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

The E156K mutation in the CRYAA gene affects the epithelial-mesenchymal transition and migration of human lens epithelial cells

Purpose

To investigated the biological effects of E156K-mutated αA-crystallin (CRYAA) in human lens epithelial cells (HLECs).

Methods

FLAG-tagged, human, full-length, wild-type (WT), or E156K-mutated CRYAA was expressed in HLECs under CRYAA knockdown. CRYAA expression was determined by quantitative reverse transcription polymerase chain reaction and western blotting (WB). Rhodamine cytoskeleton staining was used to observe the changes in cell morphology following transfection with WT or E156K-mutated CRYAA plasmids. WB was performed to assess the expression of markers related to epithelial-mesenchymal transition (EMT) and migration.

Results

Rhodamine cytoskeleton staining revealed changes in the morphology of cells transfected with E156K-mutated CRYAA and opposite responses occurred after treatment with a β-catenin inhibitor. Cells transfected with E156K-mutated CRYAA expressed remarkably higher levels of the mesenchymal biomarkers N-cadherin and vimentin but decreased levels of the epithelial biomarker E-cadherin, whereas opposite trends were observed in cells treated with the β-catenin inhibitor, ICG001. The migratory capability of E156K-mutated CRYAA cells was significantly greater than that of WT cells (P < 0.001). This effect was accompanied by significantly increased expression levels of phosphorylated (p)-focal adhesion kinase (FAK) and p-Src. These changes were decreased significantly by treatment with FAK and Src inhibitors.

Conclusion

E156K-mutated CRYAA induced EMT, in which the HLECs lost cell polarity, and acquired a mesenchymal phenotype with greater migratory capability. These biological effects may be associated with activation of the Wnt/β-Catenin and FAK/Src signaling pathways.

Long noncoding RNA expression profile in HLE B-3 cells during TGF-β2-induced epithelial-mesenchymal transition

Background

Recent evidence has shown that long noncoding RNAs (lncRNAs) are involved in the process of epithelial-mesenchymal transition (EMT). However, little research has focused on the expression profile of lncRNAs during EMT in human lens epithelial cells (LECs) and their functions have not yet been described.

Methods

Dysregulated lncRNAs and mRNAs in normal human lens epithelial B-3(HLE B-3) cells and during transforming growth factor β₂(TGF-β₂)-induced EMT were analyzed via lncRNA microarray. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway analyses of differentially expressed mRNAs were performed to identify their functions and pathologic pathways. Six candidate lncRNAs were validated via quantitative real-time reverse transcription polymerase chain reaction(qRT-PCR) to confirm the microarray data.

Results

A total of 775 lncRNAs (325 up-regulated and 450 down-regulated) and 935 mRNAs (329 up-regulated and 606 down-regulated) were differentially expressed in HLE B-3 cells during TGF-β2-induced EMT compared to normal HLE B-3 cells. GO and KEGG Pathway analyses indicated the functions of differentially expressed mRNAs in the TGF-β₂-induced EMT in HLE B-3 cells. qRT-PCR confirmed the trends indicated in microarray analysis for all 6 candidate lncRNAs.

Conclusion

Our study lays the foundation for future research in lncRNAs related to EMT in HLE B-3 cells and could provide new avenues for the prevention and treatment of posterior capsule opacification (PCO).

Differential responses of human lens epithelial cells to intraocular lenses in vitro: hydrophobic acrylic versus PMMA or silicone discs

BACKGROUND

The purpose of this study was to determine the influence of different materials of intraocular lenses (IOLs) on human lens epithelial cell behavior, including adhesion, migration, proliferation, apoptosis, and epithelial-mesenchymal transdifferentiation (EMT) in vitro.

METHODS

Human lens epithelial cells (SRA 01/04) were grown on hydrophobic acrylic (Acrysof), polymethylmethacrylate (PMMA), and silicone IOLs. Cellular adhesion, migration, proliferation, and apoptotic assays were performed to assess cell behavior. The expression of EMT markers (fibronectin and type I collagen) produced by cells on IOLs was determined by immunoblotting and immunocytochemistry.

RESULTS

Human lens epithelial cells exhibited preferred adhesion and reduced apoptosis when cultured on acrylic IOLs, in comparison to PMMA and silicone IOLs. Cells grown on acrylic lenses formed a confluent epithelial monolayer. Migration of lens epithelial cells under the acrylic lens was substantially blocked in an in vitro assay. In contrast, cells grown on PMMA and silicone lenses displayed a spindle-shaped, myofibroblast-like morphology, increased apoptosis, reduced adhesion, and enhanced production of EMT proteins such as fibronectin and type I collagen. The migration of lens epithelial cells under PMMA and silicone IOLs was substantial in the in vitro assay.

CONCLUSION

This report demonstrates that hydrophobic acrylic lenses are more capsular biocompatible than PMMA and silicone lenses. The in vitro assays are reliable measurements for evaluating the responses of human lens epithelial cells to different IOL materials, and could advance our understanding of the preferential capsular opacification conferred by different IOL materials.

