Quantitative analysis of ‘plaque material’ in the inner- and outer wall of Schlemm's canal in normal- and glaucomatous eyes

The scieral spur in 37 human (age 17-87 years) and six cynomolgus monkey eyes (2-4 years) was investigated. Serial meridional and tangential sections were studied with ultrastructural and immunocytochemical methods. The bundles of the ciliary muscle do not enter the scleral spur, but their tendons, which consist of elastic fibres join the elastic fibres in the scleral spur. Within the scleral spur a population of circularly oriented and spindle-shaped cells is found. In contrast to the ciliary muscle cells, the scleral spur cells form no bundles, but are loosely aggregated. They have long cytoplasmic processes and are connected to each other by adherens-type and gap junctions. They stain intensely for a-smooth muscle actin. myosin and vimentin. In contrast to the ciliary muscle cells, they do not stain for desmin. Ultrastructurally, the scleral spur cells contain abundant thin (actin) filaments, but do not otherwise show the typical ultrastructural features of ciliary muscle cells. The scleral spur cells do not express a complete basal lamina. They form individual tendinous connections with the elastic fibres in the scleral spur, which are continuous with the elastic fibres of the trabecular meshwork. The scleral spur cells are in close contact with nerve terminals containing small agranular (30-60 nm) and large granular (65-l 10 nm) vesicles but also with terminals containing small granular (30-60 nm) vesicles which are regarded as typical for adrenergic terminals. We conclude that the scleral spur cells are contractile myofibroblasts. Their contraction might influence the rate of the aqueous outflow.

Section: Discussionmentioning

confidence: 86%

Contractile cells in the human scleral spur

Tamm

Flügel

Stefani³

et al. 1992

“…Studies with general microscopic stains and electron microscopy identified GAGs, fibrillar collagens, unevenly-spaced or curly collagen, elastic fibrils with associated sheath-derived plaque material, basement membrane and amorphous basement membrane-like materials and other non-specific ECM components. (Hogan et al 1971;Francois 1975;Grierson and Lee 1975;Lütjen-Drecoll et al 1981;Richardson 1982;Lütjen-Drecoll et al 1986;Lütjen-Drecoll and Tamm 1987;Lütjen-Drecoll and Rohen 1996;Lutjen-Drecoll 1999;Gong et al 2002) …”

Section: Ecm Components Identified Within the Tmmentioning

confidence: 99%

“…(Segawa 1979;Lütjen-Drecoll et al 1981;Rohen 1983;Lütjen-Drecoll et al 1986;Lütjen-Drecoll and Tamm 1987;Lutjen-Drecoll and Rohen 2001) The exact molecular nature of this material is not clear and a direct causal link to the increased outflow resistance has been difficult to establish. An additional caveat to these glaucoma studies is that, with few exceptions, (Rohen et al 1993) the tissue is from eyes that have been on various glaucoma medications for extended periods.…”

Section: Glaucoma and Ecmmentioning

confidence: 99%

Extracellular matrix in the trabecular meshwork

Acott

Kelley

2008

417

443

The extracellular matrix (ECM) of the trabecular meshwork (TM) is thought to be important in regulating intraocular pressure (IOP) in both normal and glaucomatous eyes. IOP is regulated primarily by a fluid resistance to aqueous humor outflow. However, neither the exact site nor the identity of the normal resistance to aqueous humor outflow has been established. Whether the site and nature of the increased outflow resistance, which is associated with open-angle glaucoma, is the same or different from the normal resistance is also unclear.The ECMs of the TM beams, juxtacanalicular region (JCT) and Schlemm's canal (SC) inner wall are comprised of fibrillar and non-fibrillar collagens, elastin-containing microfibrils, matricellular and structural organizing proteins, glycosaminoglycans (GAGs) and proteoglycans. Both basement membranes and stromal ECM are present in the TM beams and JCT region. Cell adhesion proteins, cell surface ECM receptors and associated binding proteins are also present in the beams, JCT and SC inner wall region.The outflow pathway ECM is relatively dynamic, undergoing constant turnover and remodeling. Regulated changes in enzymes responsible for ECM degradation and biosynthetic replacement are observed. IOP homeostasis, triggered by pressure changes or mechanical stretching of the TM, appears to involve ECM turnover. Several cytokines, growth factors and drugs, which affect the outflow resistance, change ECM component expression, mRNA alternative splicing, cellular cytoskeletal organization or all of these. Changes in ECM associated with open-angle glaucoma have been identified.

“…1972 ;Liitjen-Drecoll et al, 1986a). This material is also increased in the anterior portion of the ciliary muscle of glaucomatous eyes (Liitjen-Drecoll et al, 1986b).…”

Section: Introductionmentioning

confidence: 99%

Cell cultures of human ciliary muscle: Growth, ultrastructural and immunocytochemical characteristics

Tamm

Flügel

Baur

et al. 1991

Primary ciliary muscle cell cultures derived from human donors (16-9 1 years) were established and characterized by comparing them with ciliary muscle in tissue sections using immunocytochemical and ultrastructural methods. Monoclonal antibodies against desmin, vimentin, a-actinin, smooth muscle (sm) specific a-actin and von Willebrand factor were used. In tissue sections of the ciliary body, ciliary muscle cells, vascular muscle cells, pericytes, endothelial cells and fibroblasts stain for vimentin. Both types of muscle cells and the pericytes stain for cr-sm-actin, but only ciliary muscle cells stain for desmin. For tissue cultures, explants of the meridional and partly the reticular portion of the ciliary muscle were dissected and grown directly or after digestion of the explant with collagenase. Ten primary cell cultures with a typical hill-and-valley growth pattern similar to smooth muscle cells and two with a growth pattern similar to fibroblasts were established. All cultures could be subcultured up to the fifth passage. In fibroblast-like cultures S-10% of the cells stained for z-sm-actin. Staining for desmin was not observed. In smooth muscle-like cultures, all cells stained positive for a-sm-actin. Desmin staining was not seen in growing non-confluent smooth muscle-like cultures. In confluent cultures, about 10% of the cells stained positive for desmin, preferentially in areas where the cells had formed hills. No culture stained for von Willebrand factor. Staining for a-actinin in smooth muscle-like cultures showed that the dense bands of the myofilaments were arranged in register, similar to the typical ciliary muscle cell morphology seen in tissue sections. Ultrastructurally, the smooth muscle-like cultures showed the typical morphology of cultured smooth muscle cells. We conclude that the smooth muscle-like cultures consist of ciliary muscle cells.