Microplasma Induced Cell Morphological Changes and Apoptosis of Ex Vivo Cultured Human Anterior Lens Epithelial Cells - Relevance to Capsular Opacification

Inducing selective or targeted cell apoptosis without affecting large number of neighbouring cells remains a challenge. A plausible method for treatment of posterior capsular opacification (PCO) due to remaining lens epithelial cells (LECs) by reactive chemistry induced by localized single electrode microplasma discharge at top of a needle-like glass electrode with spot size ~3 μm is hereby presented. The focused and highly-localized atmospheric pressure microplasma jet with electrode discharge could induce a dose-dependent apoptosis in selected and targeted individual LECs, which could be confirmed by real-time monitoring of the morphological and structural changes at cellular level. Direct cell treatment with microplasma inside the medium appeared more effective in inducing apoptosis (caspase 8 positivity and DNA fragmentation) at a highly targeted cell level compared to treatment on top of the medium (indirect treatment). Our results show that single cell specific micropipette plasma can be used to selectively induce demise in LECs which remain in the capsular bag after cataract surgery and thus prevent their migration (CXCR4 positivity) to the posterior lens capsule and PCO formation.

Adhesion study of cultured human lens capsule cells on hydrophilic intraocular lenses coated with polyethylene glycol

PURPOSE

To evaluate the adhesion of human lens capsule cells on hydrophilic acrylic intraocular lenses (IOLs) coated with polyethylene glycol (PEG).

SETTING

Department of Ophthalmology, Faculty of Medicine, Universidade Estadual Paulista-Botucatu, São Paulo, Brazil.

DESIGN

Experimental study.

METHODS

Human anterior lens capsules obtained during cataract surgery were cultured and seeded (200 cells/IOLs) in triplicates on the surface of a copolymer comprising hydroxyethyl methacrylate, ethyl methacrylate, and methyl methacrylate IOLs (Loflex) treated or not treated with PEG. After 26 hours, the number of viable adherent cells was estimated by counting in a hemocytometer.

RESULTS

The coating of hydrophilic acrylic IOLs with PEG was effective in inhibiting cell adhesion (P < .05). Cells showing 2 distinct morphologic patterns-epithelial and dendritic-like-were observed during the in vitro establishment of the cultures. A tendency toward greater adhesion of dendritic-like cells was observed in untreated IOLs compared with treated IOLs (P = .095).

CONCLUSION

Coating hydrophilic acrylic IOLs with PEG was effective in inhibiting cell adhesion. This treatment might play a role in posterior capsule opacification prevention.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

[(-)-Epigallocatechin gallate regulates expression of apoptotic genes and protects cultured human lens epithelial cells under hyperglycemia]

(-)-Epigallocatechin gallate (EGCG), the most abundant component in green tea, has a potent anti-apoptotic activity. The purpose of this study was to investigate the protective effects of EGCG and their molecular mechanisms on high glucose-induced apoptosis of human lens epithelial cells (HLEB-3). HLEB-3 cells were exposed to various concentrations of glucose and EGCG. Cell death was assessed by MTT assay and flow cytometry using annexin V and propidium iodide. The expression of the Bcl-2 family, c-fos, c-myc and p53 was measured by real-time PCR. EGCG decreased the Bcl-2/Bax expression stimulated by a high glucose. Moreover, EGCG suppressed the high glucose-induced expression of c-fos, c-myc and p53. These findings suggest that EGCG protects HLEB-3 cells from high glucose-induced apoptosis by regulating the gene expression of the Bcl-2 family, c-fos, c-myc and p53. Thus, EGCG may have a potential protective effect against diabetic cataract formation.

Cultivation and characterization of cornea limbal epithelial stem cells on lens capsule in animal material-free medium

A simple, reproducible, animal-material free method for cultivating and characterizing cornea limbal epithelial stem cells (LESCs) on human lens capsule (LC) was developed for future clinical transplantation. The limbal tissue explants (2×2×0.25 mm) were harvested from 77 cadavers and expanded ex vivo on either cell culture plates or LC in medium containing human serum as the only growth supplement. Cell outgrowth at the edge of the explants was observed within 24 hours of cultivation and achieved viable outgrowth (>97% viability as measured by MTT assay and flow cytometry) within two weeks. The outgrowing cells were examined by genome-wide microarray including markers of stemness (p63α, ABCG2, CK19, Vimentin and Integrin α9), proliferation (Ki-67), limbal epithelial cells (CK 8/18 and 14) and differentiated cornea epithelial cells (CK 3 and 12). Immunostaining revealed the non-hematopoietic, -endothelial and -mesenchymal stem cell phenotype of the LESCs and the localization of specific markers in situ. Cell adhesion molecules, integrins and lectin-based surface carbohydrate profiling showed a specific pattern on these cells, while colony-formation assay confirmed their clonal potency. The LESCs expressed a specific surface marker fingerprint (CD117/c-kit, CXCR4, CD144/VE-Cadherin, CD146/MCAM, CD166/ALCAM, and surface carbohydrates: WGA, ConA, RCA, PNA and AIL) which can be used for better localization of the limbal stem cell niche. In summary, we report a novel method combining the use of a medium with human serum as the only growth supplement with LC for cultivating, characterizing and expanding cornea LESCs from cadavers or alternatively from autologous donors for possible treatment of LESC deficiency.

Distribution of basal membrane complex components in elongating lens fibers

PURPOSE

To localize specific components of the Basal Membrane Complex (BMC) of elongating lens fibers at defined points in their migration to the posterior sutures.

METHODS

Normal, juvenile (4-6 week old) Sprague-Dawley rat lenses (n=46) were utilized. Lenses were either decapsulated to obtain whole mounts of lens capsules or sectioned with a vibrating knife microtome. Sections (100 microm thick) were cut parallel to the equatorial plane, beginning at the posterior pole. On both sections and whole mounts, F-actin was localized using phalloidin-FITC while myosin, cadherins, and beta1 integrin were localized using immunofluorescent labeling. Specimens were visualized on a laser scanning confocal microscope.

RESULTS

F-actin labeling in the equatorial and peri-sutural regions was predominately localized to the periphery of basal fiber ends (consistent with our prior results). At sutures, labeling for F-actin in the BMC was rearranged into numerous small profiles. Furthermore, labeling intensity for F-actin was increased at sutures. Myosin was present in the BMC in all locations examined as a diffuse plaque at fiber ends. Similarly, beta1 integrin was also distributed throughout the BMC within the actin-rich borders in all regions except adjacent to and at the suture branches. In that location immunofluorescence for beta1 integrin appeared to be reduced. In the equatorial, lateral-posterior, and peri-sutural regions, cadherin showed strong localization around the periphery of basal fiber ends. However, cadherin labeling was markedly reduced in the BMC as fibers detached from the capsule and abutted to form sutures (i.e. in the sutural region). Cadherin was concentrated along the short faces of elongating fiber mid-segments.

CONCLUSIONS

It appears that F-actin, cadherin and beta1 integrin components of the BMC undergo controlled rearrangements in the final stages of migration and detachment from the capsule.

Lithium stabilizes the polarized lens epithelial phenotype and inhibits proliferation, migration, and epithelial mesenchymal transition

Posterior capsule opacification (PCO) is a common complication of cataract surgery caused by epithelial mesenchymal transition (EMT) and aberrant lens cell growth. One path to prevention depends on maintaining the quiescent lens epithelial phenotype. Here we report that lithium chloride (LiCl) is a potent stabilizer of the lens epithelial phenotype. In lens epithelial explants (controls), at low cell density, cells readily depolarized, spread out, and proliferated. By contrast, in the presence of LiCl, cells did not spread out or exhibit migratory behaviour. Using concentrations of 1-30 mM LiCl we also showed that cell proliferation is inhibited in a dose-dependent manner. Confocal microscopy and immunohistochemistry for ZO-1 and E-cadherin showed that LiCl treatment maintained tight junctions at the apical margins of cells. Taken together with measurements of cell heights, this showed that the cells in LiCl-treated explants maintained the apical baso-lateral polarity and cobblestone-like packing that is characteristic of lens epithelial cells in vivo. Significantly, the effects of LiCl also extended to blocking the potent EMT/cataract-promoting effects of transforming growth factor beta (TGFbeta) on lens epithelial cells. In TGFbeta-treated explants, cells progressively dissociated from one another, taking on various elongated spindle shapes and strongly expressing alpha-smooth muscle actin (alpha-SMA). These features are characteristic of PCO. In both rat and human capsulorhexis explants, LiCl treatment effectively blocked the accumulation of alpha-SMA and maintained the cells in a polarized, adherent, cobblestone-packed monolayer. These findings highlight the feasibility of applying molecular strategies to stabilize lens epithelial cells and prevent aberrant differentiation and growth that leads to cataract.

