title: Epidermal keratinocytes from light vs. dark skin exhibit differential degradation of melanosomes.
abstract: Modification of skin complexion coloration has traditionally been accomplished by interruption or attenuation of melanogenesis and/or melanosome transfer. Post-transfer modification of pigmented melanosomes provides an attractive and distinct avenue of modulating skin pigmentation. The processing of melanosomes during keratinocyte (KC) terminal differentiation and the degradative variability observed between light and dark skin (LS and DS) remains enigmatic. To evaluate this, we developed a model system to investigate the loss of fluorescently labeled and isolated melanosomes by cultured human KCs. The extent of melanosome loss has been qualitatively assessed using transmission electron microscopy and indirect immunofluorescence with confocal microscopy, and quantitatively assessed using flow cytometry analysis. Results show that melanosomes are incorporated into the cytoplasm of both light and dark keratinocytes (LKCs and DKCs) and trafficked to a perinuclear region. Within 48  hours, confocal microscopy images suggest that LKCs display accelerated melanosome loss. This time-dependent decrease in carboxyfluorescein diacetate (CFDA) fluorescence was then quantitatively analyzed using flow cytometry. Consistent with the results of the confocal analysis, over a 48-hour time frame, LKCs appear to lose melanosomes more efficiently than DKCs. These experiments show that melanosomes are more rapidly lost in KCs derived from LS as opposed to DS.
authors.affiliation: College of Pharmacy, University of Cincinnati, Cincinnati, Ohio, USA.
authors.forename: Jody P
authors.initials: JP
authors.lastname: Ebanks
authors.forename: Amy
authors.initials: A
authors.lastname: Koshoffer
authors.forename: R Randall
authors.initials: RR
authors.lastname: Wickett
authors.forename: Sandy
authors.initials: S
authors.lastname: Schwemberger
authors.forename: George
authors.initials: G
authors.lastname: Babcock
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Hakozaki
authors.forename: Raymond E
authors.initials: RE
authors.lastname: Boissy
mesh_terms: D002478:Cells, Cultured; D000078404:Epidermal Cells; D005434:Flow Cytometry; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D015603:Keratinocytes / Q000648:ultrastructure*; D020460:Melanosomes / Q000648:ultrastructure*; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D012880:Skin Pigmentation