An eyedrop formulation can reverse cataracts in days, a new study has revealed.
Up to a fifth of individuals aged over 40 are afflicted by cataracts, which also cause half of all cases of blindness worldwide.
The condition occurs when the lens in the front of the eye becomes clouded, obscuring vision. This happens because proteins called crystallins, which make up the bulk of the lens material, lose their normal straight, rigid shapes and become bent and misfolded. Over time, these misfits accumulate and begin to clump together, forming insoluble aggregates that scatter and blur the paths of light entering the eye leading to a loss of visual acuity.
Cataracts can be remedied relatively easily with surgery to remove the damaged lens and replace it with a plastic replica. But as the population ages, the number of patients needing this intervention looks set to double within twenty years, meaning eye clinics will nevertheless struggle to meet demand.
Now a breakthrough by US researchers might be about to make surgery unnecessary.
University of California San Diego scientist Ling Zhao and her colleagues used DNA techniques to compare the genetic make up of patients with severe congenital cataract disease with their healthy parents. They were looking for genes linked to the condition.
The approach led them to hit upon a gene called LSS, which encodes an enzyme called lanosterol synthase and was altered individuals with cataracts. Lanosterol synthase makes the substance lanosterol, which is used by cells to produce cholesterol. Since a lack of lanosterol was linked to an acceleration in cataract formation, Zhao and her colleagues wondered whether a boost in lanosterol concentrations could reverse cataracts by dismantling cystallin aggregates.
Cells engineered to produce clumps of crystallins as well as lanosterol showed fewer aggregates than cells lacking lanosterol production. Lanosterol was also able to dismantle and dissolve crystallin aggregates in the dish. Tests on lenses taken from rabbits with cataracts showed a significant drop in opacity after six days' incubation in lanosterol, and cataracts in living dogs also improved significantly following lanosterol eyedrop and nanoparticle treatments.
These results, published this week in Nature, suggest that it might be possible to prevent, or even reverse human cataracts using a simple topical treatment. At the moment the team do not know the precise mechanism through which the steroid chemical achieves its effects, but it hasn't escaped their attention that a number of other important conditions, including Parkinson's and Alzheimer's Disease, are also caused by aggregations of misfolded proteins and therefore might also be amenable to a similar treatment approach...