FGF-2 release from the lens capsule by MMP-2 maintains lens epithelial cell viability

The lens is an avascular tissue, separated from the aqueous and vitreous humors by its own extracellular matrix, the lens capsule. Here we demonstrate that the lens capsule is a source of essential survival factors for lens epithelial cells. Primary and immortalized lens epithelial cells survive in low levels of serum and are resistant to staurosporine-induced apoptosis when they remain in contact with the lens capsule. Physical contact with the capsule is required for maximal resistance to stress. The lens capsule is also a source of soluble factors including fibroblast growth factor 2 (FGF-2) and perlecan, an extracellular matrix component that enhances FGF-2 activity. Matrix metalloproteinase 2 (MMP-2) inhibition as well as MMP-2 pretreatment of lens capsules greatly reduced the protective effect of the lens capsule, although this could be largely reversed by the addition of either conditioned medium or recombinant FGF-2. These data suggest that FGF-2 release from the lens capsule by MMP-2 is essential to lens epithelial cell viability and survival.

Contact inhibition of migrating lens epithelial cells at the capsular bend created by a sharp-edged intraocular lens after cataract surgery

PURPOSE

To investigate whether the lens epithelial cells (LECs) at the capsular bend created by a sharp-edged intraocular lens (IOL) are in the G(0) phase of the cell cycle.

SETTING

Nishi Eye Hospital, Osaka, Japan.

METHOD

A CeeOn Edge silicone IOL (AMO) with sharp edges was implanted in 1 eye and a PhacoFlex II silicone IOL (AMO) with rounded edges in the contralateral eye after standard cataract surgery in 6 rabbits. Immunohistochemical staining for the Ki-67 antibody was performed 1 day, 3, 4, and 7 weeks after surgery.

RESULTS

In eyes with the sharp-edged IOL, LECs with thin, elongated nuclei accumulated at, but did not extend beyond, the capsular bend and stained negative for the Ki-67 antibody, indicating that they were in the G(0) phase of the cell cycle. In contrast, in the eye with the round-edged IOL, continuous migration of a predominantly monolayer of LECs over the IOL and onto the posterior capsule occurred. These cells were Ki-67 positive, indicating that they were proliferating.

CONCLUSIONS

Lens epithelial cells at the capsular bend of sharp-edged IOLs were in the G(0) phase of the cell cycle, indicating that they were contact inhibited. These findings support the theory the sharp posterior optic edge of the IOL inhibits LEC migration, reducing formation of posterior capsule opacification. Whether these LECs can reactivate when the capsular bend is eliminated by later formation of a Soemmerring's ring requires further studies.

Human Anterior Lens Capsule as a Biologic Substrate for the Ex Vivo Expansion of Limbal Stem Cells in Ocular Surface Reconstruction

PURPOSE

To study the potential use of human anterior lens capsule as a scaffold for stem cell transplantation in treatment of limbal cell deficiency.

METHODS

Limbal biopsies and anterior lens capsules were obtained (same eye) from 30 patients during cataract surgery. Biopsies were suspended in Dulbecco modified Eagle medium under sterile conditions and stored at 4 degrees C. Capsules were treated in distilled water under strict asepsis for 2 hours to eliminate the crystalline epithelium and stored at 4 degrees C. After initial processing, the limbal biopsy was plated epithelial-side down (48 hours) on the capsular specimen in a 35-mm culture dish. Samples were sorted into 4 groups. Group 1 was made up of 10 samples in which limbal biopsies were allowed to grow on corresponding capsules from the same eye (autologous). Group 2 was 10 limbal biopsies that were allowed to grow on capsules of different eye (allogeneic). The remaining specimens were randomized into 2 groups. Group 3 included 10 capsules on which an ex vivo expanded cell line was allowed to grow. Group 4 harbored 10 limbal biopsies that were allowed to grow on polystyrene culture plates. All specimens were incubated for 2 weeks at 37 degrees C and 5% CO2. Cell density, viability, morphology, and adherence of the cell-capsule complex were evaluated at 1, 3, 7, and 14 days.

RESULTS

Rate of cell growth and density in groups 1 and 2 were comparable to the control groups. Cell viability was 95% or superior in all groups, and desmosomes developed between growing cells.

CONCLUSIONS

Human anterior lens capsule is a potential scaffold for ex vivo expansion of limbal epithelial cells, possibly providing a substrate for ocular surface reconstruction.

Vitronectin is present in epithelial cells of the intact lens and promotes epithelial mesenchymal transition in lens epithelial explants

PURPOSE

Extracellular matrix (ECM) accumulates during the development of posterior capsule opacification (PCO). Vitronectin, an ECM component that is generally prominent in wound healing, has been detected in PCO specimens. Here we set out to investigate the distribution of vitronectin in the lens and determine how it, and other ECM components, influence the lens epithelial phenotype.

METHODS

Rat lens epithelial explants were cultured on vitronectin, fibronectin, and laminin substrata. Explants were monitored for cell migration and the appearance of markers for epithelial mesenchymal transition (EMT), using phase contrast microscopy and immunohistochemistry, respectively. Explants were also monitored for evidence of Smad signaling. Vitronectin expression was analyzed in embryonic and postnatal rodent lens development by immunohistochemistry, western blotting, and in situ hybridization.

RESULTS

Vitronectin, like fibronectin and laminin, provided a good substratum for cellular attachment and migration. However, in the case of vitronectin and fibronectin, this was accompanied by a major phenotypic change. On either vitronectin or fibronectin, but not laminin, most of the cells became elongated, spindle-shaped and were strongly reactive for filamentous alpha-smooth muscle actin. In these respects this transition was typical of the well known TGFbeta-induced EMT. In explants cultured on vitronectin and fibronectin, but not laminin, cell nuclei showed prominent reactivity for Smad 2/3. Vitronectin was also shown to be expressed during embryonic and postnatal development. Initially mRNA and protein were detected in all lens cells, however as development progressed, expression became restricted to cells of the epithelium and transition zone.

CONCLUSIONS

The results clearly show that lens cell engagement with a vitronectin or a fibronectin, but not laminin, substratum has a potent EMT promoting effect and that Smad 2/3 signaling is involved. Thus when considering strategies to slow or prevent PCO, these results highlight the need to take into account ECM molecules such as vitronectin that have the capacity to promote EMT.

Long-term capsular bag survival without functional lens epithelial cells

PURPOSE

To evaluate the survival of the capsular bag without the support of functional lens epithelial cells (LECs).

SETTING

David J. Apple, MD, Laboratories for Ophthalmic Devices Research, John A. Moran Eye Center, Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, Utah, USA.

METHODS

One hundred slides of cadaver pseudophakic eyes (from 1991 to 2000) stained with hematoxylin and eosin were analyzed to determine the presence of Soemmering's ring, integrity of the capsular bag, fixation configuration of the haptics, and presence and functionality of the LECs.

RESULTS

A Soemmering's ring was present in 69% of cases. The capsular bags were intact in 100% of cases. In-the-bag fixation was seen in 44% of cases. In 89% of cases, either no cells or nonfunctional LECs were found.

CONCLUSION

Results suggest the capsular bag can survive anatomically without the support of functioning LECs.

Removal of lens epithelial cells to delay anterior capsule–intraocular lens adherence

To test the theory that removing lens epithelial cells at the time of cataract extraction with intraocular lens (IOL) implantation or refractive lens exchange might decrease the rate at which the anterior capsule becomes adherent to the lens optic postoperatively, we performed the technique in approximately 200 eyes that were considered likely to require postoperative IOL exchange. In 4 eyes that had an IOL exchange procedure 6 to 12 weeks after the primary procedure, the anterior capsule was nonadherent or weakly adherent to the lens optic.

Development of an accommodating intra-ocular lens--in vitro prevention of re-growth of pig and rabbit lens capsule epithelial cells

Cataract surgery is routinely performed to replace the clouded lens by a rigid polymeric intra-ocular lens unable to accommodate. By implanting a silicone gel into an intact capsular bag the accommodating properties of the natural lens can be maintained or enhanced. The implantation success of accommodating lenses is hampered by the occurrence of capsular opacification (PCO) due to lens epithelial cell (LEC) growth. In order to prevent LEC proliferation, a treatment regime using actinomycin D, cycloheximide and water was developed. The effectiveness of treatment was analyzed using an in vitro, MTT-based cell culture system and an ex vivo pig eye model in which the implanted lens-in-the-bag is cultured as a whole. LEC were exposed to treatment solutions for 5 min, then the cells were allowed to recover and to re-colonize the substratum. MTT conversion by cells was transiently inhibited by cycloheximide dissolved in water and by water alone. Exposure to actinomycin D resulted in a lasting inhibition of MTT conversion and consequently cell proliferation. These in vitro data could not be fully reproduced in the ex vivo pig eye model due to essential differences between both models. Treatment with actinomycin D containing solutions, however, resulted in a nearly complete absence of cells on the capsular wall. The pig eye model is a promising approach to further evaluate the effects of peri-surgical treatment during the accommodating intra-ocular lens implantation.

