A new approach to the isolation of the water-soluble factors from nacre without any demineralization is described and examined their effect on fibroblast cells in culture. The soluble matrix in pure water from the nacre of Pinctada maxima was analysed by size-exclusion HPLC. Four fractions (SE1-SE4) of the water-soluble matrix (WSM) were further analysed by anion-exchange HPLC. The amino acid composition of the WSM showed that it is mainly composed of glycine and alanine. SE1 and SE4 had different amino acid compositions from the whole WSM. The WSM and SE4 tested on a culture of human foetus lung tissue fibroblasts increased the alkaline phosphatase (ALP) activity. SE1 caused a decrease in ALP activity. Our results support the hypothesis that WSM promotes the differentiation of cells in vitro.