Immunolocalization of TGF-beta 1, TGF-beta 2, and TGF-beta 3 in the anterior segment of the human eye.

PURPOSE: To determine the distribution of transforming growth factor type beta (TGF-beta) in the anterior segment of the human eye. This knowledge is important because TGF-beta may regulate various physiologic responses in the anterior segment by controlling cell proliferation and differentiation, angiogenesis, and extracellular matrix composition. METHODS: Immunohistochemical methods were used to localize the beta 1, beta 2, and beta 3 isoforms of TGF-beta in the anterior segment of the human eye. RESULTS: Eight of eight eyes (six eye bank specimens and two eyes enucleated because of choroidal melanoma) exhibited staining for at least one of the TGF-beta isoforms. TGF-beta 1 was found in superficial limbal epithelial cells (four of eight eyes) and in the stroma proximal to the ciliary processes (seven of eight eyes). TGF-beta 2 was found in superficial limbal epithelial cells (six of eight eyes), the conjunctival stroma (eight of eight eyes), in the ciliary processes (three of eight eyes), and in a diffuse distribution in the region of the radial and circular muscles of the ciliary body (eight of eight eyes). In addition, TGF-beta 2 was found in the stroma adjacent to the pigmented epithelium in the pars plana (eight of eight eyes). TGF-beta 3 was found in white blood cells in one of eight specimens; otherwise it was not found in the anterior segment. The corneal stroma, corneal endothelium, trabecular meshwork, iris, and ciliary epithelia did not exhibit immunoreactivity with the antibodies used in this study. CONCLUSION: TGF-beta 1 and TGF-beta 2 have a distinct and specific distribution in the anterior segment of the adult human eye.

Effect of topical mitomycin C on glaucoma filtration surgery in monkeys.

In this study, an experimental model of glaucoma filtration surgery was used to evaluate the clinical and histologic effects of a single intraoperative topical application of mitomycin C. Argon laser treatment to the trabecular meshwork produced sustained elevation of intraocular pressure in monkeys. Eight eyes of four animals were randomly assigned to receive topical mitomycin C or balanced salt solution at the time of full-thickness sclerostomy. Surgical success was substantially increased in four of five eyes that received mitomycin C when compared with three eyes that received topical balanced salt solution. Mitomycin C was also effective in prolonging surgical success in two eyes that had previously undergone surgery and failed. No significant ocular toxicity was observed in eyes treated with mitomycin C. Histologic examination of mitomycin C-treated eyes showed patent sclerostomies and hypocellular, well-formed bleb cavities. A single intraoperative application of mitomycin C has a marked effect on postoperative wound healing after filtration surgery in monkeys.

Larger optic nerve heads have more nerve fibers in normal monkey eyes.

The cup-to-disc ratio and the neural rim area are used to detect glaucoma damage to the optic nerve. Both parameters are dependent on the size of the optic disc and on the number of optic nerve fibers. We compared the size of the disc in fundus photographs with the number of nerve fibers in 25 normal monkey eyes. The number of fibers increased linearly with an increasing disc area. One must know the size of the optic disc to evaluate properly the cup-to-disc ratio or neural rim area.

Alterations in elastin of the optic nerve head in human and experimental glaucoma.

The optic nerve heads from normal and glaucomatous eyes of humans and monkeys were examined by light and electron microscopy for the presence and distribution of elastin. Elastin densely lined the insertion of the lamina cribrosa into the sclera and was prominent in the laminar beams. The long axis of elastin paralleled that of the collagen fibrils and corresponded to the directions of expected forces on the tissue. In glaucomatous eyes elastin molecules were curled instead of straight and seemed disconnected from the other elements of the connective tissue matrix. Laminar beams stretch and reorganise their substructure during glaucomatous atrophy, probably leading to changed compliance. Differences in elastin function may have a part in susceptibility to glaucomatous injury.

Quantitative study of collagen and elastin of the optic nerve head and sclera in human and experimental monkey glaucoma.

Quantitative studies of collagen density and fibril size distribution as well as elastin density were carried out in the optic nerve head and sclera of human and experimental monkey glaucoma eyes. The collagen fibrils of the normal lamina cribrosa are smaller and more uniform in size than those of the sclera. This feature may be an adaptation to maximize either elasticity or resistance to mechanical stress. In glaucomatous nerve heads, there is a major disruption of the structure of the lamina cribrosa beam structure, including a decrease in collagen density. The peripapillary sclera undergoes similar collagen density changes to those in the nerve head in human glaucoma eyes. Elastin fiber density is unchanged in the glaucomatous nerve heads that we studied.

Optic nerve head extracellular matrix in primary optic atrophy and experimental glaucoma.

Unilateral glaucomatous optic neuropathy and optic nerve transections were produced in cynomolgus monkeys, and the optic nerve heads were examined by light and electron microscopic immunohistochemistry. Glaucomatous nerve heads showed increased labeling for collagen type IV along the margins of beams in the lamina cribrosa, due to accumulation of basement membrane-like materials. We also noted material in the pores of the laminar beams that labeled with antibodies to collagen types I, III and IV, but not elastin. In transected eyes, increased type IV labeling of laminar beam margins resulted solely from redundant astrocyte basement membranes. Extracellular matrix deposition within laminar pores was not observed following optic nerve transection; hence this may be a selective response to elevated intraocular pressure. This response may alter the biochemical composition of the lamina cribrosa and its function in patients with elevated intraocular pressure.