Lens epithelial cells synthesize and secrete ceruloplasmin: effects of ceruloplasmin and transferrin on iron efflux and intracellular iron dynamics

Although an essential nutrient, iron can catalyze damaging free radical reactions. Therefore elaborate mechanisms have evolved to carefully regulate iron metabolism. Ceruloplasmin, a protein with ferroxidase activity, and transferrin, an iron binding protein have important roles in maintaining iron homeostasis in cells. Since oxidative damage is a hallmark of cataractogenesis, it is essential to determine iron's role in lenticular physiology and pathology. In the current study of lens epithelial cells, the effects of ceruloplasmin and transferrin on intracellular distribution and efflux of iron were determined. Both ceruloplasmin and transferrin increased iron efflux from these cells and their effects were additive. Ceruloplasmin had significant effects on extracellular iron distribution only in cases of iron overload. Surprisingly, both transferrin and ceruloplasmin had significant effects on intracellular iron distribution. Under physiological conditions, ceruloplasmin increased iron incorporation into the storage protein, ferritin. Under conditions of iron overload, it decreased iron incorporation into ferritin, which is consistent with increased efflux of iron. Measurements of an intracellular chelatable iron pool indicated that both transferrin and ceruloplasmin increased the size of this pool at 24 h, but these increases had different downstream effects. Finally, lens epithelial cells made and secreted transferrin and ceruloplasmin. These results indicate an important role for these proteins in iron metabolism in the lens.

Absence of SPARC in murine lens epithelium leads to increased deposition of laminin-1 in lens capsule

PURPOSE

To investigate the role of SPARC in the regulation of the expression and deposition of extracellular matrix (ECM) proteins in the lens capsule.

METHODS

Wild-type (SP+/+) and SPARC-null (SP-/-) mice of embryonic day (E)14 to 3 months of age were examined. Transcript levels of lens basement membrane (BM) components were analyzed by semiquantitative RT-PCR with mRNA from lens epithelia. Expression of ECM proteins in lens capsule and lens epithelium was analyzed by immunohistochemistry and Western blot analysis. Cell attachment was assessed by lens epithelial explant culture. Coimmunoprecipitation was performed to identify intracellular protein interactions.

RESULTS

From postnatal day 5 to 3 months of age, SPARC-null lens capsules exhibited higher levels of laminin-1 deposition relative to their wild-type counterparts, as revealed by immunohistochemistry and immunoblot analysis. An uneven and aggregated distribution of laminin-1 protein was apparent in the anterior region of SPARC-null lens capsules. SPARC and laminin-1 were expressed abundantly in the endoplasmic reticulum (ER) of lens epithelial cells. Coimmunoprecipitation identified that SPARC associates with laminin-1 before laminin secretion. Furthermore, increased laminin-1 in lens capsule promoted the attachment of lens epithelial explants in culture.

CONCLUSIONS

SPARC affects the secretion and deposition of laminin-1 protein in lens epithelial cells. Because abnormal deposition of laminin-1 in the lens BM could influence lens epithelial cell adhesion and fiber cell differentiation, the authors propose that SPARC is important to lens homeostasis through its regulation of lens BM matrix organization.

Removal of lens epithelial cells and the effect on capsulorhexis size

PURPOSE

To assess the long-term effects of lens epithelial cell (LEC) removal on capsulorhexis opening size.

SETTING

Dorset County Hospital, Dorchester, United Kingdom.

METHODS

This prospective randomized control study included 39 eyes of 38 patients. Twenty eyes were selected randomly for removal of LECs from the anterior capsule as part of routine cataract operation comprising phacoemulsification with intraocular lens (IOL) implantation. The other 19 eyes were used as controls in which the LECs were not removed. All surgeries were performed by 1 surgeon (A.T.). All patients had silicone IOL (Allergan SI-40) implantation. The capsulorhexis opening size was determined immediately after surgery and 2 weeks and 6 months after surgery. Data on treatment outcome of the cataract surgery were analyzed statistically.

RESULTS

Six months postoperatively, the size of the capsulorhexis had statistically significant increased in the study group that had LECs removed (mean increase 1.07 +/- 1.70 mm(2); paired Student t test P=.01), whereas the capsulorhexis size had statistically significant decreased in the control group (mean decrease -3.38 +/- 2.37 mm(2); paired Student t test, P<.0001). The difference in changes in the capsulorhexis areas between the 2 groups was also highly statistically significant (independent-sample Student t test, P<.0001).

CONCLUSION

Removal of anterior subcapsular LECs by aspiration helped maintain the size of the capsulorhexis opening and thus can help prevent capsule contraction syndrome.

[The influence of ionizing radiation on the development of posterior capsule opacification in vitro]

BACKGROUND AND PURPOSE

Histologically, the posterior capsule opacification (PCO) corresponds to regenerative tissue of transformed lens epithelial cells (LECs) with extracellular matrix production. In this study, the influence of ionizing radiation on proliferating LECs and the development of PCO was investigated in vitro.

MATERIAL AND METHODS

Each four and 14 pork lenses, respectively, were irradiated with 6 MeV electrons with single doses of 8, 10, 12, and 20 Gy. 1-2 h after irradiation the lens was removed by capsulorrhexis and hydrodissection. After fixation of the capsular bag in a special device the proliferation of residual LECs was examined daily. The experiment was considered to be finished when the capsular bag was completely opacified by confluent cell proliferates.

RESULTS

Single dose irradiation with electrons in a dose range from 8 to 12 Gy significantly protracted the development of PCO with complete inhibition of PCO after application of 20 Gy.

CONCLUSION

To inhibit PCO in vitro, a single dose of 20 Gy is necessary. The actual in vitro model allows an optimal investigation of PCO formation under different external influences and is therefore very suitable for radiobiological questions.

Effect of extracellular matrix on proliferation and differentiation of porcine lens epithelial cells

BACKGROUND

Proliferation and differentiation of lens epithelial cells (LECs) are important mechanisms of secondary cataract formation. After extracapsular cataract extraction the extracellular matrix (ECM) around the remaining LECs is altered compared with the intact lens. This study investigated the effects of different ECMs on cell proliferation and alpha-smooth muscle actin (alpha-SMA) expression, a marker for myofibroblasts, in cultured porcine LECs.

METHODS

Porcine LECs were cultured for 3 days (cell proliferation assay) or 4 days (alpha-SMA expression) on wells and glass cover slips, respectively, coated with laminin, fibronectin, type I collagen or type IV collagen. LECs cultured on uncoated wells or cover slips served as control. Proliferative response was measured by [(3)H]-thymidine incorporation into DNA. alpha-SMA was detected immunocytochemically with a mouse monoclonal antibody, and the relative numbers of alpha-SMA-positive cells were calculated. Statistical analysis was performed using Student's unpaired t-test.

RESULTS

Cell proliferation was significantly increased by coating with fibronectin (10,320.5+/-6,073 counts per minute; p<0.0001) (mean +/- SD), type I collagen (12,507.3+/-3,914.2 CPM; p<0.0001) and type IV collagen (9,591.4+/-4,088 CPM; p<0.0001) compared with control (1,876.5+/-998 CPM), whereas coating with laminin had no effect (1,760.8+/-812.6 CPM; p=0.7271). The ratio of alpha-SMA-positive LECs cultured on uncoated cover slips for a period of 4 days was 12.2+/-3.51%. This ratio was significantly increased by coating with fibronectin (24.3+/-4.56%; p=0.0001) and type I collagen (21.2+/-8.48%; p=0.0142). Coating with laminin (9.8+/-3.67%; p=0.1682) and type IV collagen (9.0+/-7.09 %; p=0.2491) slightly decreased alpha-SMA expression, but this effect was not statistically significant.

CONCLUSIONS

Fibronectin and type I collagen stimulated both cell proliferation and alpha-SMA expression in cultured porcine LECs. Because fibronectin and type I collagen are not normally present in the adult lens, their possible introduction into the lens capsule after cataract surgery may play a critical role in the development of posterior capsule opacification.

