Fibroblast-populated collagen gel cultures have been used as a dermal model of wound contraction and granulation in the wound healing process and as an in vitro model of dermal tissue. We evaluated the effects of various natural product extracts on collagen gel contraction-promoting activity and mechanical properties (relaxation time) using this model, and observed that some natural product extracts, such as Hibamata extract(from Fucus vesiculosus) promoted gel contraction and increased the relaxation time of the gels.In addition, we investigated the mechanism of the promotion of the gel contraction, noting increased expression of integrin α2 and β1 subunit molecules on the surface of the fibroblasts, suggesting that some extracts, such as Hibamata extract, promote gel contraction by increasing the expression of integrin molecules on the fibroblasts surface. For other types of natural product extracts, other mechanisms of the gel contraction-promoting activity, which were independent of an increase of integrins, were suggested.Although the mechanisms of promotion of gel contraction by these extracts are still unclear, it is at least clear that, more than one mechanism appears to be present. Therefore, more effective drug regimens for improving dermal tissues and wound healing may be achieved by combining drugs which increase integrin molecules and drugs with other mechanisms of action.