Cell proliferation in the growing human heart: MIB-1 immunostaining in preterm and term infants at autopsy

Few studies of human cardiac myocyte proliferation in the perinatal period have been conducted. We measured the proliferative activity of left ventric ular myocytes in tissue obtained at autopsy in three surgically induced abo rtuses, 20 preterm infants with gestational ages ranging from 12 to 35 week s, eight term infants with ages ranging from I day to 11 months, and five a dults. The preterm. infants lived less than 24 h, thus simulating the in ut ero condition of developing hearts. To assess the proliferative activity of the myocytes, we measured immunoreactivity using the monoclonal antibody M IB-1 against the recombinant Ki-67 nuclear antigen. Immunostained sections were examined by light microscopy, and the results expressed as a staining index (SI) of 0-3, according to the percentage of positively stained myocyt e nuclei. Myocyte proliferative activity remained constant during the early preterm. period and decreased in the late preterm and early postterm perio ds. Adult myocytes, regardless of cardiac weight, did not reveal proliferat ive activity as assessed by immunostaining. This proliferation pattern is c onsistent with findings in most earlier studies in animal models. (C) 2001 Elsevier Science Inc. All rights reserved.