Water Permeation of Reaggregated Stratum Corneum with Model Lipids

Stratum corneum, corneodesmosomes and ex vivo percutaneous penetration

“…For these reasons, we believe that these ''caps'' at the corneodesmosome edges are indeed fragments of hydro/amphiphilic lacunae dislocated laterally towards corneodesmosomes by intercellular lipids. It has been demonstrated previously that such lipids are capable of self-organization into lamellar structures (Wertz et al, 1986;Abraham et al, 1987;Friberg et al, 1990). Based on this evidence and on our morphological studies, we propose that the spontaneous organization of intercellular lipids is a major mechanism involved in the extracellular enzyme delivery towards their immobile junctional substrate.…”

“…Although the number of cell layers and the overall thickness of the SC do not necessarily correlate with its relative impermeability to water (Elias et al, 1981), neither the lipid content by weight of the SC can solely and fully account for the efficiency of the barrier function (Abrams et al, 1993). Layered arrangement of SC lipids (Friberg et al, 1990) and segregation of various lipid molecules into domains displaying different physical-chemical characteristics RuO 4 penetration into the blocks of skin (occluded) takes place primarily along the living epidermal layers (SG) and the stratum disjunctum corneocytes (SDj). Stratum compactum (SCp) remains less permeable and corneodesmosomes represent the first structures to be stained with ruthenium (B,C).…”

Water relations of tetrapod integument

“…While compositional features of these lipids are not yet known in detail, upregulation of the barrier during early postnatal ontogeny might be principally or entirely a quantitative phenomenon (Fig.·5). Others have also suggested that the principal determinant of barrier efficacy is the lamellar organization of exocytosed lipids in the extracellular domain, independent of the lipid molecular composition (Friberg et al, 1990;Menon et al, 1996).…”

Stratum corneum Lipid Function

“…The formation of broad lipid bilayers, consisting of amphipathic lipids such as the structurally heterogeneous cera mides, depends upon the presence of corneocytes, to which lipids are covalently bound. The rcaggregation of model lipids and corneocytes in vitro showed that not the exact chemical structure of individual lipid species deter mines the barrier to transcutaneous water loss, but the organization of lipids and corneocytes [ 13]. Recently it has been suggested that the major component of the lipid envelope on the outer surface of the corneocyte is a monomolecular layer of lipids covalently bound to the outside of the cross-linked protein envelope [70], The major lipid part has been described to be ccramide 1, consisting of 30-34 carbon co-hydroxy acids amide linked to sphingosine [16], The intercellular lamellae are responsible for the incorporation of many water molecules, the multilamellar structures, the water retention functions and the water per meability barrier, with which the ability to form bilayers without phospholipids is believed to be associated [52].…”

“…to which those lamellae adjacent to the corneocyte envelope are covalently bound. The reaggregation of model lipids and corneocytes in vitro suggests that it may not be the exact chemical nature of individual lipid species that determines the barrier to transcutaneous water loss, but rather the organization of both lipids and corneocytes [13]-…”