Evidence that the corneocyte has a chemically bound lipid envelope

Area of Science:

• Dermatology
• Biochemistry
• Cell Biology

Background:

• The stratum corneum is crucial for the epidermal water barrier.
• Lipids are key components of the stratum corneum's structure and function.

Purpose of the Study:

• To identify and characterize the lipids forming the corneocyte envelope.
• To elucidate the structural role of these lipids in the epidermal barrier.

Main Methods:

• Transmission electron microscopy (TEM) for ultrastructural analysis.
• Lipid extraction using chloroform/methanol and alkaline hydrolysis.
• In situ derivatization and molecular modeling.

Main Results:

• Initial extraction removed intercellular lamellae, indicating their role in the water barrier.
• Subsequent alkaline hydrolysis removed the lucent band, identifying it as the corneocyte plasma membrane.
• Omega-hydroxyacylsphingosines, linked via amide bonds, are constituents of the corneocyte envelope, likely esterified to proteins.

Conclusions:

• The corneocyte envelope is composed of tightly packed hydroxyacylsphingosine molecules.
• These lipids form a protective lipid envelope around each corneocyte, contributing to epidermal integrity.