Cyclosporin effectively inhibits posterior capsule opacification after phacoemulsification in rabbits: a preliminary study

Observation of Cyclosporin A: Sustained Release Intraocular Lens Implantation in Rabbit Eyes

PURPOSE

To observe the performance of cyclosporine A (CsA)-loaded intraocular lens (IOLs) implanted into rabbit eyes.

METHODS

To prepare a PLGA-based CsA-sustained release IOLs and study the in vitro drug release. Forty-two New Zealand white rabbits were randomly and equally divided into three groups, and all right eyes underwent phacoemulsification. In group A, a common polymethylmethacrylate (PMMA) IOLs was implanted, while polylactide-glycoli acid (PLGA-loaded)-PMMA-IOLs was implanted in group B, and CsA-PLGA-PMMA-IOLs was implanted in group C. All experimental eyes were examined by slit-lamp microscopy. In addition, fundoscopy and the number of corneal endothelial cells, anterior chamber flare grading, and the number of aqueous humor cells were assessed at different time points post-surgery. The wet lens capsule was weighed and histological examination was performed 6 months post-operation.

RESULTS

In the early post-operative period, the inflammatory reaction of anterior chamber in groups A and B were more severe than group C. The initial appearance of PCO in group C was much later than the other two groups (F = 68.91; p = 0.000), and PCO grade in group C was much lower than the other two groups (χ² = 36.07; p = 0.000). The mean weights of wet lens capsules in groups A and B were significantly heavier than group C (F = 134.88; p = 0.00). Histological observation showed no obvious toxic reaction in the intraocular tissues of the CsA-PLGA-PMMA-IOLs group, and the proliferation and accumulation of lens epithelial cells in groups A and B were greater than in group C.

CONCLUSION

CsA-sustained release IOLs can effectively prevent PCO in rabbit eyes without defined intraocular toxicity.

Centrifugally concentric ring-patterned drug-loaded polymeric coating as an intraocular lens surface modification for efficient prevention of posterior capsular opacification

Posterior capsular opacification (PCO) is the main postoperative complication after intraocular lens (IOL) implantation in cataract surgery, because of the proliferation of the residual lens epithelial cells (LECs) in the lens capsule. Drug-eluting IOLs, aimed to develop an in situ drug delivery device, are the promising concept in recent years. As IOLs are optical devices other than implants, the feasibility and applicability remain a challenge for drug-eluting coatings. In this investigation, a centrifugally concentric ring-patterned drug-loaded poly(lactide-co-glycolic acid) (PLGA) coating was designed and fabricated by the spin coating technique. The concentric ring-patterned morphologies and the drug loading and release properties were carefully investigated, and the spin coating parameters were optimized. A concentric annular coating with a thin center and thick periphery was obtained, which was particularly suitable for the surface modification of IOLs, as the visual pathway of the intraocular light transmission greatly requires good light transmittance of the IOLs. IOLs with the immunosuppressant cyclosporin A (CsA)-loaded coating (CsA @ PLGA) modification were then fabricated for PCO prevention. The in vitro LECs culture results showed that the CsA @ PLGA coating-modified IOLs significantly inhibited cell proliferation and induced cell death. Western blot analysis showed that the efficient cell inhibition behavior of CsA was due to the autophagy-mediated cell death pathway. The in vivo intraocular implantation results confirmed the desired PCO inhibition effect. Thus, the centrifugally concentric ring-patterned drug-loaded PLGA coating obtained by the spin coating technique provides a simple yet effective alternative of IOL modification for PCO prevention. STATEMENT OF SIGNIFICANCE: • Concentric ring-patterned polymer coating, specifically for drug-eluting IOL fabrication, was developed by the spin coating technique. • The immunosuppressant CsA inhibited LEC proliferation through the autophagy-mediated cell death pathway. • Concentric ring-patterned CsA-eluting IOLs exhibited reliable in vivo PCO prevention. • The drug-eluting IOLs fabricated by the simple and economical spin coating technique have a great potential in clinical translation.

