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Cellular changes and damage in mechanically overloaded hearts
Insights
Mechanical overload in the heart causes myocardial cell damage, with severity correlating to damage extent. Cellular changes reflect increased protein synthesis and growth, potentially leading to regression to a fetal state in severe cases.
Area of Science:
- Cardiovascular Biology
- Cellular Pathology
- Electron Microscopy
Background:
- Mechanical overload is a significant stressor on the heart.
- Understanding myocardial cell responses is crucial for treating heart conditions.
Purpose of the Study:
- To review electron microscopic findings in mechanically overloaded myocardial cells.
- To correlate observed cellular alterations with overload severity and duration.
Main Methods:
- Electron microscopy of myocardial cells from mechanically overloaded hearts.
- Analysis of cellular structures including mitochondria, myofibrils, and Golgi apparatus.
Main Results:
- Degenerative changes in myocardial cells increase with overload severity, potentially causing interstitial fibrosis.
- Cellular alterations indicate increased protein synthesis and growth of organelles.
- Severe, long-term overload can induce regression to a fetal-like cellular state.
Conclusions:
- Myocardial cell response to mechanical overload involves both adaptive growth and degenerative processes.
- The severity and duration of overload dictate the nature and extent of cellular changes.
- Observed changes suggest a complex interplay between cellular stress, adaptation, and potential dedifferentiation.
Abstract:
The electron microscopic aspects of myocardial cells in several types of mechanically overloaded heart are reviewed. Alterations which may be interpreted as degenerative changes are all the more frequent as the load is more severe. They seem to be the cause of the interstitial fibrosis which often accompanies hypertrophy. Their mechanism is dubious: swelling of mitochondria and intracellular lipidosis, which could signify cellular hypoxia, are rarely present. Other changes are characteristic of an increase of proteosynthesis and of the active growth of the main structures of the cell: myofibrils, mitochondria, T- and L-tubules. Some pictures of myofibrillar growth are not always easily distinguished from those of myofibrillar lesions. The mitochondria/myofibril ratio may be modified or not. The apparent volume of the mitochondria may remain normal while their density increases, which implies a decrease of their average size. In severe and long-lasting overloads, hypertrophy and hyperplasia of the Golgi apparatus and multiplication of granules of the auricular type evoke a regression of the cell toward its fetal type.