The Role of Vitamin A on the Histology of Skin of Adult Rats After Exposure to UVB

Abstract

Background: long-term exposure of skin to sun (UV light) may produce different dermatological changes. The aim of this experiment is to explore the protective effects of oral vitamin A on skin subjected to UVB. Methods: twenty rats were separated into: group 1 (without UVB exposure), group 2 (exposed to single daily increasing dose of UVB for one week), group 3 (exposed to UVB with oral daily administration of vit A 10000 IU for one week), group 4 (received vit A for one week). The daily doses of UVB were respectively 0.24, 0.36, 0.48, 0.6, 0.72, 0.84 and 0.96 J/cm2. Skin samples were stained with hematoxylin-eosin and Masson’s trichrome stains, in addition to Melan-A stain for melanocytes. Results: histopathological results in skin of group 2 demonstrated loss of normal architecture with increase in thickness of epidermis, hyperkeratosis and parakeratosis, moreover, skin sections detected increased number of inflammatory cells with damaged hair follicles. The basal layer shows an increase in mitotic division and necrosis, besides, epidermal edema and vascular congestion. Furthermore, collagen fibers were degraded. Immunohistochemical reaction revealed intense positive expression of Melan-A with increased proliferation and activity of melanocytes, while sections of groups 1 and 4 show normal healthy skin and negative Melan-A expression. In contrast, skin of group 3 reveals mild hyperkeratosis with normal keratin layer, in addition, the infiltration of inflammatory cells was dropped and hair follicles were preserved. Collagen bundles were slightly degraded with normal arrangement. Immunohistochemical results of this group show mild positive expression of Melan A. Conclusion: oral administration of vitamin A decreases the toxic effect of UVB radiation on skin and reduces its induced pigmentation.

Keywords

• melanocytes
• vitamin a
• melan-a