INCREASED MRNA EXPRESSION OF DECORIN IN THE PROLAPSING POSTERIOR LEAFLET OF THE MITRAL VALVEMA Radermecker*, R Liment*, CM Lapiere**, B Nusgens**
*Department of Cardiovascular and Thoracic Surgery
To improve our understanding of myxomatous degeneration of the valvar tissue as seen in mitral valve prolapse, we have compared the biosynthetic phenotype of the connective tissue cells in myxomatous segments (n=4) resected during surgery to that of homologous segments of normal valves (n=4) harvested in age-matched organ donors. The steady-state level of mRNA for selected extracellular matrix macromolecules and metalloproteinases was assessed by quantitative (internal standard controlled) RT-PCR. Among the investigated gene products, the decorin mRNA expression was significantly increased in degenerative valve as compared to normal tissue (211± 48 vs 100 ± 70, p < 0.02). The level of fibrillin 2 also tended to be increased (194 ± 88 vs 100 ± 81, p = 0.08). These results suggest that myxomatous valvar tissue is characterized by an overexpression of mRNA for decorin. Owing to the role of this small leucine-rich proteoglycan in the regulation of fibril assembly and stability, this alteration may account for or result of a defective organization of the collagen and elastic fibers in this disease and contribute to the intrinsic distensibility and fragility of the myxomatous tissue. Implications for conservative mitral valve surgery are discussed.
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