Posterior Capsule Opacification: A Review of Experimental Studies

Posterior capsule opacification (PCO) is the most common complication of cataract surgery. It causes a gradual deterioration of visual acuity, which would otherwise improve after a successful procedure. Despite recent advances in ophthalmology, this complication has not been eradicated, and the incidence of PCO can be as high as 10%. This article reviews the literature concerning the pathomechanism of PCO and examines the biochemical pathways involved in its formation and methods to prevent this complication. We also review the reported tests performed in cell cultures under laboratory conditions and in experimental animal models and in ex vivo human lens capsules. Finally, we describe research involving human eyes in the clinical setting and pharmacological methods that may reduce the frequency of PCO. Due to the multifactorial etiology of PCO, in vitro studies make it possible to assess the factors contributing to its complications and search for new therapeutic targets. Not all pathways involved in cell proliferation, migration, and contraction of the lens capsule are reproducible in laboratory conditions; moreover, PCO in humans and laboratory animals may be additionally stimulated by various degrees of postoperative reactions depending on the course of surgery. Therefore, further studies are necessary.

Cyclosporine A prevents ex vivo PCO formation through induction of autophagy-mediated cell death

The purpose of this study was to determine the Cyclosporine A (CsA) dose and minimum drug delivery time needed to prevent posterior capsule opacification (PCO) in an ex vivo canine model and evaluate the mechanism of CsA-induced cell death. Canine lens epithelial cells (LEC) were treated with CsA and changes in cell migration, proliferation, and density were monitored over time. CsA-treated LEC underwent transmission electron microscopy (TEM), immunofluorescence, and immunoblotting in the presence or absence of autophagy inhibitors to evaluate the mechanism of cell death. Lens capsules were harvested from canine cadaver eyes for an ex vivo model of PCO. Lens capsules were treated with CsA for 1, 2, 3, 4, 5, 6, or 7 days, and subsequently maintained in culture for a total of 28 days in the absence of drug. CsA reduced LEC viability in a dose dependent manner. Morphologically, CsA-treated LEC were swollen, had intact nuclei, lacked peripheral chromatin condensation, and demonstrated prominent vacuolization; TEM revealed autophagosomes. LC3-II protein expression and acridine orange fluorescence increased in CsA-treated cells. A small non-significant induction of cleaved caspase-3 was observed in CsA-treated LEC. Lens capsules treated with 5, 6, or 7 days of 10 μg/mL CsA showed a significant decrease in ex vivo PCO formation; 6 days of drug delivery prevented PCO. This study finds that morphologic changes, formation of acidic vesicles, and increased expression of LC3-II supports the hypothesis that CsA mediates LEC death via autophagy; this is a novel finding in the lens. Induction of CsA-induced apoptosis was minimal. Six days of intracapsular CsA drug delivery prevented ex vivo PCO formation.

Prevention of posterior capsular opacification

Posterior capsular opacification (PCO) is a common complication of cataract surgery. The development of PCO is due to a combination of the processes of proliferation, migration, and transdifferentiation of residual lens epithelial cells (LECs) on the lens capsule. In the past decades, various forms of PCO prevention have been examined, including adjustments of techniques and intraocular lens materials, pharmacological treatments, and prevention by interfering with biological processes in LECs. The only method so far that seems effective is the implantation of an intraocular lens with sharp edged optics to mechanically prevent PCO formation. In this review, current knowledge of the prevention of PCO will be described. We illustrate the biological pathways underlying PCO formation and the various approaches to interfere with the biological processes to prevent PCO. In this type of prevention, the use of nanotechnological advances can play a role.

Nanostructured lipid carrier surface modified with Eudragit RS 100 and its potential ophthalmic functions

This study was carried out to evaluate the ocular performance of a cationic Eudragit (EDU) RS 100-coated nanostructured lipid carrier (NLC). The genistein encapsulated NLC (GEN-NLC) was produced using the melt-emulsification technique followed by surface absorption of EDU RS 100. The EDU RS 100 increased the surface zeta potential from -7.46 mV to +13.60 mV, by uniformly forming a spherical coating outside the NLC surface, as shown by transmission electron microscopy images. The EDU RS 100 on the NLC surface effectively improved the NLC stability by inhibiting particle size growth. The obtained EDU RS 100-GEN-NLC showed extended precorneal clearance and a 1.22-fold increase in AUC (area under the curve) compared with the bare NLC in a Gamma scintigraphic evaluation. The EDU RS 100 modification also significantly increased corneal penetration producing a 3.3-fold increase in apparent permeability coefficients (Papp) compared with references. Draize and cytotoxicity testing confirmed that the developed EDU RS 100-GEN-NLC was nonirritant to ocular tissues and nontoxic to corneal cells. These results indicate that the NLC surface modified by EDU RS 100 significantly improves the NLC properties and exhibits many advantages for ocular use.

