Molecular characterization of interstitial cells isolated from human heartvalves

Background and aim of the study: Myofibroblasts have been described as poss essing certain characteristics of both fibroblasts and skeletal myocytes. T hese cells are of mesenchymal origin, were first described in wound healing , and have been found in many tissues. Myofibroblasts from other tissues ha ve been shown to contract and to express sarcomeric (muscle) genes. In addi tion, these cells express certain regulatory (transcription factor) genes. The specific alignment of the cells may, at least in part, be governed by t issue polarity signals transmitted by members of the frizzled family of ver tebrate tissue polarity genes. The aim of the present study was to characte rize interstitial cells, with regard to the expression of myofibroblasts ma rkers, isolated from the human heart valves. The expression of muscle struc tural, regulatory and tissue polarity genes has been undertaken with a view to understanding the development and contribution of interstitial cells to valve function and structure. Methods: Interstitial cells were isolated and cultured from aortic, pulmona ry, tricuspid and mitral valves of recipient hearts obtained during transpl antation. Specific oligonucleotide primer pairs suitable for polymerase cha in reaction (PCR) were designed for the genes of interest. Total RNA was ex tracted from the cultured cells and reverse transcriptase-PCR was used to d etermine gene expression. Results: Cells from the four valve types were found to express various musc le structural genes. These include the thin filament sarcomeric genes for t he cardiac isoforms of troponin T, I and C. Evidence was also found for exp ression of beta-myosin heavy chain (beta-MHC), alpha-MHC and cardiac myosin light chain 2 (MLC2) in these cells. The tissue polarity genes frizzled 2 (fz2) were expressed in all four valve types analyzed. Conclusion: Interstitial cells express a number of genes whose products may have functional significance for heart valves. These include members of th e contractile apparatus such as MHC and troponins. The presence of members of the frizzled family, which specify the orientation of cell polarization, in these cells could indicate that interstitial cells are not randomly arr anged in the valve tissue. Therefore, interstitial cells isolated from the human heart valves express a number of functionally important genes, sugges ting a role in their specialized function.