Accumulation of thrombospondin-1 in post-operative capsular fibrosis and its down-regulation in lens cells during lens fiber formation

Thrombospondin-1 (TSP-1) is a glycoprotein involved in activation of latent transforming growth factor beta (TGFbeta) expression. We examined changes in its expression pattern during human capsular opacification (PCO) and anterior subcapsular cataractogenesis (ASC), as well as in a healing injured mouse lens. Its expression pattern was also compared in a mouse embryonic lens with that in an adult lens. Based on immunohistochemistry under light microscopy, TSP-1 expression and other matrix components were evident in the anterior epithelium of an uninjured human lens, whereas fiber-differentiating cells in the equator of human lens lack TSP-1 immunoreactivity. In contrast, in post-operative human lens epithelial or fibroblastic cells, there was TSP-1 immunoreactivity, whereas it decreased in fiber-differentiating cells in PCO. Matrix components accumulated on the healing capsule also labeled with anti-TSP-1 antibody like antibodies against collagen I, IV, V and laminin. In uninjured, injured mouse lens epithelial cells and its matrix, there was TSP-1 expression. Embryonic lens cells in the posterior pole, undergoing differentiation to fiber cells, began to express TSP-1 protein at embryonic day (E) 11.5 whereas anterior epithelial cells started to express it at E13.5 in association with marked expression in central fiber cells. At E16.5, TSP-1 was detected in fibers just beneath the anterior epithelium, but the fiber mass showed minimal expression. At E18.5 and post-natally day 1, lens fiber TSP-1 expression was no longer seen. On the other hand, it was evident in both intact human anterior epithelial and dispersed mouse cells. The results indicate that there is TSP-1 expression in uninjured human and mouse lens epithelial cells and their fibrous tissue. In contrast, in post-operative lens cells differentiating to fiber cells, its expression levels decline. Further study is needed to clarify the roles of TSP-1 in modulating lens cell phenotype expression.

Deposition of silicone oil droplets in the residual anterior lens capsule after vitrectomy and lensectomy in rabbits

AIM

To examine the histology of preserved anterior lens capsule in vitrectomised and lensectomised rabbit eyes with and without silicone oil tamponade.

METHODS

Forty adult Japanese albino rabbits received two port vitrectomy and lensectomy with or without silicone oil tamponade in one eye under both general and topical anaesthesia. Anterior lens capsule was preserved during operation. After healing intervals residual anterior capsule was histologically observed under light or electron microscopy.

RESULTS

Immediately after operation, cuboidal lens epithelial cells were observed on the posterior surface of the preserved anterior capsule. During healing intervals in eyes with or without silicone oil tamponade, regenerated lens structure of Sommerring's ring and fibrous tissue formed in the peripheral and central areas of the residual capsule, respectively. Ultrastructural observation revealed the presence of many vacuoles amid matrix accumulation on the posterior capsular surface, suggesting the deposition of emulsified silicone oil droplets.

CONCLUSION

Lens epithelial cells produce regenerated lenticular structure and fibrous tissue on the residual capsule following vitrectomy and lensectomy in rabbits. Silicone oil droplets formed by its emulsification deposit in extracellular matrix accumulated on the posterior surface of the anterior capsule. Emulsified silicone may potentially enhance opacification of residual anterior capsule following pars plana vitrectomy by silicone oil deposition and subsequent activation of lens epithelial cells.

Relationship between posterior capsule opacification and intraocular lens biocompatibility

The type of healing process that occurs in response to cataract surgery and intraocular lens (IOL) implantation is dependent on a complex set of variables. Their interactions determine whether or not optical clarity is restored as a result of this procedure. In this process, wound healing entails cells undergoing either epithelial-mesenchymal transition, resulting in the generation of fibroblastic cells and accumulation of extracellular matrix, or lenticular structure formation. Such desperate cellular behaviors are regulated by the localized release of different cytokines, including transforming growth factor beta and fibroblast growth factors, which can result in post-operative capsular opacification. Other factors affecting the biological and mechanical outcome of IOL implantation are its composition, surface properties and shape.

Induction of apoptosis by the calcium antagonist mibefradil correlates with depolarization of the membrane potential and decreased integrin expression in human lens epithelial cells

BACKGROUND

Posterior capsule opacification is still the major complication in cataract surgery and is caused by migration and proliferation of residual lens epithelial cells. The challenge of a suitable therapy to inhibit capsule opacification is to specifically interfere with cellular mechanisms. Our approach using the T-calcium channel antagonist mibefradil is based on the hypothesis that this drug inhibits the signaling pathways mediated by cell adhesion.

METHODS

The influence of mibefradil dihydrochloride was investigated on primary human lens epithelial cells (hLEC) from cataract surgery and on the human lens cell line HLE-B3. Apoptosis was quantitatively analyzed by flow cytometry (% increase of the sub-G1 peak), and verified by confocal microscopy (annexin V-biotin, TUNEL reaction). The membrane potential was detected by a membrane potential-sensitive dye. Integrin expression and proliferation were measured by flow cytometry. T-calcium channels in hLEC were verified by the whole-cell configuration of the patch-clamp technique.

RESULTS

Mibefradil induced apoptosis in hLEC. Early signs of apoptosis were observed after only 4 h of incubation with mibefradil, accompanied by a significantly reduced cell area. Apoptosis correlated with inhibited integrin expression, reduced proliferation and the depolarization of the membrane potential. We could identify calcium channels of the T-type in our primary hLEC.

CONCLUSIONS

We suggest that depolarization of the membrane potential and the inhibition of integrin expression leads to the loss of cell adhesion, which is the reason for the induction of apoptosis. Thus, mibefradil seems to be a suitable drug to prevent cell adhesion, migration and proliferation.

Lens epithelial cell reaction after implantation of different intraocular lens materials

PURPOSE

To determine the influence of intraocular lens (IOL) material on anterior capsular opacification and membrane growth over the anterior IOL surface in patients who have undergone standardized small-incision cataract surgery and foldable IOL implantation in the capsular bag.

DESIGN

Randomized controlled trial.

PARTICIPANTS

Eighty-eight cataract patients (88 eyes).

