Expression of Intermediate Filament Desmin and Vimentin in the Human Fetal Heart

Background: The intermediate filament (IF) desmin provides support for contractile machinery in muscle cells, and vimentin plays an important role in maintaining the stability of mesenchymal cells and in signal transduction. However, development of IFs in heart tissue during intrauterine life in human is not well established.

Methods: In the present study, development of desmin and vimentin in human fetal hearts aged 9-28 weeks of gestation (n = 41) were investigated by immunohistochemistry with monoclonal antibodies against desmin and vimentin. Relative density of fluorescence of each sample was determined by densitometry. Left ventricle (LV) tissues from a 1-year-old child (n = 1) were examined by immunohistochemistry for postnatal comparison. Western blot analyses were done with only a few randomly selected LV tissues from fetuses of 9, 20, and 28 weeks gestation to assess trends of desmin and vimentin expression.

Results: By Western blot analyses, 53-kDa desmin and 54-kDa vimentin were present in all fetal heart tissues examined. Desmin intensity was progressively increased with increasing fetal age, whereas vimentin intensity decreased. Desmin was present only in cardiomyocytes. In the earlier period (10-14 weeks gestation), desmin was localized along the cardiomyocyte membrane and/or Z lines in regular intervals, and later (25-28 weeks gestation) it was structurally well integrated; however, its network was incomplete. Only cardiomyocytes from a 1-year-old child revealed highly developed and integrated desmin lattices. However, vimentin was present in the mesenchymal tissue including fibroblasts and surrounding blood vessels. In part, some cardiomyocytes showed a weakly positive reaction with monoclonal antibody against vimentin in 9-14 weeks gestation. Vimentin-positive areas, however, were progressively diminished with increasing fetal age. Vimentin was present only in the connective tissue and coverings of the 1-year-old child's heart. Relative density of fluorescence of desmin was increased with increasing fetal age, whereas that of vimentin decreased.

Conclusions: These results indicate that there is a fetal age (or gestation)-dependent expression of IFs in human fetal heart: desmin increases with increasing fetal age, whereas vimentin decreases.