Aquaporin 3 and E-cadherin expression in perilesional vitiligo skin

Introduction: Vitiligo is a common dermatologic disorder with debated aetiology. Most studies focused on role of melanocytes and few investigated the role of keratinocytes in pathogenesis of the disease. Aim: To investigate the keratinocyte adhesion in perilesional vitiligo skin through the immunolocalization of Aquaporin-3 (AQP3) and E-cadherin. Setting and Design: Sixty five subjects were selected. These included 40 cases with vitiligo and 25 age and gender-matched healthy subjects as a control group. Materials and Methods: Skin biopsies were taken from perilesional skin of cases and from site-matched areas of control subjects. The expression of AQP3 and E-cadherin was evaluated by immunohistochemical techniques. Statistical Analysis: Results were statistically analysed using IBM personal computer and the statistical package SPSS version 11. Fisher-exact and Chi-square tests were used to study the association between two qualitative variables. Mann-Whitney test was used for comparison between quantitative variables not normally distributed. Spearman’s correlation coefficient was used to assess correlation between two quantitative variables. The p≤0.05 was considered significant. Results: Regarding AQP3 expression,strong intensity,diffuse distribution,higher percent of expression and higher H-score (p<0.001 for all) were significantly associated with control skin compared with perilesional skin in follicular and inter-follicular epidermis. Regarding E-cadherin expression,moderate intensity,higher percent of expression and higher H- score (p<0.001 for all) were significantly associated with control skin compared with perilesional skin in follicular and inter-follicular epidermis. No significant association was found between E-cadherin and AQP3 H-scores or percent of expression and clinical data of selected cases. No significant correlation was detected between E-cadherin and AQP3 H scores or percent of expression and age of cases,disease duration or Vitiligo Disease Activity (VIDA) score. Conclusion: The following sequence of events can be suggested for vitiligo pathogenesis,based on findings in perilesional skin: AQP3 is downregulated by a primary unknown factor and this will lead to down regulation of its downstream molecules,mainly phosphatidylinositol 3-kinase,E-cadherin and catenins,which is followed by defective keratinocyte adhesion and decreased release of keratinocyte-derived growth factors. Subsequently a secondary event,physical trauma,oxidative stress or autoantibodies,may lead to exfoliation of keratinocytes and pigmented cells.