An overview of epidermal lamellar bodies: Novel roles in biological adaptations and secondary barriers

Abstract

The epidermal lamellar bodies (LBs) are specialized organelles that contain pro-barrier lipids imparting a fully lamellar internal structure, but also other cargoes such as enzymes (lipid metabolizing and proteolytic), enzyme inhibitors, and antimicrobial peptides. Thus, the LB secretory system, by virtue of delivering these cargoes to the stratum corneum (SC) interstices, is essential for forming the various skin barriers located in the SC. Ultrastructural studies have suggested that the morphologic features of LBs reflect the functional status of the SC. Several ichthyotic skin diseases as well as experimental animal models with defective epidermal lipogenesis show only partial lamellar contents or even empty appearing LB, reflecting an abnormal cargo composition. We suggest that LB polymorphism reflects a wide array of barrier adaptations to environmental challenges, rather than just a defective barrier function, based on observations on a) LB morphology in inherited skin disorders of lipid metabolism (Refsum disease, Chanarin-Dorfman syndrome) characterized by deficiency of lamellar lipids and accumulation of toxic metabolites; b) Psoriasis (with a high expression of Psoriasin antimicrobial peptide within lesions) and c) the Pitohui, a toxic bird where diet-derived toxin is eliminated via the LB secretory system that creates a chemical defense system. Morphological features of LBs from these models suggest a hitherto unrecognized function for the LBs in elimination of toxic substances from the body. We also provide preliminary evidence that indicate yet another function for the LBs- as a type of recycling endosomes allowing for uptake of certain topically applied materials by the epidermis.

The road to lysosome‐related organelles: Insights from Hermansky‐Pudlak syndrome and other rare diseases

“…Bii, Transverse view of an alpha granule that is immunogold labeled for P‐selectin (yellow) and CD63 (magenta), emphasizing an intraluminal vesicle (green). C, A lamellar body from ex vivo human skin analyzed by thin section EM (from Reference ). Scale bar, 100 nm.…”

“…Scale bar, 20 μm. All panels reprinted by permission of: (A) Taylor and Francis from Platelets , Reference , copyright 2018; (B) American Society of Hematology from Blood , Reference , copyright 2010; (C) Elsevier from the Journal of Dermatological Science , Reference , copyright 2018; (D) Elsevier from the Journal of Structural Biology , Reference , copyright 2008; (E) Springer Nature from Pediatric Research , Reference , copyright 2012; (F) John Wiley and Sons from EMBO Journal , References , copyright 1997; (G) National Academy of Sciences, U.S.A from Proceedings of the National Academy of Sciences U.S.A ., Reference , copyright 2008; and (H) from PLoS Genetics , Reference …”

The Role of Hypoxia-Inducible Factor 1α in the Regulation of Human Meibomian Gland Epithelial Cells

“…69,70 Both lamellar bodies and lipid droplets are organelles specialized for lipid storage, and there is evidence that lamellar bodies may be derived from, or transform into, lipid droplets. 71 Considering that both lipid droplets and lamellar bodies exist in the human MG, 72,73 their specific roles in lipid dynamics await clarification. Finally, it is important to note that we used different methods to quantitate the extent of neutral lipid expression in our previous versus current studies.…”

Unique features of the skin barrier in naked mole rats reflect adaptations to their fossorial habitat

“…NMRs living in crowded, humid/moist subterranean tunnels can be expected to have a robust antimicrobial barrier in their skin. It has been hypothesized that the appearance of LBs could be altered if the cargo of AMPs outweighs the lipids packaged in them, leading to polymorphism of LBs (Menon, Lee, & Lee, ). Studies on AMPs in the mole‐rat skin are needed to test this assumption.…”