Na,K-ATPase in lens epithelia from patients with senile cataracts

Sodium-potassium-adenosine triphosphatase (Na,K-ATPase) has long been recognized for its role in regulating electrolyte concentrations in the lens, within which the electrolyte balance is vital to lens transparency. In this study, we compared the abundance of the alpha-subunit of Na,K-ATPase in lens epithelia of patients with senile cataracts, in order to examine the role of this enzyme in various types of lens opacity. Human lens epithelia were collected from 27 patients with senile cataracts who had undergone phacoemulsification. The type and the severity of lens opacity were graded and scored according to the Lens Opacities Classification System II. The mean age of the patients was 67.5 years (range, 46-80 yr). Abundance of the Na,K-ATPase alpha-subunit peptide in the lens epithelium was quantified by means of Western immunoblotting. Immunoblotting revealed that the amount of Na,K-ATPase alpha-subunit tended to decrease with increased cataract severity. In hypermature cataracts, the Na,K-ATPase alpha-subunit was barely detectable. The amount of alpha-subunit of Na,K-ATPase was inversely correlated with the overall severity of cataract (r = -0.64, p = 0.002). However, the inverse correlation was significant only in the cortical region (p = 0.027). As the cortex is located adjacent to the lens epithelium, it is directly affected by the loss of function of Na,K-ATPase in the epithelium. Such loss could result in water accumulation, vesicles, water clefts, Morgagnian globule formation, and Morgagnian cataract.

Molecular architecture of the lens fiber cell basal membrane complex

Lens fiber cells are transparent, highly elongated, epithelial cells. Because of their unusual length these cells represent a novel model system to investigate aspects of epithelial cell polarity. In this study, we examined the fiber cell basal membrane complex (BMC). The BMC anchors fiber cells to the lens capsule and facilitates their migration across the capsule. Confocal microscopy revealed that bundled actin filaments converge beneath the center of each BMC and insert into the lateral membrane at points enriched in N-cadherin. Two other contractile proteins, caldesmon and myosin, were enriched in the BMC, co-localizing with f-actin bundles. The actin/N-cadherin complex formed a hexagonal lattice, cradling the posterior face of the lens. Removal of the capsule caused the tips of the fiber cells to break off, remaining attached to the stripped capsule. This provided a method for assaying cell adhesion and purifying BMC components. Fiber cell adhesion required Mg2+ and/or Ca2+ and was disrupted by incubation with beta1 integrin antibody. BMC proteins were compared with samples from the neighboring lateral membrane. Although some components were common to both samples, others were unique to the BMC. Furthermore, some lateral membrane proteins, most notably lens major intrinsic protein (MIP), were excluded from the BMC. Western blotting of BMC preparations identified several structural proteins originally found in focal adhesions and two kinases, FAK and MLCK, previously undescribed in the lens. These data suggest that the BMC constitutes a distinct membrane domain in the lens. The structural organization of the BMC suggests a role in shaping the posterior lens face and hence the refractive properties of the eye.

The relationship between morphological changes of lens epithelial cells and intraocular lens optic material

To examine the morphological changes of lens epithelial cells (LECs) occurring directly beneath and at regions contacting various intraocular lens (IOL) optic materials, human LECs were cultured on human anterior lens capsules and were further incubated upon placing above the cells lens optics made of polymethylmethacrylate, silicone, and soft acrylic material. Observations as to the morphological changes of LECs under phase-contrast microscope and scanning electron microscope were performed on the 14th day of incubation. Gatherings of LECs were observed at regions contacting the soft acrylic material under phase-contrast microscope, and gatherings of LECs were observed accurately at the same regions mentioned above under scanning electron microscope. On the other hand, LECs in contact with two other optic materials did not show morphological changes. The results suggest that LECs attached to and proliferated on not only the anterior lens capsules but also the soft acrylic IOL optics. The model used in this study may be useful in studying the relationship between cellular movement of LECs and IOL optic material.

Security of capsular fixation: small-versus large-hole plate-hepatic lenses

PURPOSE

To assess the effect of relatively large positioning holes on the security of capsular bag fixation of plate-haptic silicone intraocular lenses (IOLs).

SETTING

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

METHODS

This study tested the hypothesis that larger holes allow ingrowth of lens material, fibrous tissue, or both through them, which helps fixate the lens more firmly in the capsular bag. Five rabbits had bilateral continuous curvilinear capsulorhexis, phacoemulsification, and implantation of a plate-haptic silicone IOL. An IOL with a small, round positioning hole (Staar AA-4203V) was implanted in the right eye in each rabbit, and a large-hole IOL (Staar AA-4203VF) was implanted in the left eye. After 2 months, all rabbits were killed. The force required to extract one haptic from the capsular bag was measured with a digital force meter. All eyes had histopathological analysis.

RESULTS

It was slightly more difficult to extract a large-hole IOL from the capsular bag, although this trend was not statistically significant. However, histopathological analysis consistently showed 360 degree synechia formation through the holes, showing that the IOL could be securely fixed in position.

CONCLUSIONS

Proliferation of lens epithelial cells through a large positioning hole in a plate-haptic silicone IOL may improve the long-term security of capsular bag fixation. This will help reduce the incidence of IOL decentration and dislocation.

