The transparent ocular lens focusses light onto the retina in order to form a sharp image. The lens is remarkable in that it is able to remain transparent over many decades of life despite the lack of a blood supply or de novo protein synthesis and turnover in the lens centre. Cells in the lens centre are formed in utero and maintained throughout life, and contain long-lived proteins whose function must also be maintained. To protect against oxidative-stress induced protein damage, the lens contains high levels of antioxidants, such as glutathione and vitamin C. The development of age-related cataract is thought to be related to changes in lens antioxidants and other metabolites in specific lens regions, and leads to the protein damage, insolubilisation and opacification that characterises lens cataract. In this study, lens small molecules and metabolites have been mapped in the aging human lens to define lens metabolome changes associated with normal lens aging.

Frozen donor human lenses were sectioned at 20mm and collected on gold MALDI targets using methanol soft-landing. NEDC matrix (7mg/ml in 90% MeOH) was applied using a TM-Sprayer (HTX Technologies). MALDI imaging data sets of all lens ages were analysed simultaneously at 50-150um spatial resolution using a MALDI-TOF/TOF mass spectrometer (Bruker UltrafleXtreme) in negative ion mode. Data sets were normalised to total ion current, and MALDI images plotted using flexImaging v4.1with pixel interpolation on. Where possible, on-tissue tandem mass spectrometry was used to confirm metabolite identities.