Types of collagen synthesised by the lens epithelial cells of human cataracts

Long-term myofibroblast persistence in the capsular bag contributes to the late spontaneous in-the-bag intraocular lens dislocation

Late spontaneous in-the-bag intraocular lens (IOL) dislocation is a complication presenting 6 months or later after cataract surgery. We aimed to characterize the cells in the lens capsules (LCs) of 18 patients with spontaneous late in-the-bag IOL dislocation. Patients' average age was 82.6 ± 1.5 years (range 72-98), and most of them had pseudoexfoliation syndrome (PEX). Cells from the LCs were positive for myofibroblast (αSMA), proliferation (Ki-67, PCNA), early lens development/lens progenitor (SOX2, PAX6), chemokine receptor (CXCR4), and transmembrane (N-cadherin) markers, while negative for epithelial (E-cadherin) marker. Moreover, the cells produced abundant fibronectin, type I and type V collagen in the nearby extracellular matrix (ECM). During ex vivo cultivation of dislocated IOL-LCs in toto, the cells proliferated and likely migrated onto the IOL's anterior side. EdU proliferation assay confirmed the proliferation potential of the myofibroblasts (MFBs) in dislocated IOL-LCs. Primary cultured lens epithelial cells/MFBs isolated from the LC of dislocated IOLs could induce collagen matrix contraction and continuously proliferated, migrated, and induced ECM remodeling. Taken together, this indicates that long-lived MFBs of dislocated IOLs might contribute to the pathogenic mechanisms in late in-the-bag IOL dislocation.

Capsular fibrosis: a review of prevention methods and management

Opacification of the posterior capsule caused by residual lens epithelial cells (LEC) is still the most frequent long-term complication of cataract surgery. Beside the opacification of the visual axis with posterior capsule opacification (PCO), resulting in a decrease in visual function, fibrotic changes may also have a mechanical effect on intraocular lens (IOL) position such as axial shift, decentration, tilt and capsule striae. In this article, two types of capsular fibrosis are explored, on the one hand the anterior capsule fibrosis and on the other hand PCO. Results from clinical trials concerning their causes, natural course, incidence, influencing factors and possible methods of prophylaxis are presented.

Effect of intraoperative trypan blue on lens epithelial cells - Histomorphological analysis

Introduction

Trypan Blue is an acid azo dye commonly used as a stain to distinguish viable from non-viable cells. It is a vital stain used intra operatively during cataract surgery to stain the external surface of the anterior lens capsule for better visualization.

Aim

To analyze the histomorphological effects of trypan blue on Lens Epithelial cells and the Basement Membrane on direct exposure by staining the internal surface of the anterior lens capsule during Small Incision Cataract Surgery.

Methods

Analytical cross sectional case control study. Anterior capsule specimens of 14 Patients undergoing small incision cataract surgery at Department of Ophthalmology, Govt Medical College Hospital, Thrissur were studied. Two specimens of anterior capsule taken from the same eye form the case and control. Control specimen (sample A) was removed first, after the routine external staining with trypan blue 0.06% (w/v) for 10 seconds. The stain was washed off by balanced salt solution in every case. Then trypan blue was injected under the remaining anterior capsule and case (Test) specimen (sample B) was obtained after direct contact of trypan blue to the internal surface (lens epithelial cells) for 1 minute. Histomorphological (qualitative and quantitative) examination of both specimens done.

Results

Qualitative data analysis was done by EPI INFO software.v.7. Intactness of LECs throughout the length was statistically significant in Sample A (p = 0.000027). Partial and complete detachment of Lens Epithelial Cells, degeneration, and nuclear smudging were significantly higher in Sample B. Qualitative analysis of the basement membrane showed significant edema of the basement membrane in sample B. Basement membrane splitting observed in sample B was not statistically significant. Quantitative data analyzed using independent t test. There was a statistically significant decrease in cell density in sample B with p value less than 0.05.