METHODS

Patients were randomly assigned to receive one of four different foldable IOLs after phacoemulsification: Storz Hydroview H60M, Corneal ACR6D, AMO SI40NB, and Alcon AcrySof MA60BM. Examinations on days 7, 30, 90, 180, 360, and 720 after surgery included ophthalmologic examination, slit-lamp biomicroscopy, and photography using red reflex and focal illumination of the anterior IOL surface.

MAIN OUTCOME MEASURES

Best-corrected visual acuity was measured at each examination. In addition, the anterior capsule opacification and the membrane growth on the anterior IOL surface were graded according to a subjective method by the same researcher.

RESULTS

The fibrosis of the anterior capsule was more frequently observed in the group using Corneal ACR6D and AMO SI40NB. The Hydroview and ACR6D groups showed a higher percentage of cases with membrane growth from the rhexis edge on the anterior IOL surface. AcrySof showed the lowest presence of fibrosis of the anterior capsule, and no membrane growth was noted.

CONCLUSIONS

Anterior capsule opacification is an index of IOL biocompatibility. The natural location of lens epithelial cells (LECs) precludes the possibility of the IOL's design influencing the anterior capsule behavior. The local response of LECs varies according to the IOL studied. This may be related to the chemical and physical properties of the materials used in the different IOLs.

Histology of anterior capsule opacification with a polyHEMA/HOHEXMA hydrophilic hydrogel intraocular lens compared to poly(methyl methacrylate), silicone, and acrylic lenses

To evaluate the biocompatibility of various materials including a poly(2-hydroxyethyl methacrylate [HEMA])/(6-hydroxyhexyl methacrylate [HOHEXMA]) hydrophilic hydrogel intraocular lens (IOL) (Hydroview, Bausch & Lomb). Department of Ophthalmology, Wakayama Medical University, Wakayama, Japan. Ten opacified anterior capsules were extracted, including 3 specimens with the Hydroview IOL. They were processed for light and electron microscopy. Immunohistochemistry for alpha-smooth muscle actin (alpha SMA) and collagen types was also done to evaluate mesenchymal transition in lens epithelial cells (LECs). Anterior capsule opacification (ACO) in the 3 specimens with a polyHEMA/HOHEXMA hydrogel IOL contained more LECs and less extracellular matrix (ECM) than in the specimens with IOLs of other materials. Ultrastructural observation showed a well-organized collagenous ECM in tissues with an IOL of poly(methyl methacrylate), silicone, or soft acrylic material; an immature matrix was seen in specimens with a hydrogel IOL. The alpha SMA-positive LECs and collagen I and III, both types related to capsular wound healing, were detected in ACO.A polyHEMA/HOHEXMA hydrogel IOL facilitated the proliferation of LECs on the anterior capsule compared with other IOLs of other materials but did not completely suppress mesenchymal transition of LECs. Extracellular matrix accumulation appeared immature and less with a polyHEMA/HOHEXMA hydrogel IOL.

TGFbeta-Smad signalling in postoperative human lens epithelial cells

AIMS

To localise Smads3/4 proteins in lens epithelial cells (LECs) of fresh and postoperative human specimens. Smads3/4 are involved in signal transduction between transforming growth factor beta (TGFbeta) cell surface receptors and gene promoters. Nuclear localisation of Smads indicates achievement of endogenous TGFbeta signalling in cells.

METHODS

Three circular sections of the anterior capsule, one lens, and 17 capsules undergoing postoperative healing were studied. Immunohistochemistry was performed for Smads3/4 in paraffin sections of the specimens. The effect of exogenous TGFbeta2 on Smad3 subcellular localisation was examined in explant cultures of extracted human anterior lens epithelium.

RESULTS

The cytoplasm, but not the nuclei, of LECs of uninjured lenses was immunoreactive for Smads3/4. In contrast, nuclear immunoreactivity for Smads3/4 was detected in LECs during capsular healing. Nuclei positive for Smads3/4 were observed in monolayered LECs adjacent to the regenerated lens fibres of Sommerring's ring. Interestingly, the nuclei of LECs that were somewhat elongated, and appeared to be differentiating into fibre-like cells, were negative for Smads3/4. Fibroblast-like, spindle-shaped lens cells with nuclear immunoreactivity for nuclear Smads3/4 were occasionally observed in the extracellular matrix accumulated in capsular opacification. Exogenous TGFbeta induced nuclear translocation of Smad3 in LECs of anterior capsule specimens in explant culture.

CONCLUSIONS

This is consistent with TGFbeta induced Smad signalling being involved in regulating the behaviour of LECs during wound healing after cataract surgery.

Posterior capsule opacification and Nd:YAG capsulotomy rates after implantation of silicone, hydrogel and soft acrylic intraocular lenses: a two-year follow-up study

PURPOSE

To compare the posterior capsule opacification (PCO) and neodymium:YAG (Nd:YAG) laser posterior capsulotomy rates associated with three different posterior chamber foldable intraocular lenses (IOL).

METHODS

We retrospectively evaluated the rates of PCO and Nd:YAG laser capsulotomy in 1150 eyes two years after standard phacoemulsification with a no-stitch 3.5mm clear corneal incision (CCI) and in-the-bag implantation of one of three types of IOL: 190 eyes received a one-piece round-edged hydrogel IOL (Hydroview H60M, Bausch & Lomb); 475 eyes a three-piece round-edged silicone IOL (AMO PhacoFlex SI-40NB, Allergan); 485 eyes a three-piece square-edged soft acrylic lens (AcrySof MA60MA, Alcon).

RESULTS

The PCO and Nd:YAG laser capsulotomy rates were respectively 43.15% and 20.5% in the Hydroview H60M group, 27.57% and 9.68% in the AMO PhacoFlex SI-40NB group, 10.5% and 2.47% in the AcrySof MA60MA group.

