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Published on: April 17, 2013
Mesangial matrices act as mesangial channels to the juxtaglomerular zone. Tracer and high-resolution scanning
H Makino1, K Hironaka, K Shikata
1Third Department of Internal Medicine, Okayama University Medical School, Japan.
Abstract:
The mesangium is centrally located in the glomerulus and plays an important role in the microcirculation within the glomerulus. In order to reveal the role of the mesangial matrix in the microcirculation, the movement of native anionic ferritin into the juxtaglomerular region was tracked following the intravenous injection of ferritin into rats. The three-dimensional ultrastructures of the mesangial matrix and juxtaglomerular apparatus were studied by conventional scanning and high-resolution scanning electron microscopy after removal of the cellular components. Many ferritin particles were observed from the glomerular capillary to the mesangial matrix, in the mesangial matrix of the juxtaglomerular apparatus and in the tubular lumen of the macula densa after the injection of ferritin. Secretion of macromolecules from the distal tubules seems to be one of the exits from the juxtaglomerular zone. The mesangial matrix was continuous from the vascular pole to the periphery like a branching tree. The intraglomerular mesangial matrix was continuous to the extraglomerular mesangial matrix in the juxtaglomerular region. The mesangial matrix appeared to consist of a polygonal meshwork structure of thin fibrils and pores with high-resolution scanning electron microscopy. The thinnest fiber was approximately 6-nm wide, and the pore size was averaged 20 nm in diameter. We were able to demonstrate the meshwork structure of the mesangial matrix, thus giving the morphological basis of the mesangial matrix to serve as mesangial pathway from the intraglomerular to the extraglomerular mesangial matrix.
Insights
The mesangial matrix acts as a pathway for molecule transport within the glomerulus. High-resolution imaging revealed its meshwork structure, facilitating movement from intraglomerular to extraglomerular spaces.
Area of Science:
- Nephrology
- Cell Biology
- Microcirculation
Background:
- The mesangium is crucial for glomerular microcirculation.
- Its role in molecule transport requires further elucidation.
Purpose of the Study:
- To investigate the role of the mesangial matrix in microcirculation.
- To visualize the three-dimensional ultrastructure of the mesangial matrix and juxtaglomerular apparatus.
Main Methods:
- Intravenous injection of anionic ferritin into rats.
- Conventional and high-resolution scanning electron microscopy.
- Removal of cellular components to study matrix structure.
Main Results:
- Ferritin particles were observed moving from glomerular capillaries into the mesangial matrix and macula densa.
- The mesangial matrix exhibits a continuous, tree-like structure from the vascular pole to the periphery.
- High-resolution microscopy revealed a meshwork of 6-nm fibrils with 20-nm pores.
Conclusions:
- The mesangial matrix provides a morphological basis for a pathway connecting intra- and extraglomerular spaces.
- Macromolecule secretion from distal tubules may represent an exit route from the juxtaglomerular zone.