Discussion

Our study demonstrated that direct staining of the internal surface of anterior capsule with trypan blue affected LECs and the basement membrane. There were reduction in cell density, irreversible degeneration of Lens Epithelial Cells and basement membrane edema. Hence treating the internal surface of capsular bag with trypan blue may reduce incidence of Posterior capsular opacification.

[Capsule contraction syndrome in pseudophakia]

This is a review of the literature on capsule contraction syndrome (CCS) in pseudophakic patients that involves severe fibrosis along the margin of the anterior capsule's opening and progressive contraction of the capsular bag. Possible causes of CCS and principles of its prevention and treatment have been analyzed.

Self-assembled nanofiber coatings for controlling cell responses

Nanofibers are thought to enhance cell adhesion, growth, and function. We demonstrate that the choice of building blocks in self-assembling nanofiber systems can be used to control cell behavior. The use of 2 D-coated, self-assembled nanofibers in controlling lens epithelial cells, fibroblasts, and mesenchymal stem cells was investigated, focusing on gene and protein expression related to the fibrotic response. To this end, three nanofibers with different characteristics (morphology, topography, and wettability) were compared with two standard materials frequently used in culturing cells, TCPS, and a collagen type I coating. Cell metabolic activity, cell morphology, and gene and protein expression were analyzed. The most hydrophilic nanofiber with more compact network consisting of small fibers proved to provide a beneficial 2 D environment for cell proliferation and matrix formation while decreasing the fibrotic/stress behavior in all cell lines when compared with TCPS and the collagen type I coating. This nanofiber demonstrates the potential to be used as a biomimetic coating to study the development of fibrosis through epithelial-to-mesenchymal transition. This study also shows that nanofiber structures do not enhance cell function by definition, because the physico-chemical characteristics of the nanofibers influence cell behavior as well and actually can be used to regulate cell behavior toward suboptimal performance. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2252-2265, 2017.

Type I collagen accelerates the spreading of lens epithelial cells through the expression and activation of matrix metalloproteinases

PURPOSE

Matrix metalloproteinases (MMPs) are involved in posterior capsule opacification (PCO), but the mechanisms that promote MMP expression are yet to be determined. In this study, we investigated whether type I collagen, which is only detected in aged or cataractous lens capsules, affects the expression and activation of MMPs in primary-cultured chicken lens epithelial cells (LECs).

MATERIALS AND METHODS

Chicken LECs were isolated from chicken embryos and cultured in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum (FBS) on type I collagen-coated dishes. The activity of secreted MMPs was examined using gelatin zymography, and cell spreading was determined as the average area of randomly distributed cells. For some experiments, LECs were cultured in the presence of the broad-spectrum MMP inhibitor, GM6001. LECs cultured on uncoated dishes were used as controls. To examine the involvement of MMP in cell migration, a wound-healing assay was performed in the presence of the MMP inhibitor.

RESULTS

Chicken LECs constitutively express the pro-form of MMP-2. When LECs were cultured on type I collagen-coated dishes, they expressed the active form of MMP-2 and the pro-form of MMP-9. This expression and activation by type I collagen was also observed in the human LEC line SRA-01/04, but not the human Müller glial cell line, MIO-M1. Type I collagen enhanced cell spreading, which was suppressed by the MMP inhibitor. Type I collagen also accelerated α-smooth muscle actin expression. In addition, LEC migration was inhibited by the MMP inhibitor in a dose-dependent manner in the wound-healing assay.

CONCLUSION

Type I collagen promotes the expression and activation of MMPs in a LEC-specific manner. These results suggest that type I collagen may play a role in PCO development.

