The combination of skin ablation and 5-Fluorouracil (5-FU) ointment was previously tried in the treatment of vitiligo, and good results were specifically reported in glabrous skin without follicular melanocyte reservoirs.
Vitiligo affects 1% of the world’s population and probably has a higher incidence in dark-skinned individuals. Three repigmentation patterns are usually described: perifollicular, when the predominant repigmentation is follicular; marginal, when the predominant repigmentation is from the borders of patches; and diffuse, when repigmentation occurs across the patches of vitiligo [
Application of 5-Fluorouracil (5-FU) after mechanical dermabrasion, as a treatment for vitiligo, was introduced by Tsuji and Hamada in 1983 [
Successful repigmentation of areas devoid of hair follicles (periungueal areas and the dorsa of the feet) was first reported by Anbar after ER: YAG laser skin ablation followed by topical application of 5-FU and Nb-UVB phototherapy [
Pharmacologically, 5-FU is an antimetabolite analogue of the naturally occurring pyrimidine uracil which is metabolised via the same metabolic pathways as uracil [
Clinically, localized hyperpigmentations have been reported during systemic treatment of various cancers by 5-FU. Usually, these hyperpigmented lesions are located on the normally pigmented extremities (hands and feet) and tongue. It has been postulated that these hyperpigmentations could be considered as postinflammatory hyperpigmentations on sites submitted to repeated friction [
The most interesting information about the biological impact of 5-FU on melanocytes has been obtained by experimental studies. In the presence of low concentrations of 5-FU, keratinocytes are selectively destroyed within three weeks, while melanocytes continue to multiply and to form pigment [
Following this short review, we do not know the exact role of 5-FU in the improvement of the vitiligo repigmentation following dermabrasion. The aim of our study was to explore the possible role of dermabrasion, 5-FU, and their combination on pigment spread on guinea pig skin.
We chose guinea pigs since the epidermis of these animals is very similar to that of a man. In guinea pig skin, melanin is transferred from melanocyte processes to surrounding keratinocytes as in human skin [
Approximately, 20 cg of commercially available 5% 5-Fu cream (Efudix Medapharma Paris France) was applied once daily for two days, like in patients, on an area located on the flank overlapping the black and white skin (from 1 mm inside the pigmented area to the entire dermabraded area).
A dermabrader unit (F-319 Silverfox Malea France) with an average speed of 15,000 rpm and diamond fraises of various sizes and shapes were used for the procedure. The superficial dermabrasion was performed under local anaesthesia in at least two different directions and was stopped when uniform punctuate capillary bleeding from the dermal papilla could be seen. Finally, a total surface area of around 6 cm2 was dermabraded.
The animals were randomly divided into three groups, as detailed in Table
Consequences of different treatments on epithelialization and inflammatory.
Treatment | Time for healing | Inflammatory reaction duration | Pigment spread |
---|---|---|---|
Topical 5-FU ointment |
— | — | 0 |
Dermabrasion alone |
7 days | 8 days | Few mms |
Dermabrasion + 5-FU |
15 to 17 days | 20 to 27 days | 1.5 to 2.5 cms |
Reaction and pigment spread.
Three guinea pigs were subjected to mechanical dermabrasion on areas of the flank including white skin (Figure
Pigment spread from the pigmented area towards the achromic area. (a) Area including contiguous pigmented and achromic areas before treatment, (b) inflammatory reaction 2 weeks after dermabrasion + topical 5FU cream, (c) pigment spread 4 months after dermabrasion + topical 5FU, and (d) black hairs growth 6 months after treatment.
Histological study of pigment spread after dermabrasion + 5-FU ointment. (a)
Two guinea pigs were subjected to dermabrasion alone on similar areas under local anaesthesia without topical 5-FU ointment. Topical antibiotic cream was then applied, covered by gauze, and this continued until complete reepithelialization.
Two guinea pigs were subjected to topical 5-FU once a day for two days only on the shaved area.
Every week, pictures were taken, and planimetry was used, that is, drawing the lesions on transparent paper. We compared the pigment spread in the followup every month until the end of the study. Followup was done clinically and histologically (with the help of light and electron microscopes).
We performed biopsies from the margin including pigmented and achromic skin just after healing of the dermabraded area and at the beginning of pigment spread. Skin samples from the margin were removed under local anaesthesia with 4 mm punches on days 15 and 30 after the dermabrasion.
For light microscopy, tissues were fixed in formal saline and then embedded in paraffin wax. The slides were assessed using an Olympus microscope (Olympus Tokyo). Cryostat sections were stained with H.E.S and Dopa for melanocytes. The sections were examined at magnifications of ×400 and under oil immersion ×1000.
For electron microscope study, tissues were fixed in 1.5% glutaraldehyde in a phosphate buffer and routinely processed for transmission electron microscopy. Ultrathin sections were double contrasted and observed using a Tecnai 12 BioTwin transmission electron microscope (Philips Optique Electronique SAS: Limeil Brévannes, France).
Due to the small number of animals investigated in this study, only the mean values of different items (pigment spread distance and healing duration) were taken into account.
