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Ultrastructure of myocardium in the Hurler syndrome. Possible relation to cardiac function
Insights
Hurler syndrome patients exhibit cardiac cell vacuolization due to ganglioside accumulation, not GAGs. This cellular damage likely causes the heart disease seen in Hurler syndrome.
Area of Science:
- Biochemistry
- Cardiology
- Genetics
Background:
- Hurler syndrome is a rare genetic disorder.
- Cardiac involvement is a common and severe complication of Hurler syndrome.
Purpose of the Study:
- To investigate the ultrastructural and histochemical basis of cardiac pathology in Hurler syndrome.
- To identify the specific substances accumulating within cardiac myocytes.
Main Methods:
- Post mortem examination of cardiac tissues from eight Hurler syndrome patients (ages 5-23).
- Histochemical staining (Luxol-fast blue) and electron microscopy.
- Identification of cytoplasmic organelles: zebra bodies (ZB), membranous cytoplasmic bodies (MCB), and granulomembranous bodies (GMB).
Main Results:
- All hearts showed extensive myocardiocytic vacuolization and increased interstitial fibrous tissue.
- Cytoplasmic vacuoles contained a Luxol-fast-blue-positive substance.
- Abnormal organelles (ZB, MCB, GMB) were observed in all patients' cardiac myocytes.
- ZB and MCB suggest the accumulation of gangliosides within cardiac myocytes, rather than glycosaminoglycans.
Conclusions:
- Gangliosides, not glycosaminoglycans, are the primary stored substances within cardiac myocytes in Hurler syndrome.
- Accumulation of gangliosides leads to myocardial damage, contributing to cardiac disease in Hurler syndrome patients.
Abstract:
Cardiac tissues obtained at post mortem examination of eight patients with the Hurler syndrome, who ranged in age from 5 to 23 years, were examined by histochemical methods and electron microscopy. Extensive myocardiocytic vacuolization and increased interstitial fibrous tissue were noted by light microscopy in all hearts. The cytoplasmic (perinuclear) vacuoles contained Luxol-fast-blue-positive substance. At the ultrastructural level, abnormal cytoplasmic organelles were present within the myocardiocytes in all patients. These organelles were of three types: zebra bodies (ZB), membranous cytoplasmic bodies (MCB) and granulomembranous bodies (GMB). As ZB and MCB are believed to represent the morphological counterpart of accumulated gangliosides, these substances rather than glycosaminoglycans appear to be stored within myocardiocytes of patients with the Hurler syndrome. The accumulation of gangliosides and the consequent damage to the myocardial substratum probably contributes to the clinically evident cardiac disease, so often observed in the patients with this disorder.