Derivation of multiple cranial tissues and isolation of lens epithelium-like cells from human embryonic stem cells

Human embryonic stem cells (hESCs) provide a powerful tool to investigate early events occurring during human embryonic development. In the present study, we induced differentiation of hESCs in conditions that allowed formation of neural and non-neural ectoderm and to a lesser extent mesoderm. These tissues are required for correct specification of the neural plate border, an early embryonic transient structure from which neural crest cells (NCs) and cranial placodes (CPs) originate. Although isolation of CP derivatives from hESCs has not been previously reported, isolation of hESC-derived NC-like cells has been already described. We performed a more detailed analysis of fluorescence-activated cell sorting (FACS)-purified cell populations using the surface antigens previously used to select hESC-derived NC-like cells, p75 and HNK-1, and uncovered their heterogeneous nature. In addition to the NC component, we identified a neural component within these populations using known surface markers, such as CD15 and FORSE1. We have further exploited this information to facilitate the isolation and purification by FACS of a CP derivative, the lens, from differentiating hESCs. Two surface markers expressed on lens cells, c-Met/HGFR and CD44, were used for positive selection of multiple populations with a simultaneous subtraction of the neural/NC component mediated by p75, HNK-1, and CD15. In particular, the c-Met/HGFR allowed early isolation of proliferative lens epithelium-like cells capable of forming lentoid bodies. Isolation of hESC-derived lens cells represents an important step toward the understanding of human lens development and regeneration and the devising of future therapeutic applications.

Post-operative capsular opacification: a review

Post-operative capsular opacification is a multifactorial physiological consequence of cataract surgery. Opacification involving the central posterior capsule has a significant impact on high and low contrast acuity and low contrast sensitivity. The assessment of Posterior Capsule Opacification (PCO) on cadaver eyes, experimental studies, culture models and in clinical studies has provided an understanding of its pathogenesis. The proliferation, migration and abnormal differentiation of residual lens epithelial cells and fibers in the capsular bag have been implicated in the pathogenesis of PCO. The incidence and severity of PCO correlates to the meticulous use of surgical techniques, IOL optic edge designs and IOL materials. This article summarizes the clinical studies with recommendations for retarding the development of central PCO. It discusses experiments with pharmacological agents broadly categorized as anti-inflammatory, immuno-modulating, antiproliferative, antiadhering, antitransdifferentiating agents for the prevention of PCO. These studies will remain critical for future endeavors undertaken for eradication of PCO.

Expression of alphasmooth muscle actin in lens epithelia from human donors and cataract patients

In order to re-evaluate functional implications of alphasmooth muscle actin (alphaSMA) expression in lens epithelial cells (LECs), we assessed its presence in donor lenses without visible opacities (DON), lenses with mature cataract (CAT), and cataractous lenses with posterior subcapsular opacities (PSO) or anterior subcapsular fibrosis (ASF). The levels of alphaSMA and transforming growth factor-beta2 (TGFbeta2) mRNAs were measured by classical and real-time PCR. Expression and structural organisation of alphaSMA protein and beta-catenin were monitored by Western blotting and confocal microscopy. All DON analysed contained measurable amounts of alphaSMA mRNA. In CAT without and with PSO, mRNA expression was increased and, again more than doubled in ASF. TGFbeta2 mRNA expression varied widely between the individual samples but was slightly increased in ASF. No correlation existed between alphaSMA or TGFbeta2 expression and the age of the donors in any of the lens categories. Confocal microscopy revealed that, in DON and CAT, alphaSMA was preferentially expressed in a simple granular pattern in single or small clusters of LECs within a normally shaped cobblestone epithelium. Locally, the granules were merged into short stretches at the cell margin. In CAT, a few abnormally shaped cells contained polygonal alphaSMA structures and short stress fibres. In CAT with PSO and ASF, polygons and stress fibre bundles predominated in spindle-shaped cells. Expression patterns of different complexity were often present in the same epithelium. Apical polygons and basal stress fibres were detected within the same cell and may reflect instability of the interface between epithelium and cortical fibres and changes in adhesion to the capsule, respectively. High levels of betacatenin mRNA and protein were present in all lens types. However, with increasing complexity of alphaSMA organisation, betacatenin staining disappeared from the cell margin and basal infoldings and was shifted towards the cytoplasm and nucleus. The presence of alphaSMA in DON, the absence of any correlation between mRNA level and age, and the modest increase in complexity of alphaSMA-containing structures in CAT argue against an inevitable link between alphaSMA expression and the development of age-related cataract. Low levels of alphaSMA expression may reflect repair of normal wear and tear. In pathologic situations such as PSO and ASF, persisting stimulation and additional incentives may induce increased alphaSMA expression and more elaborate patterning, eventually leading to completion of EMT.

