Characterisation of postnatal growth of the murine heart (original) (raw)
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Growth of capillaries and myocardial cells in the normal rat heart
Journal of Molecular and Cellular Cardiology, 1987
The normal growth process of myocardial ceils and capillaries in the late postnatal period (after weaning) was studied in 33 normal male Wistar rats (group I : 5 weeks, n = 9; group II: 7 weeks, n = 7; group III: 13 weeks, n = 8; group IV: 52 weeks, n = 9). The rats were fixed by retrograde vascular perfusion via the abdominal aorta. Two transverse and 2 longitudinal sections per animal were selected at random from the left ventricular papillary muscles for light and electron microscopic stereological investigation. Length density and surface density of myocardial cells and capillaries were estimated with correction for partial anisotropy and curvature by means of the mathematical model ofa Dimroth Watson orientation distribution. The results were analyzed by allometric techniques. Relative left and right ventricular weight decreased continuously throughout the growth process; in terms of allometry, ventricular weight was proportional to (body weight) ~ The capillaries showed predominantly longitudinal growth with nearly constant cross-sectional area, whereas the myocardial cells grew by nearly harmonic enlargement into all three directions of space. The relation between total capillary length and left ventricular weight could be described in close approximation by the allometric model (r = 0.98, P < 0.001). Corresponding to the result that total capillary length was proportional to (left ventricular weight) ~ the density of myocardial capillarization (length, surface area, and volume of capillaries per unit tissue volume) decreased with increasing heart size. As allometry makes possible the quantitation of the intensity of growth processes by a single dimensionless number (the a11ometric exponent), this method permits a convenient interlaboratory comparison of growth studies, and it allows a comparison of capillary reactions during maturation and in experimental cardiac hypertrophy.
Rapid Transition of Cardiac Myocytes from Hyperplasia to Hypertrophy During Postnatal Development
Journal of Molecular and Cellular Cardiology, 1996
The switch from myocyte hyperplasia to hypertrophy occurs during the early postnatal period. The exact temporal sequence when cardiac myocytes cease dividing and become terminally differentiated is not certain, although it is currently believed that the transition takes place gradually over a 1-2-week period. The present investigation has characterized the growth pattern of cardiac myocytes during the early postnatal period. Cardiac myocytes were enzymatically isolated from the hearts of 1, 2, 3, 4, 6, 8, 10, and 12-day-old rats for the measurements of binucleation, cell volume and myocyte number. Almost all myocytes were mononucleated and cell volume remained relatively constant during the first 3 days of age. Increases in cell volume and binucleation of myocytes were first detected at day 4. Myocyte volume increased 2.5-fold from day 3 to day 12 (1416±320 compared to 3533±339 m 3 ). The percentage of binucleated myocytes began to increase at day 4 and proceeded at a high rate, reaching the adult level of approximately 90% at day 12. Myocyte number increased 68% during the first 3 days (from 13.6±3.5×10 6 at day 1 to 22.9±5.6×10 10 at day 3) and remained constant thereafter. To confirm that no further myocyte division exists after 4 days, bromodeoxyuridine (Brdu) was administered to 4day-old rats and the fate of DNA-synthesizing myocytes was examined 2 h and 2, 4, 6 and 8 days after Brdu injection. About 12% of myocytes were labeled with Brdu at 2 h and all were mononucleated at that time. Gradually, these Brdu-labeled myocytes became binucleated. However, the percentage of labeled myocytes in all groups was identical, indicating that DNA-synthesizing myocytes were becoming binucleated without further cell division after 4 days of age. Within 8 days after injection, approximately 82% of total labeled myocytes were binucleated, while the others remained mononucleated. Sarcomeric -actinin was fully disassembled in dividing myocytes of 2-day-old rats, while typical -actinin striations were present in dividing myocytes of 4-day-old rats. The results from this study suggest that a rapid switch from myocyte hyperplasia to hypertrophy occurs between postnatal day 3 and 4 in rat hearts.
