Objective  To investigate the expression of receptor-activited Smads (Smad2

Smad3) and phosphorylated Smad2

3 (p-Smad 2/3) in seborrheic keratosis.   Methods  The skin tissues of seborrheic keratosis from 45 patients (25 males and 20 females

average age: 57.6 years

average course of disease: 3.8 years) who received no treatment before and normal skin tissues from 40 patients (22 males and 18 females

average age: 48 years) undergoing plastic surgery in our hospital were examined for the mRNA levels of Smad2 and Smad3 by quantitative real-time PCR

and the protein levels of Smad1/2/3 and p-Smad2/3 by immunohistochemistry.   Results   The mRNA levels of receptor-activited Smads (Smad2

Smad3) and the protein levels of Smad1/2/3

p-Smad2/3 were significantly down-regulated in the skin tissues of seborrheic keratosis in comparison with control tissues.   Conclusion  Down-regulation of receptor-activited Smads (Smad2

Smad3) and p-Smad2/3 might interfere TGF-β signal transduction pathway and contribute to formation of aberrant hyperplastic epidermis in seborrheic keratosis.