Vitronectin is significant in the adhesion of lens epithelial cells to PMMA polymers

A major complication of intraocular lens surgery is diminished visual acuity caused by the regrowth of lens epithelial cells (secondary cataract). Polymethylmethacrylate (PMMA) is a commonly used intraocular lens material. This study addresses the mechanisms underlying the initial adhesion of lens epithelial cells to PMMA and a functionalized PMMA-based terpolymer known to inhibit cell proliferation. Rabbit lens epithelial cells were cultured on the test polymer surfaces in medium containing serum depleted of either fibronectin or vitronectin (or both) to identify the role of these proteins in the initial process of cell adhesion. Adherent cells were quantitated after 60 min, and the actin cytoskeleton and focal contact formation were compared in each serum treatment on both polymers. Vitronectin was significantly more effective for initial cell attachment to both polymers than fibronectin. Normal cell spreading on PMMA required vitronectin and was independent of fibronectin, whereas cell spreading on the terpolymer was abnormal and required the presence of fibronectin and vitronectin together. Together, these results help to explain the inhibition of cell proliferation previously shown on the functionalized PMMA. This work contributes to the design of a polymer for use in intraocular lenses that inhibits proliferation of the target cells.

Anterior lenticonus: histological evaluation and approach for cataract surgery

PURPOSE

To present 2 cases of anterior lenticonus in patients without Alport's syndrome, a surgical technique of cataract extraction in eyes with anterior lenticonus, and histological results of lenticonus specimens obtained intraoperatively.

SETTING

From St. Eriks Eye Clinic, Karolinska Institute, Stockholm, Sweden.

METHODS

Two otherwise healthy patients presented with anterior lenticonus but no history of Alport's or other pathology. Best corrected visual acuity (BCVA) was decreased. Both patients had cataract extraction by phacoemulsification with intraocular lens implantation under topical anesthesia. Two continuous curvilinear capsulorhexes (CCCs) were created. The entire lenticonus was embedded in formaldehyde buffer 4% for histological analysis.

RESULTS

In the first patient, BCVA did not improve postoperatively because of amblyopia. The patient subjectively reported a substantial improvement in visual field clarity. The surgical and postoperative course in the other patient was uneventful. The sections were positive for collagen types IV and VI, and the arrangement of the collagen fibers was highly irregular.

CONCLUSION

Anterior lenticonus was detected in patients without Alport's syndrome who were otherwise healthy. A modified 2-step CCC technique can be used to make cataract surgery in such eyes safe and relatively easy.

Immunohistochemical analysis of lens epithelial-derived membranes following cataract extraction in the dog

The objective of the study was to characterize the morphologic and immunohistochemical features of lens epithelial-derived proliferative membranes from the anterior segment of canine globes. These features were correlated with those previously identified for diseases resulting from lens epithelial cell (LEC) proliferation including posterior capsular opacification, traumatic subcapsular cataract, and subcapsular plaques associated with hypermature cataracts. Sixteen canine globes were removed as a result of glaucoma or other complications following cataract extraction. Light microscopic and immunohistochemical analysis was performed on sections from formalin-fixed, paraffin-embedded globes. The tissues were stained with a variety of antibodies for cellular markers for LECs, growth factors or other cellular constituents relevant to cellular metaplasia and proliferation. The membranes were composed of monolayers or multilayers of spindle-shaped cells on the external surfaces of the anterior and posterior lens capsule, ciliary processes, iris leaflets, and iridocorneal angle, and they could be seen extending from an obvious monolayer of LEC within the capsular sac. Variably, scattered pigment cells, presumably of uveal origin, were concurrently present. Cellular components of the membranes stained positive for vimentin, transforming growth factor-beta, basic fibroblast growth factor, and smooth muscle actin. An amorphous eosinophilic extracellular matrix consisting predominately of collagen was associated with the membranes. Proliferative anterior segment membranes following cataract surgery were morphologically and immunohistochemically similar to cellular and matrix components of posterior capsular opacification and capsular plaques seen with hypermature cataracts, both of which result from metaplasia and proliferation of LEC. The presence of these LEC-derived membranes in association with secondary glaucoma suggests that exuberant proliferation of LEC outside the confines of the lens capsular sac may cause pathologic alterations in the eye following cataract surgery in the dog.

