Original articlesCardiovascularIs the Myofibrillarlytic Myocyte a Forme Fruste Apoptotic Myocyte?
Section snippets
Material and Methods
Histologic sections from nine ISCM hearts obtained during transplantation over the past 2 years were reviewed. Section stained by hematoxylin-eosin, which showed large populations of MFL cells in subendocardial layers, were identified. A myofibrillarlytic cell was defined as a myocyte wherein a part or all of the sarcoplasm had been replaced by a clear, intracellular vacuole. The myocytes with only perinuclear clearing were rejected as sectioning artifact. Contiguous sections of the selected
Results
A total of 4131 MFL cells (Fig 1A) were examined; 1305 of these cells possessed nuclei (32%) in the examined sections. Of 1305 MFL cells, 1146 nucleated cells (88%) revealed TUNEL-positive nuclei (Fig 2A). For comparison, 842 normal appearing myocytes were evaluated. Of these, 257 cells (31%) revealed nuclei in the section, merely 5 (1.9%) nuclei were TUNEL positive. No caspase 3 staining was observed in the cytoplasm or nuclei in normal appearing myocytes. On the other hand, all MFL cells
Comment
In the present study almost 90% nuclei of MFL cells in ischemic cardiomyopathic hearts demonstrated apoptosis as detected by TUNEL-based evidence of nuclear fragmentation. Almost all of these cells also demonstrated variable degree of caspase 3 upregulation. Caspase 3 staining was more marked in the cells that had less severe vacuolization. It is logical to presume that activated caspases lead to digestion of contractile proteins to result in cytoplasmic clearance. Peptide sequence analysis of
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