CONCLUSIONS

PCO and Nd:YAG laser capsulotomy rates were significantly higher in the Hydroview H60M group and significantly lower with the AcrySof MA60MA lenses, which combine a bioactive constitutive material with the square-edged optic design.

Lens epithelial cell death after cataract surgery

PURPOSE

To determine whether lens epithelial cells (LECs) undergo apoptosis during healing after cataract surgery to further characterize the healing process of the postoperative lens capsule.

SETTING

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

METHODS

Apoptotic cells were detected in human postoperative lens capsules using the terminal deoxynucleotidyl transferase deoxy-UTP nick-end labeling (TUNEL) method. The effect of exogenous transforming growth factor-beta2 (TGF-beta2) on mouse LEC apoptosis was also examined in an organ-culture system.

RESULTS

Three of 17 postoperative specimens contained TUNEL-positive cells. In 2 lens capsules obtained earlier than 10 days, many TUNEL-positive cells, presumably apoptotic LECs, were observed beneath the residual anterior capsule. In cell multilayers in capsule opacification extracted later than 10 days, a few TUNEL-positive cells were seen in 1 specimen; most cells remained negative. In mouse lenses organ-cultured with 1.0 ng/mL TGF-beta2 for 48 hours, TUNEL-positive cells were detected beneath the lens capsule.

CONCLUSIONS

Lens epithelial cells undergo apoptosis during healing after cataract surgery, especially in the early phase. Transforming growth factor-beta2 may be a factor inducing apoptosis in in vivo LECs.

Results of hydrophilic acrylic, hydrophobic acrylic, and silicone intraocular lenses in uveitic eyes with cataract: comparison to a control group

PURPOSE

To evaluate the uveal and capsular biocompatibility of hydrophilic acrylic, hydrophobic acrylic, and silicone intraocular lenses (IOLs) in eyes with uveitis.

SETTING

Department of Ophthalmology, University of Vienna, Vienna, Austria.

METHODS

This prospective study comprised 72 eyes with uveitis and 68 control eyes having phacoemulsification and IOL implantation by 1 surgeon. Patients received 1 of the following IOLs: foldable hydrophilic acrylic (Hydroview, Bausch & Lomb), hydrophobic acrylic (AcrySof, Alcon), or silicone (CeeOn 911, Pharmacia). Postoperative evaluations were at 1, 3, and 7 days and 1, 3, and 6 months. Cell reaction was evaluated by specular microscopy of the anterior IOL surface and the anterior and posterior capsule reaction, by biomicroscopy.

RESULTS

Small round cell deposition was observed on all IOLs in the immediate postoperative period, especially in eyes with uveitis. This reaction decreased 3 to 6 months after surgery. Although the CeeOn 911 had a higher mean grade of small cells, there was no statistical difference between the 3 IOL types after 6 months in the uveitis and control groups. Foreign-body giant cells (FBGCs) increased after 1 week to 1 month. The AcrySof IOLs had the highest number of FBGCs; after 6 months, there was a statistically significant difference between the AcrySof and Hydroview uveitis groups (P =.036) and the AcrySof and CeeOn 911 uveitis groups (P =.003) but there was no difference among the 3 IOL types in the control group. Lens epithelial cell outgrowth persisted on the Hydroview IOLs in control eyes and regressed on all 3 IOL types in uveitic eyes and on the AcrySof and CeeOn 911 IOLs in control eyes (P =.0001). Anterior capsule opacification (ACO) was more severe on all IOL types in uveitic eyes and on the CeeOn 911 IOL in control eyes. Posterior capsule opacification (PCO) was more severe in uveitic eyes. The Hydroview group had more severe PCO than the AcrySof and the CeeOn 911 groups in uveitis and control eyes. Six months postoperatively, the difference was significant (P =.0001). There was no significant difference between the AcrySof and CeeOn 911 IOLs.

CONCLUSIONS

Intraocular lens biocompatibility is inversely related to inflammation. Hydrophilic acrylic material had good uveal but worse capsular biocompatibility. Hydrophobic acrylic material had lower uveal but better capsular biocompatibility. Silicone showed a higher small cell count (mild) and more severe ACO but achieved PCO results comparable to FBGC results and better than those with the AcrySof lens 6 months after surgery. Despite the differences in IOL biocompatibility, all patients benefited from the surgery.

Latent TGFbeta binding protein-1 and fibrillin-1 in human capsular opacification and in cultured lens epithelial cells

BACKGROUND/AIM

It was previously reported that collagenous extracellular matrix (ECM) in human capsular opacification contained isoforms of transforming growth factor beta (TGFbeta). In the present study, the authors performed immunohistochemistry to examine whether ECM in human capsular opacification and in cultures of bovine lens epithelial cells (LECs) contained latent TGFbeta binding protein-1 (LTBP-1), TGFbeta1 latency associated peptide (beta1-LAP), and fibrillin-1, a suspected ligand of LTBP-1 as well as a component of the extracellular microfibrillar apparatus. The aim of the study was to further clarify the mechanism of TGFbeta1 deposition in ECM of capsular opacification.

METHODS

Human capsular opacification specimens and uninjured lens capsules, as well as cultured bovine LECs, were processed for immunohistochemistry using antibodies against LTBP-1, beta1-LAP, fibrillin-1, and collagen type I.

RESULTS

LTBP-1, beta1-LAP, and fibrillin-1 all were localised to the ECM in human capsular opacification. Uninjured lens epithelium stained for beta1-LAP, but not for LTBP-1 and fibrillin-1. ECM deposited in confluent LEC cultures stained for LTBP-1, beta1-LAP, and fibrillin-1, while cultures with only sparse cellularity were unstained for LTBP-1 or fibrillin-1.