After the successive stages of inflammation including erosion and crustation, the reepithelization was completed within 15–17 days (Figures
The epithelialization was complete on day 15 after dermabrasion and 5-FU ointment. Numerous keratinocytes showed few atypical features (atypical nuclear configuration and degenerative changes). This newly regenerative epidermis contained many clustered melanocytes at the margin (Figure
Comparative aspect of melanocytes under electron microscope (linear Scale = 2
We objectivated at the margin that the keratinocytes had a normal appearance. The density of melanocytes in the pigmented epidermis returned to normality. Some bipolar melanocytes were seen crawling towards the achromic epidermis (Figure
Following isolated dermabrasion, the wound healing was more rapid, the reepithelialization was obtained within seven days, and the erythema disappeared within 15 days. After four months, the pigment spread from the border separating pigmented and white areas was very discrete, not exceeding 2-3 mms.
The aspect of the epidermis was normal with some persistent enlargement of intercellular spaces. Several normal-appearing melanocytes were observed at the margin of the pigmented area (Figure
The histological aspect of the epidermis was normal, with a reduced width of intercellular spaces between the keratinocytes themselves and between the melanocytes and the basal membrane. Under an electron microscope on day 30, the aspect and the cohesion of the epidermal cells were quite normal (Figure
Following only topical treatment with 5-FU for 2 days, we did not observe any clinical or histopathological changes at the treated site, as previously reported [
This study, performed on guinea pig skin, could contribute to better understanding of the possible role of dermabrasion, 5-FU, and their combination in the unexpected improvement of vitiligo repigmentation. This quasisimilarity between the vitiligo lesions and the achromic patches of these piebald-like guinea pigs encouraged us to compare our experimental data to clinical data previously reported in vitiligo patients treated by skin ablation and 5-FU. Before discussing these data, a short review of the repigmentation steps following dermabrasion of normal skin is needed.
In man skin, the epidermal melanin unit includes one melanocyte to approximately 36 keratinocytes. In this functional unit, keratinocytes have an evident regulatory role in skin pigmentation, and the melanocytes may exert an influence on keratinocyte proliferation. However, in guinea pig skin, during the regeneration of the epidermis following injury, melanocytes and keratinocytes seem to react independently [
In human pigmented skin, this difference between keratinocyte and melanocyte behaviour seems greater, and late repigmentation appears more slowly after healing of a skin wound. This may explain the delay in repigmentation that often accompanies wound reepithelialization. The repigmentation of human epidermis following dermabrasion has its main origin in the amelanotic portion of the hair follicle [
In guinea pig skin, we did not see any significant pigment spread following only dermabrasion of the achromic area contiguous to pigmented skin. The healing was rapidly obtained within six to seven days without any inflammatory reaction. The pigment spread from the pigmented area was insignificant and did not exceed 2 mms. On day 15, after complete epithelialization, melanocytes could not be found in light and electron microscope observation of the previously dermabraded achromic area. Our data are in a complete agreement with those previously published [
In vitiligo skin, perifollicular repigmentation but not marginal repigmentation was occasionally reported after exclusively removing the epidermis of macules of vitiligo that retained pigmented hairs [
In guinea pig skin, we did not observe any local pigment spread following the application of 5-FU cream for two days at the margin separating the pigmented and achromic areas. In the same way in human skin, normal and intact skin did not show any clinical alteration following application of 5-FU cream during topical treatment of many cutaneous disorders (actinic keratosis, psoriasis, and epithelial neoplasms) [
In guinea pig skin, we observed a consequent pigment spread from the edges. Pigment spread began one or two weeks after healing and occurred after four months in all the abraded areas. A growth of black hairs in two animals was noted after six months. Just after the healing, we observed the histological features previously described in a study devoted to inhibition of wound healing by topical 5-FU [
In vitiligo skin, the development of pigment spread was quite similar to that we observed in our animal model. In both situations, after dermabrasion or laser ablation followed by topical application of 5-FU for two days, an inflammatory reaction with erythema, erosion, and crustation was noted. Unfortunately in the vitiligo patients investigated, no serial histological studies were performed during or after the treatment. Epithelialization was completed within ten days of the treatment being stopped. Within one to three weeks after the healing, repigmentation began either from the hair follicle and spread centrifugally and either from the margins and spread centripetally. In vitiligo patients, complete or almost complete repigmentation of all treated spots was reported in 64% of cases and partial repigmentation in 18% of cases. The treatment failed in 18% of cases [
Until now, it was difficult to understand why a topical drug, such as 5-FU, well known for its antimitotic activity, could improve the proliferation and migration of melanocytes. Successively, a direct overstimulation of melanocyte proliferation (unproven in melanocytes cultures), an inhibition of agents or cells able to destroy pigment cells, and finally an immunomodulation stabilizing the vitiligo disease [
Based on our clinical and especially our histological findings obtained from this experimental study, we can propose a possible “scenario” including several successive events, allowing us to give an explanation for this enigmatic process. As was previously demonstrated in vitro, 5-FU can exert a selective and differential cytotoxicity according to the type of epidermal cells. Melanocytes seem to be much less vulnerable than keratinocytes to 5-FU, and their ability to proliferate in cultures appears to be preserved [
Neither the topical application of 5-FU nor dermabrasion alone seems to be able to induce any pigment spread either in vitiligo patients or in our animal model. In guinea pig and vitiligo skin, the application of 5-Fu on the dermabraded or ablated epidermis could cause a long-lasting, favourable microenvironment for the melanocyte migration and pigment spread.
The authors declare that they have no conflict of interests
The authors thank Laurent Victorin for his technical help.