Ultrastructural observation of the stratum corneum lipids in hairless mouse epidermis characterized by ruthenium tetroxied fixation / 医学研究生学报

Objectives: To reveal the morphological features of the stratum corneum lipids in hairless mouse epidermis. Methods: Ruthenium tetroxide and osmium tetroxide were compared as post fixative in the preparation of hairless epidermis for transmission electron microscopic examination. Results: Both reagents reveled characteristic membrane coating granules within the granular layer. Whereas, the transformation of the membrane coating granule contents into multiple lamellae at the interface between the granular and cornified layers and the persistence of these lamellae through all levels of the stratum corneum were demonstrated only by ruthenium tetroxide fixation. Conclusions: The distinctive patterning of the intercellular lamellae reflects the nonrandom organization of the stratum corneum lipids. In addition, the ruthenium tetroxide postfixation technique is a useful method in the investigation of the morphological features of the stratum corneum lipids.

The Ultrastructural Changes of Stratum Corneum Lipids after Application of Oleic Acid in Propylene Glycol

BACKGROUND: The stratum corneum presents a significant barrier to transdermal drug delivery. Approaches to improve percutaneous absorption of drugs have included iontophoresis and skin penetration enhancers. Oleic acid has been studied as a skin penetration enhancer for drugs, primarily via its action mainly on the stratum corneum lipid structure. OBJECTIVE: The purpose of this study was to assess the interaction between oleic acid and stratum corneum lipids in vivo. METHODS: Male hairless mice were treated topically with oleic acid. Barrier function was assessed by transepidermal water loss measurement and ultrastructural observation with ruthenium tetroxide (RuO₄) staining. RESULTS: Oleic acid in propylene glycol had a profound effect on epidermal barrier function and was found to be concentration dependent. Moreover, ultrastructural examination with RuO4 post-fixation demonstrated that there were marked alterations in the stratum corneum lipid structure. CONCLUSION: This study provides direct evidence that oleic acid increases the epidermal permeability through a mechanism involving the stratum corneum lipid membrane perturbation via the lacunae formation within the stratum corneum.

Epidermal Lipid Homeostasis

Stratum corneum lipids, which are enriched in sphingolipids, free fatty acids, and cholesterol, are required for epidermal barrier function. When the epidermal permeability barrier is perturbed, the transepidermal water loss returns to normal by 24-48 hours in parallel with the reappearance of stratum corneum lipids, derived from secreted lamellar bodis and accelerated lipid synthesis. Recent evidence shows that topical application of individual lipids interferes with barrier recovery while complete mixtures of cholesterol, fatty acids, and ceramides facilitate recovery after barrier disrupton. Metabolic imbalances and perturbed barrier function can be either the cause or the consequences of the pathobiology of scaling disease. Many skin diseases relating cornification and dryness are indeed related to abnormality of one or several combinations of lipids. Recently the cytokines which have changed during barrier recovery seem to be important in understanding of epidermal lipid homeostasis as well as barrier recovery.