Phacoemulsification versus extracapsular cataract extraction: a comparative study of cell survival and growth on the human capsular bag in vitro

AIMS/BACKGROUND

Phacoemulsification is rapidly replacing conventional extracapsular cataract extraction (ECCE) as the method of choice for cataract surgery in the Western world. However, posterior capsule opacification (PCO) still remains the major postoperative complication, affecting 20-50% of patients, and results from persistent cell growth of epithelial cells remaining after surgery. This study aimed to compare cell survival and growth on capsular bags following ECCE and phacoemulsification surgery using an established human capsular bag culture system.

METHODS

Sham ECCE and phacoemulsification cataract operations were performed on pairs of human donor eyes. Capsular bags were dissected free, pinned flat on a petri dish, and incubated with Eagle's minimum essential medium (EMEM) alone or EMEM supplemented with 10% fetal calf serum (FCS). Ongoing observations were made using phase contrast microscopy.

RESULTS

Cell growth was observed across the posterior capsule of all preparations studied. It was found that there was no significant difference in the rate of cell growth on the posterior capsule with the two extraction methods, such that 50% confluency was achieved in 7.0 (SD 1.8) (n = 7) days for ECCE and 7.43 (2.1) (n = 7) days for phacoemulsification surgery. The physical changes to the capsule as a result of cell growth, such as wrinkling and capsular tensioning, were also seen in both groups.

CONCLUSIONS

Cell survival and growth is dependent on the donor, rather than the surgical technique performed. There is no significant difference between phacoemulsification and ECCE surgery on the rate and nature of cell growth on the posterior capsule in vitro.

Thapsigargin-coated intraocular lenses inhibit human lens cell growth

Cataract is responsible for rendering several million people blind throughout the world and is also by far the most common cause of low visual acuity. Although cataract surgery is common, routine and effective, posterior capsule opacification (PCO) occurs in 30-50% of patients following modern cataract surgery. This condition arises from stimulated cell growth within the capsular bag after surgery. The resulting decline in visual acuity requires expensive laser treatment, and PCO therefore prevents modern cataract surgery from being carried out routinely in underdeveloped countries. The present study, using a human lens capsular bag culture system, has confirmed that cells from a wide age range of donors proliferate in the absence of added serum protein and explains why PCO is such a common problem even in aged patients. This study also provides one possible solution for PCO by using polymethylmethacrylate (PMMA) implanted intraocular lenses as a drug delivery system. PMMA lenses coated with thapsigargin, a hydrophobic inhibitor of endoplasmic reticulum (ER) (Ca2+)-ATPase, greatly reduced cell growth in the capsular bag at relatively low coating concentrations (200 nM) but, more significantly, induced total cell death of the residual anterior epithelial cells at higher concentrations (>2 microM).

Inhibition of migrating lens epithelial cells by blocking the adhesion molecule integrin: a preliminary report

PURPOSE

To evaluate the preventive effect of blocking integrins by sustained release of RGD peptide (arginine-glycin-aspartic acid sequence) or a combination of RGD peptide and ethylenediaminotetraacetic acid (EDTA) on lens epithelial cell (LEC) migration.

SETTING

Nishi Eye Hospital, Jinshikai Medical Foundation, Osaka, Japan.

METHOD

A polylactic-glycolic acid disk containing 4% RGD or a combination of 23% EDTA and 10% RGD was implanted in the capsular bag in five rabbit eyes following standard cataract surgery. The release rate in vitro was 4.4 microg/h for RGD peptide alone and 7.8 and 7.6 microg/h for combined EDTA and RGD peptide, respectively. The contralateral eye received a disk without agents as a control.

RESULTS

After 1 month, a slight inhibition of LEC migration onto the posterior capsule was observed histopathologically in eyes receiving RGD peptide. A significant inhibition was observed in eyes with combined EDTA and RGD.

CONCLUSIONS

Application of RGD peptide and EDTA and RGD peptide may inhibit LEC migration by inhibiting the integrins expressed on the LECs. Blocking adhesion molecules expressed on LECs may reduce posterior capsule opacification.

Detection of polymorphic FGF receptor 1 mRNA in bovine lens epithelium by PCR

The expression of FGFR 1, 2 and 3 but not FGFR 4 was detected in bovine lens epithelial cells. FGFR 1 expression of both the 2-lg and 3-lg forms was detected by a difference in the lengths of the PCR products. Furthermore, mRNA which included or excluded six nucleotides corresponding to two amino acids in the acid box region of FGFR 1 was detected by a difference in mobility of the homo- and hetero-duplex strands formed in the PCR reaction.

Inhibition of cell proliferation on lens capsules by 4197X-ricin A immunoconjugate

PURPOSE

To evaluate the cytotoxicity of immunotoxin 4197X-ricin A (4197X-RA) and its ability to inhibit protein synthesis and human lens epithelial cell (LEC) proliferation on the inner surface of the lens capsule.

SETTING

Houston Biotechnology, Inc., The Woodlands, Texas.

METHODS

A cell culture system was established using human LECs as a model for the proliferation of remnant LECs that occurs during posterior capsule opacification (PCO) after extracapsular cataract extraction. The LEC culture system was also used in vitro for testing compounds that might inhibit this process in vivo. Human LECs were cultured on the surface of the original lens capsule fixed to collagen. Variability was reduced by dissecting each lens capsule into equivalent halves and exposing the segments to immunotoxin 4197X-RA.

