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L. J. Dawes, G. Duncan, I. M. Wormstone; Age-Related Signaling Capacities of Human Lens Cells. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2119.
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© ARVO (1962-2015); The Authors (2016-present)
Ageing phenomena are observed following cataract surgery where a wound healing response leads to the formation of posterior capsule opacification, which is greater in the young (<40yrs) than the elderly (>60yrs). The overall objective of this study was to identify age-related differences in signaling capacity through expression of putative signaling components.
Human capsular bags were prepared by performing a sham cataract operation on donor lenses, obtained from the Bristol or East Anglian Eye banks. The resultant capsular bag was transferred to a 30mm Petri dish and secured using entomological pins. Capsular bags were maintained in serum-free (un-supplemented) EMEM. Protein synthesis was determined by 35S-methionine incorporation. Fibroblast growth factor (FGF) and hepatocyte growth factor (HGF) level was quantified using ELISA. Signaling molecules (total and phosphorylated levels of ERK, Akt, c-jun, P38 and JNK) were analysed using a suspended bead array (BIOPLEX) system. To evaluate the potential impact of paracrine stimulation, a number of capsular bags were maintained until log growth of cells occurred across the previously cell-free posterior; for the final 30 minutes of culture, donor pairs were maintained in the presence or absence of 10% FCS.
Analysis of capsular bags using ELISA, showed that lens cells from aged human donors (>60yrs) contained equivalent HGF and significantly greater amounts of FGF than younger counterparts (<40yrs) when maintained in serum free conditions. Moreover, aged capsular bags also demonstrate greater rates of protein synthesis. BIOPLEX analysis showed that activity of key signaling proteins analysed was on average 34.6 ± 4.99% lower in the aged population of cells. Addition of a global stimulus (10% FCS) increased levels of pERK, p-c-jun, pP38 and pJNK in lens cells of all ages; pAkt only increased in the >60yrs group.
Overall signaling activity is reduced as a function of age, which results because multiple signaling cascades are affected. Global stimulation can markedly promote signaling activity in both young and old. As a consequence, we hypothesise that an increased level of signal inhibitors in aged lens cells determines baseline signaling activity and growth rate.
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