant-based formulations were tested to generate the prediction model, and then six others were evaluated. The model system was then also evaluated with powder laundry detergents and hand moisturisers: their effects were predicted by the in vitro test system. The model was under-predictive for two of the ten hand-wash products. It was over-predictive for the moisturisers, (two out of six) and eight out of ten laundry powders. However, the in vivo human patch test data were variable, and 19 of the 26 predictions were correct or within 0.5 on the 0–4.0 scale used for the in vivo scores, i.e. within the same variable range reported for the repeat-test hand-wash in vivo data.
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