Epidermal Cell Proliferation and Terminal Differentiation in Skin Organ Culture after Topical Exposure to Sodium Dodecyl Sulphate

Epidermal cell proliferation and differentiation were investigated in vitro after exposure to the anionic surfactant sodium dodecyl sulfate (SDS). Human skin organ cultures were exposed topically to various concentrations of SDS for 22 h, after which the irritant was removed. Cell proliferation was measured immunohistochemically by incorporation of bromodeoxyuridine (BrdU) into the DNA of cells during S-phase, while the expression of transglutaminase and involucrin were used as markers of differentiation. Cell proliferation was moderately increased at concentrations of SDS that did not affect the histomorphology (0.1% and 0.2% SDS). A marked increase of cell proliferation was observed 22 to 44 h after removal of SDS at a concentration (0.4%) that induced slight cellular damage. Exposure of human skin organ cultures to a toxic concentration of SDS (1.0%) led to decreased cell proliferation. Transglutaminase and involucrin were expressed in the more basal layers of the epidermis after exposure to 0.4% or 1.0% SDS. Moreover, intra-epidermal sweat gland ducts were positive for transglutaminase at these irritant concentrations. These in vitro data demonstrate that SDS-induced alterations of epidermal cell kinetics, as described in vivo are at least partly due to local mechanisms and do not require the influx of infiltrate cells. However, we were unable to relate the altered cell kinetics to the release of interleukin-lα or interleukin-6. Furthermore, supplementation of the culture medium with 12-hydroxyeicosantetraenoic acid did not affect epidermal cell proliferation. Rabbit skin cultures appeared more sensitive to SDS than human skin. At nontoxic doses, the irritant induced an increase of epidermal cell proliferation, similar to that observed in human skin discs.