Adherence of human lens epithelial cells to conventional poly(methyl methacrylate), heparin-surface-modified, and polyHema lenses

Adherence and viability of porcine lens epithelial cells on three different IOL materials in vitro

BACKGROUND

The purpose of the study was to evaluate porcine lens epithelial cell (LEC) adhesion and viability on three different intraocular lens (IOL) materials.

METHODS

The IOL materials tested were poly(methylmethacrylate) (PMMA), silicone and hydrophobic acrylate. Primary porcine LECs were cultured on four discs of each material over a period of 10 days and, additionally, on six discs of the hydrophobic acrylate over a period of 20 days. Cells grown on untreated wells of a 96-well microtiter plate served as a control. Cell adhesion was photodocumentated on days 1, 2, 3, 4, 6, 8, 10, 14,17 and 20. A cell viability test using the LIVE/DEAD kit (Molecular Probes) was carried out at the end of the investigation. Experiments were run in triplicate. Statistical analysis was performed using the Student's t-test.

RESULTS

Confluent cell growth was reached on the hydrophobic acrylate discs and the control wells within 1 day and remained stable during the experiment. Only a few round cells were adherent on PMMA and silicone discs, and their number decreased during the experiment. After 10 days of culturing, the viability test (mean +/- SD) revealed 81.79 +/- 51.74% live cells on acrylate discs, which was not different from the control (105.83 +/- 21.78%, P=0.1589). Significantly lower relative numbers of live cells (P>0.0001) were found on PMMA (-0.62 +/- 2.24%) and silicone (21.47 +/- 8.42%) discs. The percentage of dead cells was significantly higher (P<0.0001) on hydrophobic acrylate discs (29.69 +/- 12.61%) compared to the control (-1.49 +/- 4.13%). After a culture period of 20 days, the percentage of live cells on hydrophobic acrylate discs (49.45 +/- 27.98%) was lower compared to day 10, but was not significantly different from control wells (58.77 +/- 10.71%) (P=0.2299).

CONCLUSIONS

Significantly fewer cells grew on PMMA and silicone discs compared to the control. Confluent cell growth and numbers of viable cells comparable to the control were observed on hydrophobic acrylate discs after a culture period of 20 days with a significantly higher percentage of dead cells.

Modulating fibroblast cell proliferation with functionalized poly(methyl methacrylate) based copolymers: chemical composition and monomer distribution effect

Poly(methyl methacrylate)-based terpolymers bearing sulfonate and carboxylate groups have been synthesized by radical copolymerization leading to polymers with random distributions of ionic monomer units. Fibroblast cells were seeded on terpolymers of various molar compositions of ionic groups. Kinetics of the cell proliferation were examined and systematically compared to the nonfunctionalized control polymer, poly(methyl methacrylate). Modulation of cell proliferation was observed on 15% ionic monomer content copolymers of various compositions (R = COO(-)/(COO(-) + SO(3)(-)) and varies from 0 to 1). The inhibition percentage of cell proliferation calculated for each polymer by comparison to the cell proliferation on the control was plotted against R and gave a maximum value for R close to 0.55. Copolymers with ionic group contents higher or lower than 15% exhibit inhibition percentages fitting with those previously observed for the same R values, showing that the hydrophilic properties are not sufficient to explain the modulation effect of this material toward cells. Moreover, for each polymer tested, cells, even if inhibited in growth, were shown to be viable, indicating that the synthesized terpolymers exhibit cytostatic properties excluding any cytotoxic effect. Such polymers may be used for the fabrication of biocompatible intraocular lenses and prevent secondary cataract.

Effect of heparin surface modification in reducing silicone oil adherence to various intraocular lenses

PURPOSE

To evaluate surface properties of various intraocular lenses (IOLs), including a newly fabricated heparin-surface-modified (HSM) silicone IOL, with special reference to their efficiency in reducing potential silicone oil adherence to the IOL optics.

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

Five groups of rigid and foldable IOLs were analyzed in an in vitro test for the percentage of silicone oil adherence: a single-piece foldable hydrophilic-acrylic IOL (n = 9); a single-piece rigid poly(methyl methacrylate) (PMMA) IOL with HSM coating of the lens optic (n = 9); a 3-piece foldable silicone optic IOL with HSM coating of the optic (n = 10); a single-piece standard rigid PMMA IOL (n = 7); and a standard 3-piece foldable silicone optic IOL (n = 9). After the IOLs were immersed in water and then in silicone oil, gross photographs taken. Image analysis was performed to evaluate the percentage of silicone oil coverage of the anterior and posterior surfaces of each IOL optic.

RESULTS

The mean silicone oil coverage of the hydrophilic-acrylic IOLs was 5.6% +/- 2.5% (SD); of the HSM PMMA IOLs, 6.2% +/- 4.3%; of the HSM silicone optic IOLs, 6.7% +/- 3.2%; and of the standard PMMA IOLs, 20.3% +/- 13.3%. The mean silicone oil coverage was greatest on the standard silicone optic IOLs, 98.2% +/- 3.1%.

