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Relationship between morphological signs of cell injury in myocardial ischaemia
1Department of Anatomy, University of Bergen, Norway.
Insights
Mild cardiac injury involves cellular edema preceding severe damage. Edema correlates with mitochondrial volume reduction and lipid droplet increase, offering insights into early ischemic heart disease mechanisms.
Area of Science:
- Cardiovascular Pathology
- Cellular Biology
- Ischemic Heart Disease
Background:
- Severe ischemic injury in the heart is well-documented.
- Understanding cellular-level changes in milder injuries remains limited.
- Previous research identified alterations in the border zone of cat hearts after coronary occlusion.
Purpose of the Study:
- To investigate the relationship between morphological variables in myocytes within the border zone of ischemic cat hearts.
- To elucidate the cellular mechanisms underlying mild to moderate ischemic injury.
- To correlate edema development with other cellular changes.
Main Methods:
- Analysis of serial sections from 220 myocytes in the border zone of cat hearts subjected to 3 hours of coronary occlusion.
- Quantification of morphological variables including cytoplasmic volume, sarcolemmal integrity, and chromatin changes.
- Assessment of mitochondrial and lipid droplet fractional volumes.
Main Results:
- Cytoplasmic volume showed a bimodal distribution in cells without chromatin changes, indicating the presence or absence of edema.
- Focal sarcolemmal disruptions were associated with moderate, often submembranous edema.
- Extensive sarcolemmal fragmentation correlated with extensive edema.
- Mild edema was observed prior to other severe cell injury signs.
- Cells with edema exhibited smaller mitochondrial fractional volume and larger lipid droplet fractional volume compared to non-edematous cells.
Conclusions:
- Cellular edema is an early indicator of ischemic injury, preceding severe morphological damage.
- The extent of edema is directly related to the degree of sarcolemmal damage.
- Mitochondrial and lipid metabolism alterations are associated with the development of edema in ischemic myocytes.
Abstract:
Morphological signs of severe ischaemic injury are well known. However, we still lack knowledge about how indices of milder injuries are related on a cellular level. In a previous study we have reported on the sequence of alterations across the border zone in cat hearts subjected to 3 h of coronary occlusion. In the present study, which elaborates that study, we have examined the relationship between morphological variables in serial sections of 220 myocytes within the border zone. In cells with intact sarcolemma and no chromatin changes, the fractional volume of cytoplasm has a bimodal distribution indicating cells with and without oedema. Whereas cells with focal disruptions of the sarcolemma have a moderate oedema, usually localized submembranously, cells with extensive sarcolemmal fragmentation have an extensive oedema. A mild oedema is seen before other signs of severe cell injury, even though more extensive oedema is closely associated with sarcolemmal fragmentation. The fractional volume of mitochondria was smaller, whereas the fractional volume of lipid droplets was larger in cells with oedema than in cells without oedema.