CONCLUSIONS

LECs upregulate LTBP-1 and fibrillin-1 during postoperative healing. LTBP-1, beta1-LAP, and fibrillin-1 colocalised to the ECM in capsular opacification and in confluent LEC cultures. TGFbeta1 is considered to deposit in ECM in the large latent form. ECM secreted by LEC may function as a scavenger or repository of TGFbeta.

Expression of transcription factor AP-1 in rat lens epithelial cells during wound repair

We examined the spatial and temporal expression patterns of proteins and mRNAs of the components of transcription factor activator protein 1 (AP-1) to examine the activation pattern of lens epithelial cells during lens wound repair following an anterior capsular injury. One eye of adult Wistar rats (n = 106) were used. After making a lens anterior capsule incision with a hypodermic needle, the affected eye was enucleated 0 and 30 min, 1, 3, 5, 8, 10, 15, 20, 24 hr after injury. Forty six globes were processed for in situ hybridization with oligonucleotide probes for c-fos, fosB, c-jun, junB and junD mRNAs, and 60 globes were immunohistochemically analysed using anti-c-Fos and anti-c-Jun antibodies. Normal lens epithelial cells expressed mRNA signals for junD, but not for c-fos, fosB, c-jun, and junB. mRNAs for c-fos, fosB, c-jun, and junB were detected in the whole lens epithelium from the vicinity to the wound to the equator from 30 min to 8 hr post-injury with their peaks after 30 min to 1 hr, but were no longer detected at 10 hr or later. Expression of c-fos mRNA in the equatorial lens cells was more marked than that of c-jun mRNA. Immunohistochemistry showed that c-Fos protein was expressed in the lens epithelial cells in both the anterior and equatorial regions of the injured lens from 1 to 10 hr after injury, and was no longer detected at 12 hr. C-Jun protein was detected only in the equatorial lens cells from 1 to 5 hr after injury, and was no longer detected at 8 hr. Lens epithelial cells except those in the equatorial region did not express c-Jun protein. These findings indicate that transcriptional activation of lens epithelial cells is initiated in the very early phase after the lens injury, i.e. 30 min post-injury, suggesting that AP-1 may play important roles in regulating lens cell behavior during lens wound repair in rats.

Lens epithelial cell outgrowth on 3 types of intraocular lenses

PURPOSE

To compare the outgrowth of lens epithelial cells (LECs) on 3 types of intraocular lenses (IOLs) to determine the influence of lens material and lens design (optic edge) on this phenomenon.

SETTING

Department of Ophthalmology, University of Vienna, Medical School, Vienna, Austria.

METHOD

Ninety eyes scheduled for cataract surgery were included in a prospective comparative study. A standardized surgical procedure was performed by 1 experienced surgeon. Patients received 1 of 3 types of posterior chamber IOLs of similar design with a 6.0 mm optic and poly(methyl methacrylate) haptic: AcrySof (Alcon), HydroView (Bausch & Lomb), or Sensar (Allergan). Each IOL type was implanted in 30 eyes. Postoperative biomicroscopic examinations were performed 1, 3, 7, 30, 90, and 180 days and 1 year after surgery. Lens epithelial cells in each quadrant of the anterior lens surface were subjectively graded. The product with the highest density and the number of quadrants with this density were used to measure LEC outgrowth.

RESULTS

Statistically significant differences (P <.05) were seen between the hydrophilic IOL and the 2 hydrophobic lenses from day 30 until the final examination. The HydroView lens had a higher number of LECs on its anterior surface than the AcrySof or Sensar IOL. There were no statistically significant differences between the 2 acrylic IOLs at any measurement.

CONCLUSION

The findings suggest that lens surface properties have a greater influence on LEC outgrowth than lens design (ie, sharp optic edge).

Smad translocation and growth suppression in lens epithelial cells by endogenous TGFbeta2 during wound repair

To determine whether endogenous TGFbeta affects lens epithelial cells during repair after an anterior capsule injury in mice, we studied translocation of Smad proteins, which carry the TGFbeta signal from cell surface receptors to promoters in nuclei. We immunolocalized Smads in murine lenses at intervals up to 8 weeks following capsular injury. Effects of injecting TGFbeta neutralizing antibodies on Smad4 location and cell proliferation were examined at 24 hr after injury. Finally, we examined whether exogenous TGFbeta2 induced Smad nuclear translocation in murine lenses in organ culture. Cell proliferation was quantitated by 5-bromo-2'-deoxyuridine (BrdU) labelling. In uninjured lenses, Smads were located in the cytoplasm. In injured lenses, nuclear localization of Smads was observed in cells next to the capsular break from 8 to 24 hr after the injury, and was observed peripheral to the break at 48 hr. Nuclear Smads then continued to be observed occasionally in a minority of cells. Injection of antibodies neutralizing TGFbeta2, but not TGFbeta1 or TGFbeta3, inhibited Smad4 nuclear translocation and resulted in the appearance of BrdU-positive anterior epithelial cells. With the lenses in culture, transient nuclear localization of Smads occurred between 3 and 24 hr in response to continuous exposure to TGFbeta2. No nuclear translocation was seen at 48 hr. Endogenous TGFbeta2 affects lens cells during wound repair after anterior capsule injury, inhibiting lens cell proliferation during the early phase. Nuclear translocation of Smads in lens epithelial cells is transient even with continuous exposure to TGFbeta2.

Shape of lens epithelial cells after intraocular lens implantation

PURPOSE

To evaluate the morphological behavior of lens epithelial cells (LECs) after human cataract surgery with implantation of a poly(methyl methacrylate) (PMMA) or silicone intraocular lens (IOL).

SETTING

Department of Ophthalmology, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya, Aichi, Japan.