Morphologic alterations in the anterior lens capsule of canine eyes with cataracts

OBJECTIVE

To examine the morphologic changes in the anterior lens capsule and lens epithelium of canine eyes with cataracts.

SAMPLE POPULATION

Anterior lens capsules from the eyes of 25 dogs with cataracts and from an additional 10 canine globes with lenses subjectively assessed to be normal.

PROCEDURE

Thickness of each anterior lens capsule was measured by use of a digital microscopic camera and imaging software. All 25 capsules from eyes with cataracts were submitted for light microscopy; 4 were also submitted for electron microscopy.

RESULTS

Thickness of the anterior lens capsule increased with age for the normal lenses and the lenses with cataracts; the change with age was similar for both groups. Light microscopy revealed fibrous metaplasia of lens epithelial cells in 7 of 25 anterior lens capsules with focal thickenings of the posterior aspect of the capsule. Electron microscopy revealed deposition of collagen and basement membrane-like material by fibroblast-like cells.

CONCLUSIONS

Results indicate that thickness of the anterior lens capsule in dogs increases with age and that this increase in thickness is not significantly different between normal lenses and lenses with cataracts. In addition, epithelial cells from lenses with cataracts may undergo metaplasia to form plaques composed of fibrous tissue and ectopic basement membrane produced by epithelial cells.

Histologic and immunohistochemical characterization of lens capsular plaques in dogs with cataracts

OBJECTIVE

To determine histologic and immunohistochemical characteristics of the multifocal adherent plaques that commonly develop on the internal surfaces of the anterior and posterior lens capsules in dogs with cataracts.

SAMPLE POPULATION

31 anterior and 4 posterior capsular specimens collected during lens extraction surgery in dogs with cataracts.

PROCEDURE

Specimens were evaluated, using light and transmission electron microscopy. Immunohistochemical techniques were used to localize cytokeratin, vimentin, alpha-smooth muscle-specific actin, fibronectin, tenascin, and transforming growth factor-beta (TGF-beta) within plaques.

RESULTS

Histologically, plaques comprised elongated spindle-shaped cells that formed a placoid mass. Cells were embedded in an extracellular matrix containing collagen fibrils, often with duplicated or split basement membranes. Immunohistochemically, normal lens epithelial cells and cells within plaques stained for vimentin. Most cells and some areas of the extracellular matrix within plaques stained for TGF-beta and alpha-smooth muscle-specific actin. Fibronectin and tenascin were also detected in the extracellular matrix.

CONCLUSIONS AND CLINICAL RELEVANCE

Canine lens capsular plaques are histologically and immunohistochemically similar to posterior capsule opacification and subcapsular cataracts in humans, which suggests that the canine condition, like the human conditions, is associated with fibrous metaplasia of lens epithelial cells. Transforming growth factor-beta may play a role in the genesis of capsular plaques. Because severity of plaques was correlated with stage of cataract development, earlier surgical removal of cataracts may be useful to avoid complications associated with plaque formation.

Degeneration and transdifferentiation of human lens epithelial cells in nuclear and anterior polar cataracts

PURPOSE

To study the possible mechanisms of cataractogenesis by evaluating the characteristics of cataractous lens epithelial cells (LECs) in different types of human cataract.

SETTING

Kangnam St. Mary's Hospital, The Catholic University of Korea, Seoul, Korea.

METHODS

Lens epithelial cells attached to the anterior capsules in eyes with nuclear or anterior subcapsular were analyzed for morphological characteristics by electron microscopy and for cellular characteristics by immunohistochemistry.

