Downregulation of gene expression in the ageing lens: a possible contributory factor in senile cataract

To study the molecular characteristics of lens epithelial cells from patients with senile cataract by cDNA microarray technique.

Lens epithelial cells adhering to anterior capsules taken during cataract surgery collected from 108 patients, aged 56-92 years (senile cataract group), were pooled. Pooled epithelial cells of normal, noncataractous lenses from one patient with ocular trauma, one patient with lens subluxation, and 25 cadaveric eyes, all under the age of 55 years, served as a control. Total RNA was extracted by conventional methods from the two groups of cells, and a fluorescent probe was prepared for each group. The probes were hybridized on 9700 known human cDNA clones. Hybridized clones were analysed using a scanning laser and the results were processed by GEMTools (Incyte Genomics) software.

A total of 1827 clones hybridized with the two probes. Of these, 400 showed differences of more than two-fold in gene expression between the two probes. Relative to controls, gene expression in the senile cataract lenses was upregulated in 318 clones and downregulated in 82. Three genes-filensin, inwardly rectifying potassium channel (IRPC), and pigment epithelium-derived factor (PEDF) were strongly downregulated (by 41.3-, 6.8-, and 5.9-fold, respectively) in senile cataract.

Cataractogenesis is associated with numerous changes in the genetic profile of the lens epithelial cells. Since filensin, IRPC, and PEDF genes are known to have important roles in the physiology and morphology of the transparent lens, substantial downregulation of their expression might contribute to the formation of senile cataract.