METHODS

Morphological observations of LECs in the patients with IOLs were made by light and transmission electron microscopy. The LECs were from 4 areas: (1) the region below the anterior capsule, touching the IOL; (2) the area between region 1 and the equatorial region; (3) the equatorial region; and (4) the central equatorial region and of the posterior capsule not touching the IOL. Case 1 had implantation of a single-piece IOL with a PMMA optic and haptics. Case 2 had a 3-piece IOL with a PMMA optic and polypropylene haptics. Case 3 had a 3-piece IOL with a silicone optic and polypropylene haptics. Areas 1 and 4 could not be observed in Case 2.

RESULTS

The major difference between the patient with a PMMA IOL (Case 1) and the patient with a silicone IOL (Case 3) was that among the 4 areas observed, collagen fibers were present only in area 1 in Case 1 but in areas 2 or 3 as well in Case 3.

CONCLUSIONS

Fibrous collagen fibers appeared in regions in which LECs adhered and there was capsule contact with the IOL optic. In addition fibrous collagen fibers appeared in more areas in the eye with the silicone IOL than in that with the PMMA IOL, perhaps because IOLs with silicone optics move slightly while in the capsular bag.

Cellular reaction on the anterior surface of 4 types of intraocular lenses

PURPOSE

To assess the cellular reaction on the anterior surface of 4 types of foldable intraocular lenses (IOLs).

SETTING

Department of Ophthalmology, University Hospital of Vienna, Vienna, Austria.

METHODS

One hundred eyes scheduled for cataract surgery were prospectively randomized into 4 groups of 25 eyes each using random number tables. Group 1 received a Hydroview IOL (Bausch & Lomb), Group 2 an AcrySof IOL (Alcon), Group 3 a MemoryLens IOL (ORC), and Group 4 a CeeOn 920 IOL (Pharmacia). Patients were examined 1, 3, 7, 30, 90, and 180 days postoperatively. Postoperative biomicroscopic examinations were done with a slitlamp, and a specular microscope was used to document the presence of cell deposits and identify areas with the highest density of cells.

RESULTS

The local tissue response revealed 2 patterns: a nonspecific foreign-body reaction to the IOL (small round, fibroblast-like, epithelioid, and giant cells) and a lens epithelial cell (LEC) reaction. The highest incidence of LECs was in the Hydroview group, in which LECs were present on 81.8% of lenses 180 days postoperatively. During the first postoperative days, small round and fibroblast-like cells were found on all IOLs. From 7 days on, the incidence and density of these cells were less severe in the Hydroview and CeeOn 920 groups. After several weeks, epithelioid cells and foreign-body giant cells were seen on some IOLs. These cells appeared more often on AcrySof, MemoryLens, and CeeOn IOLs.

CONCLUSION

This study found IOL-related differences in cellular reaction after cataract surgery. The incidence of a nonspecific foreign-body reaction to 4 IOLs is consistent with the results of previous studies. The incidence of LECs was highest in the Hydroview group and lowest in the AcrySof group. The CeeOn 920 group had the lowest incidence of all types of cells.

Adhesion of fibronectin, vitronectin, laminin, and collagen type IV to intraocular lens materials in pseudophakic human autopsy eyes. Part 2: explanted intraocular lenses

PURPOSE

To evaluate fibronectin, vitronectin, laminin, and collagen type IV adhesion to poly(methyl methacrylate) (PMMA), silicone, hydrophobic soft acrylate, and hydrogel intraocular lenses (IOLs) in human pseudophakic autopsy eyes.

SETTING

Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.

METHODS

Thirty-two autopsy eyes containing PMMA, silicone, soft acrylate, or hydrogel IOLs were assessed. The IOLs were explanted from the capsular bag, and both sides of the IOLs were immunohistochemically stained for fibronectin, vitronectin, laminin, or collagen type IV. The number of cells on the IOL surfaces was counted. The capsular bag from 1 eye containing a soft acrylate IOL was examined for fibronectin and vitronectin.

RESULTS

Hydrophobic soft acrylate IOLs had significantly more fibronectin adhering to their surfaces than PMMA (P <.01) or silicone (P <.01) IOLs, as well as more vitronectin. Silicone IOLs had more collagen type IV adhesion than the other IOLs (P <.05-.06). Collective protein adhesion differed significantly between soft acrylate IOLs and PMMA and silicone IOLs, but not between PMMA and silicone IOLs.

CONCLUSIONS

The greater amount of protein on the hydrophobic soft acrylate (AcrySof(R)) IOLs seems to support an adhesive mechanism for their attachment to the capsular bag. Fibronectin and vitronectin have functional domains to bind them to lens epithelial cells and the collagenous capsule. This kind of attachment could be a true bioactive bond and may be 1 reason the PCO and neodymium:YAG capsulotomy rates are lower in eyes with a soft acrylate IOL.

Transforming growth factor-beta isoform proteins in cell and matrix deposits on intraocular lenses

PURPOSE

To determine whether the cells that adhere to poly(methyl methacrylate) (PMMA) posterior chamber intraocular lenses (PC IOLs) implanted in human eyes produce transforming growth factor-beta (TGF-beta) isoforms and whether the acellular proteinaceous deposits on these IOLs contain TGF-beta.

SETTING

Department of Ophthalmology, Wakayama Medical College, Japan.

METHODS

Thirty-two PMMA PC IOLs explanted from Japanese patients were immunostained for TGF-beta1, -beta2, or -beta3, and observed under light microscopy.

RESULTS

Cell deposits were observed on 12 IOLs and proteinaceous deposits on 16. Components of the cell deposits were mainly of macrophage origin. The cell and matrix deposits tested positive for each isoform of TGF-beta.

