Capturing the Ceramide Complexity of the Stratum Corneum

Posted on July 14, 2022


Stratum Corneum Research Highlight

Ceramides are lipids that are found in skin cells. It is well known that ceramides make up a significant portion of the skin’s outer layer, the stratum corneum (SC). As the outermost layer of the skin, the SC is our body’s interface with the outside world. As such, it acts as a barrier to keep unwanted materials from entering our bodies and keeps water from excessively leaving our bodies. Even though we have known for a while that ceramides are a major component of the SC, a quantitative analysis capable of distinguishing ceramides with different long-chain base lengths had not been published until recently.

It is important to identify and quantify ceramides in skin because many skin conditions like atopic dermatitis and psoriasis are caused by changes in ceramide levels and composition. Ceramides consist of a long-chain base connected to a fatty acid via an amide linkage. Mammalian ceramides can have any of five long chain bases – dihydrosphingosine, sphingosine, phytosphingosine, 6-hydroxysphingosine, and 4,14-sphingadiene. Each of these long-chain bases differ in the number and position of their hydroxyl groups and double bonds. The fatty acids attached to the long-chain bases are characterized into four main types. So, if you combine each long-chain base with one of the four fatty acids, you get twenty different classes of human ceramides. These classes are further complicated by the presence of various chain lengths in the fatty acid. As you can see, the ceramide composition in human skin is fairly complex. So, identifying and quantifying each of these ceramide classes is not a small task.

Researchers at Hokkaido University decided to tackle this complex lipidome. Using a recently developed accurate and sensitive method combining the multiple reaction monitoring (MRM) mode of LC-MS/MS and various ceramide class standards from Avanti, they were previously able to successfully identify and quantify 345 species of unbound ceramides and 63 species of protein-bound ceramides with two and three hydroxyl groups and 18 long-chain carbon bases. They expanded this study to include ceramides with two and three hydroxyl groups and 16-26 long-chain carbon bases to capture the whole picture of ceramide composition in human SC.

Using the MRM mode in LC/MS/MS rather than the less sensitive product ion scanning mode, they were able to identify and quantify 1,327 unbound and 254 protein-bound ceramides with two and three hydroxyl groups and 16-26 long-chain carbon bases. This is just the first step towards more completely understanding ceramide composition of skin in patients with skin conditions such as atopic dermatitis, psoriasis, and ichthyosis. Although it has been reported that ceramide composition is altered in these conditions, the exact composition has never been identified or quantified. Being able to completely characterize the ceramide composition in these skin conditions will elucidate relationships between changes in ceramide composition and disease pathology, as well as help develop methods to diagnose and treat each disease.

As you work towards the quantification and identification of lipidomes in human biology, Avanti is constantly adding to the list of pre-mixed lipidomic mixtures for your research. Just in the first half of 2022 alone, we have launched three new mixtures – Bile Acid SPLASH, SphingoSPLASH II, and SphingoSPLASH III. If you are interested in some of the standards that are not yet available in our SPLASH mixtures, chances are we have those individual standards ready for your research. Check out our lipid standards today at https://avantilipids.com/product-category/lipidomics/lipidomix-standards!

Don’t forget to read the full research article to find out more about the whole picture of human stratum corneum ceramides at https://www.jlr.org/article/S0022-2275(22)00068-2/fulltext#%20