Recommendations for Short Term Culturing of Viable Rod Shaped Rat Cardiomyocytes
Bioenergetics: Open Access, 2014
In vitro primary cultures of isolated adult rat cardiomyocytes are becoming an increasingly popular model to study heart muscle stressors. This model can easily be manipulated in a controlled environment and results obtained can provide valuable insights into the pathophysiology of heart disease. Over the past years several improved methodologies have been described in the development of a robust technique to help maintain cardiomyocytes in culture. However, despite these advances, culturing of primary cardiomyocytes remains a challenge. In this study, we present a simple yet reproducible method for isolation and culture of viable rod shaped cardiomyocytes. Cardiomyocytes were maintained in supplemented Media 199 with or without foetal bovine serum. Their viability was assessed using trypan blue while the metabolic activity was measured using an Adenosine 5'-triphosphate assay. Results obtained in this study were used to provide general guidelines to evade pitfalls related to low cardiomyocyte yields and subsequent poor culturability of cardiomyocytes. Isolated cardiomyocytes cultured in the presence of foetal bovine serum maintained their in vitro striated rod shaped morphology for 72 hours in culture, after which, they flattened and spread out. Whereas, cardiomyocytes cultured in the absence of foetal bovine serum remained rod shaped for up to 120 hours.
Mechanobiology of cardiomyocyte development
Journal of Biomechanics, 2010
Cardiac cells are under constant, self-generated mechanical stress which can affect the differentiation of stem cells into cardiac myocytes, the development of differentiated cells and the maturation of cells in neonatal mammals. In this article, the effects of direct stretch, electrically induced beating and substrate elasticity on the behavior and development of cardiomyocytes are reviewed, with particular emphasis on the effects of substrate stiffness on cardiomyocyte maturation. In order to relate these observations to in-vivo mechanical conditions, we isolated the left ventricle of Black Swiss mice from embryonic day 13.5 through postnatal day 14 and measured the elastic modulus of the epicardium using atomic force microscope indentation. We found that the elastic modulus of the epicardium significantly changes at birth, from an embryonic value of 12 ± 4 kPa to a neonatal value of 39 ± 7 kPa. This change is in the range shown to significantly affect the development of neonatal cardiomyocytes.
Mouse Models for the Study of Postnatal Cardiac Hypertrophy
IJC Heart & Vasculature, 2015
The main objective of this study was to create a postnatal model for cardiac hypertrophy (CH), in order to explain the mechanisms that are present in childhood cardiac hypertrophy. Five days after implantation, intraperitoneal (IP) isoproterenol (ISO) was injected for 7 days to pregnant female mice. The Fetuses were obtained at 15, 17 and 19 dpc from both groups, also newborns (NB), neonates (7-15 days) and young adults of age). Histopathological exams were done on the hearts. Immunohistochemistry and western blot demonstrated GATA4 and PCNA protein expression, qPCR Real Time the mRNA of adrenergic receptors (-AR and -AR), alpha and beta myosins (α-MHC, -MHC) and GATA4. After the administration of ISO, there was no change in the number of offsprings. We observed significant structural changes in the size of the offspring hearts. Morphometric analysis revealed an increase in the size of the left ventricular wall and interventricular septum (IVS). Histopathological analysis demonstrated loss of cellular compaction and presence of left ventricular small fibrous foci after birth. Adrenergic receptors might be responsible for changing a physiological into a pathological hypertrophy.
International Journal of Molecular Sciences
Although major pathogenesis mechanisms of heart failure (HF) are well established, the significance of early (mal)adaptive structural changes of cardiomyocytes preceding symptomatic ischemic HF remains ambiguous. The aim of this study is to present the morphological characterization of changes in cardiomyocytes and their reorganization of intermediate filaments during remodeling preceding symptomatic ischemic HF in an adult human heart. A total of 84 myocardial tissue samples from middle-left heart ventricular segments were analyzed histomorphometrically and immunohistochemically, observing the cardiomyocyte’s size, shape, and desmin expression changes in the remodeling process: Stage A of HF, Stage B of HF, and Stages C/D of HF groups (ACC/AHA classification). Values p < 0.05 were considered significant. The cellular length, diameter, and volume of Stage A of HF increased predominantly by the diameter vs. the control group (p < 0.001) and continued to increase in Stage B of H...