CONCLUSION

The cells that adhered to implanted PMMA PC IOLs produced TGF-beta, and the extracellular matrix that accumulated on the surface of the IOLs contained TGF-beta. Transforming growth factor-beta from the cells on IOLs may influence the healing process of residual lens capsules after cataract surgery with IOL implantation.

Lens epithelial cell layer formation related to hydrogel foldable intraocular lenses

PURPOSE

To determine the incidence of postoperative lens epithelial cell (LEC) layer formation anterior to the Hydroview hydrogel foldable intraocular lens (IOL), the effect on vision, and the appearance under scanning electron microscopy (SEM).

SETTING

Eye Unit of a district general hospital, Delfzijl, and the Laboratory for Cell Biology and Electron Microscopy, Faculty of Medical Sciences, University of Groningen, The Netherlands.

METHODS

In the prospective study, 207 eyes that received a Hydroview hydrogel foldable IOL during 1996 were followed for almost 2 years (range 8 to 98 weeks). Eleven eyes had follow-up of fewer than 8 weeks and were excluded. Some eyes had a transparent to milky-white membrane anterior to the IOL in the plane of capsulorhexis. In the absence of other contributing factors, if best corrected visual acuity was worse than expected, it was assumed to be caused by the membrane. Depending on the membrane's thickness, determined at the slitlamp, patients were offered a neodymium:YAG (Nd:YAG) laser or surgical membranectomy. If surgically excised, the layer was studied by SEM.

RESULTS

Of the 196 eyes, 62 eyes (33.16%) developed a thin epithelial cell layer. The membrane appeared a mean of 38.5 weeks postoperatively (range 9.9 to 85.6 weeks). Eleven eyes (5.61%) had visual symptoms varying from low vision to hazy vision or light scatter. Visual symptoms were present even in cases in which the visual axis was not invaded by the membrane. Once this layer was removed surgically or by the Nd:YAG laser, vision improved and symptoms were relieved. Four eyes (2.04%) required a surgical membranectomy. Examination of these removed membranes by SEM showed their multilayer nature and that the LECs had differentiated into fibroblast-like cells with collagenous fibrils and extracellular matrix.

CONCLUSIONS

The incidence of LEC membrane formation was higher than expected and increased with time in eyes with a Hydroview IOL. The membrane caused visual symptoms by occluding the visual axis, causing striation on the membrane and the IOL to decenter, tilt, or fold. These symptoms improved after the membrane was removed.

Ocular biocompatibility testing of intraocular lenses: a 1 year study in pseudophakic rabbit eyes

PURPOSE

To evaluate the appropriate duration for conducting ocular biocompatibility studies with an intraocular lens (IOL) in the pseudophakic rabbit model.

SETTING

Alcon Laboratories, Inc., Fort Worth, Texas, USA.

METHODS

A single-piece biconvex poly(methyl methacrylate) (PMMA) IOL was implanted in the capsular bag of 18 eyes of New Zealand white rabbits; 8 eyes received sham surgeries. Rabbits were monitored clinically and then sacrificed 6 or 12 months after surgery for histopathological examination of ocular tissues.

RESULTS

Biomicroscopic examination revealed mild ocular changes in all surgical eyes during the first 3 months postoperatively. After that, there was a high incidence of posterior synechias, flare, and posterior capsule opacification (PCO) in eyes with PMMA IOLs. Posterior synechias and flare scores remained mild to moderate throughout the study, whereas PCO severity increased over time. Similar findings were observed in sham eyes. In addition, several eyes with PMMA IOLs developed IOL dislocation, hyphema, iris bombe, and a fibrous membrane covering the IOL. No discernible differences in biomicroscopic scores were observed in eyes at 6 or 12 months. Intraocular pressures and morphology of the corneal endothelium were normal in both groups. Results from histopathological analysis of the ocular tissues were consistent with observations from the biomicroscopic examinations.

CONCLUSION

The results suggest that IOL implantation studies in the pseudophakic rabbit eye should be conducted for 3 or fewer months. Regulatory guidelines requiring longer ocular implantation studies should be revised to reflect the inherently rapid and extensive ocular response in the rabbit model.

Immunolocalization of prolyl 4-hydroxylase in rabbit lens epithelial cells

PURPOSE

To localize the enzyme prolyl 4-hydroxylase in the crystalline lens and determine the ability of lens epithelial cells (LECs) to synthesize procollagen.

SETTING

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

METHODS

Phacoemulsification and aspiration of the crystalline lens followed by implantation of a poly(methyl methacrylate) intraocular lens (IOL) were performed in 1 eye each of 6 albino rabbits; the eye was enucleated 1 or 2 months later. Crystalline lenses were also extracted from the eyes of 2 rabbits. These samples were processed for immunohistochemical detection of the alpha- and beta-subunits of prolyl 4-hydroxylase.

RESULTS

A monolayer of LECs was detected on the inner surface of the intact anterior capsule. Antibodies directed against both subunits of prolyl 4-hydroxylase reacted strongly to LECs proliferating on capsules with IOLs, whereas little or no reaction was observed in quiescent LECs or in the regenerated lenticular structure.

CONCLUSION

The presence of prolyl 4-hydroxylase in LECs proliferating on the inner surface of the lens capsule suggests that these cells are involved in the production of procollagen and fibrosis during capsular injury and repair. Suppression of prolyl 4-hydroxylase activity may prevent the capsule opacification that results from cataract removal and IOL implantation.

Immunolocalization of hyaluronan and CD44 in quiescent and proliferating human lens epithelial cells

PURPOSE

To investigate the role of hyaluronan and its receptor CD44 in capsular repair, their localization in opacified human posterior capsules and in lens epithelial cells (LECs) was assayed.