CONCLUSIONS

Intraocular lenses with a hydrophilic optic have less tendency toward adherence to silicone oil than more hydrophobic designs. A foldable silicone IOL with heparin surface modification can significantly reduce potential silicone oil adherence, comparable to the level achievable with the rigid HSM PMMA designs. Two new foldable IOL styles, the HSM silicone IOL and IOLs in the general class of hydrophilic-acrylic, were highly efficacious in reducing silicone oil adherence. There is now a real choice of foldable lenses for patients with actual or potential vitreoretinal diseases.

Adhesion mechanisms of human lens epithelial cells on 4 intraocular lens materials

PURPOSE

To evaluate lens epithelial cell (LEC) adhesion on different intraocular lens (IOL) materials with particular attention to the distribution of proteins located in the focal contacts.

SETTING

Center of Biotechnological and Clinical Research in Ophthalmology, University of Bologna, Italy.

METHODS

The IOL materials tested were poly(methyl methacrylate) (PMMA), heparin-surface-modified PMMA (HSM PMMA), polyHEMA, and silicone. Primary cultures of human LECs were established from human anterior capsules obtained during cataract surgery. The mean number of cells attached per square millimeter was calculated for each material after 24 and 72 hours. Transmission electron microscopy and immunocytochemical analysis were performed to detect the proteins actin, vinculin, and talin.

RESULTS

Mean adhesiveness of human LECs increased over time with PMMA and decreased with the other materials. At 72 hours, mean LECs ranged from 54.8 cells/mm2 +/- 12.8 (SD) on PMMA to 2.1 +/- 0.7 cells/mm2 on silicone. The means for HSM PMMA and polyHEMA fell in between. The cytoskeletal proteins were arranged to produce focal contacts in only the LECs cultured on PMMA. The LECs cultured on polyHEMA, HSM PMMA, and silicone attached but failed to develop focal contacts or stress fibers.

CONCLUSION

This study confirms the multifactorial pathogenesis of posterior capsule opacification and suggests its incidence will be reduced by improving surgical techniques and using IOL surfaces that discourage cell adhesion.

Posterior capsule opacification. Part 1: Experimental investigations

Posterior capsule opacification (PCO) is the most frequent complication associated with decreased vision after cataract surgery. Previous methods of preventing PCO have not proven to be practical, effective, and safe for routine clinical procedure, but some novel concepts and methods have recently been developed. This 2-part review looks at clinical and experimental investigations of PCO, focusing on developments since 1992. Clinical aspects will be presented in a later issue. This paper addresses (1) in vitro models for PCO research; (2) pathophysiology and molecular biology of lens epithelial cells (LECs); (3) prevention of PCO. Of special interest are methods of culturing human LECs obtained by capsulotomy during cataract surgery, including those obtained with an intact capsular bag, to provide an in vitro model for investigating the pathophysiology of LECs; the effect of a sharp bend in the lens capsule that induces contact inhibition of migrating LECs; more specific inhibition of migrating LECs using an immunotoxin, b-FGF-saporin, or EDTA and RGD-peptides.

Endophthalmitis after cataract surgery: risk factors relating to technique and events of the operation and patient history: a retrospective case-control study

OBJECTIVE

This study aimed to investigate the relationship between postoperative endophthalmitis and current changes in the cataract operative technique.

DESIGN

A retrospective case-control study.

PARTICIPANTS

The 22,091 cataract operations performed from 1990 through 1993 at St Eriks Hospital formed the basis for this investigation. In a random fashion, 220 control subjects were selected to be compared with the endophthalmitis cases.

MAIN OUTCOME MEASURES

Numerous variables pertaining to the cataract extraction procedure and to the ocular and general health of patients with cataracts were analyzed regarding the development of postoperative intraocular infection. Patient age, presence of diabetes or immunosuppression, type of cataract extraction and intraocular lens (IOL), and intraoperative or postoperative complications were the principal variables assessed.

RESULTS

Fifty-seven patients with endophthalmitis were diagnosed, resulting in an overall frequency of 0.26%. Immunosuppressive treatment (P = 0.019), wound abnormality (P = 0.03), and the use of IOLs without a heparinized surface (P = 0.0023) were the only significant risk factors found in a logistic regression model.

CONCLUSIONS

The results suggest that cataract operating practice may alter the risk for endophthalmitis in that implanting a heparinized IOL and creating a tight section both seem to provide protection against this dreaded complication. Regarding patient history, an increased susceptibility was found among subjects treated with immunosuppressants. Designing a prophylactic protocol that protects against endophthalmitis more efficiently than did the study prophylaxis of 20 mg of subconjunctival gentamicin, is important not only for this patient subgroup but also for the cataract operated population at large.