Immunological identification of types I and III collagen in bovine lens epithelium and its anterior lens capsule

To define the molecular structure of bovine lens epithelium and its anterior lens capsule, we investigated the composition of lens capsule basement membrane proteins. Immunofluorescence and immunogold techniques were used to demonstrate the presence of type I and type III collagen in the lens capsule and in primary explant epithelial cultures grown on protein-binding membranes. Immunofluorescence staining with specific antibodies indicated that type I and type III collagen were constituents of lens basement membrane. We observed that deposition of type III collagen was more than type I collagen. The synthesis of fibrillar collagen by lens epithelium and its deposition in the lens capsule was established by localization of fibrillar collagen by transmission immunoelectron microscopy. These results demonstrate for the first time that normal lens epithelium synthesize fibrillar collagen which is an intrinsic component of the anterior lens capsule basement membrane.

A comparative analysis of αA- and αB-crystallin expression during the cell cycle in primary mouse lens epithelial cultures

AlphaA- and alphaB-crystallins are small heat shock proteins and molecular chaperones that prevent non-specific aggregation of denaturing proteins. Previous work in our laboratory has shown that lens epithelial cells derived from alphaA-/- mice exhibit slower growth, whereas alphaB-/- lens epithelial cells hyperproliferate at a higher rate in culture [Andley et al., J. Biol. Chem. 273 (1998) 31252; FASEB J. 15 (2001) 221]. Although both have been implicated in apoptosis and cell proliferation, direct analysis of their expression during the cell cycle has not been investigated. This study was undertaken to define the expression levels of alphaA and alphaB-crystallins during the cell cycle. Primary lens epithelial cell cultures derived from wild type mice were synchronized by serum starvation, and pulsed with bromodeoxyuridine (BrdU) at different times after re-stimulation with serum. Dual parameter flow cytometric studies with BrdU and propidium iodide (PI)-labeled cells were performed. Cells entered S phase 14 hr after serum re-stimulation. The duration of the S phase was 6 hr, and the total cell cycle transit time was between 24-27 hr. Enhanced expression of cyclin A, a protein essential for DNA synthesis was used as an additional marker to define the initiation of the S phase. Immunoblotting analysis demonstrated that the expression of alphaA and alphaB-crystallin was up to 10-fold higher in cells synchronized in G0 phase than in G1 phase. The levels of the proteins increased three-fold again as the cells entered the S phase and progressed to mitosis, but did not rise to the levels observed in G0 phase. This increase in expression of alphaA-crystallin resulted in part from enhanced synthesis during the S phase, as shown by an increase in [35S]methionine-labeling and immunoprecipitation of the radiolabeled alphaA-crystallin. The results were further confirmed by flow cytometric analysis using DNA content and alphaA-crystallin expression. The increase in alphaB-crystallin in S phase was paralleled by an increase in gene expression as shown by real-time RT-PCR analysis. These results demonstrate for the first time that in lens epithelial cells, alphaA and alphaB-crystallin levels are modulated during the cell cycle. Since the absence of alphaA and alphaB- crystallin in lens epithelial cells has been associated with disturbance of the tubulin cytoskeleton during mitosis, and with increased cell death or genomic instability, our results indicating that the alphaA- and alphaB-crystallin expression increases prior to mitosis are significant. The differential expression of these crystallins in the cell cycle may be important for optimal lens epithelial growth and lens transparency.

The presence of a transsulfuration pathway in the lens: a new oxidative stress defense system

The finding that a lens under oxidative stress accumulated free and protein-bound cysteine (protein-S-S-cysteine) in the fiber cells prompted us to examine if there is an alternative source for cysteine pools besides the active cysteine transport system in the lens, namely, the transsulfuration pathway of homocysteine-cystathionine-cysteine, which utilises methionine through transmethylation. We examined the presence of the gene for cystathionine-beta-synthase (CBS), the rate limiting enzyme that converts homocysteine to cystathionine in the transsulfuration pathway, in human lens epithelial (HLE) B3 cells using PCR with primers designed based on the sequence of human liver CBS (Forward 5'-CCA CAC TGC CCC GGC AAA AT-3'; Reverse 5'-CTG GCA ATG CCC GTG ATG GT-3'). The purified DNA fragment (586 bp) from PCR analysis was sequenced and confirmed the homology with CBS gene from other human tissues. The CBS protein band (67 kDa) was present in the HLE cells, which reacted positively with the human liver anti-CBS antibody. The enzyme protein was detected in the pig and human lenses with the highest intensity in the epithelial layer, lower but equal quantities of CBS was present in the cortical and nuclear regions. Human nuclear CBS increased while epithelial CBS decreased with aging. Oxidative stress transiently upregulated the gene expression of CBS both in HLE cells (0.1 mMH2O2) and in pig lens cultured in TC 199 medium (0.5 mMH2O2). The catalytic activity for CBS, which was assayed by measuring the production of C14-cystathionine from C14-serine in the presence of homocysteine, S-adenosyl-methionine and pyridoxal phosphate, was detectable in the HLE cells and transiently activated with H2O2. Free cystathionine accumulated when HLE B3 cells were treated with propargylglycine (PGG), an inhibitor of cystathionase, the downstream enzyme that converts cystathionine to cysteine. More cystathionine accumulation occurred when the cells were simultaneously exposed to PGG and 0.1 mMH2O2. We have shown that oxidative stress of H2O2 could increase the flux of this transsulfuration pathway by committing more homocysteine to cysteine and glutathione production as H2O2 (0.1 mM) inhibited the remethylation enzyme of methionine synthase while concurrently activating the CBS enzyme. This is the first evidence that a transsulfuration pathway is present in the lens, and that it can be upregulated under oxidative stress to provide additional redox potential for the cells.

Effects of variation in superoxide dismutases (SOD) on oxidative stress and apoptosis in lens epithelium

Among the critical antioxidant enzymes that protect the cells against oxidative stress are superoxide dismutases: CuZnSOD (Sod1) and MnSOD (Sod2). The latter is also implicated in apoptosis. To determine the importance of these enzymes in protection against reactive oxygen species (ROS) in the lens, we analysed DNA strand breaks in lens epithelium from transgenic and knockout (Sod1) mice following exposure to H2O2 in organ culture. Since Sod2 knockouts do not survive, comparison was made of lenses of partially-deficient (heterozygote) for Sod2 and the wild-type controls which have twice the enzyme level. Antioxidant potential of Sod2 was also studied in human lens epithelial cells (SRA01/04) in which the enzyme was up- and down-regulated by transfection with plasmids containing sense and antisense human cDNA for MnSOD. DNA strand breaks in the epithelium of Sod1 knockouts and Sod2 heterozygotes were much greater than in the corresponding wild-type or in transgenic mice over-expressing the enzymes when the lenses were exposed to H2O2. The functional role of Sod2 in apoptosis was examined in cultured human lens epithelial cells. Cells with higher enzyme levels were more resistant to the cytotoxic effects of H2O2, O2- and UV-B radiation. Furthermore, Sod2-deficient cells showed dramatic mitochondrial damage, cytochrome C leakage, caspase 3 activation and increased apoptotic cell death when they were challenged with O2-. Thus, mitochondrial enzyme (Sod2) deficiency plays an important role in the initiation of apoptosis in the lens epithelium.

MMP inhibition prevents human lens epithelial cell migration and contraction of the lens capsule

PURPOSE

The development of posterior capsule contraction following cataract surgery is caused by the activity of residual lens epithelial cells. Matrix metalloproteinases (MMPs) are a group of proteolytic enzymes, which are essential for cell migration and cell mediated contraction following wound healing. The authors investigated whether inhibiting MMP activity can reduce lens epithelial cell migration and as a result, lead to a reduction in cell mediated capsule contraction.

METHODS

Human donor lens capsules were cultured and treated with a broad spectrum MMP inhibitor, Ilomastat (GM6001). MMP-2 and MMP-9 production were determined by ELISA. Cell migration onto the posterior capsule and capsule contraction were digitally measured.

RESULTS

MMP inhibition significantly reduced lens epithelial cell migration onto the posterior capsule (p<0.05), and a reduction in capsule contraction was observed (p<0.05).

CONCLUSIONS

Ilomastat significantly reduced lens epithelial cell migration onto the posterior capsule surface and inhibited capsule contraction. MMP inhibition may have a role in the therapeutic treatment of posterior capsule opacification.

