Sequential growth of fetal sheep cardiac myocytes in response to simultaneous arterial and venous hypertension

Sonnet Jonker, J. Job Faber, Debra Anderson, Kent Thornburg, Samantha Louey, George Giraud

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    43 Citations (Scopus)

    Abstract

    While the fetal heart grows by myocyte enlargement and proliferation, myocytes lose their capacity for proliferation in the perinatal period after terminal differentiation. The relationship between myocyte enlargement, proliferation, and terminal differentiation has not been studied under conditions of combined arterial and venous hypertension, as occurs in some clinical conditions. We hypothesize that fetal arterial and venous hypertension initially leads to cardiomyocyte proliferation, followed by myocyte enlargement. Two groups of fetal sheep received intravascular plasma infusions for 4 or 8 days (from 130 days gestation) to increase vascular pressures. Fetal hearts were arrested in diastole and dissociated. Myocyte size, terminal differentiation (%binucleation), and cell cycle activity (Ki-67[+] cells as a % of mononucleated myocytes) were measured. We found that chronic plasma infusion greatly increased venous and arterial pressures. Heart (but not body) weights were ∼30% greater in hypertensive fetuses than controls. The incidence of cell cycle activity doubled in hypertensive fetuses compared with controls. After 4 days of hypertension, myocytes were (∼11%) longer, but only after 8 days were they wider (∼12%). After 8 days, %binucleation was ∼50% greater in hypertensive fetuses. We observed two phases of cardiomyocyte growth and maturation in response to fetal arterial and venous hypertension. In the early phase, the incidence of cell cycle activity increased and myocytes elongated. In the later phase, the incidence of cell cycle activity remained elevated, %binucleation increased, and cross sections were greater. This study highlights unique fetal adaptations of the myocardium and the importance of experimental duration when interpreting fetal cardiac growth data.

    Original languageEnglish (US)
    JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
    Volume292
    Issue number2
    DOIs
    StatePublished - Feb 2007

    Fingerprint

    Fetal Development
    Cardiac Myocytes
    Muscle Cells
    Sheep
    Hypertension
    Cell Cycle
    Fetal Heart
    Fetus
    Incidence
    Venous Pressure
    Diastole
    Blood Vessels
    Myocardium
    Arterial Pressure
    Body Weight
    Pressure
    Pregnancy
    Growth

    Keywords

    • Cardiomyocyte
    • Hyperplasia
    • Hypertrophy
    • Terminal differentiation

    ASJC Scopus subject areas

    • Physiology

    Cite this

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    abstract = "While the fetal heart grows by myocyte enlargement and proliferation, myocytes lose their capacity for proliferation in the perinatal period after terminal differentiation. The relationship between myocyte enlargement, proliferation, and terminal differentiation has not been studied under conditions of combined arterial and venous hypertension, as occurs in some clinical conditions. We hypothesize that fetal arterial and venous hypertension initially leads to cardiomyocyte proliferation, followed by myocyte enlargement. Two groups of fetal sheep received intravascular plasma infusions for 4 or 8 days (from 130 days gestation) to increase vascular pressures. Fetal hearts were arrested in diastole and dissociated. Myocyte size, terminal differentiation ({\%}binucleation), and cell cycle activity (Ki-67[+] cells as a {\%} of mononucleated myocytes) were measured. We found that chronic plasma infusion greatly increased venous and arterial pressures. Heart (but not body) weights were ∼30{\%} greater in hypertensive fetuses than controls. The incidence of cell cycle activity doubled in hypertensive fetuses compared with controls. After 4 days of hypertension, myocytes were (∼11{\%}) longer, but only after 8 days were they wider (∼12{\%}). After 8 days, {\%}binucleation was ∼50{\%} greater in hypertensive fetuses. We observed two phases of cardiomyocyte growth and maturation in response to fetal arterial and venous hypertension. In the early phase, the incidence of cell cycle activity increased and myocytes elongated. In the later phase, the incidence of cell cycle activity remained elevated, {\%}binucleation increased, and cross sections were greater. This study highlights unique fetal adaptations of the myocardium and the importance of experimental duration when interpreting fetal cardiac growth data.",
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    AU - Faber, J. Job

    AU - Anderson, Debra

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    AU - Louey, Samantha

    AU - Giraud, George

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