Lens epithelial cell proliferation in human posterior capsule opacification specimens

Influence of Lens Power on IOL/Posterior Lens Capsule Interactions and IOL's PCO Potential

Purpose

Severely myopic eyes have been associated with high posterior capsule opacification (PCO) incidence. Although it has been reported that myopic eyes have weaker or more delayed capsule adhesion than emmetropic eyes, it is unclear whether/how dioptric power and posterior curvature of IOLs affect IOLs' affinity for the posterior lens capsule (PLC) and their PCO potential.

Methods

To investigate this, acrylic foldable IOLs with increasing dioptric power of 6.0D (for high myopia), 20.0D, and 30.0D (for low/non-myopia) were tested on their binding affinity toward PLC and their ability to inhibit the proliferation and infiltration of lens epithelial cells (LECs) using an in vitro simulated human PLC (sPLC) model.

Results

We found that IOL power and posterior radius of curvature (PRC) had significant impacts on IOL/sPLC adhesion forces, which are in the following order: 20.0D ≈ 30.0D > 6.0D. Optical coherence tomography (OCT) images showed that loose binding between 6.0D IOLs and sPLC contributed to larger interface spaces and significantly greater LEC infiltration, proliferation, metabolic activity, and transdifferentiation compared to 20.0D and 30.0D IOLs. Statistical analyses showed that IOLs' PRC may have a substantial influence on IOL/sPLC physical interactions, LEC responses, and PCO incidence.

Conclusions

The overall results suggest that the high PRC of low-diopter (6.0D) IOLs reduces their binding affinity toward the PLC, facilitates LEC reactions, thus causes high PCO incidence in myopic eyes. These findings strongly support that a new design to increase IOL posterior surfaces' PLC affinity may reduce PCO potential and increase safety for myopic patients.

A 3D in vitro model for assessing the influence of intraocular lens: Posterior lens capsule interactions on lens epithelial cell responses

Posterior Capsule Opacification (PCO), the most frequent complication of cataract surgery, is caused by the infiltration and proliferation of lens epithelial cells (LECs) at the interface between the intraocular lens (IOL) and posterior lens capsule (PLC). According to the "no space, no cells, no PCO" theory, high affinity (or adhesion force) between the IOL and PLC would decrease the IOL: PLC interface space, hinder LEC migration, and thus reduce PCO formation. To test this hypothesis, an in vitro hemisphere-shaped simulated PLC (sPLC) was made to mimic the human IOL: PLC physical interactions and to assess their influence on LEC responses. Three commercially available IOLs with different affinities/adhesion forces toward the sPLC, including Acrylic foldable IOL, Silicone IOL, and PMMA IOL, were used in this investigation. Using the system, the physical interactions between IOLs and sPLC were quantified by measuring the adhesion force and interface space using an adhesion force apparatus and Optical Coherence Tomography, respectively. Our data shows that high adhesion force and tight binding between IOL and sPLC contribute to a small interface space (or "no space"). By introducing LECs into the in vitro system, we found that, with small interface space, among all IOLs, acrylic foldable IOLs permitted the least extent of LEC infiltration, proliferation, and differentiation (or "no cells"). Further statistical analyses using clinical data revealed that weak LEC responses are associated with low clinical PCO incidence rates (or "no PCO"). The findings support that the in vitro system could simulate IOL: PLC interplays and predict IOLs' PCO potential in support of the "no space, no cells, no PCO" hypothesis.

The lens epithelium as a major determinant in the development, maintenance, and regeneration of the crystalline lens

The crystalline lens is a transparent and refractive biconvex structure formed by lens epithelial cells (LECs) and lens fibers. Lens opacity, also known as cataracts, is the leading cause of blindness in the world. LECs are the principal cells of lens throughout human life, exhibiting different physiological properties and functions. During the embryonic stage, LECs proliferate and differentiate into lens fibers, which form the crystalline lens. Genetics and environment are vital factors that influence normal lens development. During maturation, LECs help maintain lens homeostasis through material transport, synthesis and metabolism as well as mitosis and proliferation. If disturbed, this will result in loss of lens transparency. After cataract surgery, the repair potential of LECs is activated and the structure and transparency of the regenerative tissue depends on postoperative microenvironment. This review summarizes recent research advances on the role of LECs in lens development, homeostasis, and regeneration, with a particular focus on the role of cholesterol synthesis (eg., lanosterol synthase) in lens development and homeostasis maintenance, and how the regenerative potential of LECs can be harnessed to develop surgical strategies and improve the outcomes of cataract surgery (Fig. 1). These new insights suggest that LECs are a major determinant of the physiological and pathological state of the lens. Further studies on their molecular biology will offer possibility to explore new approaches for cataract prevention and treatment.

