Abstract
Purpose: :
Despite recent improvements in IOL design Posterior Capsule Opacification (PCO) remains a significant clinical problem associated with cataract surgery. The Perfect Capsule device (Milvella Ltd) permits the introduction of potentially toxic agents into the closed capsular bag under controlled conditions. The aim of this study was to compare the relative effectiveness of exposing cells within the human capsular bag to a range of stresses with clinical potential and to compare the response to the same stresses applied to human lens cells cultured on plastic.
Methods: :
Human capsular bags were prepared from donor eyes and after aspirating adherent fibre cells, the bag was sealed with the Perfect Capsule. The agents: distilled water, 3M NaCl, 25mg/ml 5–fluorouracil (5–FU) and 100µM thapsigargin (Tg) were introduced for a two minute period. The bags were then perfused with Eagle’s minimum essential medium (EMEM) and a PMMA intraocular lens (IOL) inserted before dissection and pinning to the base of plastic (PMMA) culture dishes. The bags were maintained in serum–free (EMEM) for 28 days and phase images were acquired throughout. FHL124 cells were routinely cultured on plastic (EMEM supplemented with 5% FCS) and serum was removed for 24 hours before exposure to the same agents for periods ranging from 7.5 seconds to 2 minutes. Cell survival was assessed by Coomassie blue staining after 4 days.
Results: :
Initially, NaCl induced by far the most obvious signs of cell death, especially of anterior cells, while 5–FU >distilled water >Tg. However, by two weeks cell death became more apparent in the Tg exposed bags and at the end of four weeks there were no cells surviving. Cells on the posterior capsule were confluent in water–exposed bags (similar to unexposed controls), while NaCl coverage was incomplete but greater than 5–FU. Cell migration onto the anterior IOL surface was inhibited by NaCl, 5–FU and Tg but not in water or controls. At the end of 4 days culture of FHL124 cells exposed for 2 minutes to NaCl, 5–FU or Tg there were no cells surviving, while there was 50% cell survival compared with controls in water treated cells. Interestingly, with 7.5 seconds exposure almost 90% cell death was achieved with NaCl and 5–FU, while Tg and water were less effective.
Conclusions: :
Human lens cells are much more sensitive to hyper–osmotic than hypo–osmotic stress with a rapid onset of cell death of cultured cells exposed to NaCl. This was confirmed in capsular bags although adherent fibres appear to offer additional protection which can be overcome by the very hydrophobic Tg.
Keywords: posterior capsular opacification (PCO) • cell survival • stress response