Shikonin inhibits the proliferation of human lens epithelial cells by inducing apoptosis through ROS and caspase-dependent pathway

Shikonin is a compound from the herbal plant Lithospermum erythrorhizon that has been proved to possess powerful anti-proliferative effect on many kinds of cancers and to be safe in in vivo study. Posterior capsular opacification (PCO), the most frequent complication of cataract surgery, is mainly caused by the uncontrolled proliferation of retained human lens epithelial cells (HLEs). In this study, we investigated the effect of shikonin on the proliferation of HLEs and explored its underlying mechanism of action. Shikonin significantly inhibited the proliferation of HLEs in a dose- and time-dependent manner. Its anti-proliferative effect was exerted through induction of apoptosis. Reactive oxygen species (ROS) generation played an essential role in this apoptotic process. Interestingly, scavenging of ROS completely blocked the apoptosis induced by shikonin. In addition, the treatment of shikonin in HLEs significantly increased the ratio of Bax/Bcl-2, disrupted mitochondria membrane potential (MMP) and activated caspases. The inhibition of caspase largely blocks the apoptosis. The changes of MAPK pathway were also demonstrated. Shikonin effectively inhibited the phosphorylation of ERK, while it activated the phosphorylation of JNK and p38. These results suggested that shikonin inhibited the proliferation of HLEs by inducing apoptosis through ROS generation and the caspase-dependent pathway and the MAPK pathway was also involved.

Design, characterization, and in vitro cellular inhibition and uptake of optimized genistein-loaded NLC for the prevention of posterior capsular opacification using response surface methodology

This study was to design an innovative nanostructured lipid carrier (NLC) for drug delivery of genistein applied after cataract surgery for the prevention of posterior capsular opacification. NLC loaded with genistein (GEN-NLC) was produced with Compritol 888 ATO, Gelucire 44/14 and Miglyol 812N, stabilized by Solutol(®) HS15 by melt emulsification method. A 2(4) central composite design of 4 independent variables was performed for optimization. Effects of drug concentration, Gelucire 44/14 concentration in total solid lipid, liquid lipid concentration, and surfactant concentration on the mean particle size, polydispersity index, zeta potential and encapsulation efficiency were investigated. Analysis of variance (ANOVA) statistical test was used to assess the optimization. The optimized GEN-NLC showed a homogeneous particle size of 90.16 nm (with PI=0.33) of negatively charged surface (-25.08 mv) and high encapsulation efficiency (91.14%). Particle morphology assessed by TEM revealed a spherical shape. DSC analyses confirmed that GEN was mostly entrapped in amorphous state. In vitro release experiments indicated a prolonged and controlled genistein release for 72 h. In vitro growth inhibition assay showed an effective growth inhibition of GEN-NLCs on human lens epithelial cells (HLECs). Preliminary cellular uptake test proved a enhanced penetration of genistein into HLECs when delivered in NLC.

Doxorubicin-loaded MePEG-PCL nanoparticles for prevention of posterior capsular opacification

AIMS

Cytotoxic drugs are considered as potent candidates for the prevention of posterior capsular opacification (PCO), but the toxicity incited to healthy intraocular structures is a major concern. In this study, the authors evaluated the effect of PEG methyl ether-block-poly(ε-caprolactone) (MePEG-PCL) doxorubicin (DOX)-loaded nanoparticles (NPs) for prevention of PCO and their influence on intraocular tissues.

METHODS

MePEG-PCL DOX NPs were prepared and characterized. The cytotoxic effect of DOX NPs on lens epithelial cells was compared with free drug. Its effect on PCO prevention following single subconjunctival delivery to lensectomized rabbits was assessed. Toxicity to intraocular structures was evaluated by specular microscopy, electroretinography and histopathology. The availability of DOX in aqueous humor was determined by HPLC.

RESULTS

The cytotoxic effect of DOX NPs was higher compared with free DOX due to prolonged retention within the cells. A significant reduction in degree of PCO was observed in DOX NP-treated eyes compared with untreated controls. There was no significant change in the density and morphology of corneal endothelial cells or the histology of intraocular structures. Electroretinographs of treated eyes did not change compared with the pretreatment values. DOX could be detected by HPLC in the aqueous humor up to 48 h following single subconjunctival injection.

CONCLUSION

The authors conclude that DOX-loaded MePEG-PCL NPs show promise as a new approach to selectively kill highly proliferative lens epithelial cells in vivo following cataract surgery, while sparing normal tissue.