Changes in the spatial expression of genes with aging in the mouse RPE/choroid

We recently used microarray and reverse transcriptase PCR (RT-PCR) analysis to show an upregulation of cathepsin S (CatS) and glutathione peroxidase 3 (GPX3) in the aging mouse RPE/choroid. To evaluate the mRNA distribution and levels in the RPE and choroid, in situ hybridizations were performed. Eye sections from 2-month-old and 24-month-old C57BL/6 mice were probed for CatS or GPX3 mRNA by in situ hybridization. The ratio of mRNA labeled cells to total cells counted per section was compared between the two age groups for the RPE and choroid separately. The CatS labeled RPE cell ratio increased significantly with age. The GPX3 labeled RPE cell ratio did not increase with age. The increases in mRNA levels for CatS and GPX3 found in the aging C57BL/6 RPE/choroid appear to represent an increase in both the numbers of cells expressing these messages and an increase in the level of expression in individual cells.