Intercellular junctions of the iris epithelia in Macaca mulatta

Area of Science:

• Ocular Anatomy
• Cell Biology
• Histology

Background:

• The iris, a key ocular structure, comprises anterior myoepithelium and posterior pigmented epithelium.
• Understanding intercellular junctions is crucial for iris function and drug delivery.
• Previous studies have hinted at specialized junctions but lacked detailed ultrastructural analysis.

Purpose of the Study:

• To ultrastructurally characterize intercellular junctions in the rhesus monkey iris.
• To investigate the permeability barrier formed by these junctions.
• To compare iris epithelial junctions with those in the ciliary epithelium.

Main Methods:

• Conventional electron microscopy
• Freeze-fracture technique
• Ultrastructural tracer (horseradish peroxidase) studies

Main Results:

• Anterior myoepithelium: puncta adhaerentia, desmosomes, gap junctions.
• Posterior pigmented epithelium: zonula occludens, zonula adhaerens, gap junctions, and desmosomes.
• Zonulae occludentes in posterior pigmented epithelium form a barrier preventing tracer entry into the posterior chamber.

Conclusions:

• The posterior pigmented epithelium possesses a tight junctional complex (zonula occludens) analogous to the nonpigmented ciliary epithelium.
• This zonula occludens acts as a significant barrier, regulating permeability between the ciliary body stroma and the posterior chamber.
• Detailed ultrastructural analysis reveals specialized junctions critical for iris barrier function.