The Study Of Association Between Atopic Dermatitis And Sebaceous Glands Function

[Background]Atopic dermatitis(AD) is a common, chronic inflammatory skin disease that causes significant impairment in the quality of life. Clinically, AD manifests as pruritic, dry,eczematous lesions accompanying with many allergic diseases such as allergic rhinitis and allergic asthma. The pathogenesis of AD is unclear yet. Interactions of genetic background,environmental factors, inflammatory infiltration and barrier dysfunction result in the initiation and maintenance of AD.The finding of the role of skin barrier dysfunction in the pathogenesis of AD is the most important progress in the study of AD during the past10 years, which greatly promoted the understanding of the pathogenesis of AD and pushed the progress of treatment for AD. Previously, studies on skin barrier dysfunction focused on the damaged skin barrier integrity caused by filaggrin(FLG) gene mutation and corneous layer intercellular lipid change. However, skin barrier dysfunction beyond the FLG is still poorly understood.Sebaceous glands(SG) are essential cutaneous appendix. It evolves from the epidermis appendix structure in the process of embryonic development. It locates closely with hair follicles, and the duct of SG opens in follicles infundibulum. Functions of SG include the production of sebum, which coats the skin as a continuous hydrolipidic film,maintaining a harmony micro-enviroment with the symbiotic microbiota. SG also produce foetal vernix caseosa, contribute to the three-dimensional organization of the skin surface lipids, influence on follicular differentiation and regulate the hypothalamus-pituitary-adrenal-like axis of the skin.These multiple important functions of sebaceous glands award it the name of “ brain of the skin ” and the most important“cutaneous endocrine gland”[1].Studies have found that the glycerol excretion by sebaceous glands could maintain the skin barrier integrity[2]. The antimicrobial peptides secreted by sebaceous glands can participate in the process of defence against many pathogenetic microorganisms[3]. Studies have also found that the sebaceous glands are dysplasia and smaller in patients with AD,and the amount of sebum excreted by sebaceous glands in patients with AD is less than normal person. AD patients usually have less oily skin[4].All of these suggest the sebaceous glands and sebum secretion are most likely to be involved in the pathogenesis of AD. The role of sebaceous glands is more clear in acne vulgaris and seborrheic dermatitis. However,the correlation between sebaceous glands and AD is still unclear. Our study analyzed the sebum excretion rates in patients with AD.[Aims]1. To investigate the ability of sebaceous glands excretion in patient with AD;2. To analyze lipid composition of the surface of the skin in patient with AD;3. To discuss the correlations among sebum excretion rates with the severity of AD,the serum total Ig E concentration,and transepidermal water loss level.[Methods]1. Sebutape patches(SP) were used to measure the sebum excretion rates in patient with AD and healthy controls;2. SCORAD was used to assess the severity of disease in patients with AD;3. Immuno CAP allergen detection method was used to detect serum total Ig E concentrations in patients with AD;4. Water vapor permeability tester(Vapo Meter) was used to detect the TEWL levels inpatients with AD;5. Thin layer chromatography(TLC) was used to analyze the composition of skin surface lipid in patients with AD and its healthy controls.[Results]1. The sebum excretion rates in patients with AD are lower than that of the healthy controls;2. There is no correlation between SER and SCORAD scores of AD patients;3. There is no correlation between SER and serum total Ig E concentrations in patients with AD;4. There is no correlation between SER and the transepidermal water loss levels in patients with AD;5. In the skin surface lipids in patients with AD at least contain two ingredients of squalene and cholesterol.[Conclusions]Sebum secretion ability in patients with AD is significantly lower than that of the normal controls, which indicates that the sebaceous glands may be involved in atopic dermatitis.