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Fibronectin in the trabecular meshwork: immunofluorescent and immunoelectron microscopic findings
Insights
Fibronectin (FN) is secreted by trabecular meshwork (TM) cells and is concentrated in the subendothelial region of the human eye. This protein is found lining the trabecular endothelial cells, not in the central core.
Area of Science:
- Ocular Biology
- Extracellular Matrix Research
- Immunohistochemistry
Background:
- Trabecular meshwork (TM) cells are crucial for maintaining intraocular pressure.
- Fibronectin (FN) is a key component of the extracellular matrix with roles in cell adhesion and migration.
- Understanding FN distribution in the TM is important for glaucoma research.
Purpose of the Study:
- To investigate the secretion and localization of fibronectin (FN) in normal human trabecular meshwork (TM).
- To characterize the distribution pattern of FN within the TM tissue and in cultured TM cells.
Main Methods:
- Indirect immunofluorescence staining using anti-FN monoclonal antibodies on cultured TM cells and frozen TM sections.
- Immunoelectron microscopy with an avidin-biotin-peroxidase complex method to determine precise FN distribution.
- Analysis of TM tissue from human eyes obtained due to traumatic rupture.
Main Results:
- Cultured TM cells showed intense FN staining in cell walls and extracellular matrices.
- Frozen TM sections exhibited strong FN positivity in the subendothelial region.
- Immunoelectron microscopy confirmed FN presence lining the trabecular endothelial cells, with no signal in the central trabecular beam core.
Conclusions:
- Trabecular meshwork cells actively secrete fibronectin (FN).
- FN is predominantly localized in the subendothelial layer and around TM endothelial cells.
- These findings provide insights into the structural composition of the normal human TM.
Abstract:
We examined the fibronectin (FN) secretion of cultured trabecular meshwork (TM) cells in a normal human eye by indirect immunofluorescent technique using mouse anti-human FN monoclonal antibody and FITC-conjugated goat anti-mouse IgG. To localize FN on frozen sections of normal TM, which were obtained from 7 enucleated eyes owing to traumatic eyeball rupture, the same indirect immunofluorescent method was used. Immunoelectron microscopy was applied to demonstrate the distribution pattern of FN in the normal TM of 2 human eyes using an avidin-biotin-peroxidase complex method. In the tissue culture of TM, the TM cell walls and extracellular matrices showed an intense staining with antibody to FN. Indirect immunofluorescent staining of FN on frozen sections of TM showed strong positive reactions in the subendothelial region. There was no reaction in the central core of the trabecular beam. Immunoelectron microscopy revealed the reaction products to FN in the areas lining the trabecular endothelial cells.