Spatial characteristics of receptor-induced calcium signaling in human lens capsular bags.
OBJECTIVE
Despite recent improvements in intraocular lens (IOL) design, posterior capsule opacification (PCO) arising from lens cell growth remains a major problem. Calcium signaling has been shown to play a major role in driving human lens cell growth, and therefore it is necessary to understand the underlying mechanisms.


METHODS
Calcium signaling was studied in capsular bags (ex vivo) removed from donors who had undergone earlier cataract surgery. Fresh capsular bags were also produced from intact donor lenses and cultured in serum-free EMEM for up to 8 weeks. Both preparations were loaded with Fura-2, and ratiometric imaging of cytoplasmic calcium was performed using epifluorescence techniques. Changes were monitored in response to 10 microM ATP (adenosine triphosphate), 10 microM acetylcholine, and 10 ng/mL epidermal growth factor (EGF), and data were collected from equatorial, posterior, and anterior regions. Calcium transients were also recorded from anterior epithelial specimens in response to pilocarpine.


RESULTS
All equatorial cells of ex vivo bags responded to ATP and EGF, but not to acetylcholine, and this pattern was maintained in the cultured bags. Posterior capsule cells of both preparations also had similar properties, in which a large proportion of the cells responded to ATP and EGF, but not to acetylcholine. Conversely, most anterior cells of the in vivo bags responded to pilocarpine, whereas no cells in the cultured bags responded. All cells in the fresh anterior epithelium responded to pilocarpine.


CONCLUSIONS
Ex vivo capsular bags retain the region-specific calcium-signaling characteristics of the native lens. Apart from losing M1 muscarinic expression properties, the in vitro capsular bags also reflect region-specific signaling properties and therefore provide a good model for the investigation of the contribution of calcium-signaling to PCO.
Collison
David J
DJ
School of Biological Sciences, University of East Anglia, Norwich, United Kingdom. david.collison@uea.ac.uk
Wang
Lixin
L
Wormstone
I Michael
IM
Duncan
George
G
D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000368:Aged; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D016257:Fura-2 / Q000031:analogs & derivatives* / Q000378:metabolism; D006801:Humans; D007903:Lens Capsule, Crystalline / Q000187:drug effects / Q000378:metabolism*; D018721:Muscarinic Agonists / Q000494:pharmacology; D009924:Organ Culture Techniques; D010862:Pilocarpine / Q000494:pharmacology; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D018048:Receptors, Purinergic P2 / Q000378:metabolism*
D018721:Muscarinic Agonists; D018048:Receptors, Purinergic P2; D010862:Pilocarpine; C049925:fura-2-am; D004815:Epidermal Growth Factor; D000255:Adenosine Triphosphate; D020794:Receptor Protein-Tyrosine Kinases; D000109:Acetylcholine; D002118:Calcium; D016257:Fura-2