Bone marrow-derived myofibroblasts are present in adult human heart valves

Background and aim of the study: Endothelial, smooth muscle and cardiomyocyte chimerism has been shown to occur in the human heart. It is currently unknown whether the bone marrow contributes to cellular components of adult human heart valves. Here, it was determined whether bone marrow-derived smooth muscle-like cells (SMLC) are present in the heart valves of adult subjects. Methods: By combining immunofluorescence staining and fluorescence in-situ hybridization (FISH) for X and Y chromosomes, the heart valves of gender-mismatched bone marrow transplant patients were examined for the presence of chimeric cells expressing calponin, a smooth muscle-specific protein. Concomitant staining for CD68 antigen was carried out to exclude cells of a monocytic lineage. Results: The mean percentage of bone marrow-derived SMLC in valves was 0.28 +/- 0.03%, with the total proportion of chimeric cells estimated at 0.71 0.05%. The mean proportion of CD68+ cells was 0.33 +/- 0.05%. Not a single cell stained doubly for calponin and CD68 antigen. Conclusion: These data establish, for the first time, human bone marrow as a source of progenitor cells contributing to SMLC in adult human heart valves.