Epidermal Barrier in Human Fetus and Newborn

Background : The lipids of the statum corneum, which originate from polar lipid precursors provided by the cells of the stratum granulosum via the exocytosis of lamellar bodies, with cornified cell envelope form competent epidermal barrier stucturally and functionally. The ontogeny of the epidermal barrier is not clearly defined because of difficulty of sampling and methodology which defines epidermal lipids. Object : From ultrastructural observation of skin samples obtained from human fetuses and newborn on serial developmental timings, we tried to clarify the sequential development of epidermal barrier Methods : Skin samples were obtained from 13 human fetuses from EGA(estimated gestational age) 10 to 23wks and 2 newborns. Specimens were obsereved by fluorescent confocal microscopy with nile red to identify the distribution of epidermal lipids, by transmission electron microscope with lanthanum to investigate the functional permeability barrier, with RuO4 to observe the intercellular lipid bilayer and morphology of lamellar bodies, with ion capture cytochemistry to investigate the formation of epidermal calcium gradient. Result : 1. In nile red stain, the amount of epidermal lipid increased during fetal period. At EGA 23wks, the lipid distribution revealed linear and continuous pattern. 2. In lanthanum tracer study, the electron dense tracer permeated all the intercellular space of the epidermis up to periderm and subepidermal space until EGA 21wks. At EGA 23wks, the tracer permeated intercellular space of epidermis weakly. It might be predicted that incomplete epidermal barrier is present at this time. 3. In RuO4 stain, precursor of lamellar body was observed at EGA 15wks, and intercellular lipid bilayer was observed at EGA 16wks. As gestation increases, there was a steady increase in epidermal lipid bilayers. 4. In ion capture cytochemistry, epidermal calcium gradient was first observed in follicular epidermis at EGA 20wks, and in interfollicular epidermis at EGA 23wks. From these results, it is concluded that the basic structures of epidermal barrier are formed at EGA 23wks, but it is not complete, and epidermal barrier arises first from follicular epidermis.ope