RESULTS

Protein synthesis and LEC proliferation were almost completely inhibited at relatively low 4197X-RA concentrations after short exposure. The inhibitory effects persisted up to 3 weeks after withdrawal of the immunotoxin and after several media exchanges.

CONCLUSION

Immunotoxin 4197X-RA may help prevent PCO after primary cataract surgery.

Human lens epithelial cell proliferation in a protein-free medium

PURPOSE

The ocular humors are relatively low in protein, yet cell growth in the human capsular bag still occurs after extracapsular cataract extraction (ECCE) surgery. This resilient growth gives rise to posterior capsule opacification (PCO) in a significant proportion (30%) of patients. This study compared the ability of human lens cells to proliferate in serum-supplemented and protein-free medium.

METHODS

Sham cataract operations were performed on human donor eyes. The capsular bag was dissected free, pinned flat on a petri dish, and incubated in Eagle's minimal essential medium (EMEM) alone or in EMEM supplemented with 10% fetal calf serum. Observations were made by phase-contrast microscopy. At the endpoint, capsules were studied by fluorescence or electron microscopy. Mitotic activity was identified using Bromo-2-deoxyuridine labeling and detection techniques. When required, an intraocular lens was implanted when surgery was performed.

RESULTS

It was found that human lens cells from a wide age spectrum of donors proliferate and migrate on the lens capsule in the absence of added protein. The rate of growth was age-dependent, such that the posterior capsule was completely confluent after 8.0 +/- 0 days (n = 3) and 24.4 +/- 5.3 days (n = 3) for donor lenses aged < 40 years and > 60 years, respectively. The outgrowth of epithelial cells gave rise to capsular contraction, wrinkling, and increased light scatter. Growth on the anterior surface of the intraocular lens was less prolific than on the posterior capsule.

CONCLUSION

The protein-free model replicates many features of clinically-observed PCO. The resilient cell growth on the natural collagen capsule explains the high prevalence of PCO, especially in younger patients, and suggests that inflammation and external growth factors are not necessary for PCO. Furthermore, the protein-free capsular bag system can be used to explore fundamental questions concerning the autocrine control of lens epithelial cell survival and growth.

Diathermic capsulotomy versus capsulorhexis: a biomechanical study

PURPOSE

To compare the mechanical quality of a capsulotomy opening performed by diathermy with that made by capsulorhexis (tearing).

SETTING

Department of Ophthalmology, Vejle Hospital, Denmark.

METHODS

This study included 12 pairs of human cadaver eyes and 20 pairs of pig eyes. One in each pair was randomly selected for one capsulotomy technique. The capsulotomy edge was stretched in a materials testing machine until break; force and elongation values were continuously recorded.

RESULTS

In humans, the extensibility of the diathermic capsulotomy edge was approximately half that of the capsulorhexis edge (mean 38% +/- 4 [SD] versus 68% +/- 6), and the force required to break the edge was reduced by a factor of five (26 +/- 8 mN versus 134 +/- 36 mN).

CONCLUSION

The mechanical quality of the diathermic capsulotomy edge is significantly less than that of the capsulorhexis edge, which indicates that the diathermic capsulotomy edge would withstand less surgical manipulation.

Age-related changes of the ciliary sulcus: implications for implanting sulcus-fixated lenses

PURPOSE

To examine age-related anatomical changes of the ciliary sulcus and the implication of these changes for placement of posterior chamber intraocular lenses (IOLs).

SETTING

Department of Ophthalmology, University of Heidelberg, Germany.

METHODS

In this study, 64 human autopsy eyes from 38 donors were divided by age into six groups from younger than 40 years (Group 1) to 80 years and older (Group 6) in 10 year increments. External diameter, capsular bag size, and lens thickness were determined for each eye. The horizontal and vertical diameters of the ciliary sulcus were measured and histological sectioning, staining, and light microscopy performed.

RESULTS

The external diameters of the eyes showed no age correlation; the lenses exhibited the expected increase in thickness with age. The mean vertical diameter of the ciliary sulcus decreased in all age groups from 12.02 mm +/- 0.12 (SD) to 10.71 +/- 0.91 mm and the mean horizontal diameter, from 11.36 +/- 0.24 mm to 10.33 +/- 0.76 mm. Statistical analysis confirmed the overall significance (P < .05) of the differences among age groups.

CONCLUSION

The ciliary sulcus became smaller with age. This might affect the size of sulcus-implanted IOLs and should be noted for transsclerally sutured IOLs.

Retinoic acid: identification of specific receptors through which it may mediate transcriptional regulation of fibronectin gene in bovine lens epithelial cells

To elucidate in detail the regulatory mechanisms by which the fibronectin mRNA and protein are altered by all-trans retinoic acid (RA) in bovine lens epithelial (LE) cells, we have investigated the transcription mechanism and the occurrence of nuclear receptors for RA in the nuclei of cultured LE cells. The rate of transcription of fibronectin (FN) mRNA increased by 130% in response to RA. The RA receptors in nuclear extracts prepared from LE cells show specific all-trans [3H]-RA binding sites. Saturation binding of all-trans RA to these receptors and the Scatchard plot analyses of the binding data yielded an apparent dissociation constant (Kd) of about 12 nM and Bmax of about 48 pmoles/mg protein. Bovine retinoic acid receptors (RARs) have not been reported previously. Our results demonstrate for the first time that RA regulates FN expression and that regulation is at the transcriptional level in LE cells. Thus, retinoids may have an important role in the functional adhesion of epithelium to the lens capsule.

