Ultrastructural dynamics in myocytes of developing heart

Marta Novotová¹, Jérôme Piquereau², Dominique Fortin², Renée Ventura-Clapier²

¹Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, ²INSERM, U-769, University of Paris-Sud 11, Chatenay-Malabry, France

* marta.novotova@savba.sk

Cardiac and skeletal muscle cells of adult mammals are highly differentiated. Each subcellular compartment is a functional and structural entity. The cytoskeletal organization during postnatal development plays a crucial role in the dynamic appearance of micro-domains and the energetic efficiency of cardiomyocytes. Disruption of micro-domains would compromise the energetic equilibrium of the adult heart and participate in heart failure. The postnatal development is accompanied by the specific expression and localization of the creatine kinase isoenzymes (Hoerter et al., 1994). This suggested that a tight relationship exists between the cytoarchitecture, energetics, and contractility. Cardiomyocyte maturation during the first postnatal weeks is characterized by the fast decrease in mitotic activity, increase in the myofibrillar and mitochondrial volume, development of the sarcoplasmic reticulum and, during the final phase, appearance of the tubular system. Ultrastructure of cardiomyocytes of three, seven and twenty one day old mice revealed that cell architecture was less organised 3 days post partum and was already mature at 7 days. These results demonstrate that architectural organisation of cardiomyocytes, necessary for efficient energetic regulation takes place between 3 and 7 days post partum in mice. Development of cardiac muscle was dominated by high mitochondrial dynamic regarding their structure, size, number, and location. These observations point out that cytoarchitecture is not static but highly dynamic and quickly responds to changing needs of the organism.

This study was supported by the Slovak–French cooperation Stefanik SK-FR-0021-07.

References

Hoerter JA, Ventura-Clapier R, Kuznetsov A (1994). Compartmentation of creatine kinases during prenatal development of mammalian heart. Molecular and Cell Biochemistry 133/134: 277-286.