Contractile cells in the human scleral spur.

Area of Science:

• Ocular Anatomy
• Cell Biology
• Ophthalmology

Background:

• The scleral spur is a key anatomical structure in the anterior segment of the eye.
• Its cellular composition and function, particularly in relation to the ciliary muscle and aqueous humor dynamics, remain areas of investigation.

Purpose of the Study:

• To investigate the cellular ultrastructure and immunocytochemical characteristics of the scleral spur.
• To determine the relationship between ciliary muscle tendons and the scleral spur.
• To explore the potential role of scleral spur cells in regulating aqueous humor outflow.

Main Methods:

• Examination of serial meridional and tangential sections from human and cynomolgus monkey eyes.
• Application of ultrastructural and immunocytochemical techniques.
• Analysis of cellular morphology, protein expression (alpha-smooth muscle actin, myosin, vimentin, desmin), and cell junctions.

Main Results:

• Scleral spur cells are distinct from ciliary muscle cells, lacking bundled organization and desmin expression.
• These cells exhibit characteristics of myofibroblasts, with abundant actin filaments and connections to elastic fibers.
• Nerve terminals, including adrenergic ones, were observed in close proximity to scleral spur cells.
• Scleral spur cells form tendinous connections with elastic fibers continuous with the trabecular meshwork.

Conclusions:

• Scleral spur cells are identified as contractile myofibroblasts.
• Their unique cellular features and innervation suggest a role in modulating aqueous humor outflow.
• Contraction of these cells may influence the rate of aqueous humor drainage, potentially affecting intraocular pressure.