The importance of the epithelial fibre cell interface to lens regeneration in an in vivo rat model and in a human bag-in-the-lens (BiL) sample

Human lens regeneration and the Bag-in-the-Lens (BIL) surgical treatment for cataract both depend upon lens capsule closure for their success. Our studies suggest that the first three days after surgery are critical to their long-term outcomes. Using a rat model of lens regeneration, we evidenced lens epithelial cell (LEC) proliferation increased some 50 fold in the first day before rapidly declining to rates observed in the germinative zone of the contra-lateral, un-operated lens. Cell multi-layering at the lens equator occurred on days 1 and 2, but then reorganised into two discrete layers by day 3. E- and N-cadherin expression preceded cell polarity being re-established during the first week. Aquaporin 0 (AQP0) was first detected in the elongated cells at the lens equator at day 7. Cells at the capsulotomy site, however, behaved very differently expressing the epithelial mesenchymal transition (EMT) markers fibronectin and alpha-smooth muscle actin (SMA) from day 3 onwards. The physical interaction between the apical surfaces of the anterior and posterior LECs from day 3 after surgery preceded cell elongation. In the human BIL sample fibre cell formation was confirmed by both histological and proteome analyses, but the cellular response is less ordered and variable culminating in Soemmerring's ring (SR) formation and sometimes Elschnig's pearls. This we evidence for lenses from a single patient. No bow region or recognisable epithelial-fibre cell interface (EFI) was evident and consequently the fibre cells were disorganised. We conclude that lens cells require spatial and cellular cues to initiate, sustain and produce an optically functional tissue in addition to capsule integrity and the EFI.

Circ-GGA3 promotes the biological functions of human lens epithelial cells depending on the regulation of miR-497-5p/SMAD4 axis

The cause of posterior capsular opacification (PCO) is the dysfunction of lens epithelial cells (LECs). Circular RNA (circRNA) was found to regulate cell biological functions, including LECs. However, the role of circ-GGA3 in PCO formation is unclear. Quantitative real-time PCR was used to measure the expression of circ-GGA3, miR-497-5p and SMAD4. Cell proliferation, invasion and migration were determined via MTT assay, EdU staining, transwell assay and wound healing assay. The protein expression of epithelial-mesenchymal transition (EMT) markers, fibrosis markers, TGF-β/SMAD pathway markers and SMAD4 were determined by western blot assay. The interaction between miR-497-5p and circ-GGA3 or SMAD4 was confirmed using dual-luciferase reporter assay. Circ-GGA3 was highly expressed in PCO patients, and its silencing inhibited the proliferation, invasion, migration, EMT process and fibrosis of TGF-β2-induced LECs. Circ-GGA3 could sponge miR-497-5p to regulate SMAD4. Further experiments revealed that miR-497-5p inhibitor recovered the negative regulation of circ-GGA3 knockdown on the biological functions of TGF-β2-induced LECs, and SMAD4 overexpression also abolished the suppressive effect of miR-497-5p. In addition, circ-GGA3/miR-497-5p/SMAD4 axis could activate the TGF-β/SMAD pathway. Our results indicated that circ-GGA3 could enhance the biological functions of LECs, suggesting that circ-GGA3 might be a potential target for PCO therapy.

Thermoresponsive GenisteinNLC-dexamethasone-moxifloxacin multi drug delivery system in lens capsule bag to prevent complications after cataract surgery

Cataract surgery is the most common intraocular procedure. To decrease postsurgical inflammation, prevent infection and reduce the incidence of secondary cataract, we built a temperature-sensitive drug delivery system carrying dexamethasone, moxifloxacin and genistein nanostructured lipid carrier (GenNLC) modified by mPEG-PLA based on F127/F68 as hydrogel. Characterizations and release profiles of the drug delivery system were studied. In vitro functions were detected by CCK-8 test, immunofluorescence, wound-healing assay, real time-PCR and western blotting. The size of GenNLCs was 39.47 ± 0.69 nm in average with surface charges of - 4.32 ± 0.84 mV. The hydrogel gelation temperature and time were 32 °C, 20 s with a viscosity, hardness, adhesiveness and stringiness of 6.135 Pa.s, 54.0 g, 22.0 g, and 3.24 mm, respectively. Transmittance of the gel-release medium was above 90% (93.44 ± 0.33% to 100%) at range of 430 nm to 800 nm. Moxifloxacin released completely within 10 days. Fifty percent of dexamethasone released at a constant rate in the first week, and then released sustainably with a tapering down rate until day 30. Genistein released slowly but persistently with a cumulative release of 63% at day 40. The thermoresponsive hydrogel inhibited the proliferation, migration and epithelial-mesenchymal transition of SRA 01/04 cells, which were confirmed by testing CCK-8, wound-healing assay, western blot, real time-PCR (RT-PCR) and immunofluorescence. These results support this intracameral thermoresponsive in situ multi-drug delivery system with programmed release amounts and release profiles to cut down the need of eye drops for preventing inflammation or infection and to reduce posterior capsular opacification following cataract surgery.