Lens epithelial cell migration onto the posterior capsule in vitro

PURPOSE

To investigate lens epithelial cell (LEC) proliferation on the posterior capsule in an in vitro model.

SETTING

Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan.

METHODS

We cultured the cells remaining on the postoperative capsular bag and expanded the capsule with an open poly(methyl methacrylate) ring to simulate actual postoperative conditions. Using human and rabbit cadaver eyes, we monitored the migration and proliferation of LECs onto the postoperative capsular bag by time-lapse videomicroscopy.

RESULTS

The remaining viable cells migrated onto the posterior capsule through the equator and directly from the anterior capsule. The cells typically proliferated in a monolayer because of contact inhibition of cell movement and division, but they proliferated in a multilayer at some regions where nonviable cells had accumulated and there were capsular folds.

CONCLUSION

A means to block both routes of cell expansion must be developed to prevent LEC migration onto the posterior capsule.

Lens epithelial cell proliferation onto the intraocular lens optic in vitro

PURPOSE

To determine how lens epithelial cells (LECs) proliferate onto an intraocular lens (IOL) after extracapsular cataract surgery.

SETTING

Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan.

METHODS

We cultured the capsular bags retaining LECs of eight human eye-bank eyes and six rabbit eyes that had had extracapsular lens extraction with in-the-bag implantation of a poly(methyl methacrylate) (PMMA) IOL and a PMMA ring. Cell proliferation onto the IOL optic was monitored by a time-lapse video system.

RESULTS

Cells proliferated onto the IOL optic via the anterior capsulotomy margin, the inner surface of the anterior capsule, and the posterior capsule. They formed cell sheets similar to the membranes observed in clinical cases.

CONCLUSIONS

Since the cells proliferated from the anterior capsule as well as from the posterior capsule onto the IOL optic, the membranes observed clinically on the IOL optic may be LEC sheets.

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

PURPOSE

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

SETTING

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

METHODS

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

RESULTS

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

CONCLUSION

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

[Devitalization of lens epithelium cells by dye-enhanced therapy]

Hitherto secondary cataract has been usually treated by Nd:YAG laser, which results in a dissection of the capsule with possible complications e.g. retinal detachment. Selective removal of the epithelial cells from the posterior capsule has not been possible. By use of dyes in connection with laser light of a suitable wavelength, lens epithelial cells could potentially be selectively destroyed. We investigated the dye indocyanine green, which has a peak absorbtion at the emission wavelength of commercially available diode lasers.

METHODS

Human lens epithelial cells and 3T3 cells (mouse embryonal fibroblasts) were grown in MEM with 10% FBS. Confluent and preconfluent layers were incubated with indocyanine green and treated with a diode laser attached to a slit lamp (810 nm, Zeiss VISULAS, Zeiss Oberkochen, Germany).

RESULTS

Indocyanine green alone was toxic in concentrations above 5 mg/ml (60 min). Combined with laser treatment (200 mW, 100 ms, 160 microns), indocyanine green led to cell damage in preconfluent cultures at concentrations above 0.01 mg/ml (10 min). After about 2 days irradiated cells became necrotic and began to desquamate from the culture disc. Cells in confluent cultures could be devitalised at concentrations above 0.05 mg/ml (10 min) using the same power. In contrast, neither indocyanine green alone nor diode laser alone could interfere with epithelial proliferation.

DISCUSSION

The experiments show the possibility of dye-enhanced therapy of lens epithelial cells with indocyanine green and diode laser. In contrast to other photosensitizers, indocyanine green is widely used in human function tests. Therefore its use for the treatment of secondary cataracts may merit discussion.

[The influence of macrophage on the rates of cultured rabbit lens epithelial cell proliferation and DNA synthesis]

Cell and H3-TDR liquid scintillation countings were adopted to investigate the influence of macrophage on the proliferative rate of cultured rabbit lens epithelial cells, in vitro. After 24 hours of the action of macrophage opsonic fluid on the cell culture, the rates of cell proliferation and DNA synthesis in the experimental group were higher than those of the control group (P < 0.05) and maintained so to the fifth day. It is demonstrated that the macrophage and its active factors can promote the proliferation of the lens epithelial cells, that is possibly related to the posterior capsular opacification after extracapsular cataract extraction.

A non-enzymatic method for lens decapsulation which leaves the epithelial cells attached to the fibers

We have developed a method to mechanically decapsulate the lens yet leave the epithelial cells attached to the fibers. This method uses divalent ion chelaters to loosen the capsule-epithelial interactions and bumetanide to control cell swelling. Light microscopy, scanning electron microscopy, and in-vitro fluorescence microscopy demonstrate that the capsule is removed and the epithelial cells remain adherent to the fibers when these procedures are used. Ion channel activity and epithelial gap junction communication remain following decapsulation. This decapsulated lens preparation should prove useful for many kinds of lens studies.

