Related Experiment Videos
Periodic acid-Schiff staining abnormality in microvillous atrophy: photometric and ultrastructural studies
A D Phillips1, M Szafranski, L Y Man
1University Department of Paediatric Gastroenterology, Royal Free Hospital, London, United Kingdom.
Background:
The accumulation of periodic acid Schiff (PAS)-positive material in the epithelium in microvillous atrophy (MVA) is diagnostic but unexplained. It occurs earlier in the epithelial life cycle than the formation of microvillous inclusions and warrants further investigation.
Methods:
Scanning photometry was used to assess the distribution of the PAS-positive material within epithelial cells and to assess how this changed with position on the crypt-villus axis. Thiery staining was applied to test the PAS positivity of the secretory granules, and quantitative ultrastructural morphometry was used to study secretory granule distribution in the epithelium.
Results:
The PAS abnormality arose in upper crypt epithelium in congenital and late-onset MVA and continued up the villus. Thiery staining demonstrated that the secretory granules were PAS positive. Quantitative morphometry showed that secretory granules in congenital MVA were predominantly present in upper crypt and declined in the low villus. In late-onset MVA, secretory granules arose in the upper crypt but predominated in the low villus region. No evidence of secretory granule coalescence with the apical membrane was seen, although evidence of crinophagy was observed. Secretory granule profiles were seen, indicating that they formed part of a membrane-bound vesicular network within the cell, rather than existing simply as discrete bodies. The Golgi complex appeared normal.
Conclusions:
The secretory granules are responsible for the PAS-positive staining in upper crypt and low villus regions in MVA. They appear to form an intracytoplasmic vesicular network, undergo crinophagy, and decline in prominence in the low to midvillous region. The absence of evidence of coalescence with the apical membrane indicates that the secretory granules arise from a post-Golgi block in exocytosis rather than from endocytosis of gut luminal contents. Periodic acid-Schiff positivity in upper villous regions arises from microvillous inclusions and lysosomal bodies.
Insights
Periodic acid-Schiff (PAS)-positive material in microvillous atrophy (MVA) originates from secretory granules in the upper crypt and villus epithelium. This finding clarifies the source of the diagnostic staining in MVA.
Area of Science:
- Gastroenterology
- Cell Biology
- Pathology
Background:
- Microvillous atrophy (MVA) is characterized by diagnostic periodic acid-Schiff (PAS)-positive material in the epithelium.
- The origin and timing of this PAS-positive material accumulation are not fully understood.
- It appears earlier in epithelial development than microvillous inclusions, necessitating further investigation.
Purpose of the Study:
- To investigate the source of PAS-positive material in the epithelium of patients with microvillous atrophy.
- To determine the distribution and characteristics of PAS-positive material along the crypt-villus axis.
- To elucidate the cellular mechanisms underlying PAS positivity in MVA.
Main Methods:
- Scanning photometry to assess PAS-positive material distribution.
- Thiery staining to identify PAS-positive secretory granules.
- Quantitative ultrastructural morphometry to analyze secretory granule distribution and cellular structures.
Main Results:
- PAS positivity was observed in the upper crypt and villus epithelium in both congenital and late-onset MVA.
- Thiery staining confirmed secretory granules as the source of PAS positivity.
- Secretory granules formed an intracytoplasmic vesicular network and underwent crinophagy, with no evidence of apical membrane fusion.
Conclusions:
- Secretory granules are the primary source of PAS positivity in the upper crypt and low villus regions in MVA.
- The findings suggest a post-Golgi block in exocytosis rather than endocytosis.
- PAS positivity in upper villous regions is attributed to microvillous inclusions and lysosomal bodies.