Scientists at Karolinska Institutet in Sweden have announced they have succeeded in describing the structure and function of the stratum corneum at a molecular level after thirteen years of research.
"You could say that we've solved the puzzle of the skin barrier, something that has never been solved before - a great potential significance for dermatology,” university associate professor Lars Norlén told CosmeticsDesign-Europe.com
According to the research team, the new methodology can benefit the cosmetics industry by determining how an active ingredient penetrates and interacts with different molecular components of the skin barrier.
“Now that we know the molecular organization of the lipid matrix, we can for the first time also construct relevant in-vitro models of the skin barrier for cosmetic product development and testing,” adds Norlén.
A first for the industry
According to the professor, one contributing reason for why it has taken so long to solve the puzzle is “probably that the staining patterns of conventional electron micrographs of the stratum corneum have been misinterpreted”
Explaining further, Norlén says that it could be a little interpretation mistake that may have delayed the structure determination being solved until now.
“When interpreting conventional electron micrographs it has been taken for granted that stain exclusively associates with hydrophilic structures such as lipid head-groups,” he explains.
Adding that in reality; “We know now from our native unstained microscopy data, a not insignificant part of the stain accumulates in the most hydrophobic central part of the lipid bilayers.”
According to the research published last month in the Journal of Investigative Dermatology, molecular organization of the skin's lipid matrix was determined in situ in its near-native state using a methodological approach combining very high magnification cryo-electron microscopy (EM) of vitreous skin section defocus series, molecular modeling, and EM simulation.
To conduct their study, the researchers developed an entirely new experimental approach involving rapidly freezing tiny skin samples and studying them under a low-temperature electron microscope.
"This has given us an unprecedented opportunity to determine the function of native cells and tissues in situ without having our data muddied by the addition of dyes, solvents or plastics," says Norlén.
Report findings also indicated that lipids are organized in an arrangement not previously described in a biological system i.e., stacked bilayers of fully extended ceramides (CERs) with cholesterol molecules associated with the CER sphingoid moiety.
The authors propose that this particular arrangement rationalizes the skin's low permeability toward water and toward hydrophilic and lipophilic substances, as well as the skin barrier's robustness toward hydration and dehydration, environmental temperature and pressure changes, stretching, compression, bending, and shearing.