Ultrastructural changes of epidermal calcium gradient and lipid lamellar membrane in depigmented skin lesions of vitiligo patients

Abstract

To investigate the effects of melanin disappearance in vitiliginous skin on the ultrastructure of epidermal calcium distribution and the stratum corneum (SC) lipid lamellar membranes. Five outpatients with stable vitiligo vulgaris and 5 healthy controls were recruited from August 2014 to February 2015 at Department of Dermatology, Renmin Hospital of Wuhan University. The ultrastructural changes of lipid lamellar membranes of the skin were assessed using transmission electron microscopy (TEM) technique in combination with ruthenium tetroxide (RuO4) staining. The concentration and distribution of calcium precipitates in the epidermis were studied using calcium ion-capture cytochemistry combined with TEM. The multilayered lipid lamellae existed within the intercellular space of the normal SC with a characteristic alternating electron-dense and electron-lucent pattern. Expanded intercellular space, fragmentation and lamellar separation were observed in the depigmented skin lesions from vitiligo patients, the bulbous regions of lipid lamellae were filled with electron-dense amorphous materials. Large clumps of calcium precipitates were visualized in the stratum granulosum (SG) of normal skin, fine calcium precipitates and stage Ⅳ melanosomes were noted within the normal stratum basale (SB). In depigmented skin lesions of vitiligo, both the size and number of calcium precipitates in the SG were dramatically decreased. Melanosome was barely seen in the vitiligo SB. Disrupted ultrastructure of SC lamellar membranes and disappearance of calcium gradient co-exist in the skin lesion of vitiligo, indicating that melanin in epidermis may play a role in formation of epidermal calcium gradient and maintenance of structural integrity of permeability barrier.