In a skin equivalent HaCaT cells have a preserved capacity to receive melanosomes but melanocytes do not remain in the basal location

Determination of the antioxidant capacity of an antioxidant combination using the fluoroscan assay in vitro and visualization of its effects using histological methods

The effects of a well-defined combination of antioxidants on oxidative stress were investigated in vitro using classical techniques together and its protective effects against UV damage were investigated using a newly developed skin model. After determining the cytotoxic potential of the combination, its quenching effect on the oxidative stress induced by hydrogen peroxide was quantified by a nonfluorescent (C-H2DCF-DA/AM)/fluorescent (C-DCF) dye system using the fluoroscan assay. Two different skin models consisting of normal human skin fibroblasts and the keratinocyte cell line HaCaT were developed and subsequently used to visualize the protective effects of the combination against UVA damage. No evidence of any cytotoxic potential of the combination could be seen. Supplementation of human skin fibroblasts demonstrated a clear, dose-dependent enhancement of the antioxidative capacity of these cells. Histological findings confirmed the beneficial effects of the antioxidants present in the combination in the skin models used. Supplementation induced morphological changes leading to a thicker epidermal layer providing evidence of the positive effects of the treatment on the viability of the keratinocytes after UVA irradiation. This in vitro study provided convincing evidence of the combined antioxidative action of alpha-tocopherol, beta-carotene, tomato extract, grape seed extract, ascorbic acid and selenium yeast, and indicated a potential beneficial action of the combination against oxidative stress caused by external oxidative stress factors such as UV irradiation.

Melanocyte detachment after skin friction in non lesional skin of patients with generalized vitiligo

BACKGROUND

In vitiligo, melanocytes are gradually lost in depigmented macules of the skin. The disappearance of melanocytes has, however, not been clearly observed and consequently the aetiology of the disease (autoimmune, neural, cytotoxic) is still elusive. The starting point of vitiligo macules is frequently determined by local conditions such as wounds and excoriations, but may also follow minor traumas such as pressure or repeated friction. This prominent feature is often neglected.

OBJECTIVES

To clarify the biological consequences of repeated friction on the attachment and survival of melanocytes in non lesional vitiligo skin.

METHODS

Light reproducible skin friction was performed for 4 min on the volar forearm of 18 patients with extensive vitiligo and five controls with normal healthy skin. Biopsies from the test area and control skin were taken at 1, 4, 24 and 48 h following friction. Serial sections were examined with standard light microscopy, transmission electron microscopy, histochemistry and immunohistochemistry (dihydroxyphenylalanine, HMB-45, E-cadherin and an early apoptosis marker, M30 cytoDEATH antibody).

RESULTS

The observation of sections at 1 and 48 h after friction on vitiligo skin and at all time points in controls revealed no changes. In contrast, in vitiligo skin at 4 and 24 h after friction, several melanocytes had undergone detachment and were found in various suprabasal positions, including the stratum spinosum, granular layer, and within and outside the stratum corneum.

CONCLUSIONS

Detachment and transepidermal elimination of melanocytes following minor mechanical trauma in non lesional vitiligo skin is probably the cause of depigmentation occurring in the isomorphic response (Koebner phenomenon). We propose that transepidermal elimination of melanocytes in vitiligo should be regarded as a possible mechanism of chronic loss of pigment cells, perhaps previously damaged by another process.