Posterior capsule opacification: What's in the bag?

Cataract, a clouding of the lens, is the most common cause of blindness in the world. It has a marked impact on the wellbeing and productivity of individuals and has a major economic impact on healthcare providers. The only means of treating cataract is by surgical intervention. A modern cataract operation generates a capsular bag, which comprises a proportion of the anterior capsule and the entire posterior capsule. The bag remains in situ, partitions the aqueous and vitreous humours, and in the majority of cases, houses an intraocular lens (IOL). The production of a capsular bag following surgery permits a free passage of light along the visual axis through the transparent intraocular lens and thin acellular posterior capsule. Lens epithelial cells, however, remain attached to the anterior capsule, and in response to surgical trauma initiate a wound-healing response that ultimately leads to light scatter and a reduction in visual quality known as posterior capsule opacification (PCO). There are two commonly-described forms of PCO: fibrotic and regenerative. Fibrotic PCO follows classically defined fibrotic processes, namely hyperproliferation, matrix contraction, matrix deposition and epithelial cell trans-differentiation to a myofibroblast phenotype. Regenerative PCO is defined by lens fibre cell differentiation events that give rise to Soemmerring's ring and Elschnig's pearls and becomes evident at a later stage than the fibrotic form. Both fibrotic and regenerative forms of PCO contribute to a reduction in visual quality in patients. This review will highlight the wealth of tools available for PCO research, provide insight into our current knowledge of PCO and discuss putative management of PCO from IOL design to pharmacological interventions.

Effect of anterior capsule polish on visual function: A meta-analysis

PURPOSE

To investigate the relationship between anterior capsule polish and visual function.

METHODS

Data were obtained from Pubmed, Embase, Web of Science, WanFang, VIP and CNKI up to the end of May 2018, without any date or language restrictions for trials. The modified Jadad scale and the newcastle-ottawa scale were used to assess the quality of included studies. Uncorrected visual acuity (UCVA) and posterior capsule opacification (PCO) were used as outcome variables. Data on anterior capsule polish were pooled using weighted, random-effect meta-analysis.

RESULTS

One randomized controlled trial and 4 observational cohort studies involving 2533 patients were included in the analyses. There was a statistically significant difference of UCVA (OR 1.92, 95% CI 1.41-2.61) between the polish group and the control group, indicating that anterior capsule polish improved UCVA. Further studies with continuous data also suggested that anterior capsule polish was associated with good UCVA (MD 0.11, 95% CI 0.06-0.16). Posterior capsule opacification rate for 1-year or longer follow-up were extracted for 2561 eyes in 3 studies. Posterior capsule opacification rate was lower in the anterior capsule polish group according to summary odds ratio on PCO rate (OR 0.42 95% CI 0.24-0.73).

CONCLUSIONS

Anterior capsule polish prevents complication of modern cataract surgery and benefits on visual function in short term follow-up period.

Anterior Capsule of the Lens: Comparison of Morphological Properties and Apoptosis Induction following FLACS and Standard Phacoemulsification Surgery

Purpose

Comparative evaluation of morphological features of anterior capsules and apoptosis induction in epithelial cells after femtosecond laser-assisted cataract surgery (FLACS) and standard phacoemulsification surgery.

Methods

Group 1: 30 FLACS anterior capsulotomies and Group 2: 30 manual anterior continuous curvilinear capsulorhexes. All patients were operated on by the same experienced surgeon. Morphological features of the anterior capsules and apoptosis induction in epithelial cells were evaluated.

Results

All patients revealed a significant mean best-corrected visual acuity (BCVA) improvement 3 months after surgery, and no major intraoperative nor postoperative complications occurred. The capsular epithelium appeared to be preserved in both groups. Scanning electron microscopy analysis revealed irregular saw-tooth shaped edges in capsules from Group 1 whereas capsules from Group 2 showed regular and smooth edges. A statistically significant higher expression of the downstream apoptotic effector cleaved caspase 3 was observed in Group 1.