Expression and regulation of SPARC, fibronectin, and collagen IV by dexamethasone in lens epithelial cells

Cataract formation is a deleterious side effect of some hormone therapies, thus, it is important to understand how hormones regulate lens basement structure and function. We have examined the effects of dexamethasone (DEX) on the regulation of Secreted Protein Acidic and Rich in Cysteines (SPARC), fibronectin (FN), and collagen IV (CN IV). To radiolabel newly synthesized proteins, cultured monolayers of bovine anterior lens capsule epithelial (ALCE) cells were pulsed with [(3)H] proline. To identify proteins, an immunofluorescent technique, immunoprecipitation with specific antibodies, and electrophoretic separation on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used. DEX increased production of total proteins, whereas it specifically decreased synthesis of FN and CN IV. A decrease in FN and CN IV synthesis by DEX in ALCE cells may decrease adhesion of lens epithelium to the basement membrane (BM), which may in turn cause pathogenesis. Messenger RNAs were identified by Northern blot analyses using specific DNA probes. Treatment of lens epithelial cells with DEX causes a 100-150% up-regulation of SPARC mRNA in a concentration-dependent fashion. The increase in the expression of FN mRNA by DEX was in a dose-response fashion and varied from 50-600%. A 24-hour treatment with DEX (10(-6)M) increased CN IV mRNA levels to 386% over baseline levels. Thus showing a differential upregulation by DEX of mRNAs of SPARC, FN, and CN IV. Results of nuclear run-on transcription assays indicate that regulation of RNAs by DEX may occur, in part, at the transcriptional level. The aberrant expression of lens basement membrane proteins by DEX may contribute to abnormal lens cell function and ultimately to anterior subcapsular cataract.

Morphology and organization of posterior fiber ends during migration

PURPOSE

To characterize structural parameters of the basal membrane complex (BMC) and to determine the arrangement and organization of posterior fiber ends during elongation/migration in lenses with branched sutures.

METHODS

Lenses from normal, juvenile (4-6 week old) Sprague-Dawley rats (n=16) were utilized. Posterior fiber ends were assessed on both whole mounts of lens capsules and on decapsulated lenses. The size, shape and organization of migrating fiber ends was assessed by scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) along the entire posterior surface. The area of the BMC was measured using image analysis software and subjected to statistical analysis.

RESULTS

Posterior fiber ends had a characteristic regional arrangement during elongation and migration along the capsule. These regions were termed the equatorial, the lateral-posterior (posterior from the equator to within 150 microm of the sutures), the peri-sutural (150 microm surrounding the sutures), and the sutural. The area of fiber ends (seen by SEM) was compared to the area of fluorescent F-actin profiles (seen by LSCM). There was no significant difference (p=0.324) between the average basal end area (40.21 microm2) and the average area of F-actin profiles (40.65 microm2). The average fiber end area in the lateral-posterior, peri-sutural, and sutural regions was 63.19 microm2, 71.95 microm2, and 25.75 microm2, respectively. In the equatorial region, footprints were aligned in rows oriented toward the posterior pole, consistent with the arrangement of straight, meridional rows. Initially, fiber ends within the lateral-posterior region were arranged in short irregular rows having variable orientation with respect to the posterior pole. The remainder of these ends were randomly arranged. In the peri-sutural region, fiber ends approaching suture branches were aligned in short rows oriented at angles to the posterior pole. At the sutures, fiber ends appeared to become rounded, presumably during detachment from the capsule.

CONCLUSIONS

The results confirm that F-actin profiles delineate the BMC of posterior fiber ends. Furthermore, the average area, shape and arrangement of fiber ends varies in a predictable pattern during migration. The data suggests that elongating fiber ends follow defined migration patterns along the posterior capsule to their sutural destinations. This controlled process is crucial to the formation of ordered suture patterns, thereby minimizing their adverse effects on lens optical quality.

Alpha lipoic acid changes iron uptake and storage in lens epithelial cells

Alpha lipoic acid (LA) is a cofactor in mitochondrial dehydrogenase complexes. Previous studies have shown that when administered exogenously LA has antioxidant properties, which include free radical scavenging, metal chelation and regeneration of other antioxidants. The cells convert LA into dihydroplipoic acid (DHLA), which in the presence of iron can act as a prooxidant. In vitro DHLA reduces Fe(+3) to Fe(+2) and removes iron from ferritin, increasing the risk of Fe catalyzed free radical formation. In the present study we examined the in vivo effects of lipoic acid treatment on Fe metabolism in cultured lens epithelial cells, and found that LA decreases Fe uptake from transferrin, increases Fe deposition into ferritin and increases the concentration of this protein. When administered together with ascorbic acid, lipoic acid changes the characteristic heavy to light chain ratio of ferritin makeup. The decreased Fe uptake and increased storage diminishes the size of the cytosolic highly reactive Fe pool (LIP). These changes are associated with increased cell resistance to H(2)O(2) challenge. Therefore, LA may reduce the risk of Fe induced oxidative damage and also might be useful as a treatment of Fe overload.

[To establish and observe the experimental lens regeneration model in rabbits]

PURPOSE

To establish the lens regeneration model in New Zealand rabbits, observe the lens regeneration process to investigate the mechanism of lens epithelial cell growth and lens regeneration.

METHODS

Lens extraction by endocapsular phacoemulsification was performed on 8 experimental eyes in New Zealand albino rabbits weighing approximately 1.5 - 2.5 kg. To restore a relative intact capsule bag, a little needle tip was inserted through the limbal wound to perform a 2 mm-lined anterior capsulotomy, which just permitted the insertion of a 21G phacoemulsification tip. Phacoemulsification extraction was applied to remove all lens cortical material and then Healon was injected intracapsularly to distend the capsule bag. With slitlamp, the procedure of le ns regeneration were observed and taken photographs. A histologic study on regenerated lens were also performed.

RESULTS

The relative 3 different results on experimental eyes according to the size of anterior capsulotomy in surgical procedure. In 4 eyes, when the size of anterior capsulotomy is approximately 2 mm and the capsule bag is relatively intact, lens regeneration occured and it has a relatively normal translucent cortex and central nuclear opacity. Among other 4 surgical eyes, the lower half part of lens regeneration was still observed in one eye though the upper half of anterior capsule was damaged, whereas in other 3, owing to the whole anterior capsule lack nearly, lens regrowth was not noted in areas of pupil under the slitlamp biomicroscopy observation and the posterior capsule appeared as gray-white membrane opacity. Histologic study showed that lens epithelial cells in equatorial zone proliferate and differentiate into lens fibers and continues to refill the whole capsule bag. Lens fiber alignment was regular in the periphery of regenerated lens, whereas in the center opacity nuclear, the bulk of the regenerated lens material consisted of an eosinophilic disorganized lens fibers. In addition, there were much of irregular cellular proliferation in capsule wrinkling.

CONCLUSION

Capsule is the support material of lens epithelial cells regrowth. Lens regeneration occurred in rabbits after restoring lens capsular integrity following endocapsule phacoemulsification lens extraction, which was the result of the lens epithelial cells proliferation and differentiation. The cellular proliferation and differentiation was associated with the of capsule morphosis.

Visualization of the hyalo-capsular ligament in the living eye

BACKGROUND

The presence of a prominent, retrolental line is shown biomicroscopically.

METHODS

A 25-year-old patient with a prominent circular retrolental line is reported. Slit-lamp stereophotographs of the lens were obtained.

RESULTS

A prominent, circular, retrolental line was observed in a female patient - who showed no evidence of ocular disease other than myopia of -5.0 D - and was photographically documented.

CONCLUSION

The prominent retrolental line observed in the patient could correspond to the inner border of the hyalo-capsular ligament of Wieger.

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.

Effect of minoxidil on rabbit lens epithelial cell behavior in vitro and in situ

BACKGROUND

Lens epithelial cell (LEC) proliferation and the associated production of extracellular matrix (ECM) are responsible for capsular opacification after cataract-IOL surgery. Minoxidil is an inhibitor of lysyl hydroxylase, an enzyme involved in procollagen hydroxylation. To evaluate the potential efficacy of minoxidil in inhibiting postoperative capsular opacification, we examined the effects of minoxidil on LEC behavior in cell and organ cultures.

METHODS

We examined minoxidil effects on collagen production, migration and proliferation of cultured rabbit LECs as well as its ultrastructural effects, and also its effects on the cell population in organ-cultured capsular bag.

RESULTS

No cytotoxicity was identified by MTT assay at the concentrations up to 3.0 mM of minoxidil, whereas it decreased the collagen production in LECs. Minoxidil also inhibited migration and proliferation of cells. Ultrastructural observation revealed the presence of dilated endoplasmic reticulum in LECs treated with minoxidil, indicating the accumulation of protein, probably underhydroxylated collagen precursors. The capsules cultured with minoxidil appeared less opaque than control specimens. On histological examination the numbers of cells on equatorial capsules were found to be significantly lower in minoxidil culture than in control culture. No lens cells were detected on the central posterior capsule of minoxidil culture, whereas they were seen in control.

