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Alpha-1-antitrypsin deficiency and juvenile liver disease. Ultrastructural observations compared with light
Insights
Alpha-1-antitrypsin deficiency (PiZ) in children causes retained proteins in liver cells, primarily in the endoplasmic reticulum. This defect occurs before the Golgi complex, impacting some, but not all, hepatocytes.
Area of Science:
- Hepatology
- Pediatric Gastroenterology
- Cell Biology
Background:
- Alpha-1-antitrypsin deficiency (PiZ) is a genetic disorder that can lead to liver disease in children.
- Neonatal cholestasis is a common complication, but its role in disease progression is unclear.
- Understanding the cellular mechanisms of PiZ liver disease is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the ultrastructural changes in the liver of children with alpha-1-antitrypsin deficiency (PiZ).
- To correlate clinical findings, including neonatal cholestasis, with liver histology and electron microscopy.
- To determine the site of intracellular protein accumulation in PiZ hepatocytes.
Main Methods:
- Liver biopsies from 16 children (1 month to 20 years) with PiZ deficiency were analyzed.
- Light microscopy was used to classify liver status (healthy, fibrotic, cirrhotic).
- Electron microscopy examined hepatocyte ultrastructure, focusing on endoplasmic reticulum and Golgi complex.
Main Results:
- All PiZ patients showed periodic acid-Schiff positive globules in periportal hepatocytes.
- Electron microscopy revealed accumulation of retained secretory material in the smooth endoplasmic reticulum of all PiZ patients.
- Affected hepatocytes displayed Golgi complex hypotrophy or disappearance; VLDL transport was unaffected.
- The defect appears to occur before the Golgi complex, not strictly age-dependent.
Conclusions:
- Alpha-1-antitrypsin deficiency (PiZ) causes intracellular protein retention in hepatocytes, primarily within the endoplasmic reticulum.
- The defect in protein transport occurs before the Golgi complex.
- Subclinical cholestasis does not appear to trigger cirrhosis development in this cohort.
Abstract:
Sixteen children (aged between 1 month and 20 years) with alpha-1-antitrypsin deficiency (PiZ) were investigated by liver biopsy on one or more occasions. Eight patients had suffered from neonatal cholestasis, and two of them were investigated during the cholestatic period as well. The clinical status and liver function tests were compared with the light and electron microscopical findings. According to the light microscopical analyses at the latest investigation, the cholestatic and noncholestatic patients were classified as healthy, fibrotic or cirrhotic cases. All livers displayed periodic acid-Schiff positive, diastase-resistant globules in some but not all periportally located hepatocytes. By electron microscopy accumulation of retained secretory material was found in all PiZ patients. This accumulation was most conspicuous in the smooth endoplasmic reticulum of hepatocytes. alpha-1-antitrypsin deficiency seems to affect some, but not all hepatocytes. In the affected cells disappearance or hypotrophy of the Golgi complex could be observed. The intracellular transport of very low density lipoproteins (VLDL) was apparently not affected. The migration block in alpha-1-antitrypsin deficiency seems to occur before transportation to the Golgi complex. The extent of the involvement was not strictly age-dependent. There was no ultrastructural evidence of subclinical cholestasis as a possible triggering factor in the development of cirrhosis.