SETTING

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

METHODS

In 8 patients, circular sections of the anterior capsules obtained during cataract surgery, the extracted crystalline lens, and the opacified lens capsules resulting from intraocular lens implantation were examined immunohistochemically to detect hyaluronan or CD44.

RESULTS

Both hyaluronan and CD44 were found in the extracellular matrix that accumulated on the inner surface of the capsular bags. In contrast, LECs exhibited immunoreactivity to CD44 but not to hyaluronan.

CONCLUSIONS

The cell surface antigen CD44 was expressed ubiquitously by LECs. Expression of its ligand hyaluronan by proliferating LECs suggests that this glycosaminoglycan may be important in the development of posterior capsule opacification.

Immunolocalization of prolyl 4-hydroxylase subunits, alpha-smooth muscle actin, and extracellular matrix components in human lens capsules with lens implants

Lens capsules become fibrotic after the extraction of a cataract. To understand this phenomenon, we evaluated the immunolocalization of prolyl 4-hydroxylase (an enzyme involved in procollagen hydroxylation), and extracellular matrix components and cytoskeletal components in a normal human lens capsule and in others with intraocular lenses. Lens capsules containing intraocular lenses were removed from a patient with proliferative vitreoretinopathy and three with proliferative diabetic retinopathy during vitreous surgery. Two circular sections of the anterior capsules with lens epithelial cells were obtained by anterior capsulotomy during cataract surgery. In addition, a lens capsular bag was obtained immediately after phacoemulsification. The lens capsules were processed for light microscopic immunohistochemical detection of the alpha and beta subunits of prolyl 4-hydroxylase, extracellular matrix components (including collagen types, laminin and cellular fibronectin) or cytoskeletal components (such as cytokeratin, vimentin and alpha-smooth muscle actin). Monolayer lens epithelial cells were seen on the inner surface of the normal anterior capsules. Each intraocular lens was found to be fixed in the capsular bag. Light microscopic immunohistochemistry showed that these proliferating cells expressed vimentin and alpha-smooth muscle actin; in contrast, quiescent lens epithelial cells did not stain for alpha-smooth muscle actin. Marked immunostaining for subunits of prolyl 4-hydroxylase was detected in lens epithelial cells proliferating on the capsules, while no or only faint prolyl 4-hydroxylase immunoreactivity was detected in quiescent lens epithelial cells immediately after phacoemulsification. Collagen types I, III and VI and cellular fibronectin were observed diffusely in accumulated connective tissue on a capsule with an intraocular lens. Type IV collagen immunoreactivity was seen both in the capsules and in the connective tissue accumulation on the capsules. Collagen V and laminin were detected in association with cellular proliferation. Collagen VII and VIII and laminin 5 were not seen. We concluded that during wound healing of the lens capsule after cataract extraction, the lens epithelial cells that proliferate on the inner surface of the capsule transform it into a myofibroblastic phenotype, expressing prolyl 4-hydroxylase and alpha-smooth muscle actin. These proliferating cells are involved in the production of collagen on the lens capsule. This results in a postoperative fibrotic process and contraction of the lens capsule.

Cell proliferation on the outer anterior capsule surface after extracapsular lens extraction in rabbits

PURPOSE

To use light microscopy to evaluate the presence and distribution of cells that proliferate on the outer surface of the anterior capsule after experimental lens extraction in rabbit eyes.

SETTING

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

METHODS

Extracapsular lens extraction, with or without implantation of a poly(methyl methacrylate) intraocular lens, was performed in 10 adult albino rabbits under general anesthesia. Animals were killed 1 month postoperatively. Each eye was embedded in paraffin and examined by light microscopy.

RESULTS

A capsular bag composed of the anterior and posterior capsules was observed. Mononuclear cells, presumed to be lens epithelial cells (LECs), had proliferated in the space between the capsules as well as on the outer surface of the anterior capsules, in association with an accumulation of extracellular matrix.

CONCLUSION

After lens extraction, LECs migrated to and proliferated on the anterior surface of the anterior capsule.

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.

Light and scanning electron microscopy of rabbit lens capsules with intraocular lenses

PURPOSE

To examine postoperative changes in the lens capsules of rabbit eyes after phacoemulsification and aspiration of the crystalline lens and implantation of posterior chamber intraocular lenses (IOLs) using light and scanning electron microscopy.

SETTING

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

METHODS

The crystalline lens was emulsified and aspirated and an IOL implanted in the capsular bag or ciliary sulcus of each eye in adult albino rabbits under general anesthesia. Animals were killed after 4 weeks, and the lens capsules were removed. The specimens were observed under phase-contrast microscopy and processed for light and scanning electron microscopy.

RESULTS

Phase-contrast microscopy revealed presumed lens epithelial cells (LECs) on the central posterior capsules in association with regenerating lenticular fibers and Elschnig pearls in the peripheral capsules. Scanning electron microscopy showed the accumulation of fibrous extracellular matrix on the surface of the posterior capsule in eyes in which the IOL was implanted in the ciliary sulcus. Deposition of packed material attached to the surface of IOLs and of Soemmering's ring were observed in eyes with in-the-bag IOL fixation. At a higher magnification, a parallel arrangement of lenticular fibers was seen in the regenerated lens structure on posterior capsules. An identical structure was observed under light microscopy. Outgrowth of presumed LECs from residual anterior lens capsules and adhesion of macrophages and giant cells were observed on the IOL surface.

CONCLUSION

Two types of postoperative changes were observed in lens capsules after implantation of IOLs: accumulation of fibrous extracellular matrix and newly formed lenticular fibers. These changes are attributed to the proliferation of LECs and can induce posterior capsule opacification after IOL implantation.

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.