In an effort to tissue-engineer a human heart valve, our intention is to isolate interstitial cells from human heart valves, cultivate and expand them, and use these cells for seeding in artificial polymers. To create a functional artificial valve it is important to understand the different types of genes expressed in cells to be used for transplantation. Myofibroblasts express both muscle and non-muscle proteins. The interstitial cells of the valves may be aligned in a specific orientation that may be regulated by members of the frizzledfamily of genes. In this study, using RT-PCR, we investigated the expression of cardiac-specific sarcomeric proteins in interstitial cells isolated from the valves. We have shown expression of thin filament proteins as cardiac troponin T, I and C. Beta- and alpha-myosin heavy chain mRNA was detected in all samples isolated from the valves. Preliminary evidence was found for the presence of fz1, a member of the tissue polarity gene family frizzled,in these interstitial cells. The four valve types, aortic, pulmonary, mitral and tricuspid, expressed both cardiac thin and thick filament proteins as well as fz1