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Internalized gap junctions in ciliary epithelium of rabbit and rat. A transmission electron-microscopic study
1Department of Anatomy and Histology, Varna Institute of Medicine, Bulgaria.
Insights
Internalized gap junctions (IGJ) in ciliary epithelial cells are formed via invagination-endocytosis and degraded by autophagy. This process in pigmented cells may influence aqueous humor production.
Area of Science:
- Ophthalmology
- Cell Biology
- Histology
Background:
- Gap junctions (GJ) mediate cell-to-cell communication in the ciliary epithelium.
- The fate and formation mechanism of internalized gap junctions (IGJ) remain unclear.
Purpose of the Study:
- To investigate the mechanism of IGJ formation and degradation in rabbit and rat ciliary epithelial cells.
- To explore the potential role of IGJ in aqueous humor production.
Main Methods:
- Transmission electron microscopy (TEM) was employed to examine ciliary epithelial cells.
- Over 500 gap junction vacuoles and invaginations were analyzed morphologically.
Main Results:
- Internalized gap junctions were predominantly observed in pigmented epithelial cells.
- A novel "lucidation" phenomenon was noted in invaginating GJ membranes.
- Morphological evidence of autophagic degradation of IGJ was present.
Conclusions:
- Internalized gap junctions in the ciliary epithelium likely form through an invagination-endocytosis pathway.
- Autophagic degradation is the primary mechanism for clearing IGJ.
- This IGJ internalization process may be significant for regulating aqueous humor production.
Abstract:
Transmission electron microscopy was used to examine internalized gap junctions (IGJ) in rabbit and rat ciliary epithelial cells. A prominent feature of all the specimens studied was the presence of different images of IGJ membrane that entrapped a portion of an adjoining cell. We documented and analyzed more than 500 gap junction (GJ) vacuoles and invaginations, the latter comprising less than 20% of all the structures examined. With ten exceptions found in non-pigmented cells, all the IGJ were unidirectionally internalized within the cytoplasm of pigmented epithelial cells. Morphological signs of autophagic degradation of GJ vacuoles were observed. An essential finding was that once a GJ membrane started to invaginate, a "lucidation" of a part of the protruding cytoplasm occurred; no planar GJ membranes exhibited such an alteration. The present finding suggest that IGJ derived from the epithelium of ciliary processes arise through an invagination-endocytosis mechanism and are degraded autophagically. This phenomenon may be relevant to aqueous humor production.