The effects of locally produced chitosan (CPSRT-NC-bicarbonate) in the intervention of keloid pathogenesis were investigated in vitro. A human keratinocyte-fibroblast co-culture model was established to investigate the protein levels of human collagen type-I, III and V in a western blotting analysis, the secreted transforming growth factor-beta 1 (TGF-beta 1) in an enzyme-linked immunosorbent assay (ELISA) and the mRNA levels of TGF-beta 1's intracellular signaling molecules (SMAD2, 3, 4 and 7) in a real-time PCR analysis. Keratinocyte-fibroblast co-cultures were maintained in DKSFM:DMEM:F12 (2:2:1) medium. Collagen type-I was found to be the dominant form in primary normal human dermal fibroblast (pNHDF) co-cultures, whereas collagen type-Ill was more abundant in primary keloid-derived human dermal fibroblast (pKHDF) co-cultures. Collagen type-V was present as a minor component in the skin. TGF-beta 1, SMAD2 and SMAD4 were expressed more in the pKHDF than the pNHDF co-cultures. Co-cultures with normal keratinocytes suppressed collagen type-III, SMAD2, SMAD4 and TGF-beta 1 expressions and CPSRT-NC-bicarbonate enhanced this effect. In conclusion, the CPSRT-NC-bicarbonate in association with normal-derived keratinocytes demonstrated an ability to reduce TGF-beta 1, SMAD2 and SMAD4 expressions in keloid-derived fibroblast cultures, which may be useful in keloid intervention. (C) 2012, The Society for Biotechnology, Japan. All rights reserved.