Cataracts are the commonest cause of preventable blindness in the world. During surgery the natural lens is replaced with a polymeric intraocular lens (IOL), leaving the capsular bag in situ. The most common postoperative complication is scarring which is known as posterior capsule opacification (PCO). PCO occurs when residual lens epithelial cells (LECs) dedifferentiate and migrate onto the previously cell free posterior capsule. By modifying the IOL surface properties we can manipulate the cellular response. BioInteractions Ltd. is an innovative supplier of biomaterials, which aim to minimise, the host response, and provided the materials for this study. The aim of this study was to evaluate potential IOL coatings to reduce PCO. This can either be achieved by enabling a monolayer of LECs to attach to the posterior surface of the IOL, thus sandwiching the IOL to the capsular bag, or prohibiting cell attachment to the IOL entirely. Materials and Methods: Various coatings were investigated incorporating functional groups of poly ethylene glycol (PEG), sulphates, sulfonates, glycosaminoglycans (Heparin, (HEP) hyaluronic aid, (HA) and chondroitin sulphate (CS)) and zwitterionic monomers (10-30%). Ways to prevent dedifferentiation was also evaluated. LECs were seeded onto all coatings and monitored for a period of 7 – 14 days in cell culture. LECs were examined morphologically, cell nuclei were counted and growth curves were plotted. Water contact angle (CA) measurements were taken to measure the wettability of the coatings. Scanning electron microscope (SEM) analysis was performed to examine the topography of the coating. White light interferometry (WLI) analysis was conducted to analysis the surface roughness. Dedifferentiation of LECs and the use of TGFβ3 to neutralise or prevent dedifferentiation were also investigated. Results and Discussions: Coatings with a greater number of water-based layers were the most hydrophilic, and did not offer the appropriate cell binding sites required to promote cell attachment. In general, little cell attachment was observed on HEP and HA coatings provided by BioInteractions Ltd., cell attachment varied on CS coatings provided by BioInteractions Ltd. When HA and CS were covalently bound onto amine coated coverslips a reduction in cell attachment was observed. The LEC response varied across different ratios of zwitterionic monomer within the coatings. Zwitterionic coatings were not cytotoxic to LECs and surface analysis demonstrated no clear link between wettability and roughness compared to cell attachment. Addition of transforming growth factor beta 2 (TGFβ2) was chosen as a successful dedifferentiation model. Addition of TGFβ3 had little influence at reversing dedifferentiation however it may offer some protection against differentiation. PCR analysis showed a change in regulation of collagens, integrins, matrix metallopeptidase and fibronectin 1 genes, when LECs were incubated with TGFβ2, TGFβ3 or untreated (control LECs). These genes may play important roles in PCO. Conclusions Incorporation of functional groups influenced the cellular response, however the coatings with more water-based layers prohibit cell attachment. The cellular response varied depending on GAG type and the conformation of GAG on the surface coating. HA and CS bound to amine-coated coverslips prohibited cell attachment at higher concentrations, indicating their potential to prohibit LEC attachment. There was no clear link between wettability and cell attachment on the novel zwitterionic coatings. The ratio of zwitterionic-component:arylic-based monomer(s) influenced cell attachment. TGFβ2 successfully dedifferentiated LECs. Further work is required to understand the influence of TGFβ3 on dedifferentiation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:579376 |
| Date | January 2013 |
| Creators | Lace, Rebecca |
| Contributors | Williams, Rachel; Sheridan, Carl |
| Publisher | University of Liverpool |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://livrepository.liverpool.ac.uk/10615/ |
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