The effect of decanal on collagen synthesis via the cAMP pathway. Hs68 cells were treated with decanal or the vehicle and exposed to UVB. The SQ22536 or the vehicle was pretreated for 1 h before the decanal treatment. ( A ) Collagen contents; ( B ) mRNA expression of matrix metalloproteinase ( MMP) 1, MMP3 and MMP9 ; and ( C ) mRNA expression of collagen type I alpha 1 chain ( COL1A1 ), COL1A2 and COL3A1 were analyzed. The final procollagen type I level was normalized to the total cellular protein content. Data are shown as the mean ± SEM ( n = 3). Significant differences are indicated as * p