Cellular adhesiveness on implanted lenses in monkeys

Evaluation of cellular adhesions on silicone and poly(methyl methacrylate) intraocular lenses in monkey eyes: an electron microscopic study

PURPOSE

To assess the biocompatibility of intraocular lens (IOL) material by studying the number of cells adhering to IOLs in monkey eyes.

SETTING

Department of Ophthalmology, Kyushu University, Fukuoka, Japan.

METHODS

Silicone or poly(methyl methacrylate) (PMMA) IOL implantation was performed in 21 monkeys. One eye of each animal had surgery. The IOL-implanted eyes were enucleated 1, 2, 3, 5, and 7 days and 1, 3, 4, 5, and 9 months after the procedure. One eye was studied at each time. Cells on the anterior IOL surface were photographed using a scanning electron microscope, counted and assessed with NEC, Graphtec, and Nikon equipment, and then observed using a transmission electron microscope.

RESULTS

Leukocytes, macrophages, and giant cells were found on the anterior IOL surface. Numerous cells were observed on the PMMA IOLs in the early postoperative period; they gradually decreased. Few cells were seen on the silicone IOLs during the course of the study. The giant cells became larger during the postoperative period.

CONCLUSION

The foreign-body reaction to silicone IOLs in monkey eyes was less than that to PMMA IOLs.

Deposition of extracellular matrix on silicone intraocular lens implants in rabbits

PURPOSE

To examine the deposition of extracellular matrix on silicone intraocular lenses (IOLs) implanted experimentally into rabbit eyes by electron microscopy and to determine the immunolocalization of extracellular matrix components, including collagen types and cellular fibronectin, on these IOLs.

METHODS

We performed phacoemulsification and aspiration of the crystalline lens and implanted a foldable silicone IOL in the capsular bag of one eye of each of 26 adult albino rabbits under general anesthesia. After 8 weeks the animals were killed and the eyes were enucleated. The silicone IOLs were processed for electron microscopy and for immunohistochemical detection of collagen types I, III, and IV and cellular fibronectin.

RESULTS

Electron microscopy revealed deposition of a presumed cell matrix complex on the optic portion of all silicone IOLs, as well as the adhesion of presumed macrophages and foreign-body giant cells. Cellular deposits showed immunoreactivity for cellular fibronectin. Fibrous or membranous deposits exhibited immunoreactivity for cellular fibronectin and collagen types I and III. A few type IV collagen-immunoreactive deposits were also seen.

CONCLUSION

Deposits of extracellular matrix components were observed on silicone IOLs. These deposits may form the scaffolding for the adhesion and proliferation of cells. These matrix components appeared to be the products of cells adhering to the surfaces of IOLs, including lens epithelial cells, macrophages and foreign-body giant cells, indicating that the process of granulation was incomplete.

Deposition of extracellular matrix on intraocular lenses in rabbits: an immunohistochemical and transmission electron microscopic study

BACKGROUND

We examined by transmission electron microscopy the accumulation of extracellular matrix on intraocular lenses (IOLs) implanted experimentally into rabbit eyes, and evaluated the immunolocalization of such extracellular matrix components as collagen types I, III, and IV, and cellular fibronectin on these IOLs.

METHODS

Phacoemulsification and aspiration of the crystalline lens were performed and an IOL was implanted into the capsular bag of each eye of each of 16 adult albino rabbits under general anesthesia. After up to 12 weeks, the animals were killed and the IOLs were removed. Specimens were processed for transmission electron microscopy or for immunohistochemical detection collagen types I, III, and IV, and cellular fibronectin.

RESULTS

Transmission electron microscopy revealed an accumulation of extracellular matrix between the residual anterior lens capsule and the surface of an IOL explanted 4 weeks after surgery. Collagen types I and III and cellular fibronectin were detected immunohistochemically on each IOL in association with cellular deposits. Type IV collagen-immunoreactive matrix was not seen on the optic portion, but was detected on the haptic portion of one of six IOLs examined.

