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The origin of psammoma bodies in the human arachnoid villi
Abstract:
The fine structure of the human arachnoid villi was studied to clarify the origin of psammoma bodies. Within the villous surface layer, collagen fibrils and fine granular material clustered forming microcores of variable caliber measuring up to 10 microns. An early stage of psammoma body formation was seen more frequently in these villous microcores than in the meningocytic whorls. The villous microcores contained a large number of membrane-free matrix granules as well as a small number of membrane-bound matrix vesicles and matrix minerals. The matrix granules were irregularly oval structures with electron-lucent halo, measuring 0.05-0.70 micron in diameter. Hydroxyapatite crystals were frequently precipitated within and around the matrix granules which aggregated with calcifying matrix vesicles and matrix minerals. Numerous calcifying matrix granules were present within and around enlarging psammoma bodies. The matrix granules may serve as the principal calcification nidi of psammoma bodies in the human arachnoid villi. The possible mechanisms of matrix granule biogenesis are extrusion of preformed arachnoid cell structures or secretion of fine granular material with its extracellular assemblage.
Insights
Researchers identified matrix granules within human arachnoid villi microcores as key to psammoma body formation. These granules are crucial for calcification, originating from cell structures or secretions.
Area of Science:
- Neuroscience
- Cell Biology
- Histology
Background:
- Psammoma bodies are calcified structures found in various tissues, including the meninges.
- Their precise origin within the human arachnoid villi remains incompletely understood.
- Previous theories focused on meningothelial cells, but alternative origins are being investigated.
Purpose of the Study:
- To investigate the ultrastructural basis of psammoma body formation in human arachnoid villi.
- To identify the initial cellular or extracellular components involved in psammoma body calcification.
- To elucidate the role of microcores within arachnoid villi in psammoma body development.
Main Methods:
- Transmission electron microscopy was used to examine the fine structure of human arachnoid villi.
- Ultrastructural analysis focused on identifying microcores and their contents.
- Morphological characterization of matrix granules, vesicles, and mineral deposits was performed.
Main Results:
- Microcores within the villous surface layer were identified as sites of early psammoma body formation.
- These microcores contained abundant membrane-free matrix granules, matrix vesicles, and minerals.
- Hydroxyapatite crystals frequently precipitated within and around matrix granules, indicating their role in calcification.
- Matrix granules were observed to aggregate with calcifying vesicles and minerals during psammoma body enlargement.
Conclusions:
- Matrix granules within villous microcores are likely the principal calcification nidi for psammoma bodies in human arachnoid villi.
- Psammoma body formation may involve the extrusion of cell structures or secretion of granular material.
- This finding offers a new perspective on the pathogenesis of psammoma bodies in the meninges.