RESULTS

Human LECs beneath the anterior capsule were degenerated in nuclear cataracts and were transdifferentiated in anterior polar cataracts. In senile nuclear cataractous lenses, LECs beneath the anterior capsule showed degenerative changes in morphology. In nuclear cataracts, LECs were immunohistochemically positive for cytokeratin and vimentin, while those in anterior polar cataracts were positive for vimentin only. The LECs of anterior subcapsular cataracts were transdifferentiated into spindle-shaped fibroblast-like cells without cellular junctions and embedded within a fibrillar meshwork mass. The extracellular matrixes in the anterior capsule of anterior subcapsular cataracts were immunohistochemically positive for fibronectin, laminin, collagen type I, and collagen type IV.

CONCLUSIONS

Lens epithelial cells in different types of cataracts have distinct cellular characteristics and may possess a bipotential nature with the ability to transdifferentiate into mesenchymal cells. This may be an underlying mechanism for the development of cataract and capsule opacification.

Histology of anterior capsule fibrosis following phacoemulsification

PURPOSE

To determine the histology and immunohistochemistry of anterior capsule fibrosis.

SETTING

Department of Ophthalmology and Neurosurgery and Institute of Pathology, University of Siena, Siena, Italy.

METHODS

Tissue sections from 3 patients with anterior capsule fibrosis after phacoemulsification and intraocular lens implantation were examined histologically.

RESULTS

The proliferating tissue was devoid of vessels and composed of dense fibrous tissue and numerous activated fibroblasts with contractile capacity (myofibroblasts). No TGF-beta, which is the most important cytokine in modulating myofibroblasts, was present in the fibrotic tissue.

CONCLUSION

The absence of the cytokine TGF-beta and inflammatory cells in the proliferating tissue confirms the unique character of the reparative activity within the eye.

Capsular bag distention syndrome noted 5 years after intraocular lens implantation

PURPOSE

To describe a case of capsular bag distention syndrome with opaque contents noted 5 years after intraocular lens implantation.

METHODS

A 66-year-old man underwent phacoemulsification after circular capsulorhexis and intraocular lens implantation in the left eye. Five years later, the posterior capsule was vaulted far posteriorly, the capsular opening was apparently sealed by the lens optic, and the bag contents were slightly opacified. Two years later, the contents of the hyperdistended capsular bag showed intensified opacity, causing definite blurred vision.

RESULTS

The opacified medium was emptied from the capsular bag posteriorly into the vitreous after Nd:YAG laser capsulotomy, and the distended capsule was restored.

CONCLUSIONS

Our findings suggest that the contents were collagens produced by residual lens epithelial cells or necrotic and/or apoptotic autolyzed lens epithelial cells.

Relationship between intraocular lens biomaterials and posterior capsule opacification

PURPOSE

To determine whether posterior capsule opacification (PCO) is influenced by intraocular lens (IOL) material.

SETTING

A British teaching hospital eye department.

METHODS

Ninety eyes were prospectively randomized to receive a poly(methyl methacrylate) (PMMA), silicone, or AcrySof IOL. All lenses had 6.0 mm optics and PMMA haptics. A standardized surgical protocol was performed by a single surgeon using an extracapsular technique with capsulorhexis. Patients having surgical complications were excluded and all patients had standardized medication and follow-up. Posterior capsule opacification was assessed by a digital retroillumination camera using a dedicated software program based on the analysis of texture in the image and calculated as the percentage area of opacified capsule. Data were analyzed 2 years postoperatively.

RESULTS

There was a significant difference in percentage of PCO at 2 years among the three lens types (P < .0001). The AcrySof lenses were associated with less PCO (median 11.75%) than PMMA (43.65%) and silicone (33.50%) lenses (P < .001 and P = .025, respectively). The difference between PMMA and silicone lenses was not statistically significant.

CONCLUSION

Intraocular lenses made from AcrySof were associated with a significantly reduced degree of PCO.