CONCLUSION

Minoxidil inhibited LEC migration and proliferation in vitro, as well as collagen secretion. Collagen secretion may be essential for LEC migration and proliferation. Minoxidil also attenuated repopulation of LECs on the inner surface of organ-cultured capsules. Minoxidil may be a potential inhibitor of postoperative capsular opacification.

Postoperative inflammation after lens epithelial cell removal: 2 year results

PURPOSE

To evaluate the influence on postoperative inflammation of lens epithelial cell (LEC) removal after phacoemulsification.

SETTING

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

METHODS

This randomized prospective single-surgeon study comprised 60 patients with senile cataract only. After a temporal clear corneal incision was made and phacoemulsification performed, no LECs were removed in Group A, LECs in the nasal half were removed in Group B, and LECs were removed from the entire anterior capsule in Group C. The LECs were removed with a Rentsch capsule curette (Geuder). In all eyes, a foldable hydrogel intraocular lens (Hydroview, Bausch & Lomb) was implanted. Anterior chamber flare was evaluated through dilated pupils in a double-masked fashion using a Kowa FC-1000 laser flare-cell meter (LFCM). Measurements were done preoperatively as well as 1, 3, 7, 14, and 28 days and 3, 6, 12, and 24 months postoperatively.

RESULTS

In all 3 groups, the flare and cell values increased on the first postoperative day followed by a successive decrease thereafter. One month after surgery, the blood-aqueous barrier (BAB) was nearly restored in all groups. Between the first and fourth week, the flare values in Groups B and C were slightly lower than in Group A; however, mean flare and cell values among groups were not statistically significantly different at any measurement.

CONCLUSION

The removal of LECs from the anterior capsule with a Rentsch curette did not influence postoperative BAB changes detected using an LFCM.

Lens epithelial cell regeneration of a capsule-like structure during postoperative healing in rabbits

PURPOSE

To determine whether lens epithelial cells (LECs) can regenerate the lens capsule during healing after lens extraction and intraocular lens (IOL) implantation.

SETTING

Department of Ophthalmology, Wakayama Medical College, Japan.

METHODS

Extracapsular lens extraction and IOL implantation were performed in 5 adult albino rabbits. Lens capsules were examined histologically and immunohistochemically 3 and 5 months later.

RESULTS

Lens epithelial cells proliferated and regenerated lens fibers within the capsular bag. A multilayered homogenous capsule-like structure was present in the equatorial region. The structures contained type IV collagen but not type I collagen.

CONCLUSION

Lens epithelial cells can regenerate lens capsule-like structures during healing after lens extraction. Postoperative LECs without phenotypic conversion to a fibroblastic type may produce this structure.

Serum withdrawal induces a redistribution of intracellular gelsolin towards F-actin in NIH 3T3 fibroblasts preceding apoptotic cell death

The intracellular distribution of gelsolin in NIH 3T3 cells was examined by immunostaining using affinity-purified polyclonal gelsolin antibodies before and after induction of apoptosis by serum withdrawal. Serum deprivation induced detachment of an increasing number of NIH 3T3 cells, but also apoptosis in attached cells as verified morphologically by chromatin condensation, nuclear fragmentation and labelling of their periphery by FITC-annexin V. Ongoing apoptosis was also demonstrated by activation of caspase-3 activity and chromatin cleavage into high-molecular-mass fragments, although no internucleosomal chromatin degradation (DNA-ladder formation) was detected. When cells were maintained in the presence of 10% foetal calf serum, gelsolin immunoreactivity was evenly distributed in the cytoplasm. No obvious co-localisation of gelsolin and the actin-containing stress fibres was detected under these conditions. At day one after serum withdrawal, a redistribution of gelsolin to actin filaments was detected within a few attached cells by double fluorescence staining. The number of cells exhibiting this redistribution increased at days two to four. In addition, the stress fibres increased in thickness and their length was continuously reduced. At day four, many cells contained shortened stress fibres, which had lost their longitudinal orientation. Additionally, the cytoplasm of a number of attached cells was highly condensed around their nuclei and a homogenous distribution of both gelsolin and actin was detected in the remaining cytoplasmic rim. Up to day two, these effects were reversible after re-addition of serum to attached cells. A similar redistribution of gelsolin immunore-activity was observed after induction of apoptosis by cycloheximide, but not after initiation of necrosis by hydrogen peroxide. In NIH 3T3 cells no alteration in the expression of gelsolin at the level of protein (Western blot) or specific mRNA (Northern blot) was observed after serum withdrawal. Using Western blotting, no proteolysis of gelsolin was detected up to day 4, although caspase-3 activity was found to have increased fivefold after serum withdrawal. These results suggested that in these cells F-actin severing might occur in the absence or advance of gelsolin cleavage by caspases. Intact gelsolin on its own may be sufficient for the dissolution of the microfilaments, since micro-injection of gelsolin into primary bovine lens cells led to a transient disappearance of the stress fibres and to a reduction of their attachment area to the substratum. In NIH 3T3 cells similar effects of micro-injected gelsolin were only observed at day one after serum withdrawal.

FGF: an autocrine regulator of human lens cell growth independent of added stimuli

PURPOSE

Posterior capsule opacification (PCO) arises because of a persistent growth of lens epithelial cells. Cultured human lens cells residing on their native collagen capsule and maintained in serum-free medium actively grow and thus show an intrinsic capacity for regulation. In the present study, the authors investigated the role of the putative FGF autocrine system in human capsular bags.

METHODS

Capsular bags were prepared from human donor eyes and maintained in a 5% CO(2) atmosphere at 35 degrees C. On-going observations were by phase-contrast microscopy. Cellular architecture was examined by fluorescence cytochemistry. De novo protein synthesis was determined by the incorporation of 35S-methionine. Basic fibroblast growth factor (FGF) and FGF receptor (R)-1 were detected using enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR) techniques. FGFR-1 inhibition was achieved using the specific antagonist SU5402.

RESULTS

Human lens epithelial cells can maintain metabolic activity for more than 1 year in a protein-free medium. Basic FGF was shown to be present in capsular bags throughout culture and also in capsular bags removed from donor eyes that had previously undergone cataract surgery. Furthermore, FGFR-1 was identified. Inhibition of FGFR-1 caused a significant retardation of growth on the posterior capsule. On no occasion did any treated bag reach confluence, whereas all match-paired control samples did.

CONCLUSIONS

The results provide evidence that FGF plays an integral role in the long-term survival and growth of human lens epithelial cells, independent of external stimuli. Inhibition of FGFR-1 by specific synthetic molecules, such as SU5402, could provide a potential therapeutic approach to resolving PCO.

Visualization of elementary mechanosensitive Ca2+-influx events, Ca2+ spots, in bovine lens epithelial cells

Local increases in the intracellular Ca2+ concentration ([Ca2+]i) in several regions within the bovine lens epithelial cell during application of mechanical stress were clearly visualized in the presence of lysophosphatidic acid (LPA), a bioactive lysophospholipid, using real-time confocal microscopy. We called the phenomenon 'Ca2+ spots'. Ca2+ spots started in a circular area with a radius of about 1.5 m. These Ca2+ spots spread concentrically, resulting in a mean global increase in [Ca2+]i. The local increase often occurred in a stepwise manner or repetitively at the same region. The spatiotemporal properties of the Ca2+ spots were completely different from those of the Ca2+ wave induced by ATP, a Ca2+-mobilizing agonist. Ca2+ spots were inhibited by decreasing the extracellular Ca2+ concentration or by the presence of Gd3+, an inhibitor of mechanosensitive (MS) channels, but not by thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+ pump, suggesting that Ca2+ spots arise from Ca2+ influx through Gd3+-sensitive MS channels. On the assumption that, in lens epithelial cells, the open probability of the MS channel is 0.4, the membrane potential is 56 mV and the channel conductance is 50 pS, the estimated maximum flux of Ca2+ in a Ca2+ spot (0.4 x 10-17 to 4.7 x 10-17 mol x s(-1)) was comparable to currents of one or a few MS channels. On real-time three-dimensional confocal imaging analysis, which permitted simultaneous imaging of basal and apical planes of cells at 37.6 ms intervals, Ca2+ spots on the apical plane were more clearly visualized than those on the basal plane. From these results, we propose that the Ca2+ spot is an elementary Ca2+-influx event through MS channels directly coupled with the first step in mechanoreception In addition, our results strongly suggest that LPA functions as an endogenous factor affecting mechanotransduction systems.