[Human lens epithelial cell culture and its proliferative inhibition in vitro]

The cultures of human lens epithelial cells taken from both normal and cataractous lenses were established in vitro. The biological characteristics and the histological changes of the cells were investigated. 5-Fluorouracil (5-Fu), Homoharring tonine (HH) and Harmeline (H) were used for the inhibition of the proliferative cells in the experiment. The results revealed that the in vitro survival capacity of the human lens epithelial cells is limited and the proliferative capacity of the cells is negatively correlated to the donor age. HH and H can effectively inhibit the lens epithelial cell proliferation. Based on the results of this report, performing small and smoothly edged anterior capsulorhexis in extracapsular cataract extraction may possibly decrease the incidence of the post-operative opacification of the posterior capsule.

Establishment of epithelial lines from cryopreserved lenses and capsule-epithelial preparations

PURPOSE

To determine if lens epithelial lines can be established from cryopreserved whole rabbit lenses and from cryopreserved capsule-epithelial preparations (CEPs).

METHODS

Lenses or freshly isolated CEPs were cryopreserved and subsequently thawed. Thawed whole lenses were cultured for 48 hours in growth medium and fixed, and whole mounts were examined for mitosis. In addition, CEPs were peeled from cryopreserved lenses and placed in tissue culture. Viability of cryopreserved cells was assessed measuring attachment efficiency and growth.

RESULTS

Whole mounts from cryopreserved lenses that were thawed and placed in organ culture in a serum-containing medium exhibited numerous mitotic figures. Freshly isolated CEPs that were cryopreserved and CEPs from cryopreserved lenses generated cell lines. Attachment efficiency was 90% within 3 hours of plating. When 50,000 cells from cryopreserved CEPs were cultured in growth medium, 10(6) cells were noted after 7 days of culture. The cells completed 27 population doublings and showed no sign of senescence.

CONCLUSIONS

Rabbit lens epithelial cell lines can be initiated from cryopreserved lenses or CEPs.

Cell biological analysis of the human cataractous lens: implication of lens epithelial cells in the development of aftercataract

Lens epithelial cells (LECs) from 3 patients with congenital cataract aged 2, 4 and 12 months, respectively, were cultured. The findings were compared with those from 26 eyes of 26 patients with senile cataract, with ages ranging from 60 to 89 years. The significantly higher growth potential of LECs in patients with congenital cataract compared to those with senile cataract, seems to be the cause of the higher frequency of aftercataract following cataract surgery in infants.

Modulating radiation cataractogenesis by hormonally manipulating lenticular growth kinetics

There is considerable evidence that the lens epithelium is the primary site of injury leading to the development of cataracts following radiation exposure. That the damaged cells of the epithelium are the progenitors of the aberrantly differentiating fibers associated with the cataract is indisputable. So too is the observation that post-radiation proliferative activity in the lens epithelium is required for cataracts to develop. The natural hormonal regulation of lens epithelial mitotic activity in the frog offers the opportunity to alter the cell cycle of the lens epithelium in vivo, thus enabling the direct examination of the role of lenticular mitosis in the cytopathomechanism of radiation-induced cataracts. The cell cycle of the lens epithelium of northern leopard frogs was manipulated by hypophysectomy (to halt mitotic activity) and pituitary hormone administration (to stimulate baseline mitosis and reverse hypophysectomy-induced mitotic suppression). Animals were hypophysectomized, irradiated and injected with pituitary hormone replacement. Irradiated animals, irradiated animals + hormone replacement and irradiated hypophysectomized animals served as controls. Cataract development was evaluated by slit-lamp biomicroscopy and correlated with histologic determinations of mitotic index and meridional row disorganization on lens epithelial whole mounts. In another study, hypophysectomized-irradiated animals received varying concentrations of replacement hormone in an attempt to quantitatively modulate lens epithelial mitotic activity and determine the effect on cataractogenesis. It was found that irradiated-hypophysectomized (mitosis halted) frogs failed to develop opacities, while those with hormonal replacement (mitosis reinstated) developed cataracts.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of cell adhesion to lens capsule by LCM 1910, an RGD-derived peptide

Opacification of the posterior lens capsule, (secondary cataract), is one of the major complications of extracapsular cataract extraction. The lens epithelial cells remaining after surgery migrate and proliferate along posterior capsule, and give rise to structures such as pearls and cells with contractile properties, which considerably hamper vision. One pharmacological approach aimed at limiting this phenomenon would be to stop this cell migration, thus inhibiting their proliferation. It has been shown that cells adhere and migrate on their support via adhesion molecules such as integrins. Generally, the tripeptide sequence Arg-Gly-Asp (RGD) is the recognition motif for these receptors. In this study, cell adhesion inhibition in the presence of RGD peptides and derivatives was measured on extracellular matrix and lens capsule. One of these compounds, the [N alpha-acetyl-NG(H+)-arginyl]-glycyl-[C beta (H)-C alpha -benzyl]-aspartamid- HCl] (LCM 1910), significantly inhibited cell migration at millimolar concentrations, and could be of interest in prevention of secondary cataract.

Localization of acidic fibroblast growth factor, basic fibroblast growth factor, and heparan sulphate proteoglycan in rat lens: implications for lens polarity and growth patterns

PURPOSE

Previous research in this laboratory has shown that fibroblast growth factor stimulates lens epithelial explants to proliferate, migrate, and differentiate into fibers in a progressive dose-dependent manner. The lens has distinct compartments where cells proliferate (germinative zone), migrate, or get displaced (equator) and differentiate into fibers (transitional zone). These compartments occur in an anteroposterior spatial sequence and the authors hypothesized that fibroblast growth factor plays a critical role in determining these spatial patterns of lens growth and lens polarity. To investigate this hypothesis the distribution of fibroblast growth factor in the lens was analyzed.

