الفهرس 
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Abstract
Vitiligo is a disease presented by asymptomatic depigmentation but with a heavy psychological burden. In vitiligo, melanocytes are targeted by multiple aggressions leading to marked reduction of pigment cells and eventually to their complete destruction. Vitiligo recovery depends on a viable melanocyte reservoir. The complete knowledge of this melanocyte reservoir is very important to understand the mechanisms of repigmentation and may help for designing newer strategies for vitiligo therapy.
Melanocyte stem cells (MelSCs), in the lower permanent portion (LPP) of the hair follicle are known to be the most important melanocyte reservoir for skin and hair pigmentation. The possibility of MelSCs in skin areas without hair follicles where repigmentation occurs with a diffuse pattern may suggest the existence of melanocyte reservoir that would include the interfollicular epidermis as well.
This melanocyte- melanocyte stem cell lineage is known to be regulated by many signaling pathways through cell-cell interactions especially with neighboring keratinocytes to control its survival, differentiation, proliferation and migration. A series of studies elucidated Notch signaling as a key component among keratinocyte–melanocyte interactions and proved the role of Notch signaling in preservation and maintenance of the melanoblasts and MelSCs.
The question is: Are the melanocytes and melanocyte stem cells still present in different subtypes of vitiligo? And if they are still present and unaffected, can they induce repigmentation or there are aberrant signaling pathways controllingHence, in the current study we tried to evaluate the melanocyte- melanocyte stem cells reservoir in different clinical types of vitiligo using the immunohistochemical expression of HMB45 and TRP2 (Dct). A possible role of Notch signaling pathway in vitiligo was also examined.
This case-control study was carried out on 70 subjects. These included 50 patients of different clinical varieties of vitiligo and 20 age and sex matched normal subjects. Patients were selected randomly from the outpatient dermatology clinic, Menoufiya University Hospital in the period between June 2010 and June 2012. All patients were subjected to history taking and complete general and dermatological examination. Then after taking a written consent, a punch biopsy was taken from lesional skin of all vitiligo patients and from perilesional skin of 20 cases only.
Each biopsy was processed to form paraffin block. Several paraffin sections, each 4 micron thick, were cut from each block, one of them was stained by haematoxylin and eosin to evaluate pathological changes and the other sections were cut on poly L lysine coated slides for immunostaining with HMB45, TRP2 and Notch-1 mouse monoclonal antibodies.
Haematoxylin and eosin stained sections were examined microscopically to evaluate and verify epidermal and dermal pathological changes. They revealed keratinocytes vacuolization in 92% of cases, basement membrane thickening in all cases, residual epidermal or dermal melanin pigment in 42% of cases, perivascular inflammatory infiltrate in 94% of cases, dermal angiogenesis in 46% of cases and pigmented hair follicles in 18% of cases. Also perilesional skin biopsies showed mild degree of keratinocyte vacuolization, mild dermal perivascular inflammatory.