The histological characteristics,distribution and variability of epidermal growth factor(EGF) and epidermal growth factor receptor(EGFR) during development of skin in the goat fetus were studied with histological and immunohistochemical methods.The results showed that the epidermis formed at the 6th gestational week,the thickness increased gradually because of transition from simple epithelium to stratified epithelium,and then decreased after the 15th week.The dermis was present at the 10th week,and the dermal derivatives appeared after the 11th week.All structures of the skin matured gradually during prenatal development.Low expression of EGF and EGFR could be observed at the 6th week and increased thereafter.Before the 11th week,EGF was mainly located in the cytoplasm of the basal layer of cells of epidermis,hair follicular epithelial cells and fibroblasts,and EGFR was mainly located on cell membranes of these cells.From the 11th to 16th week,the expression of EGF and EGFR extended from basal layer cells,prickle cells,hair follicular epithelial cells and fibroblasts to vascular endothelial cells,epithelial cells of sweat glands and arrector pili muscle.EGF was mainly detected cytoplasmically,and EGFR was located on membranes of these cells.From the 17th week to birth,EGF was mainly located in cells of the basal layer and hair follicular epithelial cells as the skin thinned and staining intensity continued to increase.The expressed amount of EGF and EGFR tended to increase throughout the whole development stage encompassed by gestational weeks 6 to 21 and the two components of the EGF signaling system were highly correlated.The results suggest that EGF and EGFR play important roles in the development of skin and its derivatives.
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