METHODS

Immunohistochemistry was used to localize acidic fibroblast growth factor and basic fibroblast growth factor in the cells and capsule of lenses from neonatal, weanling, and adult rats. Because of its functional relationship with fibroblast growth factor, heparan sulphate proteoglycan was also localized in the lens.

RESULTS

In all ages examined, cytoplasmic acidic fibroblast growth factor is present in the germinative and transitional zones of the lens and both acidic fibroblast growth factor and basic fibroblast growth factor are present in the capsule. A major finding is the co-localization of fibroblast growth factor and heparan sulphate proteoglycan reactivity in the lens capsule in the form of laminae. These laminae become more prominent as the capsule thickens and differences in arrangement of laminae between anterior, equatorial, and posterior regions of the capsule also become apparent.

CONCLUSIONS

The presence of fibroblast growth factor in lens cells and capsule in neonatal, weanling, and adult rats indicates an important role for fibroblast growth factor in lens cell biology. Moreover, the regional distribution of fibroblast growth factor, particularly in the lens cells, indicates that it may influence determination of lens polarity and growth patterns.

Beta-adrenergic mechanisms affect cell division and differentiation in cultured chick lens epithelial cells

Primary cultures of chick lens annular pad (CLAP) cells were exposed to beta-adrenergic drugs and lipid soluble cAMP analogues. In dose-dependent manners, these agents inhibited re-entry into the cell cycle when these normally post-mitotic cells were cultured in the presence of serum. The inhibition of cell division was evidenced by a lack of DNA accumulation and greatly reduced tritiated thymidine incorporation into DNA. Treated cells were also largely inhibited from spreading onto the substrate. Instead, the epithelial monolayers originally placed into culture formed nearly spherical aggregates. Treated cultures continued to synthesize crystallins and exhibited increased levels of a 49-kDa cytoskeletal protein which accumulates in fiber cells. These results indicate that beta-adrenergic mechanisms may be involved in regulating cell division and terminal differentiation of lens fiber cells.

Surface properties of intraocular lens materials and their influence on in vitro cell adhesion

An in vitro model to assess lens epithelial cell adhesion to a variety of intraocular lens materials was developed. Rabbit anterior lens capsules were isolated and cultured in serum-containing medium. Test surfaces included poly(methyl methacrylate), two new silicones (SLM-1/UV, SLM-2/UV), two hydrogels (HEMA, Lidofilcon A), and polytetrafluoroethylene (PTFE). Following the application and culturing of cells on the test surfaces, adherent cells were removed by trypsinization and counted at eight and 24 hours. The material surfaces were characterized by electron spectroscopy for chemical analysis and scanning electron microscopy. The captive bubble technique was also used to assess interfacial free energy. More cells adhered to PMMA than to the other materials tested (P less than .01). The two silicones, HEMA, and PTFE did not differ significantly from each other; Lidofilcon A had the lowest cell adhesion of all materials tested. Cell adhesion results were related to the interfacial free energy of each material. Materials of low (less than 5 ergs/cm2) or high (greater than 40 ergs/cm2) interfacial free energies had lower cell adhesion than materials of intermediate free energies (5 to 40 ergs/cm2) which exhibited the highest cell adhesion.

Removal of lens epithelial cells by dispersion with enzymatic treatment followed by aspiration

We conducted a preliminary trial of a method of lens epithelial cell removal in cataract surgery that combined mechanical and pharmaceutical treatments. The cells were first loosened from their junctional complexes with Dispase, a preparation of a neutral protease used for separating cells in tissue culture. To avoid intraocular tissue damage, the enzyme preparation was dissolved in sodium hyaluronate and injected into the capsular bag, which was carefully preserved during endocapsular cataract surgery. The cells were then removed by irrigation and aspiration. The results of experiments in vitro and in rabbits and, judging from the histopathologic examination, with negligible damage to the zonules or corneal endothelium.

Study of the lens epithelial cell density in cataractous eyes operated on with extracapsular and intercapsular techniques

Epithelial cell counting was performed in 47 fragments from lens anterior capsules obtained during extracapsular and intercapsular surgery. Mean cell count was 3,277 cell/mm2; there was no correlation between cell number and age and no significant difference in cell counts between extracapsular and intercapsular surgery. There were, however, significant differences between advanced cataracts and the other cataract types (2,947 vs. 3,356). This may be important in explaining the differences in regenerative opacification of the posterior capsule in the different types of cataracts.

Extracapsular cataract extraction with keyhole capsulorhexis and lens epithelial cell removal

Circular capsulorhexis with its round continuous anterior capsule opening allows secure fixation of a posterior chamber intraocular lens. The smooth capsular margin edge reduces stress concentration and the risk of radial tears but it makes nucleus delivery in planned extracapsular cataract extraction very difficult. This report describes a technique of small circular capsulorhexis with one relaxing incision that gives a keyhole-shaped capsular opening. A new irrigating capsule retractor for nucleus hydrodissection is also described. This technique is safe and highly reproducible and it allows secure posterior chamber lens fixation.

