Immunohistochemical distribution of desmin in the human fetal heart.

Desmin is a member of the intermediate filaments, which play crucial roles in the maturation, maintenance and recovery of muscle fibers. Its expression has been examined in human cardiac muscle, rat and chicken, but its spatial distribution in the human fetal heart has not been described. The present study investigated desmin expression in the human fetal heart and associated great vessels in 14 mid-term fetuses from 9 to 18 weeks of gestation. Immunoreactivity for myosin heavy chain (MHC) and alpha smooth muscle actin (α-SMA), as well as neuron-specific enolase (NSE), was also examined. Increased expression of desmin from 9 to 18 weeks was clearly localized in the atrial wall, the proximal portions of the pulmonary vein and vena cava, and around the atrioventricular node. Desmin-positive structures were also positive for MHC. Meanwhile, the great vessels were also positive for α-SMA. The distribution of desmin exhibited a pattern quite different from that described in previous studies of rat and chicken. Thus, desmin in the human fetal heart does not seem to play a general role in myocardial differentiation but rather a specific role closely related to the maturation of the α-isozyme of MHC. Desmin expression in the developing fetal heart also appeared to be induced by mechanical stress due to the involvement of venous walls against the atrium.