Radix astragali was fermented with Bacillus subtilis natto, and the effect of fermented products (HQB) and non-fermented products (HQNB) on collagen production in human dermal fibroblasts (HDF) were investigated. It was found that HQNB significantly improved cell growth and proliferation of HDF cells. However, the enzyme-linked immunosorbent assay and Western blot analysis demonstrated that HQB, but not HQNB, significantly and dose-dependently stimulated the biosynthesis of type I procollagen in both aged (81 y) and young (22 y) HDF cells. Real-time reverse transcription-polymerase chain reaction revealed that expression of type I, type III procollagen and transforming growth factor beta 1 (TGF-beta 1) mRNA was significantly stronger in HQB-treated HDF cells than that of HQNB-treated and un-treated HDF cells, suggesting that there was a close correlation between the mRNA expression and protein production in the fibroblasts response to HQB stimulation. The results also suggested that HQB could stimulate the collagen biosynthesis in human dermal fibroblasts, which is, at least in part, associated with the regulation of procollagen biosynthesis resulting from HQB-induced TGF-beta 1 expression and the mitogenic activity in HDF cells, and therefore, is expected to reduce the age-dependent loss of extracellular matrix proteins. (C) 2008 Elsevier Ltd. All rights reserved.