In order to identify candidate ingredients, the company’s researchers used genomic analysis to highlight the differences in gene expression between young and old skin, before investigating which cosmetics compounds might help.
According to P&G scientist Rosemarie Osborne, the method holds significant potential for the industry and wouldn’t have been possible without the sequencing of the human genome.
“Such a genomics approach is one of the unexpected benefits from the human genome project,” she told CosmeticsDesign.
Highlight barrier genes
The scientists used DNA microarrays to highlight the genes involved in the metabolism of stratum corneum lipids with expression levels that altered between young and old, sun exposed and sun protected skin.
Ceramides, cholesterol and fatty acids are the major lipids of the stratum corneum and are essential to barrier function, but the P&G researchers found that the expression of the lipid metabolism genes were downregulated in both intrinsically aged and photoaged skin.
The down regulation of the stratum corneum lipid pathways is likely to contribute to the decreased capacity of aged skin to maintain and repair its barrier function, according to the scientist.
The next step in the work was to identify what cosmetic compounds might help restore the expression levels of the lipid pathways genes, explained Osborne.
Tissue models to test candidate ingredients
Here the team used human skin equivalent cultures in order to test the effect of a number of cosmetic compounds on gene expression.
“With tissues engineered models we can obviously poke and prod in a way that would be much too invasive for an in vivo study,” said Osborne.
Hexamidine, one of the ingredients in the Pro X range, was identified as a compound that helped increase the expression of the barrier related genes, as was niacinamide (vitamin B3), she explained.
“The tissue engineered models act as a sort of pre screen to a clinical trial when the effect of the compound can be seen in vivo,” she said.