It sounds like science fiction, but researchers say spinach could help treat dry eye disease.
A team led by the National University of Singapore adapted part of photosynthesis for the human eye, using membrane stacks from spinach leaves in eye drops for lab-grown human eye cells and mice engineered to have a condition similar to dry eye disease.
The approach worked. When exposed to ambient light, the nanoparticles added to mammalian eye cells began producing NADPH, a chemical “battery” that cells use to protect against harmful damage.
NADPH counters reactive oxygen species, or ROS, which drive inflammation and cellular stress in dry eye disease.
“This is an exciting finding as we have, for the first time, demonstrated that plant photosynthetic machinery can be transplanted into mammalian tissue to generate biologically useful molecules, powered entirely by the same light that enables our vision,” biomolecular engineer Xing Kuoran, from NUS, said.
“We, too, can have limited photosynthetic abilities.”
The researchers call the technology LEAF, short for light-reaction enriched thylakoid NADPH-foundry.
Thylakoids are the NADPH-generating components of chloroplasts, the structures that carry out photosynthesis in plant cells.
The team chose spinach because it has a high chloroplast yield, its biomachinery is relatively easy to extract using methods outlined in earlier studies, and the plant is inexpensive and widely available.
The researchers found that within 30 minutes of light exposure, the NADPH generated by light reduced ROS activity and returned immune cells in the cornea to a protective, anti-inflammatory state.
The process also worked in tear samples from patients with dry eye disease. LEAF treatment reduced levels of harmful oxidants, including a 95 percent drop in hydrogen peroxide.
“With LEAF, we now have a technology that harnesses ambient light to directly restore the molecule that dry eye disease depletes,” biomolecular engineer David Leong Tai Wei, from NUS, said.
“As it is derived from spinach, delivered as a simple eye drop, requires no external device or power source and using the ambient light that is used for vision, we believe it has a strong potential for clinical translation.”
In mice treated twice daily for five days, LEAF outperformed Restasis, a commonly prescribed treatment for dry eye disease.
The researchers said preparations for clinical trials are already underway.
They also want to test the treatment over longer periods because the LEAF particles currently degrade in the eye cells they are dropped into and lose effectiveness after a few hours.
The team said the same approach could also be used for other inflammatory conditions where defense against ROS is needed and the tissue can be exposed to visible light.
“It is almost surreal when thinking of a possible future reality where human cells can have some limited but beneficial form of photosynthetic ability not only in the eye but elsewhere, too,” Leong said.
The research was published in Cell.
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