COMPETENCE OF EMBRYONIC MAMMALIAN HEART-CELLS IN CULTURE - DNA-SYNTHESIS, MITOSIS AND DIFFERENTIATION

  • 1 January 1981
    • journal article
    • research article
    • Vol. 30  (119) , 189-208
Abstract
The competence for DNA synthesis, mitosis and differentiation of cardiac muscle and non-muscle cells of 14- and 18-day rat embryos was studied in vitro. The heart cells of 14-day embryos were relatively more competent in DNA synthesis and mitosis than those of 18-day embryos. These in vitro findings conformed with those of the in vivo studies. Cardiac muscle and non-muscle cells of the younger age group showed higher labeling indices than those of the other age group during 7 days of culture. The general profile of DNA synthesis was similar in both age group cells. Maximum labeling indices in muscle and non-muscle cells were observed after 24 h of culture. The number of labeled cells was always higher in non-muscle cells than in muscle cells. As the culture continued, the labeling indices declined in both cell types of the 2 age groups. On day 7, 10% labeled cardiac muscle cells and 45% labeled non-muscle cells were observed in the 14-day embryonic group compared to 5% cardiac muscle cells and 35% non-muscle cells of the 18-day embryonic group. When the rate of in vitro differentiation of myofibrils, intercellular junctions and some cellular organelles, were compared between cells of 2 different age group hearts, no significant difference was observed. During the 1st wk of culture, a considerable number of muscle cells contained myofibrils throughout the length and girth of the cells. The intercalated discs differentiated over a period of 3 wk of culture. As the culture proceeded, adjoining cardiac muscle cells differentiated desmosomes and gap junctions. Cardiac muscle cells retained these structural specializations and did not undergo dedifferentiation in long-term culture. Overgrowth of 1 cell type by another was the regular occurrence in all heart cell cultures studied.