CTSB and age-related macular degeneration: Similar to cathepsin B, the gene expression of cystatin C was also upregulated significantly in the AMD mice without treatment compared to the young counterparts (P < 0.01), but Fructus lycii ethanol extract dose-dependently eliminated the increase in cystatin C gene expression, and a significant effect was observed even if at a low dose compared to the AMD mice without treatment (P < 0.01) (Figure 3(a)).