[Effect of daunomycin on epithelial cells of the crystalline lens. Experimental and clinical study]

Daunomycin action on human lens epithelial cells has been tested in vitro, with different exposure times. A clinical study on 30 eyes, operated on by the same surgeon, has been carried out according to the Cologne protocol. Cell cultures, with different techniques were grown. This demonstrates that Daunomycin can destroy the lens epithelial cells. We can not currently say what dosage and protocols are necessary to achieve a prevention of secondary cataract.

Structural analysis of lens epithelial explants induced to differentiate into fibres by fibroblast growth factor (FGF)

Recently we identified fibroblast growth factor (FGF), which is present in significant amounts in neural retinas, as a potent inducer of lens fibre differentiation in our epithelial explant cultures. Fibre differentiation was assessed by synthesis of fibre specific, proteins, beta- and gamma-crystallins, and by cell elongation. However, to establish whether FGF induced the dramatic structural changes characteristic of fibre differentiation we carried out an ultrastructural analysis. In this study epithelial explants exposed to either the acidic or basic form of FGF were shown to undergo the structural changes characteristic of fibre differentiation in the intact lens. These include: (i) cell elongation, (ii) a reduction in cytoplasmic organelles, (iii) the formation of specialized cell-cell junctions, including finger-like processes and fingerprints, ball and socket junctions, tongue-like flaps and imprints, and gap junctions, and (iv) nuclear pyknosis. This shows that FGF faithfully reproduces structural events associated with fibre differentiation as well as the molecular events reported previously, thus providing further evidence that FGF in the eye is important for the control of normal lens fibre differentiation.

Amyloid P protein in pseudoexfoliative fibrillopathy

Amyloid P protein was demonstrated by immunostaining in all 14 samples of ocular and conjunctival pseudoexfoliative (PSX) material studied, although amyloid was not found by Congo red staining or ultrastructurally. Immunostaining of PSX aggregates for other common amyloid proteins, including amyloid A, prealbumin, and immunoglobulin light chains, was negative in most cases. In three eyes with advanced neovascular glaucoma there was irregular immunostaining of the PSX aggregates for 2-4 of these other amyloid proteins, besides diffuse staining of the iris and vitreous. Control cases of neovascular glaucoma without PSX disease showed minimal amyloid P, but similar tissue staining for prealbumin and immunoglobulin light chains, consistent with an origin from vascular leakage. The presence of amyloid P protein, a minor serum component, in PSX aggregates in all cases with or without evidence of vascular leakage, indicated a more specific association. Ultrastructural localization of the protein on the periphery of PSX fibers suggest it is not an intrinsic fiber component. Since PSX material has an immunological relation to elastic tissue, we propose that PSX fibers have peripheral binding sites for amyloid P protein, similar to those present on normal elastic fibers.

Synthesis of lens capsule and plasma membrane glycoproteins by lens epithelial cells and fibers in the rat

The lens of the eye possesses a capsule which is a greatly hypertrophied basement membrane. To investigate the synthesis of glycoproteins destined for this capsule, 3H-fucose was injected into the vitreous body of intact rats weighing approximately 200 gm. The animals were killed from 10 min to 14.5 months later, and their lenses were processed for electron microscope radioautography. At 10 min after injection, more than 58% of the silver grains were localized to the Golgi apparatus of the lens epithelial cells. By day 1, the heaviest sites of reaction were the plasma membrane (more than 50% of total label), the basal cytoplasm, and the adjacent lens capsule, where a heavy band of reaction was seen. The remainder of the capsule exhibited a lighter diffuse reaction. In the lens fibers, the label was at first localized to clusters of vesicles but then migrated to the plasma membrane and to the region of the capsule adjacent to the basal surface of these fibers. Light microscope radioautographs of the lens capsule at later time intervals revealed that by 1 month after injection the diffuse reaction had disappeared, and only the strongly labeled band remained. By 14.5 months after injection, this band had migrated partially across the lens capsule, but the capsule itself had increased considerably in thickness. On the other hand, the distance between the labeled band and the free edge of the capsule had decreased from that seen at the time of injection.

Human lens epithelial cells in culture: a quantitative evaluation of growth rate and proliferative capacity

Human lens epithelial (HLE) cells were explanted into medium containing different concentrations of foetal calf serum (FCS) and serum substitute. The proliferation of cells was measured as a function of time in culture and the growth parameters (growth rate and proliferative capacity) were determined by the application of the Gompertz growth function. Human lens epithelial cells have a limited growth capacity in culture of five to seven population doublings and this decreases with age. The population doubling level (PDL) was determined empirically and from fits of the Gompertz equation. The values of the PDL determined experimentally and theoretically are compared for a series of different culture conditions. Exposure of the cells to raised levels of FCS caused a reduction in proliferative capacity; the PDL decreased from 6.3 to 5.5 when the serum was raised to 50% although the growth rate increased. Serum substitute caused a decrease in the growth rate without changing the proliferative capacity and also altered the cellular morphology. It is hoped that the method described will have applications to the study of posterior capsule opacification following extracapsular cataract extraction and phacoemulsification and will aid in the development of preventive therapies.