CONCLUSION

Each component of the extracellular matrix that is deposited on the IOL supplies scaffolding for the adhesion and proliferation of cells. These components are considered to be produced by cells such as lens epithelial cells and macrophages that adhere to the IOL surface.

Lens epithelial cell outgrowth and matrix formation on intraocular lenses in rabbit eyes

PURPOSE

To evaluate the presence and distribution of lens epithelial cells (LECs) and extracellular matrix on intraocular lenses (IOLs) implanted in the capsular bag in rabbit eyes.

SETTING

Department of Ophthalmology, Wakayama Medical College, Wakayama, Japan.

METHODS

Five adult albino rabbits had phacoemulsification and IOL implantation in both eyes. Two or 11 months later, the animals were killed by intravenous pentobarbital. The IOLs were removed and observed under scanning and transmission electron microscopy.

RESULTS

In addition to the macrophages and giant cells on the IOLs, all eyes had a monolayer of flattened cells growing out from the residual anterior lens capsule and a fibrous meshwork of extracellular matrix. Unlike those of a macrophagic origin, these cells had no central cytoplasmic elevation of nuclei and few cell surface microvilli and were considered to be proliferating LECs.

CONCLUSION

Lens epithelial cells are involved in the eye's cellular reaction to IOLs and in the formation of extracellular matrix on IOLs. Further study of LEC behavior on IOLs should be done to improve IOL biocompatibility.

Extracellular matrix on intraocular lenses

We examined the distribution of extracellular matrix components in the proteinaceous matrix on explanted IOLs using immunohistochemistry to clarify the nature of proteinaceous deposits on the surfaces of IOLs. We examined 15 polymethylmethacrylate (PMMA) IOLs and one silicone IOL explanted from patients. The IOLs were immunostained for cellular fibronectin, types I and IV collagen, and vitronectin. Various amounts of fibronectin, types I and IV collagen, and vitronectin were detected in the extracellular matrix on all IOLs with cellular deposits. Types I and IV collagen and cellular fibronectin were present in the extracellular matrix and were probably the products of cells adhering to the IOLs. Vitronectin in the fibrous extracellular matrix appeared to represent an adsorption material derived from the aqueous humor. These proteinaceous deposits associated with cellular deposits indicate unsuccessful formation of granulation tissue and could influence IOL biocompatibility.

Natural history of cellular deposits on the anterior intraocular lens surface

Previous cytopathological studies have demonstrated the presence of cellular deposits on the poly(methyl methacrylate) (PMMA) intraocular lens (IOL) surface. In this prospective study, IOL surface specular microscopy was used to document the natural history of these deposits in the first year following PMMA IOL implantation. Intraocular lens surface specular microscopy was performed 1, 3, 6, and 12 months after endocapsular cataract surgery in 27 otherwise normal eyes. Postoperatively, IOLs were assessed for the presence of inflammatory cells, with the number of cells graded from 0 (none) to 4 (many). Two inflammatory cell types were visualized: small and giant cells. Small cells were found on 81.5% of IOLs at 1 month, 73.1% at 3 months, and 30.4% at 12 months. Small cells were found in only small numbers (peak mean cell score of 1.26 +/- 0.94 at 1 month). Giant cells were found on 59.3% of lenses at 1 month, 73.1% at 3 months, and 39.1% at 12 months. The number of giant cells on each lens peaked at 3 months (mean cell score 2.0 +/- 1.55), when 50% of lenses achieved a giant cell score of 3 or 4. Inflammatory cell deposits are, therefore, a normal occurrence on the PMMA IOL surface for up to 1 year after surgery. This cellular response consists of two distinct processes: a small cell response, which peaks by 1 month, and a later giant cell response, which peaks at 3 months.

Cellular fibronectin on intraocular lenses explanted from patients

We investigated the origin of fibronectin (FN) on five posterior and four anterior chamber explanted intraocular lenses (IOLs) using immunohistochemical methods. Cellular deposits (assumed to be macrophages) and fibrous or membrane-like proteinaceous deposits on the IOLs showed immunoreactivity to an antibody against cellular FN. These proteinaceous deposits were believed to be products of the cells that adhered to the IOLs.