Abstract
IFSCC Magazine, 12 (2009) (2) 87–91Tight junctions between adjacent epithelial cells control paracellular permeability of solutes and maintain cell polarity by fencing lipid bilayer components into demarcated apical and basolateral domains. In the present study we investigated the role of epidermal tight junctions in two skin physiological processes, ‘formation of the epidermal calcium ion (Ca2+) gradient’ and ‘polarized lamellar body secretion’. The former is based on the fact that the epidermal Ca2+ gradient is closely related to epidermal differentiation and the latter on the knowledge that polarized lamellar body secretion is essential to supply intercellular lipids to the stratum corneum. We hypothesized that tight junctions might form the Ca2+ gradient in the epidermis by sealing cell‐cell contact at the stratum granulosum and allow the lamellar bodies to be normally secreted toward the stratum corneum by giving granular cells polarity. In our experiments we discovered that tight junctions control not only both intercellular Ca2+ permeability and fluorescent ceramide analog (Cer‐FL) secretion in cultured normal human keratinocyte cells but also both intercellular calcium distribution and polarized lamellar body secretion in the skin equivalent. Thus, tight junctions should be responsible for linking a series of processes from epidermal differentiation to stratum corneum barrier formation. Our findings suggest that tight junctions should have a crucial role not only in epidermal barrier function but also in both epidermal differentiation and stratum corneum barrier function. Keywords: Calcium gradient, cell polarity, lamellar body, skin barrier, tight junctionIFSCC Basic Research Award winning paper presented at the 25th IFSCC Congress 2008, Barcelona, Spain
Published Version
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