[Effect of intraocular lens design on posterior capsule opacification: an in-vitro model]

BACKGROUND

The development of posterior capsule opacification (PCO) is one of the commonest complications of modern cataract surgery. The various designs of intraocular lenses (IOL) seem to exert a barrier effect on the proliferation and migration of lens epithelial cells and the following development of PCO.

METHODS

We set up a cell culture model (advanced 3D capsular bag model) and investigated six differently designed IOL made of different materials as to their effect on cell proliferation. Proliferation and migration of the cells were analysed and documented over a period of 28 days. A cell viability test using the LIVE/DEAD kit (Molecular Probes) was carried out at the end of the investigation.

RESULTS

In all tests, lens epithelial cells adhered to and migrated onto the capsular bag. During the culture period, lens epithelial cells migrated only to the optical rim of two of the implanted IOL. On the other four, lens epithelial cells migrated further and covered the whole optical area of the IOL.

CONCLUSIONS

Certain lens designs seem to have a reducing effect on the development of PCO. Our advanced in vitro capsular bag model is a suitable cell culture model for the investigation of the reducing effect of various IOL on the development of PCO.

[Human lens cells in culture. I. Isolation of adult lens epithelial cells from lens capsule preparations and reactivation of nucleus-containing fiber cells]

BACKGROUND

Bovine lens epithelial cells in culture revealed a high sensitivity against micromolar concentrations of linoleic acid. To prove the assumption that unsaturated free fatty acids are risk factors for cataractogenesis, human lens cell lines are needed. Furthermore, the reactivation of nucleus-containing fiber cells to mitotic growth may hint at their role in after cataract genesis.

MATERIAL AND METHODS

Epithelium-capsule-preparations obtained by capsulorhexis were cultured in serum containing medium. Subculturing of these adult human lens epithelial cells was done by trypsinization. Fiber cell bundles from the equator region of a fetal human lens were transferred into culture medium. Aggregates of nucleus containing fiber cells were isolated from floating fiber cell bundles by trypsinization. Subculturing and cryoconservation of suitable cell lines.

RESULTS

Primary culture of epithelium-capsule-preparations results in flattening, migration and proliferation of adult human lens epithelial cells. Nucleus containing fiber cells were reactivated to mitotic growth after adhesion to a suitable substratum. Established cell lines were received from adult human lens epithelial cells and fetal human fiber cells after repeated subculturing.

CONCLUSIONS

Lens-capsule-preparations available from cataract surgery are well suited for the isolation of human lens cell lines, which were needed for testing cytotoxicity of drugs and for tracing of cataractogenic risk factors. The finding that nucleus containing fiber cells from the equator of human lenses can be reactivated to proliferating cells let us suppose, that these cells, which can not be removed easily from the posterior lens capsule, contribute to the after cataract formation.

The effect of photodynamic therapy with bacteriochlorin a on lens epithelial cells in a capsular bag model

Photodynamic therapy (PDT) with bacteriochlorin a(BCA) has proved to be a successful treatment for many cancers and to be cytocidal for different cell lines in culture. The present study aimed to investigate in vitro the potential of this treatment for killing lens epithelial cells (LECs) left in the human capsular bag after extracapsular cataract extraction (ECCE). Capsular bags were prepared from donor eyes using an ECCE procedure and incubated in various concentrations of bacteriochlorin a(1.6-50 microg ml(-1)) during various incubation periods (2-10 min). Subsequently, the capsules were illuminated during various exposure times (2-15 min) with a diode laser (wavelength 760 nm). After treatment, the capsular bags were cultured for 7 days in Eagle's minimal essential medium supplemented with 2% fetal calf serum. The specimens were fixed in glutaraldehyde/paraformaldehyde and examined with routine light microscopy, Hoechst staining for DNA and transmission electron microscopy. Proliferation of LECs on the posterior capsule was assessed in flat mounts. Capsular bags receiving BCA without illumination and capsular bags receiving illumination only served as controls.BCA alone or light alone have no effect on structure and proliferative activity of LECs. At a threshold protocol of incubation in BCA at 10 microg ml(-1)for 10 min and subsequent illumination for 15 min, proliferative activity of cells is largely arrested and nearly all LECs on the capsule exhibit severe signs of apoptosis. Photodynamic therapy with bacteriochlorin a induces cell death and suppression of proliferation inlens epithelial cells and could be a promising means of prevention of posterior capsule opacification.

Effect of large positioning holes on capsule fixation of plate-haptic intraocular lenses

PURPOSE

To compare the centration and fixation of silicone plate-haptic intraocular lenses (IOLs) with different-sized positioning holes.

SETTING

Eye Clinic of the Johannes Gutenberg-University Mainz, Mainz, Germany.

METHODS

In a prospective randomized study, 51 Chiroflex C10 and 56 Chiroflex C11 IOLs were implanted under standardized conditions by the same surgeon. The IOL position was documented at the end of surgery and by retroillumination on the first day and 5 months postoperatively. The positioning-hole area was evaluated by ultrasound biomicroscopy (50 MHz) 5 months postoperatively.

RESULTS

One day postoperatively, no IOL in either group was decentered more than 1.0 mm. After 5 months, 33% of the C10 and 42% of the C11 IOLs were decentered between 0.5 and 1.0 mm, and 11% of the C10 and 8% of the C11 IOLs were decentered more than 1.0 mm (maximum 1.23 mm and 1.41 mm, respectively). Up to the first postoperative day, 20% of the C10 and 22% of the C11 lenses were rotated more than 15 degrees. At 5 months, an additional 15% of the C10 and 19% of the C11 lenses were rotated. Ultrasound biomicroscopy showed no tissue or capsule adhesion in the holes in most cases (85% C10 group; 71% C11 group). No difference was statistically significant.

CONCLUSIONS

Larger positioning holes did not prevent IOL decentration or rotation; thus, this IOL design appears unsuitable for correcting astigmatism. Because tissue in the positioning hole was rare with both lens types, it is doubtful that enlarged plate-haptic perforations will prevent IOL luxation into the vitreous cavity after capsulotomy.

A new type of biocompatible bridging structure supports axon regrowth after implantation into the lesioned rat optic tract

We have developed a new type of polymer/cell/matrix implant and tested whether it can promote the regrowth of retinal ganglion cell (RGC) and other axons across surgically induced tissue defects in the CNS. The constructs, which consisted of 2-2.5-mm-long polycarbonate tubes filled with lens capsule-derived extracellular matrix coated with cultured neonatal Schwann cells, were implanted into lesion cavities made in the left optic tract (OT) of 18-21-day-old rats. In one group, to promote Schwann cell proliferation and perhaps also to stimulate axon regrowth, basic fibroblast growth factor (bFGF) was added to the lens capsule matrix prior to implantation. In another group, to determine whether application of growth factors to the somata of cells enhances the regrowth of distally injured axons, the neurotrophin NT-4/5 was injected into the eye contralateral to the OT lesion. NT-4/5 and bFGF treatments were combined in some rats. After medium-term (4-10 weeks) or long-term (15-20 weeks) survivals, axon growth into implants was assessed immunohistochemically using a neurofilament (RT97) antibody. RGC axons were visualized after injection of WGA/HRP into the right eye. Viable Schwann cells were present in implants at all times after transplantation. Large numbers of RT97+ axons were consistently found within the bridging implants, often associated with the peripheral glia. Axons were traced up to 1.7 mm from the nearest CNS neuropil and there was immunohistochemical evidence of myelination by Schwann cells and by host oligodendrocytes. There were fewer RGC axons in the implants, fibers growing up to 1.6 mm from the thalamus. Neither NT-4/5 nor bFGF, alone or in combination, significantly increased the extent of RGC axon growth within the implants. A group of OT-lesioned rats was implanted with polymer tubes filled with 2-2.5-mm-long pieces of predegenerate peripheral nerve. Surprisingly, polymer/cell/matrix constructs contained comparatively greater numbers of RGC and other axons and supported more extensive axon elongation. Thus, implants of this type may potentially be useful in bridging large tissue defects in the CNS.

The anterior lens capsule used as support material in RPE cell-transplantation

PURPOSE

To investigate the use of an ocular basement membrane as support material for transplanted porcine RPE cells.

METHODS

Porcine RPE cells were grown on bovine corneal extracellular matrix (ECM), isolated bovine- and porcine lens capsules, and tissue culture plastic. Cell density, and cell morphology were studied by phase contrast microscopy and transmission electron microscopy.

