Type-VI collagen in the human iris and ciliary body

Abstract

The distribution of type-VI collagen in the human iris and ciliary body was investigated by means of immunohistochemical techniques and compared with that of type-IV collagen, fibronectin and laminin. As has been described for other tissues, type-VI collagen surrounds type-I and -III collagen fibers. The aggregated form of type-VI collagen (the "long-spacing" or "curly" collagen), which has already been described in the trabecular meshwork and sclera, was also observed at the ciliary muscle tips surrounding the anterior elastic tendons of this muscle. In addition, staining for type-VI collagen was seen directly adjacent to the basement membranes of the ciliary muscle cells, the iris muscles, the uveal vascular endothelia and nerves, but not adjacent to the epithelial basement membranes. The staining did not form a discrete line like the immunoreaction for type-IV collagen, but bundles of marked fibrils extended into the surrounding connective tissue. We assume that type-VI collagen similar to type-VII collagen forms part of an anchoring system for these tissues. As type-VII collagen has been described only in connection with epithelial basement membranes, both type-VI and type-VII collagens may represent anchoring fibrils, however for different tissue components.

Immunohistochemical and Ultrastructural Localization of MP78/70 (βig-h3) in Extracellular Matrix of Developing and Mature Bovine Tissues

“…Type VI collagen has previously been reported to be a constituent of perimysium and endomysium in skeletal muscle from adult chickens (Swasdison and Mayne 1989). The distribution of Type VI collagen found in the other tissues was also in agreement with previous studies Zimmermann et al 1986;Timpl and Engel 1987;Amenta et al 1988;Rittig et al 1990;Zhu et al 1994). The distribution of MP78/70 in fetal bovine skin ( Figure 3D) appeared to be similar to that described for ␤ig-h3 in human tissue (LeBaron et al 1995), with the highest signal being in the matrix close to the dermal/epidermal junction.…”

“…Type VI collagen microfibrils are also found in association with the cell surface and attached to certain basement membranes (Maier and Mayne 1987;Rittig et al 1990;Zhu et al 1994). Recently Hirano et al (1996) have presented immunohistochemical evidence for the co-localization of ␤ig-h3 with Type VI collagen microfibrils in the cornea of patients with Fuchs' dystrophy.…”

R(+)-Methanandamide and Other Cannabinoids Induce the Expression of Cyclooxygenase-2 and Matrix Metalloproteinases in Human Nonpigmented Ciliary Epithelial Cells

“…MMP-1, also referred to as interstitial collagenase, efficiently targets a specific site found in the fibrillar collagen types I and III (Jeffrey, 1998). In the case of the uveoscleral pathway, collagen types I and III have been described as the major components of the fibrillar collagen in the extracellular matrix of the interstitial spaces among ciliary muscle fiber bundles (Rittig et al, 1990;Weinreb et al, 1994). MMP-3 efficiently cleaves specific sites found in collagen types IV, IX, and XI, as well as in fibronectin and aggrecan core protein (Nagase, 1998).…”

Increase in types IV and VI collagen in cherry haemangiomas

“…Comparable differences in localization of type IV collagen and laminin have been observed in normal basement membranes like those of the epidermis [10], of the glomerular capillary loops of murine [28] and rat [5] kidney, and of the vessels in the human iris [37]. The reason for the increased production of type IV collagen is not clear, but factors causing abnormal angiogenesis might also stimulate the production of excessive amounts of extracellular matrix.…”

“…We also stained type III collagen, which is regarded as the major component of reticulin fibres in the adventitial dermis [29]. In previous ultraimmunohistochemical studies we were able to demonstrate that in the human eye, broad-banded aggregates similar to zebra bodies or fibrous long-spacing fibres stain with polyclonal antibodies against type VI collagen [25,37]. We therefore studied the localization of type VI collagen in the sheath material of cherry haemangioma capillaries both light-and electron-microscopically.…”