Comparative study of the effects of optic design on lens epithelium in vitro

We performed two tissue culture experiments designed to compare the effects of various posterior chamber optics on lens epithelium. In the first experiment, we recorded, by phase contrast microphotography, the migration of rabbit lens epithelium exoplants placed adjacent to the optic of various posterior chamber lenses. In the second experiment, we used phase contrast microphotographs to document the effects of various posterior chamber optics when gently placed on a confluent layer of rabbit lens epithelium. From our in vitro studies, we conclude the following: There is inhibition of lens epithelial migration and even cytotoxic effects from direct contact with polymethylmethacrylate optics; glass optics have appreciably less effect on lens epithelium; polymethylmethacrylate optics with ridges (complete annulus or incomplete) do not inhibit lens epithelial migration as well as planoconvex lenses, and they do not have a cytotoxic effect except at the points of contact between the ridge and the supporting surface.

Inhibition of retinal pigment epithelial cell attachment by a synthetic peptide derived from the cell-binding domain of fibronectin

Retinal pigment epithelial (RPE) cells are dispersed into the vitreous cavity during retinal reattachment surgery and attach to the vitreous gel and internal limiting membrane. Subsequent migration and cell-mediated contraction can result in traction retinal detachment. Fibronectin (FN) can enhance the attachment of various cell types. We now report that FN enhances the attachment of human and porcine RPE cells. A synthetic tetrapeptide, arg-gly-asp-ser (RGDS), derived from the FN cell-binding domain, has been shown to interfere with attachment of some cell types. We now report that RGDS inhibits RPE cell attachment to FN in a dose-dependent manner with 70% inhibition at 1 mg/mL. Also, RGDS inhibits attachment to types I and II collagen, as well as to lens capsule basement membrane by 40%, 50%, and 25%, respectively. Therefore, RGDS or its derivatives may have some eventual role in the management of proliferative vitreoretinopathy.

Growth and differentiation of human keratinocytes cultured on eye lens capsules

The efficiency of the outgrowth of human epidermal and hair-follicle-sheath keratinocytes was studied using three different growth substrates: plastic, type-I collagen and bovine eye lens capsules (the Epicult system). It was shown that the eye lens capsule is the best substrate, since a higher percentage of cultures showed outgrowth, and the outgrowth of epidermal keratinocytes was much more rapid. This effect is related to the faster migration (not proliferation) of cells grown on lens capsules as compared to the two other substrates. The view that lens capsules can replace the basement membrane present in vivo was supported by the finding that two basement-membrane components, i.e., laminin and fibronectin, are present on lens capsules. It was shown that, in cultures grown on lens capsules, bullous-pemphigoid antigen is restricted to the basal layer, indicating that the differentiation of these cells is comparable to that of keratinocytes grown on irradiated, non-viable pig dermis.

Association of alpha-crystallin with actin in cultured lens cells

The nature of the beaded filaments in the lens fiber cell has been debated for some time. One explanation is that beaded filaments represent an association of alpha-crystallin with actin filaments. By using a double labelling technique that allowed us to view actin filaments and alpha-crystallin in the same cell we have demonstrated that some of the alpha-crystallin in lens cells is indeed associated with actin.

Growth, synthesis and regional specialization of the embryonic chicken lens capsule

The growth, synthesis and regional specialization of the lens capsule has been studied in chicken embryos and compared to adult chickens and mammals. During the final 15 days of embryonic development the surface area of the capsule increased 11-fold. This represents the minimum estimate of capsule growth, since it also increased in thickness during this period. Autoradiographic examination of [3H]proline- or 35SO4-labeled, detergent-cleaned, flat-mounted capsules suggested that all lens cells participated in capsule synthesis. This was supported by the observation that both lens epithelial and fiber cells incorporated [35S]-methionine into collagenase-sensitive proteins with molecular weights similar to type IV collagen. Histochemical staining of detergent-cleaned capsule explants (DCCEs) revealed regional differences in the carbohydrate composition of the capsule. Differences in collagenous proteins were also seen between the anterior and posterior regions of the capsule of the embryonic lenses. Following SDS-PAGE and silver staining a total of six collagenase-sensitive proteins were seen with molecular weights between 150 and 180 K. Three of these polypeptides were common to both anterior and posterior capsules, one was found only in the anterior capsule and the other two were found predominantly in the posterior capsule. No regional differences were seen in the collagenous proteins of capsules from adult chickens, rats or hamsters. The possibility is discussed that the unique pattern of collagenous polypeptides seen in embryonic capsules is related to the rapid growth of the embryonic lens.

Lens epithelial cell adhesion to lens capsule: a model system for cell-basement membrane interaction

Adhesion of calf lens epithelial cells to lens capsule, their natural basement membrane was found to be considerably more rapid than either to plastic or to type I or type IV collagen coated surfaces. No polarity of the basement membrane was observed as the cells were able to attach to either side of the anterior or posterior lens capsule; a prerequisite for adhesion to the lenticular side of the anterior capsule was the prior removal of its epithelial cell layer. The attachment was energy-dependent and required calcium and magnesium ions, but was not enhanced by the presence of serum. Neither exogenous fibronectin nor laminin was able to stimulate attachment or spreading of lens cells to the capsule even when the cells had been treated with cycloheximide. Since rapid adhesion and spreading takes place in this lens cell-lens capsule system without requirement of exogenous macromolecules, it provides a favorable model for investigating the determinants in epithelial cell-basement membrane interactions.