RESULTS

RPE cells grown on porcine anterior lens capsule and on ECM obtained better morphology and higher final cell density than cells grown on plastic and on bovine anterior lens capsule. It was possible to transplant the porcine anterior lens capsule to the subretinal space in pigs. Within two weeks of observation, the lens capsule was well tolerated in the subretinal space.

CONCLUSION

The anterior lens capsule seems to be promising as support material for use in RPE cell-transplantation.

Ex vivo canine lens capsular sac explants

BACKGROUND

Lens capsular sac explants from human cadaver eyes were used to investigate posterior capsular opacification (PCO). The purpose of this study was to characterize a similar model using canine tissue and to determine whether transferrin (Tf), transforming growth factor beta-2 (TGF-beta2), and insulin-like growth factor-1 (IGF-1) are secreted by lens epithelial cells (LEC) of these ex vivo sacs.

METHODS

The lens from canine eyes was removed by extracapsular cataract extraction, the lens sac dissected free, pinned to a petri dish, and cultured in either serum-supplemented or serum-free medium. Morphologic characteristics and growth rate to confluence on the posterior capsule were studied by phase-contrast microscopy. Vimentin, alpha smooth muscle actin, and panTGF-beta expression by LEC were determined by immunohistochemistry. Tf, TGF-beta2, and IGF-1 levels were measured by ELISA in the supernatant of sacs cultured in serum-free medium.

RESULTS

The mean time to confluence of LEC onto the posterior capsule was 5.4+/-1.1 days (n=22) and 14.7+/-3.7 days (n=14) for sacs in serum-supplemented and serum-free medium, respectively. Following development of confluence, explants displayed opacification and light scatter from cellular proliferation and capsular contraction. Confluent LEC expressed vimentin, alpha smooth muscle actin, and TGF-beta2, and both Tf and TGF-beta2 were secreted into the culture supernatant.

CONCLUSION

Canine lens sac explants have characteristics virtually identical to those of human origin, and appear to be a useful alternative tissue source for this model when human cadaver eyes are unavailable. Tf and TGFbeta-2, but not IGF-1, are secreted by LEC in explanted lens sacs and may influence the proliferation and metaplasia of LEC during the development of PCO.

Lens cell populations studied in human donor capsular bags with implanted intraocular lenses

PURPOSE

Posterior capsule opacification is an ongoing cellular redistribution process. The level of viable cell coverage was therefore determined in human donor capsular bags with implanted intraocular lenses, and cellular morphology and ultrastructure were investigated in relation to cell type and level of differentiation.

METHODS

Donor capsular bags, retrieved at intervals of 4 months to 13 years after surgery, were investigated by phase optics before fixation. Postfixation techniques included scanning electron microscopy and transmission electron microscopy of sections and immunofluorescent staining of cytoskeletal proteins in wholemounts.

RESULTS

All the capsular bags contained a large population of viable cells on the capsular surfaces. Cells on the anterior face of the anterior capsule and in the spaces around the intraocular lens had an elongated morphology and expressed alpha-smooth muscle actin. The cells formed light-scattering, multilayered aggregates and strands that were surrounded by layers of extracellular matrix. The regions between the intraocular lens and the equator of the bags were populated by monolayers of epithelial cells of normal morphology and ultrastructure, on both the anterior and posterior capsules. In some regions the apical surfaces of the two epithelial monolayers were in contact, and in some parts of the equatorial regions, differentiation of cells into well-organized fiberlike cells was evident.

CONCLUSIONS

Human capsular bags contain a large population of viable cells for many years after cataract surgery. Cells in the regions around the intraocular lens undergo transition to a mesenchymal type. Cells peripheral to these regions can form a stable closed microenvironment in which both normal epithelial morphology and differentiation to fiberlike cells are maintained.

Plasma membrane calcium ATPase gene expression in bovine lens epithelium

Plasma membrane calcium adenosine triphosphatase (Ca(2+)-ATPase) is an energy-dependent protein responsible for transporting cytosolic calcium across the plasma membrane. Multiple plasma membrane Ca(2+)-ATPase isoforms are expressed from four genes (PMCA1-4) and alternative mRNA splicing. We have studied PMCA gene expression in bovine lens epithelium tissues by reverse transcription-polymerase chain reaction, Southern blot, and Northern blot hybridization. All four PMCA genes are expressed in the lens epithelium, the PMCA3 transcript being the most abundant. The transcripts for PMCA1, PMCA2, and PMCA4 exist in decreasing order of abundance. There is no evidence for the expression of any novel PMCA genes in bovine lens epithelium.

Retrovirus-mediated transfer of a suicide gene into lens epithelial cells in vitro and in an experimental model of posterior capsule opacification

PURPOSE

The most common complication of cataract surgery is the development of posterior capsule opacification (PCO). Hyperplasia of the lens epithelium is one of the main cellular events following phacoemulsification and was found to be an important feature contributing to opacification of the posterior capsule. We investigated the feasibility of killing the residual lens epithelial cells by retroviral-mediated transfer of the herpes simplex virus-thymidine kinase (HSV-tk) gene, a well-studied suicide gene, into rabbit lens epithelial cells followed by ganciclovir (GCV) treatment.

METHODS

The capacity of retroviral vectors to transfer genes into rabbit lens epithelial cells was determined either in vitro (culture of rabbit lens epithelial cells) or in vivo (experimental model of PCO in rabbits) using cDNA encoding the beta-galactosidase (LacZ) reporter gene. To evaluate the efficiency of suicide gene therapy (infection with retroviral vectors encoding the HSV-tk gene followed by GCV treatment) we determined the sensitivity of HSV-tk infected lens epithelial cells to different concentrations of GCV in vitro. Then, in an experimental model of PCO, rabbits were treated with HSV-tk retroviral vectors at the end of the surgery and they received repeated intracameral and intravitreal injections of GCV at the concentration determined by the in vitro experiments.

RESULTS

Infection efficiency using LacZ retroviral vectors was about 29% in vitro and 10% in vivo. After infection of the HSV-tk cDNA in vitro, the cell killing effect of GCV was evaluated. A significant enhancement (four- to five-fold) of the cell sensitivity to GCV was shown in FLY-DFGtk as compared with mock infected (P < 0.01) cells even without selection of the HSV-tk positive cells. The GCV concentration leading to 50% reduction in cell number (IC50) was 50 microg/ml. In vivo infection with a HSV-tk vector led to the tk gene transfer into lens epithelial cells. Despite this local HSV-tk gene expression, we could not prevent capsule opacification.

CONCLUSIONS

Lens epithelial cells were successfully infected both in vitro and in vivo by beta-galactosidase and HSV-tk genes via retroviral vectors. In vitro infected lens epithelial cells displayed a strong sensitivity to GCV treatment. In vivo, we could not prevent capsule opacification in the rabbit model, very likely due to the limited level of the HSV-tk gene expression. However, our results suggest that virus-mediated suicide gene therapy might be a feasible treatment strategy to prevent capsule opacification with a more powerful vector.

Experimental staining of the anterior lens capsule in albino rabbits

PURPOSE

To study the value and safety of staining the anterior lens capsule in albino rabbits.

SETTING

Ophthalmology Department, Cairo University, and Ophthalmic Pathology Department, Research Institute of Ophthalmology, Cairo, Egypt.

METHODS

The experiment was divided into 3 stages. First, the capacity of different concentrations of crystal violet solution to stain the anterior lens capsule of postmortem albino rabbit eyes was tested. The toxicity of different concentrations of the dye (2% to 0.25%) was then tested to determine the highest concentration that was nontoxic to the cornea and trabecular meshwork. The third step was to detect possible toxicity of lower concentrations (0.1% to 0.05%). Different dye concentrations were injected into the anterior chamber of the rabbit eyes. The eyes were examined after 1 and 3 days, 1 week, and 1 month using light microscopy and scanning and transmission electron microscopy.

RESULTS

Different concentrations of crystal violet stained the anterior lens capsule, allowing for easy capsulorhexis. The use of the 2% and 1% concentrations was accompanied with irreversible damage to all corneal layers. The use of the 0.5% concentration caused damage to stromal keratocytes and endothelium. The use of the 0.25% concentration did not damage any corneal layer or the trabecular meshwork. Lower concentrations of 0.1% and 0.05% also stained the capsule, providing good visibility for successful capsulorhexis, and were less toxic to the corneal endothelium.

CONCLUSION

Staining the anterior lens capsule with 0.25% to 0.05% concentrations of crystal violet solution caused no injury to the cornea or trabecular meshwork in albino rabbit eyes.