Background: Psoriatic lesions may resolve with hypo- or hyperpigmentation. The involvement of melanocytes in this dichotomous clinical outcome is not fully investigated. Objectives: Qualitative and quantitative assessment of melanocytes in untreated lesional and non-lesional psoriatic skin (n = 15) and healthy controls (n = 10). Methods: Skin biopsies were labelled immunohistochemically (APAAP technique) with the antimelanocyte monoclonal antibodies (MoAbs) HMB45, Melan A, tyrosinase and microphthalmia-associated transcription factor (MITF). The labelled melanocytes were evaluated by an independent investigator with a digital image analyser. Results: Lesional melanocytes, in contrast to those in non-lesional and healthy skin, exhibited features of activation in the form of dilatation, prominent and long dendrites and intense labelling. The number of melanocytes was significantly increased in psoriatic lesions in comparison with non-lesional psoriatic and healthy skin as shown by counts of cells labelled with the MoAbs HMB45 (3-fold; p < 0.001), Melan A (1.6-fold; p < 0.01) and tyrosinase (1.5-fold; p < 0.01). In contrast, labelling with MITF revealed no significant difference (1.2-fold increase; p > 0.05). Likewise, no significant difference between non-lesional psoriatic and healthy skin control was found (p > 0.05). Furthermore, no positively labelled dermal cells were detected, apart from few only detected with Melan A. Conclusions: Epidermal melanocyte activity and numbers are increased in the epidermal compartment of psoriatic lesions providing an explanation for postinflammatory hyperpigmentation.

Keywords:
Melanocytes, Psoriasis, Immunohistochemistry
1.
Brajac I, Kastelan M, Prpić-Massari L, Perisa D, Loncarek K, Malnar D: Melanocyte as a possible key cell in the pathogenesis of psoriasis vulgaris. Med Hypotheses 2009;73:254-256.
2.
Arakawa A, Siewert K, Stöhr J, Besgen P, Kim SM, Rühl G, Nickel J, Vollmer S, Thomas P, Krebs S, Pinkert S, Spannagl M, Held K, Kammerbauer C, Besch R, Dornmair K, Prinz JC: Melanocyte antigen triggers autoimmunity in human psoriasis. J Exp Med 2015;212:2203-2212.
3.
Kelley BP, Doherty SD, Calame A, Hsu S: Acquired dermal melanocytosis of the hand at the site of treated psoriasis. Dermatol Online J 2009;15:2.
4.
Rhodes AR, Harrist TJ, Momtaz-TK: The PUVA-induced pigmented macule: a lentiginous proliferation of large, sometimes cytologically atypical, melanocytes. J Am Acad Dermatol 1983;9:47-58.
5.
Stark E, Faltinat D, von der Fecht R: An automated device for immunocytochemistry. J Immunol Methods 1988;107:89-92.
6.
Prieto VG, Shea CR: Immunohistochemistry of melanocytic proliferations. Arch Pathol Lab Med 2011;135:853-859.
7.
Ivan D, Prieto VG: Use of immunohistochemistry in the diagnosis of melanocytic lesions: applications and pitfalls. Future Oncol 2010;6:1163-1175.
8.
Ohta S, Imaizumi Y, Okada Y, Akamatsu W, Kuwahara R, Ohyama M, Amagai M, Matsuzaki Y, Yamanaka S, Okano H, Kawakami Y: Generation of human melanocytes from induced pluripotent stem cells. PLoS One 2011;6:e16182.
9.
Ohsie SJ, Sarantopoulos GP, Cochran AJ, Blinder SW: Immunohistochemical characteristics of melanoma. J Cutan Pathol 2008;35:433-444.
10.
Wang CQ, Akalu YT, Suarez-Farinas M, Gonzalez J, Mitsui H, Lowes MA, Orlow SJ, Manga P, Krueger JG: IL-17 and TNF synergistically modulate cytokine expression while suppressing melanogenesis: potential relevance to psoriasis. J Invest Dermatol 2013;133:2741-2752.
11.
Bolognia JL, Pawelek JM: Biology of hypopigmentation. J Am Acad Dermatol 1988;19:217-255.
12.
Brenner M, Hearing VJ: Modifying skin pigmentation - approaches through intrinsic biochemistry and exogenous agents. Drug Discov Today Dis Mech 2008;5:e189-e199.
13.
Nagy-Vezekényi C, Zs-Nagy I: Studies on the ultrastructure of psoriasis and of the ‘normal' skin of psoriatics. Acta Derm Venereol 1971;51:435-443.
14.
Zeigler M, Chi Y, Tumas DB, Bodary S, Tang H, Varani J: Anti-CD11a ameliorates disease in the human psoriatic skin-SCID mouse transplant model: comparison of antibody to CD11a with cyclosporin A and clobetasol propionate. Lab Invest 2001;8:1253-1261.
15.
Alper M, Kavak A, Parlak AH, Demirci R, Belenli I, Yesildal N: Measurement of epidermal thickness in a patient with psoriasis by computer-supported image analysis. Braz J Med Biol Res 2004;37:111-117.
16.
Whiteman DC, Parsons PG, Green AC: Determinants of melanocyte density in adult human skin. Arch Dermatol Res 1999;291:511-516.
17.
Nordlund JJ: The melanocyte and the epidermal melanin unit: an expanded concept. Dermatol Clin 2007;25:271-281.
18.
Trejo O, Reed JA, Prieto VG: Atypical cells in human cutaneous reexcision scars for melanoma express p75NGFR, C56/N-CAM and GAP-43: evidence of early Schwann cell differentiation. J Cutan Pathol 2002;29:397-406.
19.
Bovenschen HJ, Tjioe M, Vermaat H, de Hoop D, Witteman BM, Janssens RW, Stoof TJ, van de Kerkhof PC: Induction of eruptive benign melanocytic naevi by immune suppressive agents, including biologicals. Br J Dermatol 2006;154:880-884.
20.
Costa LA, Belinchón I, Betlloch I, Pérez-Crespo M, Mataix J: Multiple lentigines arising in resolving psoriatic plaques after treatment with etanercept. Dermatol Online J 2008;14:11.
21.
Abdel-Naser MB, Wollina U, El Okby M, El Sheimy S: PUVA induced lentigines arising in vitiligo: involvement of vitiliginous and normal appearing skin. Clin Exp Dermatol 2004;29:380-382.
22.
Abdel-Naser MB, Hann SK, Bystryn JC: Oral psoralen with UVA therapy releases circulating growth factor(s) that stimulate cell proliferation. Arch Dermatol 1997;133:1530-1533.
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2016
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