Conclusions

The saw-tooth appearance was likely due to the progressive sequence of laser pulses on the capsule. The low energy/high frequency properties of the laser pulse, combined with an overlapped pulse pattern, resulted in highly continuous morphology of capsule edges. The higher apoptosis induction in FLACS group might be due to photodisruption-dependent plasma generation and formation of cavitation bubbles.

Proliferating cell nuclear antigen immunoreactivity in the ovarian surface epithelium of mice of varying ages and total lifetime ovulation number following ovulation

Everytime an oocyte is released at ovulation, the ovarian surface epithelium (OSE) is ruptured and must be restored by epithelial cell proliferation. Ovulation site closure was studied in mice of various ages along with total lifetime ovulation number to investigate the known association of these factors with the risk of epithelial ovarian cancer. Ovaries from Swiss Webster mice were collected at various time points postovulation from 3-mo virgin animals (estimated median total lifetime ovulation number, 92; n = 40 mice), 8-mo virgin animals subject to incessant ovulation (estimated median total lifetime ovulation number, 652; n = 15 mice), and 12-mo breeders (estimated median total lifetime ovulation number, 208; n = 35 mice). Diameters of ovulation sites were estimated by scanning electron microscopy. No differences were found in the rate of ovulation site closure between the groups. Sections of ovaries were analyzed using immunohistochemistry for proliferating cell nuclear antigen (PCNA). The highest density of immunoreactive cells was observed in all animal groups in the cuboidal cells around the rupture site the day after ovulation. Despite the similarity in ovulation site closure rates between groups, the total number of OSE cells that were positive for PCNA in both the 8- and 12-mo animals was significantly reduced, so the number of stained cells appeared to be insufficient to cover the ovulation site. These data suggest that other mechanisms, such as proliferation of the extraovarian mesothelium, may play a role in the re-epithelialization of the ovary.

Effects of bacterial toxins on air-exposed cultured human respiratory sinus epithelium

The present study was designed to investigate the effects of the bacterial toxins lipopolysaccharide (LPS) and lipoteichoic acid (LTA) on air-exposed cultured human respiratory sinus epithelium. The morphological changes, proliferation, and differentiation of sphenoid sinus mucosa were examined after incubation with different LPS or LTA concentrations. Air-exposed cultured sinus mucosa differentiated from pseudostratified respiratory epithelium to squamous ciliated epithelium with few goblet cells. High concentrations of bacterial toxins induced a significant increase in mucus production and a decrease in ciliated cells. Ki67 immunostaining showed an increased cell proliferation after incubation with moderate levels of LPS or LTA. High concentrations of bacterial toxins, on the other hand, induced a decreased proliferation. Involucrin expression was clearly altered by incubation with high levels of bacterial toxins, indicating an increased degree of terminal differentiation. These results indicate that the bacterial toxins LPS and LTA both induce comparable dose-dependent morphological changes in sinus epithelium.

Comparison of the biocompatibility of 2 foldable intraocular lenses with sharp optic edges

PURPOSE

To compare the clinical performance of 2 foldable intraocular lenses (IOLs) with sharp optic edges in terms of uveal and capsular biocompatibility.

SETTING

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

METHODS

Fifty eyes scheduled for cataract surgery were included in this comparative study. A standardized surgical protocol was used, and all operations were performed by 1 experienced surgeon. Two posterior chamber lens types of similar design with a 6.0 mm sharp-edged optic and poly(methyl methacrylate) haptics were used. Twenty-five eyes received an AcrySof acrylic IOL (Alcon), and 25 eyes received a CeeOn 911A silicone IOL (Pharmacia). Relevant data were collected at a 3-year follow-up examination. To evaluate uveal biocompatibility, anterior chamber laser flare and cell measurements and inflammatory cell reactions were monitored. Cellular biocompatibility was investigated by examining anterior capsule opacification (ACO), posterior capsule opacification (PCO), and lens epithelial cell (LEC) ongrowth on the IOL's anterior surface. Factors such as intralenticular glistenings and IOL decentration were also evaluated.

RESULTS

Anterior chamber flare and cells and the inflammatory cell reaction were significantly lower in the CeeOn 911A group. There was no statistically significant difference in ACO, PCO, and LEC ongrowth between the 2 groups. The AcrySof lenses showed significantly better centration and a higher density of intralenticular glistening.

CONCLUSIONS

The findings show that a sharp-edged optic design is, to date, the most effective method of reducing the rate of PCO. Despite a subclinical foreign-body reaction in the AcrySof group, both lenses had a high degree of capsular and uveal biocompatibility.