Up-regulation of osteonectin/SPARC in age-related cataractous human lens epithelia

Abstract

Purpose: To characterize gene expression patterns between epithelia isolated from cataractous and normal human lenses.

Methods: Reverse transcriptase differential display was used to identify differential expression between cataractous and normal epithelia. RT-PCR was used to compare pooled and individual RNA samples.

Results: One transcript, up-regulated in cataractous as compared to normal epithelia, was identified as osteonectin which is also known as SPARC (secreted acidic protein rich in cysteines). RT-PCR confirmed over-expression of this RNA. High levels of osteonectin mRNA were also detected in six individual epithelia dissected from cataractous lenses.

Conclusions: The present study provides evidence for up-regulation of osteonectin in human age-related cataract and suggests that osteonectin, a protein involved in cell-cycle control, extracellular matrix and Ca++ binding, plays an important role in human lens homeostasis and may be involved in processes leading to lens opacity.