Differential levels of elastin fibers and TGF-β signaling in the skin of Caucasians and African Americans

Abstract

BackgroundWhile skin color is the most notable difference among ethnic skins the current knowledge on skin physiological and aging properties are based mainly on Caucasian skin studies. ObjectiveTo evaluate histological differences in elastin fiber network and differential responsiveness to TGF-β in skin of Caucasians and African Americans. MethodsThese studies were undertaken using human skin biopsies, primary dermal fibroblasts, Western blot analyses, immunofluorescence microscopy, cDNA array and quantitative real-time PCR. ResultsIn Caucasian subjects, tropoelastin expression and elastin fibers in photoprotected skin was substantially less than in age-matched African American skin. Expression of tropoelastin in photoexposed skin of African American was similar to their photoprotected skin, suggesting that photoexposure did not affect elastin fibers in African American skin to the same extent as Caucasian skin. An elevated level of TGF-β1 present in media from dermal fibroblasts derived from African American skins correlated well with the higher levels of TGF-β mRNA in African American skins analyzed by cDNA array. Treatment with TGF-β1 resulted in a considerably higher induction of elastin mRNA in dermal fibroblasts from African Americans than from Caucasian fibroblasts, indicative of enhanced TGF-β signaling in African American skins. Furthermore, UVA exposure decreased levels of elastin mRNA in Caucasian fibroblasts compared to African Americans fibroblasts. ConclusionThese results suggest that there are ethnic differences in the elastin fiber network and in TGF-β signaling in African American and Caucasian skin, and that African American have less UV dependent loss of elastin than Caucasian which may contribute to the different perceived aging phenotypes.